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Any way to build composite gunnels with out a vacuum bagging rig?
- Thread starter bark-eater
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That's some great info. I never had the guts to try that option because I didn't know if there would be enough flex afterwards for the gunwale to conform to the hull.
I imagine it's very easy to slice the carbon open to expose the slit when the epoxy is still green. I also image it would be a good idea, after wetting out, to have the gunwales sitting slit side down to keep epoxy from pooling in that area, which could be a mess to clean out.
Alan
The short answer is “yes” and “definitely makes sense but I don’t think that is what I did”. The long answer:
I did this over a year ago, so some details a bit foggy. I don’t recall any issues whatsoever with slicing out the carbon over the slot, but I was a bit nervous that the gunwale would be too stiff to bend over the sheer.
The first one I left to dry overnight suspended between two chairs with a small weight attached in the middle to give me some built in curvature from middle to bow and stern. But when I removed the weight I found that it did not really hold any curve and was still flexible enough. The second side I didn’t bother trying to pre-bend and it also went on fine.
I had no issues with build-up inside the slots, and the pre-bend I tried to do would have meant that it dried on it’s side. Maybe that was sufficient to redirect any excess epoxy, but squeegeeing out with a gloved hand removes pretty well all excess anyway. Next time though, I will be letting it dry slot down.
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Traveler… where do you purchase your sleeves and what do you recommend for sizing? Does the gunnel still bend appropriately or should it be in a form to match the sheer.
Thank you
Hi CTC. I purchased the carbon sleeve online from Soller Composites - always good to deal with. I’ve only done this once, and I used 3/4 inch sizing for the pack canoe, in 8 ounce weight, but this is a pretty small and light boat (27-28 pounds all in if I recall), with a small gunnel profile. For a heftier canoe I think 1 inch sleeve along with something closer to, or a hair over, a 1 inch by 1 inch uniwale-type gunnel might be better, although the bigger the gunnel size the harder it is going to be to bend onto the sheer line. But I think something around 1x1 in cedar would still be very doable.
The key is to put the gunnel on fairly soon after the epoxy cures to the green stage - probably no longer than 10-12 hours after you apply it. In my experience, carbon continues to cure harder and harder over many days and it probably will not be flexible enough to bend around the sheer if you let it sit too long.
Hope this helps
The key is to put the gunnel on fairly soon after the epoxy cures to the green stage - probably no longer than 10-12 hours after you apply it. In my experience, carbon continues to cure harder and harder over many days and it probably will not be flexible enough to bend around the sheer if you let it sit too long.
Hope this helps
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Thank you… yes it does… I’m interested in trying this on a project canoe for fun… if I go ahead … I’ll let you know how it went… much appreciated!
Cheers!
Traveler and CTC: This may have just been a "typo", but in case it's a misunderstanding, the carbon doesn't actually have anything to do with the hardening of the epoxy. Epoxy does take a long time to fully cure (weeks, months), though you can speed the process by heating in a process referred to as heat cure, where temps are raised to on the order of 150-200 degrees F. for a couple hours. It's a huge hassle, so don't even think about it. Most resins cure enough in a few days that they're usable anyway, and in a gunnel situation, few builders or repairmen will be working fast enough to get a boat done that the maybe 90+% cure stage isn't reached before launch anyway.
Carbon could play a minor role in what you're doing as elongation of carbon is low, often on the order of 1/2 to 2%, compared to E- or S-glass at 4 to above 5%, so the glass will stretch more when forced to bend like you're describing. The carbon won't perform as well, but Traveler has obviously shown that it will work, at least as long as the shearline isn't too dramatic. Those wild upswept end curves on some boats would likely preclude this method though, even using glass instead of carbon. The wood itself might even protest this without pre-forming it, in which case the fabric sleeve would also be pre-formed, so no problems.
Some like this boat:
From Dream to Reality by Peter Morrison, Nepean, ON Canada
Posted on June 12 2014 By Peter Morrison My dream of building a Bear Mountain boat started in the mid 1980s when I was in University and I bought a copy of Canoecraft. I couldn’t believe that someone with average carpentry skills could build such a beautiful and functional canoe. Twenty-five...
www.bearmountainboats.com
All good points, especially the one that suggests you should choose your canoe plan carefully. All the canoes I have built have had one-piece slotted gunwales, and all except this pack canoe using plain white ash. The gunwale on my last one (an Ashes Solo Trip) was a bear to get on and it had only a moderate sheer line rise to the stems (something like 12.5 inches deep in the center to 18 inches at the bow, I believe). Whether you use carbon sleeve or just plain wood, the design sheer line should be a very important consideration.
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I really like this …if you have time to explain, how do you make your thwarts…p.s. your source for carbon fiber sleeves is by far the most cost effective out their…. Thank you for that!
The best ones I have seen done were by "Patricks Dad" over on the BearMountain site.
Basically, he used a 5# foam uniwale, with a routered slot to loosely fit the sheer.
The process was:
- fit "epoxy proof" tape/barrier to the sheer to prevent bonding of the uniwale to the canoe
- the carbon fiber sleeve is sized to go around the outside and then inside the slot. The sleeve diameter can be altered with a stretching (narrower) and compressing (wider)
- gunnel with carbon fiber sleeve, is placed on the sheer and "adjusted" as required to fit snugly.
- add epoxy to just the outside portion, use a gloved hand run along the gunnel to remove excess. You are finishing the exterior part of the gunnel, the inside is protected.
- let setup to green stage or more (not critical)
- remove from sheer, remove tape from sheer
- wetout slot and then add slightly thickened epoxy
- place on boat and remove any squeeze out
This way the gunnels are preshaped, and the only goal of the initial steps is shaping and finish of the carbon sleeve, the second steps are for attachment and removal of any squeeze out.
Brian
The details on how I built this boat are in a thread called “Pack Canoe Redux” on this site (sorry, I don’t know how to make a direct link to another thread in a post so you will have to search that title) - was not a happy process but came out ok in the end.
You just go to the beginning of the thread, copy the address, and paste the address in the text entry box . . . as I will now do:
Pack canoe redux
After finishing a tandem tripper last year I had some paint and most of a canoe’s worth of strips left over so I decided to use them up on a pack canoe build (Ashes Solo Pack, extended to 14 feet). Very straightforward, stemless design with 3/16 strips and 4 ounce s-glass. I didn’t really take...
www.canoetripping.net
The software will show the thread and "unfurl" it.
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Thank you!
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Thank you Glen!
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