I’ve received some feedback in the form of doubt with respect to the recent project of the carbonfiber strips reinforcing the basement wall. To those folks, I offer up this video, assembled by Fortress Stabilization Systems as proof of concept. (If I can figure out how to embed a raw video file again).

Before I get too deep into this one, no, I’m not crazy and yes, this will really work! The engineering behind it is sound and there’s evidence of it’s success elsewhere!

The problem: A good friend of mine recently purchased a fixer-upper house and knew that there was some problems with the 60′ front basement wall….the front yard was trying to get into the basement and had cracked the (what we later found out) incredibly inadequate 4 inch block that was used to build the foundation. The wall had a long horizontal crack, nearly the length of the wall, and in some places had bulged out 2 inches. Before he signed the deed, he had estimates. Jacking up the house and completely replaceing the wall = $30,000 and he had two estimates in the same range. What was interesting, however, was a third company that proposed an $11,000 solution by gluing carbon fiber strips to the existing wall. This wouldn’t straighten it but would stabilize it to keep it from shifting further. Naturally, this caught my attention and investigation into the process caught my imagination. I said to Mark, I have all the tools to do this and we can do it for less than $1,000 and do it better! (Mark seems to have a lot of faith).

I don’t have much of a “before” shot - but here’s an angle looking down the wall. Remember, this is only 4″wide block where it should have really been, at the very least, 8″ (better to be 12″).

The company that proposed this had video on their website that showed their testing of the process. A test wall they had constructed was loaded up with a hydraulic ram and cracked at only 500 pounds of force. Now that the the wall was cracked and buckled in a very similar fashion to this one, they applied their carbon strips (which were pre-cured) with vacuum. Once cured, they fired up the ram and put more pressure on the wall until it failed. Their test wall, even with the pre-damage, now withstood 12,000 pounds of pressure before it yielded - and it wasn’t the carbon that failed - the carbon, where it was epoxied to the block, sheared the concrete below it and came off the wall taking a whole lot of concrete with each strip. It was the shear strength of the concrete, not the carbon and not the bond of the carbon to the concrete, that ultimately failed.

So why carbon and not something less expensive like Kevlar or even fiberglass? The answer is because the carbon, for all practical purposes, will not stretch. The Kevlar, while strong, will stretch a little more than carbon and any movement in the wall can degrade it over time.

We decided to do one better and instead of using a pre-cured strip (which would be much easier to work with), we decided to vacuum bag wet uni-directional carbon directly to the wall. Before we did this, however, we needed to seal the block and even out some of the major irregularities (like grout lines). After masking off a vertical 6″ area every 4 to 5 feet, we rolled West System epoxy with slow hardner onto the wall with a 4″ paint roller. We made sure to get it really wet so the epoxy would soak deeply into the concrete…and soak it did. It sucked it up like a sponge. Then we came back with epoxy thickened with milled fiberglass (in hindsight, cabosil would have been easier to work with), and filled in the grout lines and squeegied it on the whole surface to fill in most of the pock-marks in the wall. Then a layer of peel-ply went ontop of that would smooth out the filler even more and give us a really good surface for secondary bonding once removed. There was still some minor irregularity in the wall - but it wasn’t critical. The epoxy at this stage did a couple of things for us. 1) it made the wall smoother so the carbon will be mostly straight and setup to handle loading in tension (what it’s best suited for) and 2) sealed the block so we could pull a vacuum over each strip.

Using 10 rolls of mastic vacuum bagging tape, we sealed the perimeter of the prepared areas and wetted out an 8′ long 4″ strip of uni-directional carbon fiber tape. A skim coat of unthickened fast cure epoxy was brushed onto the wall. The carbon strip went up followed by a bleeder ply of plastic (with tiny holes). Then a long thin piece of felt was applied to transfer the vacuum evenly followed by a top layer of vacuum bagging film. The amount of vacuum we were able to achieve was incredible and with the high flow of a compressed air venturi vacuum generator, we were able to vacuum up to five strips at a time.

After about four or five solid days of work (spread out over a month), we finished the repair and that wall isn’t going ANYWHERE. The carbon is sucked down so tight to the wall, you can see the compression in the weave of the fabric and it is physically part of the wall structure now. The vacuum and compression effectively “pre-tensions” the carbon and makes the bond to the concrete as strong as it can possibly be. There’s my carbon fiber concrete story.

FINALLY! After weeks of watching the breeze ruffle the yard cover of my new (to me) a-cat for the last couple of weeks, I had a day to take it to the lake. I’ve sailed on an a-cat only once and it was in really light and patchy breeze a couple of years ago. The breeze was set to be a nice 8 to 10 knots on my home lake (Keowee) this past Saturday and with butterflies of excitement in my belly (geesh, am I 10?) I hooked up the boat trailer and headed to the lake at 7am. After fiddling with the boat and sorting out some of the setup for an hour and a half, I wheeled it down the ramp, where I began to realize some of the shortcomings of the current setup for single handing….the beach dolly. It was impossible to put the dolly under the boat on my own and even more ridiculous to extract them by myself (and get them on the beach) once the boat was in the water. The sailing was magnificent and I’m really happy with the boat.

Another thing afforded to me with this long weekend was some free time to work in the shop (of which I have had NONE in the last several months). After seeing what one of our local a-cat sailors had come up by scavenging pieces of an old MC Scow dolly, I pulled out the resin, fiberglass, and one of two old fiberglass windsurfer masts I’ve been keeping around for just such a project.

The goal is to build an extended handle that attaches to the middle of my standard, single axle - two wheeled, dolly. This extension will have an upright fitted with a small cradle that will engage the dolphin striker on the boat. The idea is to place the upright on the extension so that the axle (and cradles) are behind the center of gravity of the boat and a bit of the forward weight supported at the striker. The boat will sit off the ground pleasantly while on the dolly and the grip of the upright on the dolphin striker eliminates the need to tie the dolly to the boat to keep it from sliding. The big advantage of this is that with the dolly sitting at the water’s edge, I can lift the bows of the boat onto the cradles and slide it up to until the striker rests on the upright. Once on the dolly, I can wheel it away and do all this without needing a second pair of hands. I am contemplating an addition to the dolly with a foot operated latching “spike” that I can quickly drive into the beach so the cradles will stay slightly in the water waiting for my return.

First, I needed to make some fiberglass tubing to build the attachment on the dolly for the mast. Using some thin 2mil plastic, I wrapped the dolly axle and only taped it on the extreme ends (so it’s easier to remove later). Spraying the axle with some lubricant before putting on the plastic will also help in removal (though I didn’t do this). I then wrapped about 12 layers of 6oz fiberglass wetted with epoxy resin. Then I wrapped it very tightly with vinyl electrical tape which provides some compression and leaves a really nice finished surface.

Next, I took the windsurfing mast, I cut it in two (it used to be a 2-piece mast, but I couldn’t separate the halves), and sanded the bigger lower section until I had a very slight taper. Using the same technique as on the dolly axle, I wrapped 12 layers of 6oz cloth and epoxy resin around the mast and wrapped with vinyl tape. Once cured, this one separated easily because of the taper.

Now I needed some fiberglass plate to make some gussets so I vacuum bagged 4 layers of 17oz Knytex and some 6oz scraps left over on a piece of Lexan plastic and cut to shape.

Now, I mitered the extension tube/socket to fit the axle tube using a rather impromptu method with a slightly undersized hole-saw and then some sticky backed sandpaper wrapped around the hole saw to widen the miter slightly.

Once that was done, I tacked everything lightly together with some super-glue and then filleted all the joints with a thickened mixture of epoxy and cabosil and let it bake in the sun to cure. Once cured, I plugged the openings with anything I could find laying around (making up any gaps with vinyl tape) and setup one wrap of 17oz Knytex. This one needed to be vacuum bagged; not necessarily to make it lightweight or for strength, but to make sure the knytex conformed tightly to the compound shape of the assembly. With more thickened epoxy and cabosil in the tight corners I wetted out and laid in the Knytex over the assembly (this is a great fabric for this application because of it’s unique 45 degree knitted weave, it conforms easily to compound shapes).

After a little sanding (not much at all), some primer and paint, the socket to the axle was ready to receive the extension and have a hole drilled for a bolt to hold the extension in place. I will eventually rivet this to the dolly axle, but will need to wait until the whole assembly is together and under the boat to get the angles correct.

Up next, the assembly of the extension, handles, and upright for the dolphin striker.

I had some issues and wasn’t able to finish Undecided in time for spring fever. I did get the white gelcoat sprayed on but because of the two tone scheme, I had to wait until the white completely cured to mask and spray the port side yellow color. With a small weather window last Saturday morning, I got all the supplies out again, setup my mixing station, my cleaning station (ready in-case the gelcoat should kick early in the gun), and masked everything off. With mixing cups, stirrers, MEKP, and the duratec ready, I opened the pint of yellow gelcoat (supplied with the boat) and it was solid as a rock. Crap. The gelcoat comes from a west coast supplier and because it’s considered hazardous material, is practically impossible to ship expediently. So I sanded away the orange peel on the white side and called it a day.

I was having website problems and couldn’t post about the Duratec. It mixed in nicely and it certainly did give the gelcoat a good cure in open air. However, it went down exceptionally lumpy but I’m not certain it wasn’t a problem with my spray gun.

By the time I had sanded away the lumpy bumpies, it needed another coat as some of the repair was showing through. I’m going to purchase a new nozzle for my spray gun (larger diameter) and see if that won’t resolve this issue. In the past, I’ve sprayed gelcoat, thinned about 10%, with this same gun with MUCH better results - still with orange peel but much smaller and easier to deal with without have to remove so much material.

The sailing season is about to crank up again and I can’t wait. Here’s some good bean footage in anticipation…

No, I’m not shipping Tad’s boat back to him in pieces…but I did use packaging tape and tongue depressors to hold the correct shape for the slab side I cut out of his port outside hull (thread started HERE) to repair the crushed bow.

I’ve been pretty useless for the last week with an inner ear infection leaving me with vertigo and unable to focus my eyes on anything for a while. This was further enhanced with a head cold so it’s been dark room with eyes shut for me for a while….make me unconscious until the world quits spinning. It’s not gone completely but I can finally begin to function again. Fortunately the weather was gorgeous this weekend and provided a great opportunity to get some work done on Undecided again.

With the “still installed” half of the bow section straightened and reinforced, it was time to begin on the yellow piece that I had previously cut away. I had pondered how to get the shape held in place while the fiberglass reinforcement cured and came up with several different ways of doing it. I finally settled on fix it first, then put it in place and here’s how the weekend went:

First, I ground away all the inside fiberglass and foam from behind the damaged/creased areas until I was at the outermost layer of fiberglass and tapered the edges for good transition to the new fiberglass. This got rid of the weak stuff and made the panel more flexible so I could gently entice it back into the correct shape.

Armed with a handful of tongue depressors and packaging tape, I braced the outer skin until the shape looked just right. I held the panel up to the hull several times and adjusted the alignment of the bracing to get it right. Then back in the shop, I laid in about 6 layers of 7oz fiberglass and epoxy resin and set it in the sun to cure.

Next, with several short pieces of tongue depressors (these things are extremely useful), I glued in a small handful in the hull, held in place with clothes pins, to provide a ledge to support the newly reinforced bow section upon re-installation.

Once everything had setup later that day, I mixed up a slurry of epoxy and milled glass fibers to make a thick glue to put everything back together with. The milled fiberglass additive is not the lightest thing in the world but makes for a VERY rigid adhesive. In contrast, micro balloons make a great lightweight filler but the resulting adhesive is crushable with only fingernail. I can’t recall where I learned this, but if you take a zip-lock baggie fill it with the goo, and cut a small bit off the corner, it makes a terrific application tool ala cake icing. I applied the thickened mixture to all joining surfaces and taped the panel in place on the hull with a few small wooden wedges in place to maintain the proper spacing.

She looks a bit like Frankenstein at this point…but it’s looking more like a boat now…and very straight again.

I debated a bit on how to reinforce this seam and had originally thought I would need to grind into the inside layer of fiberglass and rebuild outward from there. However, the glued in repair alone was so rigid and solid, I had very little doubt that I could just leave it like that and it would be perfectly fine. To be completely sure, I ground out the outer skin of glass and tapered the edges back to build in a seam layer to really bond everything together. Meanwhile, Gunther supervised and kept watch over the other boats in the backyard by barking and chasing every fur or feather covered creature to venture onto the property or into the air space (I did eventually put his anti-bark collar on him because he took to barking at the neighbor’s kids).

With four layers of 7oz glass gradually tapering out in width over the seam and a little filler over some of the other imperfections, the bow will be left to cure good and hard for the next few days. If the weather stays warm through next weekend, I should be able to start final shaping and finish up this repair by laying down some gelcoat followed by some buffing. I do have a new (to me) gel-coat additive product to try, Duratec, that claims to allow the gelcoat to lay down like paint, makes it harder, and takes care of the air drying inhibition. Sounds too good to be true…I wonder what it does to the opacity of the gelcoat.

Here’s the time and cost breakdown in case you’re wondering.

First session; cutting out hull, repairing white side, 4 hours
Second session; reinforcing yellow side and reattaching to hull, 6 hours
grinding out seam, glassing seam, and adding some filler; 2 hours

Cost thusfar; epoxy resin, $15, fiberglass, $15…no real tool consumption yet (other than the $15 dremel diamond bit I dropped) but the sanding and fairing are yet to come.

I started some work yesterday on a friend’s boat that suffered an altercation with a tow boat during the Tradewinds regatta several weeks ago. It had some pretty bad damage to the bow of the port hull where it was split, crushed, and bent off to the side. In case you’re wondering, you’re not looking at two different boats, this boat has a color scheme where it is white on one side and yellow on the other - it’s a pretty wild optical illusion on the water.  Appropriately enough, the boat’s name is “Undecided”.

It took me a little while to figure out how to approach this repair as there was undoubtedly pretty extensive damage to the foam core inside each hull half. This damaged structure had to be removed. The tricky part was to figure out how to replicate the bow shape because these hulls are asymmetrical (i.e. I can’t necessarily copy one bow to the other). I tossed around ideas about pulling a mold off the Team Seacats blue I20 port hull but dismissed that as far too time consuming. I decided, instead to cut away the most damaged side (the yellow) and clean up the inside of the other and then figure out how to brace it to hold it’s shape so it can be glassed/reinforced. Once that would be done, then I can clean up the cut away portion and work to get it bonded back in place…that’s the plan anyway.

With my trusty diamond encrusted cutter in my Dremel, I went to town on the bow cutting away a panel of the yellow side of the hull so I could gain access to the damage on the inside half.

I then ground away all the broken fiberglass and delaminated foam and was pretty much left with just the thin outer skin which was still trained to bend in the damaged direction. The remaining foam was tapered gently to avoid a stress point with the repair area.

I then took several measurements and came up with a bracing plan to re-train the skin into the proper shape, placed clear packaging tape on the back of the couple of cracks (to keep the epoxy from running through). With the shape verified to be true, I started laminating about 6 layers of 7oz glass with epoxy around the clamps.

Because it was beginning to drizzle and the temperature was about 50 degrees (you need about 60 degrees for the epoxy to cure properly), I roughed out a cheap plastic tent over the repair area and plugged in a small space heater. I was able to monitor the temperature with a remote digital thermometer / humidity gauge that I keep in my shop and was able to keep the repair at a toasty 75 degrees. One day, I’ll have a garage for doing this stuff in.

A quick spot check this morning before leaving for work this morning was good - the inside bow now holds a very straight and true shape and I only have a few minor areas to touch up and fair on the exterior. A little more glassing where the clamps were and I’ll be ready to move onto the yellow cut-away section for repair. The weather is going to get a little colder this week but fortunately I can do the repair on the cut-away section inside my workshop.

No, this isn’t some sexual inuendo…I’ve recently received several requests for information about performing a bottom (or keel) job on a beach cat. Because our boats are so mobile, occasionally they find themselves sliding up a sandy, shelly, or even rocky beach. If you are really careful, the bottoms of your boat hulls will stay nice and clean but invariably something will happen resulting in some speed robbing scratches and dings. I’ve done a few refinishing jobs on the bottom of catamarans and learned a few things along the way. First, there are some simple, but key, tools you will need:

• Sanding Board - you can purchase one of these from various locations. 3M makes a good one but it’s pricey at about $45-$60. The key to the sanding board is that it be semi flexible on the long axis. A good sanding board will also have handles to make things a little more ergonomic. I scratch built mine using some scraps of plastic and aluminum and the long and tall handles I built allow me to really control the shape of the board when necessary (picture below)

Sanding Board

• Filler - There is a “Marine” version of Bondo filler and while it is a nice and easy product to work with, I’ve recently found a “premium” Bondo Brand automotive filler that is wonderful to work with and still much cheaper (anytime they slap “marine” on the name of something, the price goes up 150%). Traditional Bondo leaves a sticky top surface that will generally clog up the first piece or two of sandpaper to touch it. The premium version, while a bit more expensive, doesn’t have this tacky layer and is much easier to work with in this respect. Note that the Bondo brand fillers use a polyester resin base so they are well suited to working with gelcoat (you want to avoid using epoxy whenever possible because of possible bond issues with gelcoat application).

• Sandpaper - if you are keen to save a buck or two, you need to get this out of your head when it comes to sandpaper. The time you spend sanding is directly relative to how long you push a piece of paper to it’s death. Keep fresh sandpaper working and you’ll save yourself a lot of time. I have found that Lowe’s carries rolls of sticky-back sandpaper that are about $12 per roll and it is not only very efficient but works great for any size sanding block or board. Our Lowe’s here carries rolls in three grits - 80, 120, and 240 (I think - I’ll double check and update this post). You will definitely need the 120 and 240 - the 80 can come in handy sometimes in the early stages. You’ll also need wetsandpaper 400 and 600 grit. A trailer supply house (Northern Tool) or paint supply house carries wet sandpaper for sale by the sheet and is generally cheaper than a home center box store.  If you have a colored boat (not white) you may want to finish off with some 800 or 1000 grit paper as this will help your boat retain the shine for longer periods of time.

• Side/angle Grinder - not completely necessary but it helps to make short work out of deep soft spots for repair. It can be like doing surgery with a chainsaw but is very effective for damage tear-out if you are careful with it.  I use a layered sanding disk (with flaps of sandpaper).

Angle Grinder

• Electric (or pneumatic) palm sander - good for initial shaping of a repair but not much else.

• Pneumatic Paint Spray Gun - there is no need to go crazy here as a generic “home use” spray gun intended for latex paints will work just fine with gel coat. Although it will work, I don’t recommend the buzz bomb self-contained sprayer as it is very difficult to clean. A $40 suction gun designed for latex paints will do just fine (bigger nozzle the better - I’ll put down a nozzle size reference this evening when I get a chance to reference what I have). Gelcoat is thick and will not lay down flat worth a darn anyway so there’s no need to go spend big bucks on an automotive HLVP sprayer that’s just going to spit and spat it out irregularly anyway. Besides, spraying something that catalyzes into a solid can potentially bring death to a paint gun.

• Sanding Sponge - this is to work with your wet sandpaper and can be found at a home center box store.

• Old Washer hose - cut one end off so you just have an extended soft rubber hose for wetsanding you can attach to a garden hose. You’ll find that if you use a hose with a metal fitting you will frequently ding/scratch the finish you are working on.

• Saw Horses - you need to get the hulls up to an operable height. I have some saw horses constructed from 2×4’s and a simple brace kit - works very well to support the hulls removed from the beams. I did screw end stops on the saw horses to prevent the hulls from slipping off the edge while sanding (the straps shown below constantly got in the way).  Not shown below, I also added some diagonal bracing to the horses because the sanding motion was causing them to become increasingly wobbly.

Saw Horses

• Rubber Boots - if you’re going to be doing the wet sanding in cool weather, a crappy pair of $12 Wal-Mart rubber galoshes are indispensable.

• 5oz fiberglass - standard weave will work fine…no big need for anything exotic unless you are working on an exotic boat using kevlar or carbon in the hull construction.  If you feel the need to do one better, get s-glass as it is a stronger variety of fiberglass than the more standard E-glass.  Walmart variety “Bondo” brand fiberglass packs (roughly a 5oz fiberglass) will do but you pay a LOT for those vs. an online supplier.

• Polyester (or vinylester) resin - get a decent resin…check working time, you don’t really want something with an extended working time (like a laminating resin).  You don’t need to work with it very long on smaller repairs and a faster cure is nice.  Vinylester is the stronger of the ester resins but usually has a reduced shelf life of a month or so - it will turn to gel and slooooowly harden after that.  The MEKP liquid that is commonly called an ester resin “hardener” is actually an accelerator.  Ester resins will harden on their own if given enough time - polyester resins very slowly and vinylester resins harden pretty fast on their own.  Use ester resins if you intend to finish with gelcoat.  Use epoxy if you are going to paint.  Epoxy bonds better to everything but is not the best substrate for gel coat.

• Fiberglass detail roller - this is a small roller with a ridged small diameter aluminum rod on it.  It’s is VERY useful for squeezing air out of a hand laid composite structure before cure.  You can find these at US Composites.

• Mixing cups and stir sticks.  Graduated mixing cups save a lot of time and a mixing ratio chart is a big time saver (one available at www.fiberglasssupply.com - though I had to make some modifications for smaller amounts).  You may also want to invest the $11 in a set of West System metering pumps.  While they won’t be ‘metering’ anything for the polyester resin, they make dispensing of the resin very clean - a nice bonus.  You can find these at aircraft spruce.

• Baby medicine dropper - you can usually peddle one of these from a local pharmacy for free - grocery stores usually have them near the pharmacy as well.  Get the bulb / suction type, not the plunger / syringe type.  The plunger will not stand up to the MEKP.  You will use this for measuring larger amounts of MEKP for the gel coat batches to avoid counting drops…unless you actually enjoy counting to 132.

• Respirator rated for “organics”.  The styrene contained in ester based resins and gel coat melts soft human tissue (like lungs and sinuses) and is very bad for you.  Wear a respirator.  You can get them with refillable cartridges at Lowe’s or Home Depot for $35 - which is a lot cheaper than chemotherapy.  Also pick up a pack of latex or nitril gloves - you’re going to need them.

• Solvents, rags, and paper towels - Generally acetone will do most everything you need it to for cleaning out spray guns, tools, and prepping surfaces.  If you have moisture that you need to remove (like in a foam core), use denatured alcohol as it will encapsulate the water molecules and evaporate it away rather quickly.  For spraying the gel coat, I’m cautiously recommending the use of Duratec High-Gloss Additive.  I haven’t used this product but after the difficulties that I have had and some post-trouble advice from people in the industry, I believe this will make things much easier.  It’s available at the Fiberglasssupply.com

• Gel coat - for a bottom job on a 20 foot catamaran, you will use anywhere from 1/2 to 1 Gallon depending on the quality of the gel coat.  I sprayed two Nacra 20’s (four hulls) in one day - one blue and one white.  The blue one took a little less than 1/2 gallon and the white one took nearly the entire gallon to get the coverage needed.  Quality of the gel coat could have been a factor as they came from two different suppliers.  Most gel coat suppliers can only mix in quarts or gallons - so get the gallon and you’ll have plenty left over.  I was fortunate enough to have the name of the original supplier of the gel coat used on the blue boat AND the color code - it made ordering very easy.  The company that I ordered this from is Sher-Fab Unlimited, Inc in California and theirs was the gel coat that had excellent coverage.

• Buffer and a buffing agent.  Use a real high-speed rotary buffer with a lambs wool (or synthetic lambs wool) pad.  The low-cost random orbiting buffers you can find for $30 at Wal-Mart are NOT what you need.  You need raw power to cut the gel coat to a shine.  I recommend 3M brand “Perfect-it 3000 Rubbing Compound” to use with your buffer and wool pad.

If you wish to go back through the documented history with the Team Seacats Nacra 20, start Here:  http://www.teamseacats.com/category/boat-construction/page/8/ . There are more pictures and reference material that might be useful.

On to the process:

I like to disassemble the hulls, trampoline, and beams so that I’m working only with the hulls.  You will be spraying gelcoat so it’s just as easy to remove everything now, avoid the mess, and allow yourself better access.  I mount the hulls upside down on saw horses and screw wood blocks (padded) in place to prevent the hulls from moving around while sanding.  When working on the bows, I strap the sterns in place to keep from tipping the overhung bow.

Before sanding, you want to remove any waxes / silicones that might be on the hull.  Wipe the hulls down vigorously with acetone well past the areas that you intend to gel coat.  If you don’t, the sanding action will rub these agents deeper into the surface.

Start sanding with 120 grit and the sanding board.  The trick to using a sanding board is to ALWAYS keep the board parallel with the long axis of the hull.  You can sand up-down, side to side, angle to angle, round and round, but ALWAYS keep the board parallel to the length of the hull.  The sanding board will gently bend and you should understand this and use this to keep it bending to the lengthwise shape of the hull.  The job of the sanding board is to bridge the gaps between recesses and dings and if used properly, although learning to use a sanding board is a bit of an artform, makes fairing a hull a relatively straight forward process and making a really nice final result achievable for the novice (like me).

If you have some soft spots, you need to fix them now.  Use the side grinder or a dremel to cut into the hull through the outer layer of glass.  Carefully cut into the damage into the foam until you have no more soft foam, crushed foam, or voids.  It is noteable at this point to understand that any resin applied to a pre-cured resin will have very little chemical bond and will hold predominantly through a mechanical bond.  You need to shape the repair area with this in mind and provide a lot of surface area for a good mechanical bond.  Generally speaking, if you have to dig into the hull 1/2 inch to clean out the damage, you should taper out the hole to a diameter of at least 5 inches or more.  The outer skin of glass is usually pretty thin so pay close attention to getting some sort of a taper on the skin.  Below is pictured a soft spot I had to fix - you can see the lighter ares of the fiberglass where they have broken strands due to some impact. The second picture shows the tapered edge of the resulting repair area.  The dark spot in the left-most picture is where water had been penetrating to the foam core…this damage was barely visible until I started sanding and filling.  It was a result of a large ding but I didn’t test it for soft spots until I had difficulty getting it fair - the damaged foam core was springing under the long board leaving a constant trouble spot that I couldn’t get faired.

 

 

Now use some 5oz fiberglass and cut many pieces to fill this void - start with smaller pieces in the deepest part of the repair and make them gradually larger until the last couple of pieces extend slightly beyond the repair area.  Make an attempt to rotate the fiber orientation of each repair piece 30 to 45 degrees per each layer for a really strong repair.  Mix up some resin, brush the resin into the foam with a disposable “chip” brush and start applying and dabbing each layer of fiberglass as you go.  After two layers, try to use the fiberglass detail roller to work out the small air bubbles and excess resin.  Two more layers of glass and again with the roller, repeat.  It will take some experience to estimate how much glass it will take to fill the void - I think I used six layers for this one (but later sanded away at least two).  I’ve found that you can wet out and laminate the entire repair like this one in one pass.

Once cured, use the palm sander and some 120 grit to shape the repair close to the final shape.  You don’t want to take this too far - you will use the long board later to get the final shape.  Any minor indentations or pin holes can be filled with Bondo filler but if you have a significant recess in the repair, you need to rough up with 80 grit and laminate some more fiberglass.

OK, so now we have fixed any soft spots and the rest can be filled using filler.  The next step is to sand all those imperfections that the long board skirted over with 80 grit (make a small roll of sandpaper and sand by hand) so you have a good rough surface for the filler to adhere to.  Once sanded, these spots will be difficult to see - this is why you marked around them with a pencil right after scuffing the hull with the long board.  It’s time to mix up some filler.  Mix up a fair amount and make sure you get enough hardner in the mixture.  It’s not something that requires great precision, but if you’ve not worked with Bondo before, you may want to make a test batch to ensure you can get the ratio close.  Too much hardner and it cures in minutes.  Too little hardner and you end up with a difficult to remove gummy mess.  You’ll need a squeegee to apply it - plastic hotel room keys work great (and are cheap! - start collecting) and of course the “Bondo” brand squeegees available at most stores work just fine too although they can be difficult to clean to be reused.  When reusing a squeegee you can’t have any trace of hardened filler or it will leave a pattern or trash in the filler you are applying.  Applying the correct amount can be tricky but after some time, you’ll get the hang of it.  Don’t be afraid to come back for a second pass with the filler - but just be sure to scuff up all the surface for good adhesion.  Ideally, no dings should be deep enough to require much filler.  Max depth should be about 3/32″.  Anything deeper should be initially filled with fiberglass and resin.

Now whip out the long board again and plan to spend some time sanding.  Using 120 grit, you want everything to be really straight and smoof. If you start to see the clear glass through the gel coat - STOP SANDING.  You don’t want to sand away any of the thin outer skin.  Put more filler in the area to bring the low spot up instead.You will likely find yourself having to come back to fill a few shallow spots and sand again but remember that patience, gentle pressure, and fresh sandpaper REALLY pays off here.

Once you feel like you’ve made a pretty good go at it, spend some time to really inspect things before going any further.  Note that it is difficult to inspect for low spots now because of the different colors of the hull.  If you wish, you can spray a light coat of some cheap automotive primer (be sure it is DRY sandable primer!!!! - not just “wet sandable”…that stuff sucks) over the entire  surface and sand it away - places where the primer is left are low and will need a little more work.  Personally, I don’t find this necessary and find it perfectly adequate to close my eyes and rub my hands down the hull while muttering “nuh nuh nuh nuh nuh nuh….nuh nuh nuh nuh nuh”.

Once you are happy that things are nice and fair, you need to taper some of the sanding area to the limit of where you intend to spray gel coat.  With the 240 and a sanding sponge, lightly scuff up the surface beyond the faired areas where you will spray too.  You don’t want to spray gel coat on a shiny surface since adhesion may be at risk. 

Now it’s time to clean the dust away.  Wash the hulls with water and then rub them down with several clean acetone cloths - nothing tricky here.

Up next; spraying gel coat - the hows, the toos, and a whole lot of don’ts.

I’m working to help a friend revive a 1981 Hobie 16 catamaran and will chronicle some of the success and failures on this boat here over the next couple of weeks. We rigged the boat and made a long list of things that need to be addressed; new lines, trampoline, most of the line hardware, a little fiberglass work, and a rebuild of the trailer lights and bearings. Structurally, the boat is in good shape. After $600, we have a big box of parts and have put on the new trampoline that was made by Mainsail Marine (one of Team Seacats sponsors!). The black mesh trampoline is terrific! Other than pressure wash the boat, installing the trampoline is about all we’ve accomplished to date. Unfortunately, I didn’t take any pictures of the boat before we pressure washed it - it had been sitting under pine trees for at least 10 years.

I just realized that I haven’t sailed my F18 at all this year with all the prep-work of the I20 and sailing on OPB (other people’s boats). I decided to utilize the long weekend to re-fair the bottom of the hulls since she’s had a pretty rough go with the 2005 Steeplechase and all the recent neglection. After a lot of sanding, I’ve got a reasonably good finish…I didn’t quite go far enough with the 320 grit and still have some minor sanding scratches visible but I may go back and fix that later. Fortunately, there was plenty of gelcoat thickness that I didn’t have to shoot any gelcoat. I did leave the filler exposed (but polished) on a few major dings I fixed.

It’s time to really start thinking about some of the big races we have coming up.  Last week, I took the cover off and spent an evening inspecting the blue Team Seacats Nacra 20.  Everything looks good except that I found one of the shroud tangs (a stainless steel plate that holds up the mast!) was loose in the hull.  I could wiggle it back and forth and side to side and lift it up and down almost 3/16″.  Not good.  I put in a call to Performance Catamarans and after a conversation with Jack, I had a better understanding of how this plate is configured.  The plate is t-shaped and has some holes through which some heavy fiberglass tow is run and resined to the hull.  Then a cover of some heavy knit fiberglass goes overtop of this to make it watertight. Because the plate is t-shaped, it really shouldn’t be much of a failure concern.  However, the fact that it wiggles around means that it can continue to wear to the point that it may be a concern.  For repair, my hope was that it was watertight and that I would be able to drill a couple of small holes in the side of the hull through which to apply vacuum and draw in epoxy resin…but I wasn’t quite so lucky.

The recess in the edge of the hull from which the plate protrudes forms a great spot to seal off for vacuum….but I had a problem…the plate was not sealed inside the hull.  I took my camera and extended my arm up to my shoulder to get some pictures to see what was happening (thank goodness we added the forward ports last year!). I also trickled some water from the top to see if I could figure out where the leak was.

In the left-most picture you can see a trickle of water coming out from under the bunji tube (this is where the trapeze retention bunji goes through the hull).  The leak is not the buji tube but is coming through the tang (this would explain why this hull was taking on a little water while under sail).  Above this area, you can see a glassed in plate where one of the spinnaker blocks screws to the deck and the vertical structure to the right in the left picture is the front of the daggerboard trunk.  After running some denatured alcohol through the tang to dry up the water, I mixed up some thickened epoxy and smeared it over this leak with a gloved hand.

 

After that setup, I was disappointed that I still hadn’t found all the leaks, so I resorted to plan “B”.  Instead of drawing a vacuum, I would pressurize a cup of epoxy and force it into the hull.  I think this will hold as a repair - at the very least, it should seal up the leaks so I can pull a vacuum on it next.  I put a piece of tubing inside a piece of plastic spiral wrap - the spiral wrap will keep the sealing clay from clogging up the exit of the tube and the narrow entry into the hull.  I then pressed in clay filling up the entire recess and sealing in the tube.  I then rigged up a cup with some more clay and a top plate, mixed up some epoxy, and lightly pressurized the cup forcing about 4 oz of epoxy resin cleanly into the hull.

I did eventually find the other opening in the fiberglass backing - it is definitely sealed now (it was at the top where it mates with the mounting plate for the spinnaker sheet block) and the tang is VERY firm in the hull.  I’ll be sailing this boat at Spring Fever next weekend so hopefully we’ll give it a good test.

I finally got out the sandpaper for the F18 bow (remember the repair I started a while back?). After a wetsanding with 600 grit and a couple of passes with the buffer, voila! Good as new. The timing is good to since I’m expecting to do some sailing this weekend.

Originally uploaded by Team Seacats.

If you ain’t got that cling….Sorry - for some reason I made the association between gel coat, jello, and that old cling wrap commercial. I got the gel coat sprayed on the repair but it didn’t quite qualify for the level of “schmoof”. During the last gel coat project, I received some advice from David Lennard (that I didn’t follow at the time) to brush on a thin coat of gel coat before spraying subsequent layers with the hope that it would prevent pin holes. I did it this time and it worked marvelously! However, when I started spraying the first coat of gel coat, I forgot to tune the flow rate on the paint gun and the first pull of the trigger unleashed a fire hose like amount of gel. Instead of doing the right thing and wiping it off, I continued to spray. The intial large volume left the coat a little lumpy - it ~almost~ wanted to drip. Subsequent coats made it better but it will still require just a little extra wet sanding to get it right. That aside, the finish on the fresh gel coat is a lot better than what we achieved before because I really started spraying each coat on pretty darn thick. I thinned the gel coat with an equal part of styrene and added about 1.5% hardener. For the last couple of coats, I added about 2% of surfacing agent (parafin wax disolved in styrene). The surfacing agent floats to the surface of the gel coat and seals it from the air. This is important because the outer layer of gelcoat won’t cure if it is contact with air. All in all, I think I applied 12 coats because I knew I was going to have to sand a bit. Anyway…I don’t think I’ll have the chance to sand it tomorrow since I need to get everything packed up and spend some quality time with Bonnie. It will have to wait until after the regatta. Just in case we have no wind, I might take some sandpaper with me this weekend.

EDIT: I later determined that the surfacing agent for gel coat is just too finicky to work with. Different temperatures and humidities require different percentages. I now spray a thin layer of PVA (Poly Vinyl Alcohol) on top of the fresh gel coat to seal it from the air and get a good cure…the PVA method is simple and bulletproof and just rinses away with water.

Originally uploaded by Team Seacats.

That’s what I say when explaining to Bonnie how the repair is looking….it’s shmoof.

The fiberglass and polyester resin (poly because I’m finishing with gel coat) cured nicely. I shaped the repair carefully with a palm sander and some 100 grit paper finishing up with 150. I used a wood-worker’s curve guide to compare the radius with the repair and the new bow and they look very very close in shape. Then I cleaned the repair with acetone and used an air nozzle to blow out and clean out the few pin holes. I applied a skim coat of bondo filler and let it set for about 45 minutes before sanding it with my long board and some 150 grit paper. Once I had it nicely shapped, I hand sanded with a foam block and some 300 grit (just lightly to clean it up). It was getting a little late and it’s really humid thanks to Tropical Storm Alberto. Don’t get me wrong, I’m not complaining - we really need the rain. It’s supposed to stop raining early tomorrow so maybe it will dry up enough to spray some gel coat on the repair. If it doesn’t, that’s OK because the hull is sound again - even more so than it was originally. We’ll make this weekends regatta in Atlanta no problem.

Originally uploaded by Team Seacats.

I got the crack cut away and the fiberglass laid on the F18 this evening. The underlying problem was a poor joint with voids. I imagine it cracked either while being deeply submerged during one of the two pitchpoles (where the bows were submerged to substantial depths!) from the regatta several months ago or from standing on the side of it while trying to get it to spin into the wind properly to be righted. At any rate, the joint was pretty bad to begin with - should be stronger than new when the polyester resin sets up tonight. Tommorow, I’ll clean up and fair the repair area and if the weather permits, spray some gelcoat back on it Wednesday evening.