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Main Boards => The Bowyer's Bench => Topic started by: GaryB on March 18, 2009, 11:42:00 PM
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I was almost finished tillering and shaping the limbs when out of nowhere one of them developed a hard twist. Before I was able to destring it, it delamed and snapped the outer 7 or 8 inches off the limb. As I sat there in disbelief, I gave the glass a tug and it pealed off the wenge tapers leaving exactly the same surface I spread the smooth-on on to. The wenge has no evidence of glue on it. It looks like it repelled the glue.
I'm not sure what I did wrong, but this is what I did. After the dry run I cleaned all surfaces with acetone. I preheated glass and tapers in the hotbox (150 deg. for about two hours) and warmed up the glue. In my delam paranoia, I decided to clean everything with acetone again incase the heat pulled any oils to the surface. I only gave the acetone about 10 minutes to evaporate. I then mixed the glue 1 to 1 and applied it to the surfaces, stacked the lams with the riser, lined everything up, pumped up the fire hose to 65 lbs. and put it all in the hot box for about 8 hours at 150 deg. and let cool for 10 hours. The glue lines looked good to me. Although, this was my first, so I really don't have anything to compare it to.
I really don't know what I did wrong. I live in Alaska and the temps have been well below zero. It's possible the glue froze in shipping. Did I screw up by cleaning with acetone and not letting it dry long enough? Was the wenge the problem? I used maple for the other lams and they seemed to adhere better. Any Ideas?
A couple buddies and I have got the bug and when the bow delamed I was pretty disenchanted by the whole thing. Anybody have any sources for bulk smooth-on, glass, laminations and other supplies. The shipping charges are killing us when ordering when ordering anything from the lower 48. We are considering making our own parallels and tapers. Any help would be greatly appreciated.
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From your description I think the wenge was the problem.Perhaps the acetone drew out more oils or the surface of the wood was too smooth. I don't use acetone on any part of a bow before glue up. Others do. I use a stiff brisled brush that I only use for cleaning bow parts. It has worked well for me.
When building bows some are going to break. It is the nature of the beast. While disenchanting the best cure I know of is to start another.
Can't help on the bulk supplies but making your own lams is doable if you have access to a drum sander or you can build your own lam grinder.
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What was the temperature of your shop and the smooth-on during mixing of the glue? I had a similar problem on a couple of bows I glued in my shop with temps in mid 50's. Came to find out that the smooth-on needs to be mixed at 70 or better for the the proper reaction to take place between the two parts. This came directly from a rep at smooth-on. I now heat the shop and glue before mixing and have had no problems. Hope this helps.
Ken
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use paper towels and don't reuse, and did you put glue on both side of your wood lams??
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I have had problems with smooth-on with temps in the 50's or below. Now we heat the shop and glue before glueing up.
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Thnx PV,
I'm with you. I think the wenge/acetone combination had something to do with it. All other joints held together fairly well.
It took me not more than fifteen minutes to start planning my next bow. thanks for the encouragement. I do have access to a drum sander. Do you know where I can get my hands on a set of plans for the sled?
Ken E,
Yeah I thought about that. My shop is normally quite cool, but I turned the heat way up before I applied the glue. Above 70 deg.
Tim-flood,
I used rags not paper towels, but they were clean. I did spread glue on both surfaces.
Bowana,
How do you heat the glue? And to what temperature.
Thanks for the help.
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GaryB, We have a oven (hotbox) we made for glueing up the bows. It has a couple of 200 watt bulbs in it and heats up to 150 to 180 degrees. I usually let the smooth-on heat up for about 30 minutes before mixing and glue-up. Temp is only about 80-90 degrees for the short time the glue is in there. Hope this helps.
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Thanks Bowana.
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Gary you can build a sled with a pair of tapers.
I just picked up a real drum sander and have been making up sleds today. My computer is screwed up unfortunately and I can't post pics so I'll try to describe it.
Glue up a block of plywood large enough to end up with a squared up 2 1/2" D X4 1/2" W X36"L plank.
Use double sided tape to tape a pair of tapers to the bottom of the plank and run it through the drum sander. I put a stop block at the butt end to hold the lams in place for grinding.
Make sure the tapers are a matched pair as you will be duplicating whatever they are. I check them on my cast iron table saw. It is the truest surface I have in the shop.
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That's simple enough. My buddy has a couple sets of tapers that I can use. thanks a ton PV.
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If you just spend a little while thinking it over a sled ain't that hard to make. As far as the glue goes I do not have the cold weather problems some of you guys have. I live in central Texas and it seldom even freezed here. But if it is under 70 degrees in my shop I law the two cans of Smooth On on my little oil filled radiator and rotate them for a spell. It also makes the glue easier to measure out equally and to spread. I will also heat my lams just a bit with a heat gun on low. If you are interest in ordering some bulk lams for your bows I can help you out. Bob
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Thanks Bob.
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I had the same problem on some Bocote lams that I used acetone on. It seems that even acetone leaves an oily residue because it is not 100% glue. I was told to just sand with 36 grit brush off and glue.
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I use acetone to clean all of my lams and not had any problems with 100+ bows last year. I did however have a problem with one bow I made for myself of Chechen. It was the first time I had used this type of wood. Not thinking, I didin't test moisture content. I made a two piece takedown bow about 85lbs and when stringing it on my bench stringer, it delaminated from the handle to the tip. Almost completely clean separation between chechen veneer and uniweft inner lam. Bewildered, I checked the wood from witch I cut the lams from and tested 12% moisture content. I am convinced that I found the problem.
I have heard storied of poor quality acetone bought from places like Home D and Lowe's but can't validate them.
BigJim
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Yes me too. They say that if you wipe 100% pure acetone on a window it will evaporate completely and the cheap stuff will leave a residue. I was using the cheap stuff from Lowes.
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For a sled just get the thickest lamination's you can fined,action wood is the best blank's,I have found.I actetone everything with just a rag but I don't use the same rag twice.But you never said about how you strung your bow did you used a stringer or a device it might of delaminated bye way of one limb twisting more than the other.
I have never warm the glue up,and they sit on the cement floor until I need them and my hot box is outside but it is built of a special utilitdor R20 material,with 4 200 watt light bulb's.My temp is about 180'f
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i did have that problem one time with some bloodwood. it shot really well for about 2 months. then i left in the sun in my car for about 1 hrs on a cold day, but that was enough for the belly lam on the bottom limb to let go. i also had it still strung. i now use a brass bristle brush that is some soft. It cleans everything pretty darn good.
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Good stuff guys. Thanks! I used a stringer to string it grey hawk. It did twist and slip off once while stringing.