How to flip the tips on a tri lam

[Zradix]

Hey Gang,

Soon I'll be trying my second attempt at..and hopefully 1st successful tri lam.

I'm thinking I'd like to flip the tips.
This bow will be hickory back, walnut core, osage belly.
All lams pre-tapered thickness.

I've read osage bends nicely with heat.
I can't find much info on hickory or walnut.

Can I just heat all 3 of these woods with a heat gun dry and clamp them into the tip flipping form?

Should I do all the lams or just maybe the core and belly?

Should I do each lam separately or all 3 at once?

Are ya supposed to only heat from one side or the other...or evenly?

Any help, instruction or tips would be GREATLY appreciated.
I'm quite worried about screwing up the wood especially since my goto wood guy is taking  break....

Thank you!
   

[Pat B]

If your lams are thin enough you might be able to just clamp them in the form without heat. If you have to heat them I think you'd have better luck heating and bending one at a time. I've never done it with lams before so you might just have to try it and see.
 I know osage bends well with dry heat but hickory prefers steam for thicker wood and walnut is probably the same but if they are thin enough dry heat might work. The glue will hold the shape if you can get the lams to bend.

[Zradix]

Thanks Pat.
When you say just clamp them into the form..
Do you mean a "tip flipping form" ( I don't know what it's called) or the glue up jig?

Thanks    

My thought...and I might be way off here...is that by flipping the tips, the tips would be more stiff and therefore could be lighter/thinner  w/o bending too much at draw.

This bow's limbs will be straight through the riser and I'm planning on having the tips blocked up about 3" at glueup with the bend starting about 1/3 in from the tips...maybe a bit closer to the riser.

Kinda trying to get about as close to being a recurve as I can without the string touching the belly..or slapping it after the shot...lol

[LittleBen]

I have flipped hte tips on a number of tri-lams and I find heat is not necessary.

If you're making a tri-lam with 3 equal thickness lams of .002" taper, and a total stack of .500" then each lam is only about .165" at the butt and ~.090" thick at the thin end.

Wood that thin will bend very easily. Even Ipe.

Hickory, walnut and Osage will all bend very nicely at thicknesses like that.

Anything much over .120" thick in the area to be bent starts to get a little tough, but can be done depending on the wood and the grain.

I've done recurves, and a number of R/D longbows with and without flipped tips this way.

John, the bow you and I had been discussing was done without heating the tips at all and the ipe slat was .190"-.200" butt thickness with a .002" taper and the bow is only about 60", so the thickness of the Ipe at the bend during glue up was nearly .130" I think.

I'll try and get some more pics of bows with flipped tips that didn't use heat. I only really use heat for selfbows or simple composite bow (backing and belly, no core)

[LittleBen]

John, what length and width are you going with and what riser length?

[LittleBen]

Sorry to go post crazy, but here are some examples.

This would need to be steam bent  http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=print_topic;f=125;t=001950

These would not need any heat/steam bending to achieve with properly tapered lams:
 http://***********.bowsite.com/TF/pics/00small20336471.JPG
 http://i127.photobucket.com/albums/p133/wytetale/longbow059.jpg
 http://forums.bowsite.com/tf/pics/00small33343426.JPG

[Zradix]

Thanks Ben.

This is the one you've been helping me with...wood isn't here yet so I have plenty of time to over-think the build...lol    

It certainly would be nice not to have to do the step.

I can understand how these thin little lams glued into shape don't have much strength to fight back.

The lam end thickness back to belly will be 0.072", 0.112", and 0.132"....on paper.

Thank you

[Zradix]

SWEET! Thanks for the links Ben
       

[Zradix]

Originally posted by LittleBen:
John, what length and width are you going with and what riser length?

The plan...
62" 1.25"W 12"Riser/PL, 1.25" W six inches past riser then taper to .5" tips.

[LittleBen]

You can definately bend them without heat or steam, just do a dry run to test.

So extrapolating, your lams are .150" hickory, .190 walnut, and .210 osage? total stack of .550"?

What length, width and riser length?

Sounds like it should be a really nice bow. I haven't used osage so it's hard to say how much weight that will be but I'd guess good for at least 50#+ at a length of 66" or so. Can't wait to see this one turn out.

By the way, I ended up using that striped riser we talked about for a bow for my cousins Son. I'll post some pics soon.

[Zradix]

I'm amazed the last 2 could be done w/o heat bending.
Every time I've seen one like that I figured it was flipped.

I love the bow in the top link of the 3 link group.
I've seen that one before...makes me drool a bit every time..lol
Very similar to what I'm trying...just (ha just) curved in the middle.

[LittleBen]

Yeah I like that bow alot too. I actually tried to contact he guy who built it but didn't manage to. I wanted a form for it so I saled the photo to zctual size and printed it to make a copy form. Never got to it. Just made a similar R/D form. Actually my little cousin's bow will be nearly that exact style.

I don't wanna tell you what to do but I'd start wider 1.5" if you can, and start longer if you can.

That way you have more room to play around.

I think the idea of keeping it full width for at least 6" is a good one. Will help prevent limb twist. I tend to keep mine a little wide to near midlimb for this reason.

[Echatham]

zradix i havent done exactly what youre doing, but when i added a two lamination underlay on that static recurve osage i posted a couple weeks ago, i used maple and walnut, and i couldnt get them to retain enough bend to conform to the curve with dry heat so i boiled them and that did the trick.  have also seen a bamboo backed osage with static recurves where the bowyer boiled the tips (both osage and bamboo together) and then clamped them in the form together.  worked really well.  just gotta watch your moisture content before going to town on it after that i guess, although im guessing with the heat involved with boiling it might pretty well dry itself out once you take it out.

[Zradix]

Sorry Ben..

62" boards
0.12" hickory back centered parallel for 14" then taper .002
 0.16" core centered parallel for 14" then taper .002"
0.18" osage belly centered parallel for 14" then taper .002"
.12+.16+.18=.46"

1.25" wide for 24" (12" each way from center) then taper to 1/2" tips

12" powerlam section of riser..not sure about the length of the belly side of the riser yet..7-8" or about.

I'll bet that one turned out pretty.
...the dark wood (walnut?) sure looked to have pretty figuring in the pics...especially for as thin as they were.    

[Zradix]

Thanks Eric.

Your bows sure have come a loooong way quickly bud.
   

[Bowjunkie]

I've never heated and bent the lams in a tri-lam. They bend easy into semi or full recurves. The only way I'd heat them is if I was making a static bent into a very tight radius. Never had the recurves 'pull out' or anything. What other concerns are there? I must be missing something.

By the way .006 taper per inch is a lot. If it were me, I would not taper the osage belly lam... that way, it leaves more wood for adjusting tillering/timing, weight, and if you still want to take off more later you can.

[Bowjunkie]

I just looked at Ben's pics and concur with him on what needs heat and what doesn't.

[Echatham]

thanks Zradix, everyone gets better and it keeps me goin.  im thoroughly addicted now    :D

[LittleBen]

John, yeah I just lookeda t your specs and I think you're probably right on there. Again, can;t wait to see this turn out.

I don't necessarily agree with Bowjunkie that .006" taper is too much, but I do agree that not tapering the belly will give you a bit more leeway in tillering ... sort of. Probably the safest way is to not taper as he said, but go and caliper the limbs along there length after tillering and you calculate the taper that was necessary. I would venture to guess it will end up very close to .006" but only time and testing will tell.

I should mention that since I leave my bows fairly wide mid limb, that they require more taper than a nearly pyrimidal limb would.

[Zradix]

Thank you all for the help Guys.
There really isn't much I can do for changes at this point..order is placed and I'm pretty sure work has begun.

My thought...however wrong it may be...was that my stack may be a tad high for 45-50#.
The design with the flat section of lams extending a bit from the fades and keeping full width for a while may very well lead me to scrape some off the belly around and just after the fades.

Couple that with hearing over and over again to "get it bending at the fades first" and I'm even more inclined to think I'll be scraping the fade area.

so.... I picked a total taper rate that was what I felt could be slightly on the high side...with the thought of by scrapping the fade area just a few times it would reduce the total taper and get me more inline with the norm....and hopefully a well tillered bow somewhere in the preferred draw weight range.
...HOPEFULLY!!! LOL!