Gluing in Multilam Reflex

[bownarra]

Do what Alan suggests.

[Tommy D]

Trying to get my head around this...

So one method is starting with reflex and some of it out; the other way is glueing in Deflex and pulling some of that back into reflex.

Let’s say you end up with the same profile ... will there a difference in performance?

[DC]

I'm slowly getting the opinion that "pull out" only applies to shape that has been heated in. If you glue in a shape and through tillering and exercise you lose some of that shape I think that's set. If that's the case then the bow that took the most set will probably have the worst performance due to damaged wood.

[willie]

Its not about which way you flex the first glue-up, its about how thick the belly/core glue up is when you apply the backing.

Imagine a 10 lam bow. each lam glued in succession. you could make adjustments to side profile with each glue-up and create a very intricate shape to start tillering with, but since a thin lam is not strained much when bent, you would have created very little prestress to help the belly at full draw.

[Tommy D]

Hmmmmm .... yes getting my head around this. Just worried that if I glue the core and belly first into some sort of deflex prestress, I wont be able to pull much reflex into it with the thinner bamboo. I suppose I could glue it up, floor tiller it a bit and then glue on the backing.

Might be over thinking this all!

[DC]

I've glued up well over 1/2" Yew with 1/8" boo and bent it on a caul after gluing(while the glue is wet) and it holds the bend well. If I put in 4" of reflex it will hold 3" of it. Basically if you can bend it, the Boo will hold it. With thicker bellies the danger is in the belly breaking while you are trying to bend the reflex in it.

[willie]

Might be over thinking this all!

not at all

I could glue it up, floor tiller it a bit and then glue on the backing.

the less belly wood you have to remove in the end, the more effective I think.

If your core and belly are full width when you do the first glue-up, It should be easier to get the deflex bend in the center of the bow. you might need a different jig setup for the first glue-up.

[Tommy D]

I've glued up well over 1/2" Yew with 1/8" boo and bent it on a caul after gluing(while the glue is wet) and it holds the bend well. If I put in 4" of reflex it will hold 3" of it. Basically if you can bend it, the Boo will hold it. With thicker bellies the danger is in the belly breaking while you are trying to bend the reflex in it.

This Ipe stuff does not like to bend!!

[willie]

This Ipe stuff does not like to bend!!

yes, but if the ipe and the core are 2 different lams they will fit the deflex form easier. using ipe in a perry design well might even require being a trilam.

[mmattockx]

This Ipe stuff does not like to bend!!

Does steaming improve this any, or is it unbendable regardless? How thick is the piece you are trying to bend?


Mark

[Tommy D]

The consensus on the forum seems that heat and steam do very little to bend Ipe. Kerfing is the only way to go. And even the I have got some pieces less than 2mm thick that do not want to bend severely. Think spring steel. It’s interesting stuff. If I do the thin core and bamboo glue up first I can get some decent shapes as they are thinner. The belly lam is thicker and untapered so will only really do long mild bends. If I glue that to a core then I doubt I will pull much reflex out of it. I have even tried to do a sharp static recurve shape with a piece almost paper thin and it won’t follow the form!!

[DC]

Here's a couple of pics. The first is as it's clamped up for the glue to cure. The second is just released from the clamps. You can see how much it's straightened out. I don't think it held as much as I wanted to I will probably have to make a new caul for the next one. This is just a boo backed yew.

[Tommy D]

You sure do keep yourself busy!

I cut out a caul today - but only the thinnest of thin Ipe will follow the curve... thinking I am gonna have to learn to splice in tips if I want a profile like that...

[Tommy D]

Ok ... not sure if this is right or not ... but it’s gonna be a sorta build- along... with free advice gratefully accepted!

So going with the Alan and Bownarra advice and  have glued in 4.5 inches of deflex here with a tapered core and a straight belly lam.

I have not glued the last 14 inches at the tip ends. I figured if you have to kerf Ipe anyways to get a bend/ more severe recurve I would just leave these bits unglued for now.

When it comes out of the hot box I will see how much deflex I can pull out and Reflex/ recurve I can put into the tips.

[DC]

I have found that using a caul like that(with a board and a post) seems to concentrate the bend around the post(s). If you use two posts and a clamp in the middle it's the same,in reverse. In order to get a nice even curve you have to cut a curve in a 2x6 or 8 and then clamp it to that. It's too late now but for next time.