bending plywood

[tpolley]

i want to build a canopy for my riding mower out of plywood. i want to give it a bit of curve from front/back and side to side. kinda like a square/rectangular bowl so that water will run off of it. my idea is to build a square or rectangular frame out of 1x4's and cut out the top part in a curve shape then nail/glue 3 or 4 thin sheets of plywood over the curvature. it will be supported with steel of some sort. i haven't got that far yet. what type of plywood should i use? what is the thinest stuff they make that would be suitible for this application? i'm not looking to spent $50 a sheet on finish grade vineer or something. i just want the cheapest stuff i can find. also any advice from professional wood workers would be appriciated.

 

[DHCrocks]

you could try laminating a few layers of masonite. It's pretty flexible and comes in 1/8" thickness. Use a waterproof glue like gorilla glue or titebond III. and coat the exposed faces with polyurathane to seal it. Plywood would probably not hold up too well, the glue will let go if exposed to moisture unless you get the marine grade which is expensive.

 

[akdiesel]

If you go cheap it wont last. You will want marine grade plywood. The same stuff they use on the two place trailers for snowmachines and atv's.
Not sure if you can get this in 1/4" or not, but that would be the best size for bends in that short of span.
you could also get the thicker stuff and simply make cuts that are about half the thickness as the wood (i think these are called curf cuts). Do it in a criss cross pattern about every 3-4 inches apart so you can get your square bubble shape you want.

 

[Slick6]

What about using OSB? (Oriented strand board) I think it's fairly more flexible than plywood of the same size. If I'm envisioning your project right, I think you could get away with 1/2" OSB and shingles. How big is this canopy?

 

[kindyr]

the trick is going to be getting the curve on two axis. a single axis is no problem. start with luan or then plywood and glue into the curve. Not sure how you'll be able to get both curves.

Any reason for not going to fiberglass? it seems like it would be the ideal material for the job.

And if you do it in wood, you may still want to run some fiberglass resin over the outside layer for weather resistance

 

[larry4406]

Call a real lumber yard (not lowes, home depot). They have bendable plywood. It is used on porches, alcoves, etc, where there are architectural features. You will need to specify which direction you want it to bend (i.e, on a 4x8 sheet, does it bend on the 4' dimension or the 8' dimension?). It will bend to fairly tight curves (I would guess at least a 3' radius). Multi-axis curves is a problem like mentioned already. It has minimal to no strength - wet noodle. It is not made by cutting shallow parallel curfs like on stair stringer bullnose (this may be your low buck approach, however). Your framing will need to provide the strength.

 

[Certainteed]

hi. you check for luaun or "premium underlayment". it bends easily and is held together with a waterproof glue. i've built boats with it. paint it with a really good paint, or cover with fiberglass/epoxy and it will last forever.

 

[rsanter]

how about you use OSB and peak it along one axis like a house roof. then cover it with composit roofing. you would only need 1-2 packages of the roofing so it wont cost much

bob

 

[nonhog]

I know you asked about plywood but I cant help but wonder about other materials Canvas would be light weight or Lexan heated and bent to your desired shape would be slick. Maybe aluminum skin over a framework ?

If you decide plywood is the best for you what about doing a hourglass type bend side to side then flat sheet front and rear ?
Seal them and coat with spray on or roll on bedliner ?
Good luck and take pics

 

[kbs2244]

Make your framework "mold" with the curves you want.
I would suggest at least an "X" from corner to corner.
Best would be to add a second "X" from mid point to mid point of the sides.
Then use brown masonite.
Cut it oversize so you can trim to size later.
It is the only stuff that will allow you to bend in both directions.
Soak it overnight with sandbags to weight it down into the mold.
Don't be afraid to get it good and wet.
The wetter, the better it will bend.
Then put in the sun and aim a fan at it for a day or two.
Paint it with a good waterproof paint on both sides.

 

[66 GMC Truckin]

How about you just go buy a canopy for $50 at your local John Deere Dealer or Home Depot and attach it to your tractor. Much easier and probably cheaper.

 

[kindyr]

in rereading this, I think me may need to clarify what kind of canopy he's talking about. I assume he was looking for one of the ones that is essentially an umbrella for the driver, attached to the tractor. I could also see how he may have meant a carport type shed for his tractor to be parked under.

for the umbrella, the store bought version at $50 pretty much sounds like the best bet to me.

for a carport, I wouldn't bother bending the wood and just make a standard sloped roof

 

[Mike83]

Sometimes the best solution to a problem is to avoid the problem. Don't mow your grass in the rain!

 

[nate379]

Weld the frame at whatever angle you want and screw the plywood to the top. Just use something fairly thin like 1/8" Louon or whatever. Doesn't need to be 1" OSB or anything.

Throw a coat of paint on it and it'll last years.

 

[TAMPAGT07]

I think I would just put a hat on and call it a day. And I would tell everbody that I had a convertible mower. They would be very impressed.

 

[Born_Annoyed]

Sometimes the best solution to a problem is to avoid the problem. Don't mow your grass in the rain!

That was good. But did you stop and think he wanted to stay out of the sun! LOL

 

[kwb]

the trick is going to be getting the curve on two axis. a single axis is no problem. start with luan or then plywood and glue into the curve. Not sure how you'll be able to get both curves.

Any reason for not going to fiberglass? it seems like it would be the ideal material for the job.

And if you do it in wood, you may still want to run some fiberglass resin over the outside layer for weather resistance

We have a winner - someone that read that the OP is trying to create a complex curve. To make that happen you need to stretch material not something you will do with plywood easily.

Two options I can think of would be to build a frame attach a sheet of ABS apply heat to the point to allow to sag or fleece into a frame with sag wet out with polyester resin and build up thickness with layers of fiberglass.

 

[jwith68]

Don't know what size of machine we're talking about here but...

http://www.loaders.com/userdocs/products/COOL_CAPS.pdf

 

[mikeyr]

That was good. But did you stop and think he wanted to stay out of the sun! LOL

Ok, so now we have a NEW problem, how to hook up decent headlights so he can mow at night

 

[Born_Annoyed]

Ok, so now we have a NEW problem, how to hook up decent headlights so he can mow at night

He could use Night Vision. Sort of what helicopter pilots use. HA HA

 

[sharpe427]

Covered the inside of a van once (c'mon...it was the 70's and EVERYBODY was doing it ). Had tight radii, used 3/4" plywood. Score one side with a circular saw (about 1/4") and LIGHTLY wet the board. I used 2 tarps and a garden hose). when it's DAMP all the way thru, attach one side and GINGERLY work your way around. Once it dries out, it will hold the shape forever. For your use, I would put the cutouts inside the arch and fill them with caulk when your done before painting.