Hmmm.
a couple of thoughts, not sure they will be helpful, but I’ll try.
I’ve wanted to build a curved top wooden trailer like yours for several years. Yours is the finest looking that I remember seeing, and I think the wheels, tail lights, and fenders, and that green paint, is what really sets it off for my tastes. The whole package is just vintage and gorgeous, and well built looking. I’ve said it before, but well done on the design and work.
What has kept me from building such a trailer, is just what you are experiencing. I don’t know that there is really a permanent, no-not-never-a-problem, approach to such projects, where you go from UV light, to rain, to humidity and heat, and cold, etc.,
Wood is jut not that great for such changes. Allowing the wood to move, is the only method that I can figure out to solve such problems, and holding it fast, will only cause it to split. Even gluing it to a stable substrate might not solve the problems you are having. The only method I know of would be to let the wood expand and contract, like it was a big cabinet door in a frame. BUT, how to make that functional on such a project, is my hurdle I can’t offer any suggestions on.
The other reason I haven’t ever built such a trailer, is that I know that I would need to store my trailer inside, and protect it, and still there would be a risk whenever it was used. I don’t have a place to store it inside, and that’s kept me from attacking the project. I think it would make a cool looking delivery trailer for the things I haul around to people’s houses, and for taking things to shows. With the economy, I’ve not been delivering much furniture, seems the mid-West quit buying, so things have shipped by truck-line to the two Coasts, and so I’ve not needed the trailer like I did 5-10 years ago. And, I don’t think we are out of the woods yet on this economy, so I’m still keeping my head down. So, the project is on-hold for me at this time.
Looking at your cracking, I think I would replace the split board if that’s do-able.
If not, I’d fill the crack with epoxy, realizing that it may just show up somewhere else at some point. I think I would rather have a split board in the middle, than for the stress to focus on the glue blocks on the edges where the structure would be split. The movement is so forceful, you won’t stop it, something will break somewhere, thus the split.
To cover the whole top, I’d suggest a technique used in Cheasepeake Bay Kayaking Kits
I’ve not done it, but have seen a video on it, and I think it would work for what you want, and still leave your cedar top looking natural. The white woven screening material will turn translucent when the epoxy is applied, and what you see through the clear epoxy/mat is the wood. It looks like a wooden boat bottom with a thick coating on top. This company has lots of information and helpful people, and I know they can solve your problem with what to put on the top. A few years back, I looked pretty seriously at doing one of their kits, a father-son project, but those have been downsized in scope these days with the “keeping head-down” bad economy plan we are in now. We did pinewood derby cars instead this year.
Still, shedding water is not the same as shedding UV light. I understand the heat of western Kansas you experienced, I’ve been working in my shop all summer, and it’s been a real blast for sure, not unlike a lot of the Country this summer.
This July, I spent a week teaching a craft class in Western North Carolina, highs in the range of 79, rained almost all week. It was just gorgeous, and it made my wife and I (both native Kansans), wonder why anyone ever left that area to find free land for homesteading in the heat and wind of the Prairie of Kansas. That draw to plow virgin ground with no tree stumps must have been quite a draw in those days. Eventhough we can’t figure it out today, they did back in those days, so here we are, and so we are trying to make the best of it, and looking forward to Fall and some rains.
Going from the heat to the cold, as you know is a problem for wood, and your cracking may still show up again after the repairs to this summer’s trip, even with the full matted epoxy boat covering I’m suggesting you consider. it’s different than fiberglass, but I’m not sure what the differences are, talking to the CLC Boat people on the phone can probably answer that for you.
Again, well done on the project, even with the big crack, it’s a gorgeous trailer.
Well, I’ve enjoyed enough house air conditioning now, better get back to the shop,
Mark
-- Mark DeCou - American Contemporary Craft Artisan - www.decoustudio.com