Team Seacats

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.

From last year’s Heineken regatta in some tropical somewhere last year. Our good buddies Trey and Alan from Team Velocity – some great footage!

I have to build several Bogys this spring…but after that, it may be time to create one of these (though I’m thinking Uni because my experience with my r/c catamaran and watching these videos, the tri’s seem to outsail their jibs frequently.)

Francis Joyon, the French Sailor who had his single-handed round the world record quickly bested by Dame Ellen McArthur, has been underway for a while on a new record attempt in a new monster trimaran built specifically for his solo record setting efforts.  Francis is on fire and not only just set a new single handed 24 hour record of 616.04 miles but is currently about 5 days ahead of Ellen’s astonishing voyage in 2005.  To put that 616.04 miles in perspective, that’s nearly 100 miles further than the Tybee 500 race and he did that distance in a day (roughly twice our average Tybee 500 speeds).

There is little doubt that Joyon is on pace to reset this record to a height that will be difficult for anyone to reach in the near future. His custom 97 foot three-hulled rocket is not only nearly as fast as the fully crewed mega G-class catamarans but it is at the brink of the physical limit of a single human to control without the aid of electro-mechanical devices. Not many people could ever sail this thing alone.  However, as magnificent as Joyon and his tri-maran are, one stray floating container, growler (piece of an iceburg), or a surfacing whale could do irreparable damage to Joyon’s machine.  Watch Joyon’s journey HERE (I hope your french is better than mine).  I’ll try to keep you updated he progresses across the Indian Ocean toward Cape Horn.

“With Larry, we will duel with two beautiful monsters. And whoever spends the most money will win.”  Says Mr. Bertarelli in a recent interview on Sail Juice Blog. This response, I would presume, is directed to Ellison’s statement earlier this week where he says “we have heard Ernesto’s vision; but what we really need is his decision”. Ernesto makes an effort to defend his position for a complete overhaul of the cup but I think he is foolish and arrogant (he said that I would say that…though I dispute that I am a conservative). Note that Bertarelli’s team has allegedly lost their sponsor for AC33 so the defense currently comes directly out of his pocket. However, don’t think for a minute that Bertarelli is stupid; He’s been racing multihulls on Lake Geneva for a long time and has a lot of experience with them and if you buy into his statement that they “have yet to commit to a specialist mutihull design team”, it is my opinion that you might be the foolish one.