about fixing crysals, loosening titebond, and pics of an bbi I've made!

[nickf]

I've been working on this one, gotto fix a 'little' problem, and needs a finsish.

Current stats:
80#@28"
62" ntn
pyramidal frontprofile, glued up in R/D

My first trilam ever I had glued up. Choose for a 7mm maple core, and based it on a similar bow, but without r/d, and with 2 lams instead of 3. Made a measuring error, and the bow ended up too stiff. This core was a little too thick, and the reason for the compression fracture in the lower midlimb, as I had to sand of most of the ipé.

Not as bad as in the other bow, with a 3mm core. This was a Hybrid, with quite a bit of reflex, and 58" tall. I had to sand so much of the originally 2 ipé lams off, that I ended up with one, paperthin lam at the belly, wich got huge compression fractures;

please don't make the same mistakes as I did, and don't start with a lightweight core if you make a trilam from an unknown design. Who would have thought that a 3mm (1/8") core would have been too thick?

Okay,
now I have one other blank with a likely too thick core. Glued together with titebond. Any idea how to delaminate it properly, without hurting the wood? will heat work? might start a new topic on this.

I'm thinking about filling the little crysal with superglue, then finish the bow. What do you guys think?






(lower bow is the surviving one)


compression fracture in the lower limb of the 'surviver'


yeah, the ipé was real thin..


and it was even worse on the quadlam-who-became-a ipé veneer bellied boo backed maple



Nick

[denny]

Nick I delaminated one once , put in the hot box trying to epoxy a handle the glue softened and it  let go for the most part. I had to help it a little.  Denny

[Pat B]

You seem to be asking a lot from your bow at 80#@28" on a 62" lam bow. 80# would be something to work up to after you work out the design. In that way you can add a thicker belly lam and work down to the desired weight from there. You seen to be building from the center out. That is the way I built boo backed multi lam bows too. I always ended up with thin bellies and most of the limb was the core. I ended up trapping the boo back to relieve the stresses on the belly and help reduce set.
  I prefer self bows because I don't have to think much to make them.   

[Justin Snyder]

How wide is this bow? I have used thicker cores with Ipe and boo trilams and never had a problem. Justin

[hedgeapple]

What is trapping?

[Pat B]

Trapping is shaping the limb cross section into a trapezoidal configuration; generally with a thinner back and wider belly. This helps to equalize the stresses on the limb.

[Gordon]

You cannot fix a crysal with superglue. Those fractures are telling you that you're asking too much from your designs for such heavy draw bows.

[Far East Archer]

Hello

I think, better to start a little longer so you have piking option if too low weight and not need so wide, ipe gets thin fast on wide bows....
Also, Backing look thick, maybe this caused weight to go up and too much stress on ipe? I not sure, Richard uses thick backing too so...?

Before I make ipe 3 mm thickness belly though not fracture. Your ipe looks good, I wonder, maybe high weight.
You can delaminate titebond with heat gun, keep it moving so you dont heat one area too much, it will come of easily quite fast. I use thin blade as wedge. I have re-use heated parts before, no problem, just dont heat treat it!.....

[OldBow]

Whew! 80# and 62"ntn
We'll look at it again in a couple of weeks for Aug Laminate BOM fun.

[nickf]

some specs:

ipé thickness: average 1/16" (1.5mm...)
lighter bow would mean bring it close to a boo backed maple.. nothing I want!

width is 1 9/16"... (40mm), straight taper to 3/8" nocks (gotto bring them down to 1/4")

think I'll patch the crysal spot, or just leave it as it is... patch will be a 2" piece of wood glued over, not fully sanded down (creating a non-bending spot...)

Nick

[DarkSoul]

Wow, 40 mm wide is very wide for a BBI in my opinion. 30 mm is more than plenty for average drawweights. Maybe 33 for higher drawweights.

Your core is not too thick, your bamboo backing is. It really should be thinner.

[Justin Snyder]

I would definitely narrow the next one down to around 1 1/4" (30mm). That would likely have brought you in close to 67#. When I use Ipe I use the thick bamboo but if it is a trilam I thin it a little more.  I always keep my core around  1/8" (3mm). With laminated bows, (or all bows for that matter) you have to consider the distance from the back to the belly. If the boo is thicker the core has to be thinner or the other way around. As thin as that ipe is I don't think you are going to patch it. Maybe sand the ipe off from fades to tip and have a really nice boo backed maple. Try another and good luck. Justin