Bloodwood FB on wenge neck: causing backbow?

billoetjen · #1 12-12-2008, 07:23 PM

Hi Folks,

I have a bass whose tone and look I just love. Warmoth mahogany body with wenge lamtop, Warmoth wenge neck with bloodwood fretboard.
About 8 months after getting the build finished, I started to notice sometime in April that I had to loosen the truss rod more and more to keep even the slightest amount of relief. Pretty soon there was nowhere else to go and the neck ended up with slight backbow (that's with pretty high-tension ECB81 Chromes on it). Of course I called Warmoth before the warranty was up, and their rep gave a much-lamented answer. I could detach it, and pay to ship it to Warmoth and they'll stick it in a heat press. Or, I could find someone local to heatpress it for me. At my expense. Maybe I'm a schmuck, but I didn't go for either idea.
I left everything as is, and now it seems mostly okay. Last Spring was very wet, even by Vermont standards. I'm wondering if the load of moisture caused the bloodwood (notoriously unstable) to expand more than the wenge. I have since read elsewhere that the combination of woods chosen for neck/fretboard can be as important as the choices of the woods, themselves. Does this make sense to you luthiers?

Will a heatpress permanently force the neck back into a proper bow?

How about an application of oil to the fretboard? Will that lock out moisture and prevent future differential expansion? What would you folks recommend? I don't want to do anything to the wenge, which has performed perfectly as a speedy, unfinished neck material.
Thanks again, in advance,

Bill

scottyd · #2 12-12-2008, 09:05 PM

Here is what I'd try, loosen the truss all the way, clamp a straight jointed board to the finger board but put a shim in the center of the board about 9th fret or so. This will force the neck to bow. Lit it sit for a couple of weeks or even longer. Once out of the clamps it should stay and you can readjust your truss how you like.

You should really put some finish on the wenge, even though it is a great wood for raw use moisture and humidity will affect it the same as any other wood. I'd use a good oil finish on the neck and quality fingerboard oil for the blood wood to seal them both.

ewimsatt · #3 12-12-2008, 10:04 PM

You could also probably relieve a lot of back bow by refretting it with the barbs on the tangs shaved off or the slots widened a little bit and the frets glued back in.

tjclem · #4 12-13-2008, 06:45 AM

I didn't know Bloodwood was "notoriously unstable"

Nelson Guitars · #5 12-13-2008, 07:12 AM

Bloodwood is not unstable in my experience.

Doesn't Warmouth use a two way truss rod? Have you tried moving past zero tension and "pushing" the neck the other way?

Just clamping the wood for a time and then releasing will not correct this problem. The heat process they are talking about will do two things. First, it will loosen the glue under the FB enough so that it will slide along the neck ever so slightly if directed to do so by the pressure of clamping a bow into the assembly. Second, if the heat is proper it will soften the lignen in the wood fibers and allow them to slip past each other and bond again when cooled. This will also induce the desired bow/relief.

The problem with the heat procedure is that you run a risk of cracking the finish along the line where the FB meets the neck. If you aren't careful you can also damage the finish just from the heat itself or the fact that it gets soft and your clamping cauls leave marks in it. You have to be really careful and expect to have to repair the finish.

Oiling the FB may help a bit, but even a "solid" finish like lacquer will not stop moisture from getting to the wood. It just slows it down.

The other thing to consider that the neck seems to be changing shape and is not static. If you induce enough relief today will it be too much relief tomorrow? Perhaps what needs to happen is that this instrument will need to be kept in a case with some desiccant when not being played. Control the RH around the instrument and you may get a more stable and playable instrument.

My two bits.

Greg N

phat5 · #6 12-13-2008, 07:41 AM

Very interesting wood combo....May we see some pics of your fine instrument?

Tia, p5

wilser · #7 12-13-2008, 07:44 AM

I would advise against using a heat press as you suggested. I use a heat blanket to remove fingerboards ...so I can only expect the fingerboard->neck bond to be compromised by the use of a heat press.

billoetjen · #8 12-13-2008, 08:56 AM

Crap!

I had a feeling that this wasn't going to be simple.
All good suggestions, all around. But all have at least one drawback.

I can't remember where I saw the references, but I've read on the web (so it must be true) reports from some woodworkers that, with all of bloodwood's positives, it is relatively unstable. So, if it's true, and it responds to moisture more than the wenge does, the combination would have the effect described.
Another piece of evidence... in the stand right next to that bass is my fretless with the same neck but with a pau ferro FB. It is as stable as if it were in a museum case.
Here's a link by the way to pics:

http://entertainment.webshots.com/album/560994103cTNPEe

Lastly, the neck is completely unfinished; which is one of the things I like best about playing this bass. That wenge is wonderful stuff. So cracking the finish is no concern. lifting the FB off of the neck is, though. Maybe a heat press is the way to go, and let the local luthier worry about the adhesive.
Oh, and Warmoth doesn't use 2 way truss rods. Wish they did!!

Thanks, TB members are the BEST!

Bill

joeyl · #9 12-13-2008, 09:01 AM

Doesn't warmoth use a double expanding truss rod? Isn't that the same as a 2 way truss? or am I being mistaken this morning

scottyd · #10 12-13-2008, 09:27 AM

Quote:

Originally Posted by Nelson Guitars

Just clamping the wood for a time and then releasing will not correct this problem.
Greg N

Nope sorry, have to disagree, this has worked in many cases. It's obvious that the neck is having problems because of it's lack of finish. It's not like the neck was built with a back bow. Moisture and humidity will sooner or later warp wood no matter what species it is. If the neck was once straight it can be so again without use of heat or the glue needing to be realeased. It's roughly the same process as when you sticker stack wood in your shop but with a little mechanical force.

Bill heating the neck is a drastic step. I would advise you try the other method first, it's easy and if it does not work, you've lost nothing.

Nelson Guitars · #11 12-13-2008, 10:12 AM

Well we will have to disagree then scottyd. Unless the clamping pressure is sufficient enough to make a physical change to the neck assembly (Tear wood fiber. Move a cold glue joint.) the wood should be sufficiently strong and stable enough to want to return to its original shape. That is one of the properties we look for in neck material, stability and resistance to change under normal conditions.

I understand the reluctance to use heat to manipulate the neck but it is a time honored technique that when done properly works rather well. I have used it many times to correct bowed necks on classical guitars where there is no truss rod to make an easy adjustment. True, these were for the most part very old instruments and likely used hide glue that can endure those sorts of temperatures without loosing any bond strength. I am not sure what would happen if epoxy or other types of glue were used. You have to watch your temperature closely and move very slowly, but it can be done and the fix stays fixed.

Here is language direct from Warmouth's web page on warranty for neck warping.

All our necks are dipped in an oil based penetrating sealer which is compatible with virtually all secondary finishes. This provides enhanced stability; however, it is not adequate protection for playing. We strongly recommend you apply a hard finish to all Maple, Mahogany, and Koa necks. Oils do not validate our warranty requirements.

We understand the attraction of raw or lightly oiled necks. They feel fast and are not sticky. Unfortunately, they are much more susceptible to moisture related warping and twisting. Our experience is that hard finished necks seldom warp. Less than 1 out of 200 (0.5%) are returned for warpage. Raw or oiled necks don't fare as well. About 10% are rendered useless from the torture. The more acidic your perspiration, the higher the odds are against you.

If you must play a raw neck, that's cool; it's ok. A neck is just a tool. Just be aware of the risk. If yours does the pretzel act, we don't want to hear about it.

For a valid warranty, a hard finish must be sufficiently thick to completely cover the wood. That means no wood is exposed and you are actually playing on the finish, not the wood. Now, it does not matter to us who applies the finish. Of course we would like to do the finish for you, but if you choose to do it yourself or have it done elsewhere the warranty is still valid.

I hope that helps.

Greg N

scottyd · #12 12-13-2008, 10:49 AM

Quote:

Originally Posted by Nelson Guitars

[i]All our necks are dipped in an oil based penetrating sealer which is compatible with virtually all secondary finishes. This provides enhanced stability; however, it is not adequate protection for playing. We strongly recommend you apply a hard finish to all Maple, Mahogany, and Koa necks. Oils do not validate our warranty requirements.

We understand the attraction of raw or lightly oiled necks. They feel fast and are not sticky. Unfortunately, they are much more susceptible to moisture related warping and twisting. Our experience is that hard finished necks seldom warp. Less than 1 out of 200 (0.5%) are returned for warpage. Raw or oiled necks don't fare as well. About 10% are rendered useless from the torture. The more acidic your perspiration, the higher the odds are against you.

If you must play a raw neck, that's cool; it's ok. A neck is just a tool. Just be aware of the risk. If yours does the pretzel act, we don't want to hear about it.

For a valid warranty, a hard finish must be sufficiently thick to completely cover the wood. That means no wood is exposed and you are actually playing on the finish, not the wood. Now, it does not matter to us who applies the finish. Of course we would like to do the finish for you, but if you choose to do it yourself or have it done elsewhere the warranty is still valid.

There's is a good amount of difference between an oil sealor and a quality oil finish such as Tru-oil.

billoetjen · #13 12-13-2008, 11:35 AM

Also on the Warmoth site: no finish required for wenge or any of several wood species used in their necks.
Now, confession time to ScottyD. I tried something very similar to your clamping suggestion. Left it for about a week with quite a bit of force on it. In the short term it worked well. But the woods have been gradually working their way back towards (but not completely) the backbow. May be something that I need to repeat from time to time.
To Phat5, appearance-wise, I like the way the wenge headstock visually matches up with the lam-top, and they're all tied together by the neck.

The phenomenon that I suspect to be at work here is like the bi-metal strip they used to use in house thermostats. Heat makes one side expand slightly more than the other, causing it to bend. In this case, moisture causes the FB to expand slightly more than the back of the neck. Perhaps the Pau Ferro of my FL (also unfinished neck) is more responds to moisture to the same degree as the wenge.
Whew, that's as technically theoretical as I ever want to get concerning my bass.

Thanks again,
B

scottyd · #14 12-13-2008, 11:55 AM

Quote:

Originally Posted by billoetjen

Also on the Warmoth site: no finish required for wenge or any of several wood species used in their necks.
Now, confession time to ScottyD. I tried something very similar to your clamping suggestion. Left it for about a week with quite a bit of force on it. In the short term it worked well. But the woods have been gradually working their way back towards (but not completely) the backbow. May be something that I need to repeat from time to time.
To Phat5, appearance-wise, I like the way the wenge headstock visually matches up with the lam-top, and they're all tied together by the neck.

The phenomenon that I suspect to be at work here is like the bi-metal strip they used to use in house thermostats. Heat makes one side expand slightly more than the other, causing it to bend. In this case, moisture causes the FB to expand slightly more than the back of the neck. Perhaps the Pau Ferro of my FL (also unfinished neck) is more responds to moisture to the same degree as the wenge.
Whew, that's as technically theoretical as I ever want to get concerning my bass.

Thanks again,
B

I think if you do it again and afterwards finish the neck you'll be good to go. Either way I wish you luck in getting it worked out.