questions about triple laminate english longbows

[lonbow]

Having built quite some selfbows, I'm looking for some new things to learn.
Currently I'm planing to built a triple laminated English longbow with about 50 lbs @ 28 ". The woods I'm planing to use is yew for the belly, elm for the core, and hickory for the backing. There are a couple of things that I don't know yet.

1. Should the hickory backing taper towards the tips? What dimensions would you suggest?

2. What are adequate dimensions for the elm wood core? What kind of taper would you re comend?

3. I'm going to glue the lamination's with a reflex of about 2 1/2 inches. I've read that gluing the belly and core lam with some DEFLEX prior to gluing the the backing on in a reflexed position improves cast. This will improve the energy storage in the inner parts of the limbs, so the bow can be made lighter. How would you do the glue up of the core and belly lam? Must the core lam be reduced to its end thickness before the glue up?

4. Should the belly lam already be tapered before the glue up or should it be done afterwards?


I would be very happy if you could help me with this project.

Thanks in advance!
lonbow

[simk]

1. You can do that. What finally counts is the overall taper.
2. Check overall taper of a well tillered Elb and copy  8mm?
3. Interesting thoughts. Much work.
4. I dont normally taper the bellylam on a straight bow.
You will have to find out what works for you best. It's cool when a good tiller is already established after glueup. But a little bit off  tillering will always bring you to the goal.
cheers

[Hamish]

My Approach


  1. I never taper the backing. It historically wasn't done with backed elbs. It was and is sometimes done on the sapwood of yew selfbows. 1/8" hickory for a backing on a 50lb bow, is good.

It is possible to do though. I can't see a good reason to do it, with hickory or other sawn backings. I do this with bamboo though, but that is a different question . If you have your heart set on tapering a backing, only taper the core/belly side not the exposed back.

2. Core for a 3 lam( yew belly). You can use 1/8" parallel core lam, if you have a thick enough yew belly. If you don't have a thick belly lam, you can use1/4" thick at the handle tapering to 1/8" at the tips. Any of these combinations you will end up with a tip that has a pleasing amount
of heartwood to core /backing.
3 &4. Core and belly at final taper dimensions before glue up, glue/reflex all 3 lams at once. Don't bother with any deflex stressing pre glue up. I can't say it would help either way, but you won't be disappointed with the peformance of a bow that isn't pre tillered by hand.

[Del the cat]

Taper the core, that avoids exposing the core as you take wood off the belly during tillering. Don't taper the backing, but please please please round it lightly especially at the edges, else it will feel horrible in the hand (I'm sure this is what some people think is hand shock... when the corners hurt your hand when you shoot)
Suggested taper for core approx 1.5mm every 6"... or what ever is feasible for the thickness of your core (don't try to taper it to thinner than zero... negative thickness wood is very difficult to handle as it is so floppy, although heat treating can stiffen it up a tad )
Del
PS. just checked the taper sled that I made when I did a tri-lam. It's 1mm every 6"