Team Seacats

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.