Re: Wood substitute? Something new?
Dude, if you're not an engineer, you SHOULD be, cuz you think like one!
Have you considered sandwiching that stuff between a couple sheets of 1/8" aluminum for your transom?
And I hear ya about not wanting to work on it again 10 years from now. That's not only an engineer thinking... that's wisdom gained from age! LMAO!
-BWR
I'm not an engineer, but have done my share of custom fabrication over the years.
I like the idea of making a sandwich with two sheets of aluminum, that would no doubt solve the strength issue. I'm not even sure you would need two sheets, on my one aluminum boat, (where I'm contemplating using it), the outer transom skin actaully measures .1", so I would only really need an inner skin of aluminum to prevent punching through with the bolts.
My greatest concern though is overall flex.
My thinking is that if glued as a double panel, in such short of a span, there is very little flex with the hp that would be applied, but one concern is what will this stuff do after say 5 years and with the sun light heating it.
With the push of a 25 hp motor on it. (The transom will tend to bow outward as the prop pushes forward). For a smaller boat, where the biggest motor here is usually an electric trolling motor, I have little concern, two glued layers of this cellular PVC with a wear plate where the motor clamps will no doubt be more than enough strength for as much as 10 or 15 hp motor. (The bare aluminum would almost handle that). On my main boat, it may see a 25 hp motor tops, it holds that now even with a well aged plywood transom with one corner well rotted. It shows no sign of deflection under normal use.
I can't help but think that this cellular PVC has to be stronger than old, wet, plywood.
To put it simply, my concerns are heat related, and long term stress related, but I can see that this stuff is no doubt very tolerant of impact and sudden short term load. It's how it will hold up under sustained use that I can't say.
As a floor in a small aluminum boat, I'd say it would be fine, even on larger spans, most boats will never see any where near the weight needed to damage this stuff. Especially while afloat when your foot print tends to get 'lighter' due the action of the boat. As seat tops and such, it's no doubt more than strong enough but I'd back it or reinforce any hardware attachments with large washer or a backing plate for longevity or wear.
It's as a transom material that I have my concerns, but the idea of using an inner aluminum skin may work if I can glue or secure it to both the inner and outer panels well enough. I suppose a good epoxy capable of a strong mechanical bond would work. The goal is to make both panels of PVC and both the inner and outer aluminum panels to act as one, so long as this can be achieved, I have little doubt is would be very suitable as a transom material.
The question is, whether it's worth all the work involved for the average guy.
For me, I'll no doubt be trying it. I'll do the smaller boat first.
I don't think it's a solution to use on larger boat, the laminated fiberglass or Seacast is still probably the right answer there.
One of my concerns with it being PVC goes back about 30 years, I was working in a car dealership shop, the shop air system was done in schedule 40 PVC 1" pipe, running about 185 PSI. The tire machine as located just below a large window, the PVC pipes were exposed the sunlight for several years. The tire machine had a slow leak, so they had a ball valve which turned off the air to the tire machine when no in use. The PVC piping wasn't very well secured to the wall either. One morning, I was at the tire machine, I turned on the air to that section of PVC plumbing, which no doubt had leaked down to near nothing overnight, and as soon as I flipped open the valve, that section of PVC under the window exploded like a hand grenade.
My guess was that it had been so UV damaged over time that the surge of pressure just burst the pipe. The result was not much more than a hand full of plastic splinters and a really loud pop but it made me very leery of UV damage to PVC. This was maybe in about 1983/84 or so. An the PVC may very well have been there for several years prior. (They opened in 1979).
Not being a plastics engineer, I can't say how much PVC tech has changed in the last 30 years but I'd assume it's undergone a lot of improvements.
The piping that exploded was the plain white PVC pipe not CPVC that's usually used for hot water applications.
I still like the idea of the multi layer fiberglass panel transom too, it would no doubt be as strong and far cheaper than any Seacast transom and far less trouble to make. The only hassle there is cutting the panels and finding a good source for the material.
