Post by John Palmer on Jan 25, 2021 10:55:53 GMT -8
First, Let me make a disclaimer that I'm not a Professional Wood Worker.
I'm just a old guy that rebuilds 1940 to 1950 trailers using the marginal materials we have available in today's market. You only have to disassemble a few old quality brand trailers to figure out the plywood that they used back in the day, is much different than what we can buy today. Maybe some place makes the same great quality today, but I certainly could not afford to pay a $100 per sheet, or higher price. A nice sheet of one side sanded 3/4" plywood is already $50 per sheet. Frankly I'm surprised that you can still buy 1/4" (5mm) Birch for under $23/sheet, and 1/8" (3mm) Birch for under $19/sheet. But you really have to pick over the stack because in general the veneer seams and glue quality is awful. You have to handle 50 sheets to find the thirteen you would want to drag home.
The rounded corner cabinets you see in older trailers are 4" radius. With a good deal of work, you can reskin the old cabinet surface with todays 1/8" (3mm) Birch plywood. I've done the two corner closet cabinets, and the booth bases in my Spartan with 1/8" Birch. I soaked the wood in water, used a cloths steamer, clamps, straps, 2 by 4's, an old smooth door, and heavy weights. I clamped the short side of the panel to the wall, then slowly pulled the long side over with straps, the entire panel was kept wet during the process. When I say slowly bent, I'm talking SLOW, like in a 8 hour period. I heated it so hot you could see the steam penetrate the plywood. It was still a tough bend on a closet wall, much easier on a shorter curved seat base. With all of the worry we do about not letting water damage our plywood paneling, you cannot see any water marks left on the plywood from the bending process. After I finally got the plywood to make the entire 90 degree bend, I just clamped it flat, and let it sit for a few days to dry out. Note, it's not glued at this point.
After a few days I removed all of my clamps, straps, weights, etc. The dry panel sprung back by about 50%, in other words, let's say the 90 degree clamped bend was now 45 degrees without the clamps. The important thing was it had been broken from laying flat, and you could easily see that it would bend and lay down back to the 90 degree bend. At this point, I sprayed both surfaces with water, then spread TiteBond II wood glue over both sides, sprayed it with some more water, then clamped the short edge (it gives you more leverage) and used the straps to pull down the long edge. I clamped it for a few days, let it dry in the sun, pull all of the clamps, used a router with a 1/2" bearing bit and trimmed the edges all around the wall. I then refinished, and installed the assemble wall panel into the Spartan. It's held up well for thousands of highway miles, large weather changes, and still looks good after three years.
With the success on bending the two closet walls, I started on resurfacing my booth corners. It has both inside and outside bends with a 4" radius, and I needed to make a 3" radius to cover the modifications to the lower base riser. I had no problems making the 1/8" Birch bend to either the inside, or outside 4" radius bends. I did it just the same as the closet walls. So now I'm on the home stretch. I tried about five times to bend the 1/8" birch down to the 3" radius, I never made it without a crack no matter how long it was soaked, or how much steam I applied. Now what?
My hardwoods store (Reel Lumber) sells poplar bendy board. They stock both 4 by 8, and 8 by 4. Both sheets are about 1/8" thick. The direction of the grain is the difference. The problem with poplar as you know is it's not a pretty wood. The bendy poplar is very plain, almost like a sheet of drywall. I went through the entire stack, and bought the piece with the worst grain pattern I could find, I wanted the poplar installed to look like the Birch grain pattern because they would only be a couple of inches apart. I used the worst grain part of the sheet, and tossed the rest. It applied very easily, sanded, stained and refinished nicely. The color and look next to the Birch turn out just fine, and has held up well. If you could find a sheet of poplar bendy with some nice grain, it's a easy option to bending the 1/8" birch.
My guess is the reason we have problems bending plywood is due to the filler layer. Today they use all kinds of garbage to toss into the filler to take up space. It's not just smooth wood that bends consistently inside the plywood. I believe that special bending plywood has the grain placed all in the same direction. As small volume builder's we do not have the option of buying the specialty wood products needed to do some of these projects. We have to do with what we have.
I would be interested on how others have overcome these kinds of obstacles.
John
I'm just a old guy that rebuilds 1940 to 1950 trailers using the marginal materials we have available in today's market. You only have to disassemble a few old quality brand trailers to figure out the plywood that they used back in the day, is much different than what we can buy today. Maybe some place makes the same great quality today, but I certainly could not afford to pay a $100 per sheet, or higher price. A nice sheet of one side sanded 3/4" plywood is already $50 per sheet. Frankly I'm surprised that you can still buy 1/4" (5mm) Birch for under $23/sheet, and 1/8" (3mm) Birch for under $19/sheet. But you really have to pick over the stack because in general the veneer seams and glue quality is awful. You have to handle 50 sheets to find the thirteen you would want to drag home.
The rounded corner cabinets you see in older trailers are 4" radius. With a good deal of work, you can reskin the old cabinet surface with todays 1/8" (3mm) Birch plywood. I've done the two corner closet cabinets, and the booth bases in my Spartan with 1/8" Birch. I soaked the wood in water, used a cloths steamer, clamps, straps, 2 by 4's, an old smooth door, and heavy weights. I clamped the short side of the panel to the wall, then slowly pulled the long side over with straps, the entire panel was kept wet during the process. When I say slowly bent, I'm talking SLOW, like in a 8 hour period. I heated it so hot you could see the steam penetrate the plywood. It was still a tough bend on a closet wall, much easier on a shorter curved seat base. With all of the worry we do about not letting water damage our plywood paneling, you cannot see any water marks left on the plywood from the bending process. After I finally got the plywood to make the entire 90 degree bend, I just clamped it flat, and let it sit for a few days to dry out. Note, it's not glued at this point.
After a few days I removed all of my clamps, straps, weights, etc. The dry panel sprung back by about 50%, in other words, let's say the 90 degree clamped bend was now 45 degrees without the clamps. The important thing was it had been broken from laying flat, and you could easily see that it would bend and lay down back to the 90 degree bend. At this point, I sprayed both surfaces with water, then spread TiteBond II wood glue over both sides, sprayed it with some more water, then clamped the short edge (it gives you more leverage) and used the straps to pull down the long edge. I clamped it for a few days, let it dry in the sun, pull all of the clamps, used a router with a 1/2" bearing bit and trimmed the edges all around the wall. I then refinished, and installed the assemble wall panel into the Spartan. It's held up well for thousands of highway miles, large weather changes, and still looks good after three years.
With the success on bending the two closet walls, I started on resurfacing my booth corners. It has both inside and outside bends with a 4" radius, and I needed to make a 3" radius to cover the modifications to the lower base riser. I had no problems making the 1/8" Birch bend to either the inside, or outside 4" radius bends. I did it just the same as the closet walls. So now I'm on the home stretch. I tried about five times to bend the 1/8" birch down to the 3" radius, I never made it without a crack no matter how long it was soaked, or how much steam I applied. Now what?
My hardwoods store (Reel Lumber) sells poplar bendy board. They stock both 4 by 8, and 8 by 4. Both sheets are about 1/8" thick. The direction of the grain is the difference. The problem with poplar as you know is it's not a pretty wood. The bendy poplar is very plain, almost like a sheet of drywall. I went through the entire stack, and bought the piece with the worst grain pattern I could find, I wanted the poplar installed to look like the Birch grain pattern because they would only be a couple of inches apart. I used the worst grain part of the sheet, and tossed the rest. It applied very easily, sanded, stained and refinished nicely. The color and look next to the Birch turn out just fine, and has held up well. If you could find a sheet of poplar bendy with some nice grain, it's a easy option to bending the 1/8" birch.
My guess is the reason we have problems bending plywood is due to the filler layer. Today they use all kinds of garbage to toss into the filler to take up space. It's not just smooth wood that bends consistently inside the plywood. I believe that special bending plywood has the grain placed all in the same direction. As small volume builder's we do not have the option of buying the specialty wood products needed to do some of these projects. We have to do with what we have.
I would be interested on how others have overcome these kinds of obstacles.
John
