Twin Neck Lap Steel Problem

[ozziebluesman]

G'day all,

I am building a twin neck lap steel for a friend. One of the bodies has a small split that has developed. I don't think it will move any further!

What do you think?

Any suggestions on a best method to fix the problem area?

I am planning a hard shellac finish!




Cheers

Alan

[J.F. Custom]

Hi Alan,

Hmmm. I would be guessing that you have either just cut this body shape out or that you've had some changes in climatic conditions in the last few days. The cracking has occurred along the medullary rays indicating shrinkage with the orientation of the grain - woods internal attempt at cupping. This sometimes occurs due to - moisture still in the timber being suddenly released; or changing the timber dimensionally releasing new tension; or change in atmosphere or potentially case hardening. This is my thinking anyway.

One other consideration here is the heat from the sanding. It would appear you have used a disc sander on the end grain. Make sure you are using a new disc that cuts quickly and effectively because end grain is tough and heat can build up quickly which can cause issues such as this too. Something to think about.

I would use some high quality thin cyanoacrylate (super) glue such as Hot Stuff. Use a needlepoint tip and let it wick into the crack. Give it plenty then clamp gently from edge to edge of the body to bring the crack back together. There will likely be some squeeze out which you can clean up when its dry. Allow it to dry for as long as possible before removing the clamps. This shouldn't cause any problem with your intended finish.

From the photo though to my eyes, it appears there are a few more checks in the end grain where the moisture change is most severe. If so, I would wick these up with some super glue as well. After all this, I would look at sealing the end grain as soon as possible - even if only temporarily as I would suggest the problem may continue if left as is. This should prevent any further checking until you can fully finish it.

I'm sure others will chime in with their opinions.

Good luck,

Jeremy.

[jeffhigh]

Hi Allan.
I don't think you are going to be able to clamp that shut.
I would tape up the end, fill the crack with sanding dust and then wick in the CA.
May not be totally invisible though.
I would also leave it a month to see if anything else happens before committing mor time to this blank.
Jeff

[J.F. Custom]

Hi again Alan,

Just for clarification - when I said "gently" clamp, the idea is to bring the gap closer making it less visible, not necessarily to close it entirely. Enough clamp pressure would certainly close it entirely, however it could be counterproductive in that you would be creating more tension through the piece again. How much pressure is a judgement you would have to make on the piece itself and how easily it wants to reverse. Sawdust will of course also make it less visible.

Further to my initial reply and in a similar vein to Jeff, I should have also mentioned the concern of the pieces stability overall now. I would do as I mentioned initially in wicking the cracks, then sealing the end grain to slow any further rapid moisture changes in the piece. Then watch it over the next period to see if it settles or continues to check or move etc. If it does the latter, you would probably be chasing your tail trying to continue with it.

Cheers,

Jeremy.

[ozziebluesman]

Thank you Jeremy and Jeff for your advice. The weather here has been hot and humid 65 70% for months. About three weeks ago there was a shift in the humidity and for a week it went down to 30% for a few days. The humidity went up again and the past few days it has gone down to 30% again. So I suspect that environment has contributed to this crack developing.

I have some thin CA from Stew Mac. Will that do the trick?

Do I fill the crack with saw dust first and then wick in the CA?

Thanks again

Cheers

Alan

[Localele]

Yes Alan and as you do up the clamp apply pressure and then release a few times to help pump the CA down into the crack.Put plenty on above the crack so there is enough to draw down in. Cheers.

[ozziebluesman]

Would you believe over night the humidity level has changed and is now 53% and this damn crack has closed up. Guess I will have to keep a close eye on it and repair when it opens up again. Or would I be better to fill it with CA glue now and clamp? There is no way I am going to get any wood dust down there now!

Cheers

Alan