Primitive Archer
Main Discussion Area => Bows => Topic started by: Jim Davis on January 07, 2018, 03:46:32 pm
-
I've had Osage and hickory part company at fades and in glued up handles. I didn't think the handles were flexing, but maybe. Osage glued to Osage has also let go.
I have used both epoxy and Titebond II and both have failed at times. Is there a more dependable glue?
-
I’ve always used tb3 with good results. Any time I’ve had it let go is if there is a bad glue line or I didn’t prep the surface properly. For prep I just sand the joint surfaces with 80 grit paper to give it a litttle texture.
Kyle
-
Same as Kyle, I never degrease any wood or use grooves. If a bow is less than 3/4" think at the handle and longer than 64" drawing 50# the handle will have some flex, enough to pop the handle anyway. Maybe not right away but over time. This lams on the handle will usually stop this.
-
Did it pull fibre from the other layer when it failed? That would be the clue for you whether you had insufficient surface preparation or not. If it just failed clean then I think you would need to have a rougher surface before glueing.
-
Will you post pics? A side view.
TBII is stronger than TBIII. Did you prep as the glue suggested?
-
Grain orientation and different wood species create movement through different expansion and contraction rates that weaken a joint.
Was the Osage to Osage the same grain configuration?
Many people mention Urac or Resorcinal as bomb proof for tricky glue-ups.
-
I've heard the same about urac. I have also had the same problem Jim. Arvin
-
Preferring to keep everything as organic as possible, I use gelatin glue. 6:1 with straight white vinegar for sizing, and a thicker 3:1 for the glue up. This stuff is strong. Probably not as strong as Titebond et al, and not as waterproof either. I have had handles "pop", ripping chunks of wood from either side, so as extra insurance, I now wrap the section of the handle to be covered with leather, with a high quality linen twine, and gelatin glue that too. Very strong. Haven't had one pop yet with this method, mind, I am fairly new at this obsession.
I think that handle and fade design has a lot to do with it too.......
-
Same as Kyle, I never degrease any wood or use grooves. If a bow is less than 3/4" think at the handle and longer than 64" drawing 50# the handle will have some flex, enough to pop the handle anyway. Maybe not right away but over time. This lams on the handle will usually stop this.
X2
A good clean glue line is a must for any glue up.
Patrick
-
I never had a handle pop after I started using urac and lengthening and feathering the fades, no problems with unibond except having it set up in the can. The last I did was with smooth on, no problems so far. That is at least at least 140 glued on handles with no pop offs.
I always matched the mating surfaces where I couldn't see light between the two pieces and roughed both pieces up with a toothing plane.
If my stave is thin I put a couple of pieces of 1/8" thick pieces down first before I put on the bulk of my handle material.
Like this;
(https://i.imgur.com/Kt1pBMJ.jpg)
-
What kind of epoxy did you use? I had one handle piece come loose almost 20 years ago, and not one since. It was purpleheart on yew, and their differences may have been the cause. Or it could have been a starved glue joint because I did things differently back then.
Anyhow... since then.... I use Smooth On EA-40, mate the pieces together as perfectly as I can, then scrape them with a toothing plane blade that is VERY slightly convex shaped. Since many of these glue ups are with curved/deflexed pieces, I do this without the planer body, while holding just the blade by hand, like a scraper, creating grooves parallel with the full length of both pieces to be glued, until they are the full depth of the teeth. Then glue with Smooth On, clamp, and set a shop light nearby for warmth.
If mixing epoxy, be certain it's adequately mixed. Spend an extra minute.
I have never had anything come loose or separate even the tiniest amount when prepped this way, including pieces that flex... sometimes I purposely flex the wood into the added on dip/handle piece. I leave no pedestal of extra thickness, and use no power lams. I've done this on short, stressed designs, and bows up to 70 lbs. It's worked every time... or maybe I've just been really, really lucky ;)
-
I wonder if design differences alter the stresses felt on a glued on riser. Both Jim and Arvin prefer pyramids and Jeff and Eric the narrower radiused type. Perhaps the flatter pyramid feels the poisson effect more at the wider fades and starts degrading there.
-
If we could see a side view of the riser area we could diagnose the problem. Guessing is fun but not very productive usually.
-
Here's a pix. Back layer is hickory. Belly and handle riser are Osage. This was a limb in one of my sleeve take-downs. I used Titebond II on the whole limb. The stub was epoxied into the sleeve with no room to flex. The fade area held, but the root apparently failed in shear?
I have other bows glued the same way that have not let go--yet. The other limb of this bow did not fail. I treated both limbs the same way. Glued up in slight reflex, which they lost.
Strung image is a different bow, but design is the same.
-
NEVER use 5- minute epoxy on limbs, way too brittle. If you want to use a store brand, I strongly suggest Devcon 30 minute set epoxy. As mentioned above mix, and mix some more. I personally only use Devcon on splices, never had a failure there, do not over clamp.
-
What's your guess...er diagnosis Pat B? ;)
-
NEVER use 5- minute epoxy on limbs, way too brittle. If you want to use a store brand, I strongly suggest Devcon 30 minute set epoxy. As mentioned above mix, and mix some more. I personally only use Devcon on splices, never had a failure there, do not over clamp.
Vinemaplebows, I must have been correcting my post while you were responding. Epoxy was only used to anchor the root in the sleeve.
-
Pat, just as I guessed...the handle riser is on the same plain as the belly. I like to start with a 3/4" board so the riser sits above the belly plain.
-
Yup. Not the glues fault here.
-
Very rarely is the glues fault.
-
OK, then I want a miracle glue, because I want to use Osage laminations that are not good enough for the back of a bow. I have a lot of Osage that is curly, twisted, and so on that should be fine for bellies, or center laminations, but has no chance as the back.
So, now that we have sung the glib chorus about it not being the glue's fault, does anybody have a constructive thought about how to make this kind of lamination work.
Further, people do this with fiberglass/wood laminations all the time. So what glue works for them?
And, ["]the handle riser is on the same plain as the belly.[/"] Please note, the riser did not delaminate. The backing did.
-
lots of shear at mid limb and the limb is bobbed abruptly on account of it being a take down.
might be some sort of stress concentration there.
I usually go to the boat building epoxies resins for challenging joints
-
The belly has to be thick enough , even if it is multi-lam, so the riser doesn't sit on the same plain as the belly of the bow. See how Eric's riser sits above the belly and the fades bring them together. So start out with a 3/4" belly, even if multi-lam, glue your riser to that then shape the side profile of the bow. A 3/4" thick center section will insure that the center of the bow, the handle area, will not bend as the bow is drawn. Your finished limb will be 5/8" to 1/2" at their thickest and maybe less so they will bend without causing the handle area to bend.
I made a bow that kept popping the handle. I wanted to save the bow so I bought hemp cordage from WalMart, wrapped it tightly and saturated that with thinned 2ton epoxy. BINGO! it still holds. Now, most of my bows have short bulbous handles and the limbs bend right up to the handle so I wrapped the entire handle.
With FG bows the FG run up the fades on the belly which locks the riser in place. The fade area, whether FG or wood bow is where most of the stresses occur in a bow because of the leverage of the limbs. If you had improperly ground fades in a FG bow, that is the likely place it would fail. I know this for a fact. ::) ???
-
What's the glib chorus?
-
Pearly I guess that was my frustrated sarcastic response, after it seemed like everyone was fixating on a "handle separation" when what I have is a backing separation. I've given up now
-
Jim do you have any pictures of your delaminated area?
Patrick
-
see 1st page
-
Sorry Jim, guess I missed that post.
Im not really sure what would cause that seperation, especially since its inside a take down sleeve.
Is the sleeve round? Or is it oval or D shape? I could see if there was some play inside the sleeve maybe. But if im right you said you epoxied it in. I could see a bit of a problem if the sleeve conection had a little play in it front to back that it could cause a problem. But not sure it would cause a delam inside the take down sleeve. Got me.
Patrick
-
Last night I broke the glue joints in the whole root area to see what the bonds were like. The Titebond II just broke apart leaving both sides coated with cured glue. The wood did not break in that area. Farther out the limb, some of the wood split, leaving the glue line bonded.
-
That's interesting. Did you glue the takedown sleeve on shortly after doing the lamination glue-up or leave it for a lengthy curing period first? Maybe residual moisture from the TB never got out of there due to being encased in epoxy and metal and hampered the ultimate cure strength?
-
the only time I had a titebond joint break the glue was old
-
PatM,
I have made several bows this way, so don't recall exactly how long I let the TBII cure before put it in the sleeve. It's possible it was epoxied in before fully cured.
I do start shaping the root after 12 hours sometimes. If I got the shaping done before the 24-hour cure time, I may well have put the epoxy to it and slipped it together.