Centerboard bummer

[sscoville]

I was just about to glue the "handle" on my centerboard.  I had the rest of it shaped already.  I happened to drop the cutoff of the laminated board and it split in two, breaking at one of the joints.  There was a visual gap I could see light through at that joint already - why I positioned it to be cut off when I shaped the board.  But, I thought, the glue should be stronger than the wood.  So, I slapped another piece of cutoff on my table and a piece of it broke off. 

I proceeded to beat my centerboard into several pieces.  I did something wrong when I glued it up and I need your help to do it right the second time.  I used yellow pine - not overly sappy - but you can smell the pine when you cut it.  I did not thicken the epoxy when I laminated the pieces (I suspect I should have thickened and this is the problem).  I adjusted my clamps more than once to make sure I had no gaps, but was not over clamping.  Anyhow, I glued the lamination at least 3 weeks ago. 

The pieces were joined together on their finished surfaces.

Talk to me.

[paul_stewart]

When you look at the broken epoxy joint is the epoxy still adhering to both pieces of wood? if "yes" then the epoxy adhered to the wood but the epoxy itself fractured as if brittle.  If "no" then the epoxy stayed intact but did not adhere to the wood.  If "yes" and "no" then the epoxy did not adhere in some places and some parts of the epoxy was brittle and fractured.  Another possibility is that the wood splintered, but it sounds like that is not the case.  I'd have to guess there was a mistake mixing the epoxy which is where most problems seem to originate.  (Defective resin or defective hardener is not as likely, I would have to guess.)  Too much hardener yields a softer weaker epoxy.  Too little hardener yields a hard brittle epoxy. 

[Charlie Jones]

Only thing I might suggest is that yellow pine is a resiny wood, if it's true yellow pine.. I'd make the CB from something else- fir perhaps.

If you must use yellow pine, I'd wash the surfaces with acetone just before applying the epoxy, which certainly should be thickened- the thickening holds epoxy in the joint.

Thicken the epoxy in any case.

[Joe Anderson]

As much as it hurts it is far better to discover the problem now than while making a critical passage.

I think your suspicions are correct. Unthickened epoxy is not suitable for laminating. When you turn your back it is likely to run out of the joint or soak into the wood leaving precious little behind to hold the joint together.

Gougeons describe four epoxy thickness. And their applications

Syrup: Unthickened epoxy for coating or applying fiberglass.

Catsup:  Laminating flat panels with large surface areas.

Mayonnaise: general bonding, filleting

Peanut Butter: Gap filling, filleting, fairing, bonding uneven surfaces.

Before Ray asks if I am gluing my boat together with catsup I want to say.

You do not actually use catsup or mayonnaise but you add fumed silica, wood flour or some other filler of your choice to obtain the desired consistency and characteristics.

[ftp=ftp://Raka.com]Raka.com[/ftp]  click on User Manuals

Good Luck

[sscoville]

Some of the joints seem to have bonded well.  I used yellow pine because it's readily available and much denser than cypress, which I use for most all else. 

[PAR]

It's quite probable a simple case of joint starvation. Many of the pines will suck up resin like a sponge, leaving you a dry joint when clamped. I've coated SYP just to come back 15 minutes later and see areas that look like they've never seen resin. An acetone or denatured alcohol bath, just before applying the wet out coats helps a lot.

Other then bright work, I have never found occasion where I didn't need some sort of filler material in the glue that I was making.

Wet the wood out carefully and completely, then apply thickened goo, then just enough pressure to bring the parts in complete contact.

SYP is a great centerboard wood, stiff, rot resistant, strong, dense, easily machined, etc., way better than Douglas fir in my opinion.

[JeffM]

Graham suggests wetting out the wood, then letting it set (so you know the wood is done absorbing it) before gluing with thickened.  That way you also don't get a problem with the prior unthickened epoxy mixing with and thinning the thickened stuff.

[Ken_Potts]

  I had exactly the same problem with a kayak I built (whick is currently returning to the earth in the back yard).  I built this kayak before I learned about filler.  Use colloidal silica or something similar to make joints between two pieces of wood - Every time.  Based on the information you provided this could be the only problem and the filler should be the first solution you explore.  Try it on a couple pieces of scrap (that don't already have epoxy on them) and you'll be pleasantly surprised.  You're about to build a bombproof centerboard. 

[Charlie Jones]

Graham suggests wetting out the wood, then letting it set (so you know the wood is done absorbing it) before gluing with thickened.  That way you also don't get a problem with the prior unthickened epoxy mixing with and thinning the thickened stuff.

Jeff- doing that is or should be, standard operating procedure. The Gougeon's have recommended it for years.

And folks- TRUE southern yellow pine is becoming as rare as hens teeth. It grows far to slowly  for the new commercial interests to bother with it . In fact,on my 70 acres of pine in east Texas, I MAY have three trees of TRUE Southern Yellow Pine.

When you cut it, you can take the sawdust, squeeze it into a ball, and it will STAY in a ball.I made the keel on the Princess I built from Yellow Pine- it was a 4 x 4 chunk from  a 105 year old house and had 162 growth rings in 4 inches

[sscoville]

I could be mistaken on this, but I think "Southern Yellow Pine" is generic for several species in the lumber industry - shortleaf, longleaf, loblolly, and slash according to one website.  My understanding is that Longleaf Yellow Pine does in fact grow very slowly, is rot resistent (at least the heartwood, has long been used in boatbuilding, and is very strong and dense.  I don't know what particular species my selection is.  I was told by an old hand at the lumber yard that the best way to try to identify the longleaf when looking at "Southern Yellow Pine" is to look at the growth rings for indications that the tree grew very slowly.

I also found this: "Southern Pine has long been the preferred species for pressure treatment because of its unique cellular structure that permits deep, uniform penetration of preservatives. Some 85% of all pressure-treated wood produced in the U.S. is Southern Pine."  This might help explain my problem and is consistent with what someone else said above - the wood may have starved my joints by absorbing much of the epoxy. 

I always try to precoat, but I probably have never waited long enough to see absorbtion.

Instead of starting from scratch, I think I'm going to attempt to disassemble all the pieces of the board, sand them, clean with acetone or something, precoat, then glue with thickened epoxy.

One more lesson in the bag.

[sscoville]

Also, I see longleaf pine scattered around here in the lowcountry of S.C. - I have a few in my yard and several in my neighborhood.  They're all young though.  Several areas around here that are protected preserves have a good bit.  I wish the lumber companies would plant more.  Interestingly, I was down at Disney World in the Spring and noticed much of the forest down there was nothing but longleaf and saw palmettos.

[Charlie Jones]

I guess it's a matter of terminology. I grew up calling longleaf Yellow Pine the "southern Yellow" My grand dad worked in a sawmill and that's how he defined it. The cones are even very different.

That 4 x 4 I referred to earlier was from a 105 year old house. BUT- we cut slices off the end and arranged then in a rough circle so the rings would sorta line up. We figured the balk came from about 8 inches out from center. Given 162 growth rings in what we had, and adding  8 more inches, we figured that tree was growing during the American Revolution, or before.

NO company is gonna bother today, with planting a tree that takes that long to mature, sad to say. And the real longleaf is very scarce now in millable quantities. Again, sad to say.

But there's some out there in old "to be torn down" buildings. I used to search it out.

And same goes for Fir- I found some fir 1x6s (FULL 1 x 6) that had been in a closed lumber yard for they estimated for 30 years, laying on a shelf. HARD stuff! Also acquired some Fir 2 x 10s that had been replaced in some high school bleachers- those boards had been on the seats for 35 years and I had them another 12- I used some of that for keel strips on a CS 17 and CS 20 I built. Grain ran from one end to the other- 16 foot long boards. Nothing like that available today. Now we are buying at least second growth, if not third or forth, at least down here- up in the NW, Fir like that may still be being cut.