Official Luthiers Forum!
http://mowrystrings.luthiersforum.com/forum/

laminated neck glue up fail
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10123&t=24870		 Page 1 of 1
Author:  Stefan [ Thu Dec 03, 2009 12:53 am ]
Post subject:  laminated neck glue up fail
Hello all,

I just glued up two maple bubinga maple bubinga maple necks for a couple of neck through basses I'm starting. Come to take the clamps off and I realize that both necks have a small gap in the glue joint, on the part of the neck that will be the underside of the of the body. There it is, I can just about squeeze my thumb nail in there. I have no idea how far in it goes, maybe just a few millimeters. I guess I could take the gouge and dig in a bit to find out.

How did this happen? I used every clamp in the house, approximately 12 of them. the pieces came straight from the jointer/planar and I used just purchased tightbond. Tightbond says leave unstressed joints clamped for 1/2 hour, I left each for 1 hour clamped and then clamped them both together to let the glue cure.

I guess I could either
1) see how deep the crack goes, and then use the necks,

2) saw the lousey joint apart rejoint and glue. The piece in question is the outer of the 5 piece lam. I may have enough wood on that piece after sawing and jointing or I may have to see if I can saw another couple of pieces from the original plank. If not I have to buy more wood which I can afford, however, I have to let the stuff dry and stabalize for a couple of months.

This wood craft thing is tricky. lately I feel it is 1 step forward two steps back.

Thanks in advance for any thoughts on this.

Stefan
Author:  Bob Garrish [ Thu Dec 03, 2009 1:22 am ]
Post subject:  Re: laminated neck glue up fail
I'd say go with option 2 or the gap will forever nag you.

Jointer errors can leave your pieces convex, which gives the ends a tendency to peel apart. This also makes it a stressed rather than unstressed joint.

So far as stopping a repeat: dry fit. I clamp the cuss out of everything, but for glue evac only. Parts should mate perfectly with nothing but finger pressure.
Author:  JohnAbercrombie [ Thu Dec 03, 2009 1:31 am ]
Post subject:  Re: laminated neck glue up fail
Stefan-
This sort of thing happens to everybody- it's a 'been there, done that' for most of us.

Bob is right on with his advice. Saw it open and re-do.
Things should fit well dry. The clamps can hold the glue-up together and take care of any tendency for the thinner lams to curl when you add the moisture with the glue.
12 clamps is certainly not too many over a bass length. ('Never too many clamps!')
Good cauls help as well.
And, something like that I'd leave overnight (in a reasonably warm shop) , in spite of the instructions.

Cheers
John
Author:  Barry Daniels [ Thu Dec 03, 2009 9:12 am ]
Post subject:  Re: laminated neck glue up fail
12 clamps is not near enough on a long lamination like that. Use as many as you can squeeze in.
Author:  Dennis Leahy [ Thu Dec 03, 2009 12:42 pm ]
Post subject:  Re: laminated neck glue up fail
I'm with Bob that the likely culprit is the jointer, but I'm thinking snipe. It takes a well-tuned and very sharp jointer, taking a light pass, to produce a flat on a 4" wide board as long as a neck. A very minor amount of snipe, say just a few thousandths, is multiplied by the number of lams that have the snipe. If you are unable to set up the jointer to cut completely snipe-free, then you're most logical choice is to use boards that are about 4 to 5 inches too long, knowing that you will simply hack off 2 to 2-1/2 inches off each end after the glue-up.

Dennis
Author:  JohnAbercrombie [ Thu Dec 03, 2009 1:48 pm ]
Post subject:  Re: laminated neck glue up fail
Barry Daniels wrote:
12 clamps is not near enough on a long lamination like that. Use as many as you can squeeze in.

I agree.
And, you can make up clamps with plywood and carriage bolts, etc if you can't find enough cheap clamps available. (They're never 'on sale' the week I need more, it seems.)

Cheers
John
Author:  Stefan [ Thu Dec 03, 2009 7:00 pm ]
Post subject:  Re: laminated neck glue up fail
Ok, more clamps then. But could I then run into an issue of a glue starved joint?
Author:  JohnAbercrombie [ Thu Dec 03, 2009 8:37 pm ]
Post subject:  Re: laminated neck glue up fail
Stefan wrote:
Ok, more clamps then. But could I then run into an issue of a glue starved joint?


My experience is that more clamps, with a bit less pressure, more evenly applied, seems to work better.
The glue starvation issue depends on the glue you are using- some glues require a very thin glue line, others (like epoxy) are more susceptible to starvation.
This can also depend on how much glue/moisture the wood surfaces 'suck out' of the joint.
Most folks only coat one side of the joint with glue- I recall a discussion on this a couple of years ago. When using epoxy a lot, I learned to coat both surfaces (thin and even coats), and I just do this out of habit with most glues now. I think (no proof) that it helps to avoid glue starvation, though there is usually some squeeze-out to deal with.

For a 'big' laminating job like yours, I tend to use epoxy - more open time and it does fill small gaps better. But it is much more expensive (and messy).

Cheers
John
Author:  Stefan [ Fri Dec 04, 2009 5:21 pm ]
Post subject:  Re: laminated neck glue up fail
thanks for all the great advice, everyone

I think I'm going to switch to epoxy for this job. I've used this before:

cold cure:
http://www.leevalley.com/wood/page.aspx?c=2&p=20013&cat=1,110,42965&ap=1 and have a fine neck to show for it.

I'm thinking about this G1 or G2 stuff:

http://www.leevalley.com/wood/page.aspx?c=2&p=20011&cat=1,110,42965&ap=1

Any thoughts on which is the best glue to use? The write up on the G2 stuff says " Ideal where flexibility is required. The joint will yawn rather than fracture." Makes me think it has lousy acoustic properties. for example hide glue will fracture under shock, and that hardness is what makes it acoustically desirable.

I don't think my joint problem is due to snipe as the separation is not at the end of the piece, but rather starts a few inches from the end. When changing jointer knives I'm careful to set the knives to within 1/1000" of the outfeed table. I've found otherwise I end up with a chunk taken off the end.

thanks again for all the great advice,

Stefan
Author:  JohnAbercrombie [ Fri Dec 04, 2009 5:41 pm ]
Post subject:  Re: laminated neck glue up fail
Stefan-
Of the three epoxies you mention, ColdCure would be my choice. I used it years ago on a canoe I built and it was OK.
(BTW, I notice that LeeValley isn't stocking G1 any more, and G2 would definitely not be on my list.)
I do use the G5(?) from the same company - 5 min epoxy, 1:1 ratio- but not for guitar jobs, just quick gluing of jigs, etc.
You may have a local source for these. (?)

No matter what epoxy you choose, you need to know what additives to use (if any). A good source of info is http://www.westsystem.com/ss/use-guides/ - the ideas there apply to any epoxy brand. I would not do any laminating of wood without adding a thickener to the epoxy. I only use 'straight' epoxy when doing fiberglass work or pore filling.

I use WEST epoxy, but it's a bit more expensive when starting out, and you really do need to buy the pumps to meter out the 5:1 ratio properly without wasting epoxy/hardener. (For small jobs you can meter with syringes.)

Another reliable and popular brand is System Three http://www.systemthree.com/index_2.asp - they used to sell a 'Sampler pack' with various additives, etc. Good info at their site as well.

Cheers
John
Author:  MRS [ Sat Dec 05, 2009 11:47 pm ]
Post subject:  Re: laminated neck glue up fail
Everyones least favorite glue (polyurethane glue) works great for resinous woods like this. I use it all the time for glue ups with exotics like this. I prefer the Elmer's polyurethane....Mike
Author:  Mike Kroening [ Mon Dec 07, 2009 10:32 pm ]
Post subject:  Re: laminated neck glue up fail
Stefan wrote:
>snip<

I don't think my joint problem is due to snipe as the separation is not at the end of the piece, but rather starts a few inches from the end. >snip<

Stefan

The area you describe is exactly where planer snipe occurs.

mk
Author:  cocobolo [ Fri Dec 11, 2009 11:14 pm ]
Post subject:  Re: laminated neck glue up fail
Stefan:
Greetings from a fellow Canuck.
It sounds as though your joint separation does not run at 90 degrees to the neck, which would likely be jointer snipe. But it runs lengthways, is that right? If that is the case, then you need to try to determine where the original problem came from.
Here's what I do before any actual gluing.
I ALWAYS do a dry run first. Even if I am doing the same thing over and over again.
For example, I'm presently doing a series of reverse curved laminations, about 50" long. Although everything has been fine so far, you never know when one of your pieces of wood will not clamp up tightly, hence the dry run. Once the dry clamping is done, I mark my triangle on the lams and disassemble. Then with the boards in the same order, do the glue up.
I'm guessing that your glue up is perhaps 40" or so long? Which would require more than 12 clamps, that's for sure. And I assume that you are using an extra clamping board on both sides. If you don't, then one (or both) of the outside boards could easily develop a gap.
I would be using about 30+ clamps for that length.
Now, as to the glue, I would tend to shy away from epoxy. I know it is touted as a cure all for just about everything, but that isn't always the case. Having said that, I should tell you that I used to buy epoxy 6 barrels at a time. So I do have just a little experience.
Since you are a Lee Vally customer, use their 202GF glue. The stuff is amazing. It leaves almost zero glue line and cleans easily.
And as others have suggested, never mind the one or two hour clamping time. Do it in the evening and leave it overnight, preferably somewhere warm.
Good luck.
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/