I'm building a plywood camper, and need this group's expertise.
I need to butt-join (don't ask me to scarf - I don't have the time or the talent!) two pieces of 1/4" Mahogany plywood. My question is: how easily does the join bend? I need to bend the plywood fairly aggressively (can't tell you the exact radius, but it's quite a bit) and if I do it the way I want, I will have to bend the joined part.
My join will be a "standard" epoxy butt-join, with epoxy resin and tape on both sides of the join.
I'm building a plywood camper, and need this group's expertise.>
I need to butt-join (don't ask me to scarf - I don't have the time or> the talent!) two pieces of 1/4" Mahogany plywood. My question is: how> easily does the join bend? I need to bend the plywood fairly aggressively> (can't tell you the exact radius, but it's quite a bit) and if I do it the> way I want, I will have to bend the joined part.>
My join will be a "standard" epoxy butt-join, with epoxy resin and tape> on both sides of the join.>
Any ideas?
I know that you don't want to hear this, but if you want a smooth bend, you're best off to scarf the plywood. Fiberglass on the joint will make is substantially stiffer than the surrounding plywood.
Scarfing is not difficult, particularly with thin plywood. All you need is a sharp block plane, a straightedge of some sort and some patience. If you're only doing one joint, what's the big deal?
On Thu, 14 Apr 2005 08:40:56 -0700, a_gunther wrote:
Lloyd Sumpter wrote:>> Hi,>>
I'm building a plywood camper, and need this group's expertise.>>
I need to butt-join (don't ask me to scarf - I don't have the time> or>> the talent!) two pieces of 1/4" Mahogany plywood. My question is: how>> easily does the join bend? I need to bend the plywood fairly> aggressively>> (can't tell you the exact radius, but it's quite a bit) and if I do> it the>> way I want, I will have to bend the joined part.>>
My join will be a "standard" epoxy butt-join, with epoxy resin and> tape>> on both sides of the join.>>
Any ideas?>>
Lloyd Sumpter>
You won't get a smooth bend if you use glass and epoxy on both sides of> the joint unless you taper the ends of each side of the joint so that> the glass doesn't make the joint thicker than the rest of the panel.> That, however, would be more difficult to do than a scarf joint. One> other method which I have used successfully in areas where the bend is> not extream and strength is not a big issue is the double lap joint.> You need a portable router for this. I use a trim bit with a piece of> spine to even up the laps. It is much faster and easier to do than> either a scarf or dealing with tape and epoxy. If you manage to get> the lap depths and the grain just right, the joint is invisable and it> bends well.>
Thanks for the reply!
I used that lap-joint on the floor, when I discovered that 6 1/2ft is 78 inches, NOT 66 inches (DOH!!!). But since the bottom of the floor doesn't show, I taped one side as well. And of course that part doesn't bend.
I think you have the image sideways, though: the seam is longitudinal. Think of a jonboat-like structure, where I'd be bending the bottom up to form a bow, and the seam is lenghwise down the keel.
But you're right - there's not a lot of strengh required here, so I might just do the lap-joint, and possibly tape one side (to ensure water-tightness!) How much do you lap (I used an inch on the floor)?
William R. Watt 14 April 2005 22:22:52 [ permanent link ]
Lloyd Sumpter (lsumpter@dccnet.com) writes:
I will have to bend the joined part.
it all depends on the radius of curvature of the bend.
-- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned
Meindert Sprang 15 April 2005 16:31:21 [ permanent link ]
"Andrew Butchart" <andrew@floatingbear.ca> wrote in message news:I9O7e.1844$5I5.86225@newshog.newsread.com...> What about making a backing block with the same curvature as your bend?
you have a small gap afterwards - that's what filler is for...
But the problem then is: how you you glue the flat ply on that curved block?
I think you have the image sideways, though: the seam is longitudinal.> Think of a jonboat-like structure, where I'd be bending the bottom up to> form a bow, and the seam is lenghwise down the keel.
That's a very different animal than I was envisioning. Since the two pieces are parallel to each other, why can't you bend them in place and glass the joint afterward? Or, you could butt join them with glass only on the inside. Since the bend is along the joint rather than across it, that should be strong enough.
On Fri, 15 Apr 2005 12:09:12 +0000, Andrew Butchart wrote:
What about making a backing block with the same curvature as your bend? If> you have a small gap afterwards - that's what filler is for...
I don't think that would work in my case, but you gave me an idea: I could do a simple join like a lap, bend the plywood into it's position, THEN apply epoxy and tape! (As I said, this seam is longitudinal along the curve) Can't see why that wouldn't work...
William R. Watt 17 April 2005 03:01:54 [ permanent link ]
Oh, for a longitudinal butt you could edge glue the pieces with epoxy and lift them carefully into place together to get a nice tight seam, then fibreglass the inside. When I butt two pieces of plywood together with PL Premuim and a plywood butt block, I first put a little epoxy all along the edge before pushing the pieces together. It saturates the end grain to keep water out and gives a better seal, at least that's my assumption.
-- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned
I don't think that would work in my case, but you gave me an idea: I could>do a simple join like a lap, bend the plywood into it's position, THEN>apply epoxy and tape! (As I said, this seam is longitudinal along the>curve) Can't see why that wouldn't work...
