Trilam R/D Longbow

[little_oak]

I am new here (first post and first bow build), but I've been reading through tons of posts trying to learn as much as I can. I've been wanting to build a longbow for a while and decided to finally make the plunge.

I have limited access to tools beyond some hand tools. So I decided to go with a 68" ready to glue kit I ordered from a guy up here in Canada. The 3 main goals I have with this bow are:
- a moderate R/D
- 50lbs at 28"
- learn as much as I can!

I realize that starting with a D/R build might not be the easiest thing. I could start with something easier, but I like the D/R designs I've seen, so I figure why not, I'll stick to something that intrigues me and gets my blood flowing. So with that, I plan on taking lots of time and probably posting lots of pictures when I get stuck.      :D     In fact, I already took a photo of the dry-run for the glue-up and was hoping to get some feedback on what I've done before I start gluing everything together.

 

[little_oak]

I should probably give some specs about the kit.
- The kit has a hickory belly, "fastflex" bamboo core, and regular bamboo backing.
- The width of the boards are 2" wide with no width tapering.
- The thickness of the hickory belly and the "fastflex" bamboo core do taper so that they are thinner at the ends.
- As can be seen in the photo, the hickory backing came with a handle block pre-tapered in.
From what I've read this will affect the amount of deflex I can add in since the handle section will want to stay straight instead of bending. I wanted to try to get some in, but I realized I probably wouldn't get very much.

The reflex I was shooting for was an inch above the back of the bow. The deflex I wasn't really sure how much I could get. The amount of deflex I have in the photo is about the most I'm comfortable taking it because the tension was pretty high.

First off: does anyone have any thoughts on the design and any troubles I might run into with trying to use this kit for this design? I'm pretty sure the kit was actually for a straight longbow with no R/D, but I do oh so like to tinker.  

I did make a couple of notes from the photo. When I measured the gap at the mid-limb point I noticed the right side is about 1/8" further down than the left side. the 2x8 I'm clamping it all to is surprisingly straight so I think the difference in the sides is real. Should I move the left clamp in some to bring the Left mid-limb down some more to match the right side?

[Buemaker]

Like you say the bowblank was most likely intended for a straight bow, so I do not think it should be bent more than you have done. The belly lam looks rather thick so If you want more bend it should be thinned some. I can see one problem you may have. Apart from the 4 clamps you are now using you will need many clamps with spacers on the bamboo back so you do not dent it. With these clamps you will clamp only the bow lams and not the 2x8. You will need more space between the 2x8 and the bow belly in order to have place for the clamps, that is unless you are using spring clamps. You could just raise the blocks the same amount to get room.

[Roy from Pa]

The way it is now, you will have a 100 pound bow..  
Make it 1.5" wide at the flares and taper it to 5/8th wide at the tips. 5/8th total thickness at the center will be good.

 

Shape the handle area like this.

 

[Bowjunkie]

The blocks under midlimb should be directly under the c clamp. See how the limb wood has been clamped to the side of, and lower than the block? Get the block under the clamp, tighten clamp just until it touches the block and then stop... don't smash it down on there with a lot of pressure. Doing so can create a flat spot there.

Like Bue said, THOSE clamps, and those at the handle, can be down under the form's base, but your blocks should ALL be a few inches taller so that the remaining clamps, placed 2 inches apart, have room to be clamped to the blank only... belly to back... unless you're going to use the rubber band method, then you might be ok.

Belly lam looks thicker than necessary. It just makes it harder to pull down into the shape you want and requires that you remove more wood afterwards to get the limb bending.

[little_oak]

Wow, Thanks for all feedback!

Roy - Thanks! You answered one of the other many questions I had.    It did seem like the bow was starting out for a much higher targeted weight than I was wanting. I was debating whether to try and taper the width or leave as is. I do like your suggestion so I think I'll go with that. That is a beautiful looking bow in the picture by the way!

My plan was to go with the rubberband method or try to pick up a bunch of spring clamps. I was wondering though if there might be any issues with using the rubberband method with the 3 layers? Will that generate enough clamping force?

Bowjunkie - Thanks for the insight! I hadn't thought about smashing down to hard creating a flat spot. I tried having the clamp directly under the midlimb but that seemed to induce a harder straighter section in the bend coming off of the handle. However, that's probably due to the thickness of the belly lam.

I think for now I'll taper the width and take a little bit of thickness off of the belly wood, then see what sort of shape I get on the form. I'll be using a hand planer for the width and a rasp for the belly thickness so it will likely be a few days before I get new results.

Thanks!

[Roy from Pa]

Cut the bamboo out to the exact shape you want the bow to be first, Before you glue up the bow.. Then do the glue up. After the glue up is dry, then cut the bow out right along the boo. Then clean up the sides with hand tools.

[little_oak]

I can see cutting the bamboo first would provide a good guideline for cutting out the bow afterward, but what other reasons are there for waiting until after glue-up to cut out the rest of the bow?

[mikkekeswick]

Wider pieces are more stiff laterally and will be lest likely to move when you clamp things up.
I'd go to your local bike shop and ask for all the damaged innertubes they have from fixing punctures. Do you have 30+ clamps?

[Roy from Pa]

but what other reasons are there for waiting until after glue-up to cut out the rest of the bow?

You can do a better job getting the boo shaped to the exact profile of the bow before glue up, and you can get a better glue joint appearance between the belly and core lam by cutting out after glue up.

Do a dry run before glue up. Run a string end to end and get the boo/bow profile straight, clamp it down. I then drill 2 small holes in the center of the handle/grip area for inserting tooth picks into to hold it straight while gluing up. The leather grip will cover the holes when all is done. I also drill 2 holes at the tips, one on each side of the limb tips, right along the boo but not into the boo. Insert tooth picks into those also when you glue it up.

[little_oak]

ok, that makes sense. Thanks!

mikkekeswick - I don't currently have that many clamps, but I do volunteer at a community bike shop so I won't be short on tubes. I realize I'm completely new at this, but from what I've read it seems like you don't need a ton of clamping force, as long as it's consistent along the full length. My thought was to use the tubes to wrap it for a consistent compression and minimize the clamps (mainly to keep it cheap since I'm a grad student). I'm definitely open to suggestions and input though.