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Laminated Gunnel questions.


Steve W

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I'm about to put a laminated gunnle on my Spindrift 11 N. I'm hoping to cut the stock tonight in getting ready. I read in the archives that laminating is done to releave stress. sounds good to me. Here are some questions.

1. I have a piece of White Oak, 12 feet long that I will resaw to use. I was thinking of laminating in a piece of cedar between the two, except for a short section where the oarlocks are. It would be lighter, bt not much, but I think it would look nice. Any comments?

2. what glue to use? epoxy is the un-natural natural choice, but it's messy around all those clamps. any alternatives?

3. The profile of the gunnels is sort of a radiused trapezoid. I would need to hold it all together and then profile it with a router after attaching I think. Am I missing an easier way to preform it?

Take Care,

Steve

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Steve, last time I did this I did it in three steps. It takes longer but for a single hander it is a lot easier to do one lamination at a time. The strips were cut to make up the trapezoid when glued up. Since the 1/4 in strips individually are pretty limber you won't need as many clamps to make them lie fair against the hull - another plus. The top edge gets the router treatment when it's all in place - easy enough to do. The bottom you can clean up with a scraper or block plane. No drastic shaping should be required if you pre-cut the strips beforehand. White oak is excellent and mixing the colours always gets a good response from the crowd. For some reason a lot of people see multihued laminations as the epitome of craftsmanship. Go with epoxy is my advice - nice & gap filling in case your laminations are'nt as tight as planned. Good luck PeterP

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Thanks Peter. I'm thinking of making the first piece of white oak cover the top of the Plywood by making a lip on the top of the first strip that covers the ply. This would be white oak. I'd then use cedar for the next strip, followed by the last piece of white oak. I don't like the idea of having an exposed plywood edge on the gunnel top. what do you all think?

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Steve, I built a 9' John Welsford design, "Sherpa" last winter in my garage. There are three lapped planks (ply) on each side and the edges are landed on "chine" strips for lack of a better word in my vocabulary. The strips were to be 3/4 thick, but the bend was too much so I laminated them. I dry fit them and cut the angles on the ends (they were hooded), and pre-drilled the screw holes. I then laid them on saw horses with the mated sides up and rolled on the epoxy using a small amount of wood flour to fill any cracks. After rolling on the epoxy, I put the mated sides back together, tying them in a couple of places with twine. I was working single handed, so I used a C clamp to hold up the epoxied strips while I started at one end screwing the strips onto the frames. The clamp was not holding pressure against the strip, but the strip ran loosely through the clamp. I was able to work my way along from one end to the other pretty quickly. I was using epoxy that kicked after about 30 minutes, so had plenty of time left over to clean up the drips, and it was messy, but turned out to be great.

After it hardened, I used a block plane to clean and even up the tops and bottoms of the strips.

I didn't laminate my rub rails, and have regretted it ever since. I used 3/4" mahogany and had a devil of a time bending it, using boiling water to soften the wood. Looking down from above at the top of the rub rail, you can see the laminated sheer clamp, the laminated ply top plank, and the rub rail, all different colors, and it really looks good. I believe you'd be ok not covering your plank top with your gunnel strip unless you thought you needed to protect the edge better. Good luck.

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On my 'Lively' CS 17 I left the plywood deck edges exposed because that is what I saw on Grahams EC winner. Lively was lanched in 2007, has never been revarnished (yet, hopefully this year) and I have had no problems whatsoever. As Hirilondel said they were sealed with three coats of epoxy and 7 coats of varnish.

Dale

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I cut solid douglas fir strips and scarfed them to 24 feet. They are 3/4 x 1 1/2. I soaked them for a week in the pool and then hung them on a fence with 25 lbs on each end setting the bend close to where I expected it to be more radiused at the bow. I made sure that the scarfed end was toward the stern to reduce over stressing when installing Less curved radius. We wetted them down daily and finnaly let them dry in the garage. After I test fitted and cut to length, I stained and sanded and stained again, covered with the first coat of varnish, let dry and brought them into the sun room. Coated with four more coats of varnish and let dry and we installed. Bend in just about perfectly, needed extra hands at the bow but they are in place and look great.

Jim

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Back to the original question of the actual process of installing these laminated strips..........once they are cut and ready to glue, the normal process is to butter them up....both sides, then working from the bow, fit them where you want them to be, and install a screw at the bow into the breast plate, each side. Then......working side to side at an equal pace, start clamping them in. Without the screws to anchor them, they will slide all over the place. Even with the screws, a few feet aft of the bow, where the bend is the greatest, they may want to roam about. I clamped a block there on each side, right below where I wanted them to finish up, and then clamped the laminations down to it and that pretty well brought them under control. You work side side to prevent the clamping pressure from racking the boat out of true. Finish at the stern. Because of the clamping pressure needed to get the laminations to take the bend, there is a tendency to squeeze out all the adhesive.......so to prevent that, I normally put either 100 grit walnut shell or something like the plastic non-skid additive System 3 sells......either one acts as a spacer in the thickened mix, to prevent total squeeze out. With epoxy, a thin coating is a weak coating and will come apart on you. The secondary benefit of the grit is it tends to "lock" them in place and they don't slide around as much. Will stay where you put them. Always frustrating to clamp something up and come back a hour later to find it has moved on you.

BTW, I seem to recall that some oak woods......and maybe white oak in particular, are not very compatible with epoxy? Something about the acids or tannins in the wood? Lovely stuff for sure and durable and with a lighter wood in the mix, gorgeous to look at. But with the screws holding it in place, it may work fine. Never tried it........just repeating what I heard or read.

Because the surfaces should mate well, and because of the ability to use a lot of clamping pressure, you may be able to use a different adhesive for these.......resorcinol comes to mind. It has no issues with white oak that I've heard of.

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This may be preaching to the choir, but remember to always use a thickener (cabosil/wood flour) when "gluing" strips together. Have done this multiple times gluing laminated gunwales on Spindrift 10s in Graham's boatbuilding class and I'm not aware of any delaminations.

Another way to make sure the hull stays fair is to dry clamp the strips on both sides simultaneously, then release one side and glue and reclamp it. Do the other side after the first hardens. We've done this when we haven't had time to glue both sides during a class period.

I'm staying out of the argument about using white oak with epoxy. I've avoided using it for the reasons noted above, but have had folks vehemently defend it, saying they've "never had a problem."

Bird-walking a bit on the difference between white oak & red oak - the passages in white oak seal as the wood dries. In red oak they don't, thus its highly susceptible to water penetration and rotting in very short periods of time.

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On my Sprindrift 12, using white oak strips, 1/4 x 2 inches, one on the outside of the 6mm Okume and one on the inside. Then I placed a cap on top made from 8 foot long Okume 6mm. All joints were made by first coating with epoxy resin, then epoxy mixed will micro baloons and maple wood flour to fill any gaps or spaces. Then the top was rounded off with a 3/8 rounding bit and a router. It came out really nice looking. There were pics posted here in 2010 in this forum but I do not know where they have been moved to. I can repost or send them to you.

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No, John, nothing special. I get my lumber from local mills, after it has been kiln and air dried, in a 4/4 thickness, then I plane and shape it as needed. I have run test joints using the white oak, sassafras, and walnut glued together. Using a wrench with a long bar as well as just smacking it with a hammer, and at 1 day, 2 weeks, 2 months, and two years, the Sassafras would break, or the Walnut, but not the oak or the glued joints. I have been using white oak for about 10 years now for boat building.

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From a practical point, the big difference with the epoxy from B & B is the mixing ratio. Graham's epoxy mixes 2 parts resin to 1 part hardener. Most likely he will send you a stop to put on the shaft of the hardener pump which will reduce the volume of 1 pump of hardener to 1/2 the volume of 1 pump of resin. Once you've confirmed you are getting proper volumes with the pumps, then its 1 pump of each for a proper mix.

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Just in case I somehow confused things, I am not referring to the epoxy mixing ratios, although that tells us that the epoxies are different chemically, which may affect the bonding to white oak. Graham has told me he did not trust white oak and epoxy, which is why I ran the bonding tests.

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John, I did the last test on the bonding two years ago. I then did the Spindrifts gunnels with white oak. I also built the center board with white oak, walnut, and sassafras. I started the bonding test about 5 years ago, but had been using epoxy and white oak for about 10 years. I have never had an epoxied glue joint fail. I have also used Gorilla Glue with great success, with stools and a baby cradle made years ago, used daily, and no signs of any failure of joints.

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All right, you epoxy coated thread highjackers......time for question number three or four.

1. In the plans for the nesting 11N, the plans show a painter attachment as a line through the stem. That seems kind of lame. Anyone ever do anything defferent, and if so, what?

2. Also, I'm going to start fairing the tape joints. I'm thinking that silica/epoxy isn't the best choice for lightness, and since impact resistance is all I'm after at this point, there must be a filler alternative.

take Care,

Steve

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