Primitive Archer
Main Discussion Area => Bows => Topic started by: willie on October 18, 2015, 05:27:57 pm
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I was thinking of laminating two 3/4" thick pieces of red oak and gluing with tb3 for a large elb design the "handle" or glueline needs to go to midlimb.
I have never brought myself to use pva glue for limb laminating before, always used epoxy,but I cannot ignore all the good things I hear about tb3 and want to give it a try.
any tips for red oak prep for tb3?
anybody use weldwood plastic resin glue anymore?
thanks
willie
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I would prep it like any other wood, but I have only used it for handles and overlays back when I made a lot of board bows when I was 10 and 11. Ed oaks not oily so you should have an easy glue up.
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Either TB or Weldwood Plastic Resin will work. TB needs flat, well matched glue surfaces and the Weldwood is a gap filing glue. You want the surfaces well mated but I'd use course sand paper or the edge of a hack saw blade to score it first.
An ELB isn't a good design for red oak. IMO
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I'd agree that red oak wouldn't be my first choice for an elb, you may be wasting two good boards if it chryshalls. Hard maple is decent though.
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Thanks Pat and David
I seemed to remember reading something about red oak not working well with certain glues, but a search turned up nothing.
red oak is not my first choice either, but I have never made an ELB before, and it seems that I need one to be able to fit a big guy for the real thing, so this is sort of a practice/experimental bow in many ways.
willie
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I agree it is not the favorite for long bow,, but if you adjust the length a bit,, it should work,, it just might no be the rocket launcher a choice wood could be,, but will probably shoot an arrow in a respectable way :) and accurately as any bow,,,, :)
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Red oak is not well suited to an ELB as previously stated but I have seen several made with width and length adjustments, and they reportably shoot well without excessive set.
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......I seemed to remember reading something about red oak not working well with certain glues, but a search turned up nothing.......
That would be with the old resorcinol glue. The tanins were the problem if I remember correctly (former boatbuilder).
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why thanks PlanB
It just so happens that I have a boat building project underway, and as I have been doing research on line for the boat, It was probably where I saw it
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It's not red oak where some have had problems, it is white oak, and I thought the problems were sometimes had when using epoxy, not TB. Your glue up should be fine. Russ
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Russ, Weldwood, the manufacturer of resorcinol glue at the time specifically noted oak on the can as inappropriate when I had a boat shop in the 70's. I was an early user of W.E.S.T System epoxy, and I (and innumerable other boat builders) have used it many times for successfully gluing white oak laminations. I wrote a technical design column for WoodenBoat magazine for three years.
Gluing hardwoods successfully with epoxy requires an understanding of a lot of different factors re. both glue resin type, admixtures, hardener type, hardwood thickness, moisture changes, surface roughness, etc.
Rules of thumb work, as long as someone has experience with the particular epoxy resin in a similar glue up used for a similar purpose. But just because one bow builder has a failure with one unnamed brand of epoxy with unspecified thickness and moisture content white oak, doesn't mean "epoxy" doesn't work with white oak. It probably means one or more of the above weren't appropriate.
Likewise when a manufacturer like Weldwood (re. resorcinol glue) specifically advises against a particular kind of wood, it's probably based on wide experience and testing. Most won't recommend against using a product they sell, unless there's a very good reason not to sell it for that purpose.
If I were laminating red oak for a bow, I'd probably reach for my W.E.S.T. System cans. Laminations should be thin. The Gougeon Brothers have always pointed out that moisture changes in thick hardwood laminations (ie over 1/4" thick) can exceed the peel strength of the wood at the glue line. That is, by the way, the weakest link in the chain, not necessarily the tensile strength of the epoxy itself.
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Willie, Take it for what its worth from a fairly new bow builder. the only failure I have had with Tightbond was in a handle build up, and the wood itself delaminated and left the glue line untouched. It was red oak on red oak.
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I have used tightbond on a lot of white oak backings and red oak. I don't think I would use red oak for an elb. I have made several and they all took more set than I like.
As mentinioned above hard maple can make a nice elb, An elb calls for a rounded belly but I would minimise the roundness as much as I could.
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Willie, Take it for what its worth from a fairly new bow builder. the only failure I have had with Tightbond was in a handle build up, and the wood itself delaminated and left the glue line untouched. It was red oak on red oak.
The peel strength of the surface layer of wood where it meets the glue line on thick hardwood is usually the weak link in the chain for any good glue up, not just epoxy.
It's often over-stressed by changes in dimension with humidity. The local forces of expansion with high humidity in hardwood can be tremendous. Thick hardwood isn't very flexible. Swelling is proportional to thickness. Thin laminations aren't often bothered. Heavy pieces are more iffy. If a glue line is damaged by swelling, it won't often show up until stressed by bending.
The W.E.S.T System for boats used thin layers of wood laminated to locally isolate each layer from humidity changes, and coated the exterior with epoxy barrier as well to minimize it further. Not saying this is appropriate for primitive bow making, just information about how this works, and why it happens.
I do know that there are ways of chamfering the fade area to raise the glue line that can reduce handle pop-off, but that's a different topic.
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Plan B - I did not say that White oak and epoxy are a problem - only that some say that it is. I too am a boat builder and frequent the wooden boat forum. As I am sure you know, there are many discussions over there about white oak and west systems. I myself have had no issues with West systems and white oak, having laminated many a canoe stem from it, but a quick search over there will turn up many such discussions and claimed incompatibility issues. I agree they are likely due to some other factor. I am not able to comment on the use of resorcinol glue as I have no experience with it. The Weldwood Urea glue I use often, and have no issues with it - but do not think I ever used it with either kind of oak - I use it with bamboo backings and ipe in place of the now discontinued URAC. Russ
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Thanks for all the input. Surprised to see so many comments on my choice of red oak, so I am going to try something else for wood. As stated earlier, this bow is sort of a quick and easy test bow for fitting a big guy, and various glue, wood, and tillering techniques that I have been meaning to experiment with.
I have only built a few wood boats with epoxy, most of my others being with metal and that other stuff which will remain unspoken on this forum.
I have used system 3 epoxy for all my previous bow laminating. and have also experimented with thermal techniques to assist in my glue ups. Rather than using additives to control the viscosity
of the epoxy, I have been using the thinnest laminating resin system 3 sells on 150 degree wood as a primer to get penetration. (Conventional wisdom says that epoxy and other glues do not penetrate.) Once that starts to kick to where it wont run and sag, I cool the bow and build up the surfaces with additional coats and wait for that coating to stiffen some, maybe even putting the bow parts outside to chill down. I assemble and clamp when the epoxy wont sag, and let it harden until I can bring it inside by the wood stove to warm up again and cure faster. Working with bow size parts lets you do things that the boat builders would find difficult and are not commonly recommended. I can do bow laminations with a single mix and without using additives.
I will say this about handle pop off. if your glue line is near the center of the thickness, It will have the most stress to deal with. The center is the neutral plane for bending, but the shear forces are at their max there. adding thinner lams on the back or belly make more sense from a strength of materials point of view.
willie
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Russ, resorcinol was awful stuff. It may still be used in plywood manufacture -- it has a characteristic maroon-brown color. But using it out of manufacture was a total pain. Glue line pressure had to be very high and uniform, glue line very thin, glue line temperature 70 degrees. It was messy stuff to mix and the proportions were odd -- it was a powder mixed with a syrupy liquid. It stained everything it touched, and it was very expensive (at the time). When epoxies hit wooden boatbuilding, nobody looked back to resorcinol. Oh yeah, it had formaldehyde in it, later proven to be a potent carcinogen. Of course my first W.E.S.T System order contain a bag of milled asbestos fibers for mixing in ::)
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Plan B-
I was just rereading your post on dissimilar expansion between the woods in a glue up.
Q. in the boat building world, was any attempt made to predict expansions and limit certain usages?
I have read that tangential, longitudinal and radial expansion rate vary widely, and wide differences between species exist also.Are these quantified in planing glue ups, or are rules of thumb generally applied?
Also, any comments on my epoxy experiments would be welcomed.
thanks
willie
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Wooden Boat Magazine? Oh man, I buy that magazine for when I wanna fantasize! Man, there is some mighty fine woodworking done by contributors to that rag!
I am going to go dream about a51 ft L. Frances Herreshoff...."got 80 ft to the waterline, nicely making wake..."
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Russ, resorcinol was awful stuff.
Sounds like it. I have heard the same from others as well.
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Yes, I was kind of disappointed to hear you weren't going to go through with it as an experiment, and I didn't mean at all to be discouraging talking about glue vs oak(s).
It's been a long time since I was boat building, and it's totally different than bows, and so I'm sorry I meandered OT!
I actually hate to laminate using epoxy and thin layers of wood, (always did) much prefer working with whole wood, and especially enjoy what is happening here on PA. Love the bows made from saplings and limbs that I see. That to me is really getting to the heart of of wood working, and a connection with ancient peoples.
Willie, I'm way behind the times on what is current in boatbuilding, so can't say if there are new scantling "rules" other than of thumb for thicknesses in laminating, and, yes absolutely shrinkage and swelling are all over the map for every type of wood, direction of grain, and also individual trees, down to even parts of individual trees. So I would guess that the older rules of thumb still apply in that field. The Gougeon Bros. wrote the book (literally) on wood and epoxy construction back in the 70's, and that book is a must read in that field, if you're interested in the technical aspects.
So I'm going to shut up now, and read about bows again, and try to build this one I'm working on so it lasts more than a month.
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Plan B
thanks for sharing your expertise about glue tech. Btw, I am still building the bow, just changed species to a more experimental one. I am the one that might be disappointed in the results tho, no sense in reinventing the wheel with R.O for a elb.
I hate "goo" also, but in the long run, I have been let down less often by epoxy than anything else.
willlie
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It has been said on here more than a few times, you can learn more from a failure than a victory. That is the other side of the coin from the "no sense re-inventing the wheel".
I am guilty of taking people's advice to NOT do something bowbuilding as a reason to do it anyway, just to see if I can use the knowledge I have already gained to find a work-around to their rules. Most of the time, I come to a deeper understanding of why they consider it a hard and fast rule, but just BARELY often enough I learn how to craft an exception to the rule. This helps me understand those underlying principles better and better.
So let the chips fly, rip some curls, slather some gloopy stuff. Just follow the advice I love to give....POST PICS!
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JW says pics please, so I dusted the sawdust off an old camera.
Its been years since I made a board bow or did any laminating, and to be honest, I gave up on the red oak because I just did not like the grain in either board I had on hand. I did discover an 1 x 3 of soft maple in the pile. It was flat sawn and I did not like the grain much better so I ripped it in half and glued it into a 2 x 2 and took a quarter inch off it for a "rift sawn" backing for the mystery wood belly I found in the Doug Fir stud pile a few months ago. It is browner than the usual DF, straight grained, ha svery fine slinters like bamboo, and smelled like turpentine when I bought it. The last pic is how the sander smears in spots. Its dense and dry with no visible pitch pockets , so I am guessing it is Larch. we will see how it tillers out.
learning lots of good stuff, like, glue in twice the reflex you want it to have after you pull the clamps.
just starting to rough it out, but I will wait a while longer before tilliering to make sure the glue is solid.
Question; How long should I wait with TB3 before floor tillering?
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