World’s Ugliest R/D at 27 inches draw!

[Tommy D]

I want to glue up a bamboo backed, ash cored, ipe bellies trilam. I have made a R/D form out of mdf. It has about an inch of deflex and 2 of reflex and the curve to reflex starts about 1/3rd between the handle and tip.

Length is 66” and it is a pyramid design from 1.25” to .5” at the tips. I have tapered the ash core. I have also ground the bamboo backing to a “knife edge” ... so it will also by default have some thickness taper.

I am thinking of gluing up the belly lams on top of the handle/ riser the way it is done with a glass bow.

Do I need a “power lam” between the bamboo and the ash core?

Please feel free to point out other glaring design flaws. I have a thick skin!

Some photos ...

[Pat B]

With the handle riser sandwiched between the back and belly lams you probably don't need a power lam. For insurance you could add a thin lam that goes out beyond the riser on each limb. 1/8" to 1/16" should be plenty if needed at all.

[Bob Barnes]

Not to help answer your question, but to ask you a question... I've made quite a few BBOs just using various sizes of blocks, but have thought about using one of my RD forms like yours.  How do you plan to allow for the nodes when doing the glue-up?  I've thought about some type of pressure strips between the nodes to make the surface flush...but haven't tried it.  If you flatten the boo, then lay out your pattern on the flat side, cut it out to shape (a little proud) before your do the thinning...then the edge thickness will remain pretty constant for your finished bow and you can actually pre-tiller the backing somewhat...plus it gives you the pattern to follow when shutting out the bow shape.  Looking forward to watching your project. 

[Tommy D]

Not to help answer your question, but to ask you a question... I've made quite a few BBOs just using various sizes of blocks, but have thought about using one of my RD forms like yours.  How do you plan to allow for the nodes when doing the glue-up?  I've thought about some type of pressure strips between the nodes to make the surface flush...but haven't tried it.  If you flatten the boo, then lay out your pattern on the flat side, cut it out to shape (a little proud) before your do the thinning...then the edge thickness will remain pretty constant for your finished bow and you can actually pre-tiller the backing somewhat...plus it gives you the pattern to follow when shutting out the bow shape.  Looking forward to watching your project. 

I am not sure what I am going to do yet - but I understand the problem. I had thought of a foam strip that would contour to the bamboo.

What I will probably do is wrap the glue up in packing tape, which should apply enough pressure for the laminations to pull together and then use inner tube bands to make that follow the shape of the form. The bending of the lams to the shape of the form will no doubt squeeze the lams together more.

This is the theory anyways...

[Bob Barnes]

Not to help answer your question, but to ask you a question... I've made quite a few BBOs just using various sizes of blocks, but have thought about using one of my RD forms like yours.  How do you plan to allow for the nodes when doing the glue-up?  I've thought about some type of pressure strips between the nodes to make the surface flush...but haven't tried it.  If you flatten the boo, then lay out your pattern on the flat side, cut it out to shape (a little proud) before your do the thinning...then the edge thickness will remain pretty constant for your finished bow and you can actually pre-tiller the backing somewhat...plus it gives you the pattern to follow when shutting out the bow shape.  Looking forward to watching your project. 

I am not sure what I am going to do yet - but I understand the problem. I had thought of a foam strip that would contour to the bamboo.

What I will probably do is wrap the glue up in packing tape, which should apply enough pressure for the laminations to pull together and then use inner tube bands to make that follow the shape of the form. The bending of the lams to the shape of the form will no doubt squeeze the lams together more.

This is the theory anyways...

That's about as far as I got when I thought about doing it too.  I was concerned with pulling the bamboo down to the form in between the nodes, creating a wavy back/bow...maybe strips of a kindergarten napping mat?

[Don W]

I did something somewhat similar except I just did 3 layers of ash with 2 power lams between each layer. I didn't use a riser. The power lams were 1/8". The back one was 18" long and belly side was about 12". I tillered to about 45#. After about 50 arrows the inside ash layer collapse at about the end of the long power lam. This may or may not help you, but make sure the transition is smooth or the bamboo will overpower the ash.

[bownarra]

I did something somewhat similar except I just did 3 layers of ash with 2 power lams between each layer. I didn't use a riser. The power lams were 1/8". The back one was 18" long and belly side was about 12". I tillered to about 45#. After about 50 arrows the inside ash layer collapse at about the end of the long power lam. This may or may not help you, but make sure the transition is smooth or the bamboo will overpower the ash.

A powerlam goes inbetween the back and belly.

Your form is good for a wood backed bow but not for a bamboo. Really the form is backwards for what you intend to do......
A powerlam is to stiffen the stack at the handle fades so that you can safely glue the riser stack directly onto the belly without risk of it popping off (and not waste a load of belly wood). So no you definately don't need one with a sandwiched riser.
If you go with your idea of riser posistioning make certain that you get a true feather edge to the fades for 1/2" or so. You should be able to hold the riser up to the light and see through it. If you don't do this you will get a poor glueline right where you don't want one!

[Tommy D]

I have the other half of the form - maybe I will look at using that so the bamboo backing sits on the top side then.

Is pre-wrapping in packing tape still a good idea - or can the lams be glued straight up with inner tube

[Tommy D]

And also would straight grained lumberyard ash hold up as a backing strip for Ipe?

[bownarra]

Pre-wrapping is a BAD idea! It will induce twist into your glue-up! Apply some packing tape onto the 'face' of your form to stop stuff sticking to it. Then get some parcel wrap (clingfilm) once the lams are glued and layed up on the form. Use a combo of parcel tape (sticky) and the wrap to make the lams comform to your form. They won't move once you have enough tape and them wrapped. Then apply your innertube wrap around the form and lams. Your first wrap should go from handle to tip. Once at the tip take another tube and wrap back towards the handle in the opposite direction. This way you illiminate any induced twist in your glue-up. Same on both limbs, 2 tubes per limb. Just cut the valve section out of the tube.
Straight grained ash is a great backing
Make sure your belly lam is thin enough to conform to the form....ipe is stiff stuff.

[bubbles]

I guess one way to deal with backings that are not uniform (bamboo/single ring backings) is to do the form the opposite way, so the belly (which will almost always be flat) goes against the form, and the inner tube/ wrappings go over the backing.

[Tommy D]

Trilam glued up; 2 power lams; wrapped in packing tape and then 2 layers rubber inner tube wrapped in opposite directions to avoid limb twist. In the hot box now...

[Bob Barnes]

nice profile and great form...looking forward to seeing it after the glue dries.  What glue do you use?

[Tommy D]

I am using Ampro epoxy from Gurit - only because I am pretty familiar with epoxy. Next one I will glue up with West G flex ... I am curious how much difference there will be ...

[Bob Barnes]

interesting...I've never used either...back when I made lots of BBOs they still made URAC and it's all that I ever used.  Thanks.