Aerodux questions

[The Schooner Etain]

Ok, I'm getting ready to put the new stem on my boat as most of you know. I've decided to laminate it together using aerodux 500 and I just want to make sure I have it right.

I went out and bought my white oak the other day, got 12 nice boards about 10' long in 2x6 and 2x8. I'm getting them cut down the center to make them only 1" thick, and I've hired a guy at the yard to make the jig and steam bend them for me while I am still working. By the time I'm done he should be ready to help me glue them up.

I bought the fast mix Aerodux, so I know the minimum temp is 50 degrees for full cure, which is better for me since I'm alittle further north and the weather here is starting to turn cold. What other prep do I need to do to the wood? A light sanding...wipe with acetone etc.

Also, do I treat each piece of wood with CPES before the glueing, or do I glue and then treat the whole thing?

Thanks for the advice in advance,
Chris

[ 10-05-2002, 07:56 PM: Message edited by: The Schooner Etain ]

[The Schooner Etain]

Almost forgot some pictures for you guys.

http://www.imagestation.com/picture/sraid34/p1a929f64861231f974dd6cf821ea3b0e/fd336156.jpg

These planks are through bolted to two more on the other side, so the hull planks won't open up on me while I swtich the stem over.

http://www.imagestation.com/picture/sraid34/p1bd66ae5912d63b4a8da03f0e94afce0/fd336155.jpg

Right above that hole is the threaded rod that used to keep the stem on. It ran right through the stem and let the water run right through it as well. Thus the rot and the hole.

http://www.imagestation.com/picture/sraid34/p4a870127911b007d25655789d71ab84b/fd336152.jpg

I had to shore up the old stem, it was about to come right off in my hand.

Hope it gives you guys a better idea what I'm dealing with.

Chris

[ 10-05-2002, 07:58 PM: Message edited by: The Schooner Etain ]

[Bob Cleek]

Well, there are lots of guys in here with more experience than I have laminating larger hunks of wood, but... I wouldn't try to laminate a curved stem out of one inch oak and I sure wouldn't steam bend it first. Far as I have ever seen, the usual practice is to keep the laminates down to around a quarter inch. This eliminates the need to steam bend them. Steaming would probably limit the springback problem, but still, the thinner laminates will eliminate it. Remember, too, the bigger the piece, the more it will swell. This fact is one reason that delamination problems are more prevalent in gluing up big pieces. Sorry... but maybe others can weigh in on this. I'd hate to see you run into problems and ruin your stock trying to bend one inch stuff. I could be wrong, though... it's happened before.

[Carlsboats]

I have had good luck using resorcinol resin glue on bent white oak. Did some laminated ribs in a sailboat that way and they have stayed nice and tight for about 35 years. But if you have to steam bend the laminates, I would bend them first, let them dry in place -- on a jig or on the boat-- then take them apart and apply the glue. You'll need some pressure -- more than would
be required with epoxy -- and the Aerodux probably should be thickened with the approved filler. Consult with the Aerodux distributor to see if they agree. They have been helpful to me, and the people I talked with seemed to be very knowledgeable.

[NormMessinger]

Neither has responded to the CPES question yet. YIKES! Surely not with Aerodux. Best call the supplier first before you do something like that.

--Norm

[thechemist]

Originally posted by NormMessinger:
Neither has responded to the CPES question yet. YIKES! Surely not with Aerodux. Best call the supplier first before you do something like that.

--NormCall BOTH suppliers.

[thechemist]

Originally posted by Bob Cleek:
Well, there are lots of guys in here with more experience than I have laminating larger hunks of wood, but... I wouldn't try to laminate a curved stem out of one inch oak and I sure wouldn't steam bend it first. Far as I have ever seen, the usual practice is to keep the laminates down to around a quarter inch. This eliminates the need to steam bend them. Steaming would probably limit the springback problem, but still, the thinner laminates will eliminate it. Remember, too, the bigger the piece, the more it will swell. This fact is one reason that delamination problems are more prevalent in gluing up big pieces. Sorry... but maybe others can weigh in on this. I'd hate to see you run into problems and ruin your stock trying to bend one inch stuff. I could be wrong, though... it's happened before.But so rarely that you have to misspeak once in a while just to maintain the air of fallibility, thus leading us to believe that The Committee is composed of ordinary humans who are occasionally wrong, right?

I see it the opposite way.

Steam bending should give a piece of wood with no residual springback, no residual shape memory, sitting there on the bench at room temperature, if I understand what the process does.

Gluing thin laminates results in small shear stresses at each glue line, both from the spring-back force [shape memory] which is STILL THERE at room temperature [if merely bent and glued but not steam-bent]. The thin laminates are only constrained from movement by the elastic modulus [up to the shear strength of the glue] and of the wood. It follows that a stiff glue such as WEST, gluing oak, may fail sooner than a more flexible one.

If wood shear stress exceeds 200-300psi, the glue joint is likely to fail. If the glue has insufficient flexibility, then moisture absorption will cause expansion slightly different in each piece of laminate, and THOSE differential movements may shear the wood at the wood-glue interface. Thicker glue lines, clamped with less stress, a more flexible glue and thinner laminates all favor survival.

The strength of a vertically-stressed beam varies as the square of the vertical dimension, and so I would expect the spring-back force to vary as the square of the lamination thickness.

Since these glue joints usually fail by cleavage at the ends, one should install screws or splines in the lamination ends, going through all the laminations, to help the structure resist such failures.

Reasonably matched grain orientations of the pieces being laminated will also help resist failures, as tangential hydrolytic expansion is about double that of radial, for most woods.

[Dave Fleming]

Springback on Steam Bent Frames, theoretically perhaps no ( is that proper English?), but in reality yes it can happen. Steam bent two Oak frames approx 2 inches x 4 inches, clamped in place, same station port and starboard, left in place on ribbands over weekend, a good 48 hours. We came back and, had to remove them for some other adjustments to bilge stringers before fastening them in place. Laid them atop one another for space saving and IIRC, they were identical. Several days passed and when it came time to put them back in and fasten, one had spread about 2 inches further than the other.
We had crayoned the location, port/starboard, on them and we tried them in place. The one was a glove fit whilst the other, one that moved, needed some serious clamp work to get back into shape. It worked and we breathed a bit easier but we kept a good eye on that one for seveal days to see if it might split at the S curve. It didn't, thankgoodness.
I also did one goo goo job on a doghouse for a Atkin Eric and though the camber was not as extreme a curve as those steam bend frames I bored and inserted, same wood, dowels from the top or hidden side at various angles to prevent any creeping/springback after taking from the glue up jig.
The dowels were inserted into bored holes with a bit of buttering of the goo before hand.

[Dave Fleming]

Question, how does one get 1 inch net rippings out of 2 inch net stock?
No loss to saw kerf and planer work, hmmm.

[Bob Cleek]

No real dispute among the Committee here, just a minor discrepancy between theory and practice. True, you wouldn't think a steam bent piece would spring back, and I wouldn't expect it to, except that in order to get it all to come out right, the process is pretty tricky and you always seem to be muscling it all into place. Fact is, with the stock he's describing, I'd be thinking about laying up the laminates, if 1" scantlings, with the seams running parallel to the molded dimension. It would sure make cutting the rabbet a lot easier.

[Jim Mathieson]

As far as Aerodux500 fillers are concerned ,I asked Brian Pritcher of Custom Paks ,that 20% filler question last week while ordering a gallon kit of A500.Brian forwarded the following to me :
quote"It will not be possible to get as much fibrous filler (ie wood flour) into Aerodux 500 as with China Clay.The precise quantities have to be determined as each filler has different surface areas.
The cheapest filler and the one where the most extension can be obtained is chalk (calcium carbonate).This has the added advantage that it is slightly alkaline and will acceletate the cure.
Wood flour or some mineral fillers may be added to increase the viscosity and reduce glue costs.
Lightly Filled Mix:
Parts by weight:
Aerodux 500 100
Hardener 100
China Clay 40
The Lightly filled mix still complies with the requirements of BS 1204.
PART
1(Type WBP)" end quote
So it sounds like China Clay is the best filler since it meets BS 1204 standards.
I was thinking what result applying CPES before gluing with Aerodux would have also.CPES adverts claim " it makes paints, varnish ,stains ADHESIVES &caulking stick and last"
I'm thinking of applying CPES to the inside of 2 Sitka Spruce masts and was wondering what effect it would have on the Birds mouth joint when then glued with Aerodux 500.?I'll ask the manufacturers as suggested.
Jim

[The Schooner Etain]

Yes yes Dave, your right, you don't get 1" from ripping 2" stock, there will be some loss there, I know that silly...but it was easier than saying 14/16ths. smile.gif

The plan right now, just to clarify, is to take 6" wide x 1" (approx.) thick x about 10' long boards and glue them together along the lengths. So the grain, which is quite straight, runs the length of the stem. So, the first board will be bent to the inside of the old stem, and run from the keel up 10' where it will be scarfed into another board to make the total distance of the inside of the old stem. Scarfs will be offset from each other of coarse.

The old stem is about 8" at it's thickest point, so we're looking at a total of 8 pieces of quarter sawn white oak laminated to each other. The only real curve is the one at the keel, the curve at the top will be a seperate piece of solid stock to make through bolting to the bowsprit easier. There is also two through bolts that run through the stem into the frames of the boat. I don't think those bolts should weaken the laminate too badly, they seemed to be fine for the solid lumber.

If all this isn't making sense, please let me know, but it sounds right to my ears.

Chemist, I'm going to talk to the suppliers of the Aerodux and the CPES, but what are your thoughts on using the two compounds together?

Thanks,
Chris

[thechemist]

Originally posted by The Schooner Etain:
<snip>
Chemist, I'm going to talk to the suppliers of the Aerodux and the CPES, but what are your thoughts on using the two compounds together?

Thanks,
ChrisAerodux is, from what I saw from a quick forum search, a resorcinol adhesive. These require well-fitting joints, clean wood and temperature control for proper cure. Thick glue lines, irregular-fitting pieces and cold nights will guarantee failure, and take you into the province where epoxy adhesives excel.

If you put on CPES for any of its impregnating benefits, guessing blindly, never having done the experiments, I would say be sure the solvents have evaporated and sand the surface clean. CPES on the surfaces to be glued with a resorcinol adhesive might make the bond better, or screw it up. I would have to do an experiment to say for sure.

[ion barnes]

Etain, Yes you should expect springback therfore the jig should be shaped to allow for it. The thickness of the strips is dependant on the amount of cuvature. The tighter the radius the thinner the the strips. TAUNTON BOOKS AND VIDEOS has in their series of books on Fine Woodworking, on volume about bending wood . Cost $14 cdn. Other help would be Boatbuilding with West System,or Ian Nicholsons" book on laminated and strip planking. Personally I would use epoxy but I dont know all your if,ands or buts.

[Seth Wood]

I asked the suppliers this same question some time ago. Their answer: do not glue anything but bare wood. CPES goes on AFTER, otherwise it could interfere with the glue. Especially if you're using resorcinol.

This is critical: I've had lamination failures due to surface contamination.

Make sure the wood surfaces are clean of contamination but also not mirror-smooth. Maybe sand with 80-120 grit, nothing finer, then wipe down with a tack cloth. Clamp well. Then CPES goes on after it's all together.

You can probably search the archives for my mis-experiences laminating 1x10s...

[The Schooner Etain]

Just got an e-mail reply back from the CPES guy. Seth is definately correct. Resorcinol based glues will not hold properly if used on wood already coated with CPES. You really must glue it first, then coat.

As for the steam bending...he had some thoughts on that as well. Although he said that he personally would go with 1/2" thick wood for the laminates, he didn't say I was wrong. smile.gif
He did mention that I should steam bend them, then let them sit for several days before glueing, which is what was in line with my plan anyways.

I'll keep you all informed of how this works out as I go along.

Chris