TBB Vol 4 tri-lam

[stickmonkey]

After reading TBB vol 4 and talking to Badger at length I built me a form and used the Dryad specs in TBB4 to build a tri-lam. I built one last year from a kit and learned a lot emailing Roy and making mistakes along the way. Mostly I learned that I never wanted to buy a kit again so after finding an osage board, thanks Kenny, I got some boo backing from echo archery- good price and fair shipping - and picked up some ipe from the decking store.

 As mentioned I talked to Steve Gardener (badger) at length on the phone several days picking his brain and getting solid answers to preform ancestors related questions. In the end I built a form with 3/4 deflex and 5" of reflex for a 66" bow. For those that may not know I went with so little deflex was that the limbs will naturally deflex on their own as the bow is worked and shot in. Pretty much the same reason for the 5" of reflex as the tips will relax a bit when tillered. In the end I am looking for 1 - 1.25 deflex and 2.75 - 3 reflex.

 A fat and long tip wedge was used so I could make the tip section very very thin as Steve does and still maintain vertical stability. I will also use his no set tiller and mass tillering techniques in hopes of producing a high performance all wood bow to hunt with this year.

Below is the blank before the handle is glued on. Less than 1/8 spring back thus far.
  [/url] [/IMG]

[fujimo]

fill us in on the tillering technique, thanks  

[LittleBen]

Very nice start. Keep us posted!

[kennym]

Lookin good Shane, one of those is on my list. But it is a ways off yet. I'll be paying attention to ya tho, so feed us the info that you can!!  

[stickmonkey]

Kenny ol badger has boo backed osage bows shooting 202 fps at 50 lbs and 500gpp and 28. I looked at how he tillers them and how the mass carried out along the limb, did a few experiments and asked more questions. Always glad to help where I can .

 I am still a rank beginner with tri-lams but wow they hold a lot of challenges and can be equal to their souless glass clones.

[kennym]

"souless glass clones"

Ouch!! LOL

[stickmonkey]

Ya, that was a bit harsh. I must have been spending too much time with the primitives lol

[LittleBen]

What length riser are you using?

[Roy from Pa]

Mercy, that's a lot of reflex..

[stickmonkey]

Yeah Roy it is but once tillered I am expecting 2.75 to 3". Since the mass will carry out to the tips staying the same thickness it calls for an eliptical tiller.

[Bowjunkie]

You're going to tiller that thing elliptical? With all that reflex and tip wedges? How long are the wedges? This should be interesting. Keep us posted.

[stickmonkey]

Originally posted by LittleBen:
What length riser are you using?

Little Ben since it's a 66 (64 ntn) I choose a 14" matched to an 18" power wedge. If it were 64" or less I would go with a 12" riser and 16" power wedge.

 Badger mentioned that since hysterisis is a large percentage of performance robbing with all wood bows, the other being vibration, making the riser and power wedge too long or too short will increase undo stress on the wood fibers which will increase hysterisis. You can always leave more wood on the fade to counter this but I prefer a smaller profile.

 Another thing badger said was to let the density of the wood determine the profile rater than sanding it to a preconceived spec. So if I were using white woods I would make my flares near 1.75 or 2" to offset the white woods lower densities and prevent increased hysterisis.

[stickmonkey]

Originally posted by Bowjunkie:
You're going to tiller that thing elliptical? With all that reflex and tip wedges? How long are the wedges? This should be interesting. Keep us posted.

It will be more eliptical tiller out to midlimb but till the tip settles I won't know for sure if I can get a true eliptical profile.

 The TW is 10" long and .080 and keeps the tip 1/2 from fade to tip. Steve and I are thinking it will let me thin the tip section a good bit and still keep it stiff.

[stickmonkey]

According to TBB4 and Mike Westvang, their tri-lam has 6.5 reflex at glue up and his photos are an eliptical tiller.

[Bowjunkie]

Thanks. I'll have to check it out when I get home.

[stickmonkey]

I used Mike's stacks and length as a guide but made a few changes based on talking to Steve and my own experiences so I am not following the build 100%.

[stickmonkey]

After gluing the riser on last night and filling in the nocks I floor tillered it a bit to get bending. The tapered lam pretty much a sure it will. From there I use a 2" shorter string to brace it and check tiller. Only a 1/4 of so it was quick putting it to even. I worked the limbs in slowly to 15" with even tiller and will now start NST(no set tillering).

 
 

[stickmonkey]

I got it tillered to 46 lbs at 26. I am looking for 50 ish so by the time I trap the back and do some finish sanding I will right on it.
 I lost 1/4 of reflex from when I started NST but I had lost an inch and 5/8 from the beginning before that. I think a good bit of that loss was from the added deflex  and the uncurlingn of the limb tips. On the next one I won't add any deflex and will raise the midlimb more and have less curl with the same amount of reFlex. Still it came out nice and may gain some back after sitting unstrung.

No time to shape the riser or add the nocks today so it will be a few days before I can get back in the shop.
 
 

[fujimo]

hey Shane, whats no set tillering- how does it differ from other types of tillering?

[stickmonkey]

Steve Gardener did post on it about 5 years ago. Do a Google search and it should pull it up or a post with a link to the NST post.

 Basically it's a way to measure when the wood is being stressed enough to start taking set as you tiller it back to you draw lenght. It did take me much longer but I got far less set than I normally do. Moisture content can play a big role in set as well so if you can check your wood before starting do so. Mine was at 9% keeping it in the house.