Commander 147

[Commander227]

Looking great Jerry! Your companion way looks first rate. I wish I had the old style. My strong back is of similar dimensions and also white oak. I used West sys. and stainless dowels. Its only been two years but it hasn't busted yet, knock on wood. I like the look of your bulkhead.... but dude.... chicks dig doors!
Mike
C227

[Commander 147]

But the three "chicks" that matter most to me are the admiral and my two grown daughters who are all OK with the curtain as long as there is a mechanical means of keeping it closed when in use. And the admiral has a custom window treatment business and already knows how she plans to make it. So I guess I'm lucky this time.

I spent some time today making templates for the new bulkheads. So far they are just partial templates, I need to do some demo tomorrow to make the bottom part but tonight I want to start bandsawing the strong back. Here is a picture with the partial templates in place with the template for the strong back. I tried in the second picture to stitch two pictures together to get a more complete view of the whole area but it only "kind" of worked.

The layout did not work out quite like I thought it would. I tried to make the upper portion of the bulkhead slant parallel to the cabin side. And I wanted 10" of support under each side of the strong back. What you see is the result of those efforts.

[Commander 147]

I just was not happy with the look of the bulk heads yesterday so today I took another inch off both sides and I'm much happier with the look of the layout. See for yourself below.

My biggest concern is that now I have 2 more inches of unsupported distance between the bulkheads. The total distance unsupported is 35-3/4". I know the beam will be stronger when glassed to the deck tying it all together but I still feel the need to find some way to test the strength of the beam. I would like to see it capable of handling 2500 lbs. Do any of you have any suggestions?

[ebb]

2 cents worth.
Early on in A338 I decided to replace the original sawn beam with a laminated one out of white oak and epoxy. Not the best choice.
On the last current page in ebb's gallery thread you can read what I later decided to do
because I really don't think that white oak can be glued.....totally, including with resorcinol.

If I was to do it over again and I couldn't find the scantlings in a piece of oak to band saw the single piece out like the original
I would definitely do the beam with vertical pieces as you suggest.
BUT also mechanically lag the pieces together with BRONZE screws.
Iron is a notorious enemy of oak, so I would not use even 316.

I really can't imagine the arch being bent by the downward pressure of the mast.
If the arch is non-bendable even when supported by partial bulkheads then the arch must be made immovable.
Gluing it to the roof is a good idea. So to the bulkheads with thru fastenings.
You might think about adding gussets on the inside, on the other side of the beam.
This can be done by adding a piece of solid oak as a strut along side the cabin down to the hull.
The struts would completely immobilize the ends of the support beam.
Imco I would not depend on the bulkheads alone to hold the beam in place.
If you do you are only adding support off the side of the beam even if you thru-fastened it to the bulkhead.

Since you are band-sawing the vertical beam pieces out you don't have to have a parallel sided
lamination. You can increase the thickness of the beam as goes toward the ends. Yousometimes see bridge structures that do this.
In other words the exposed part of the beam would LOOK like it got skinnier in the center of the span. But you could keep the scantling you are happy with but increase the height of the beam as it goes toward the bulkhead supports - essentially loosing no head-room.

Could also add extra width to the beam, an extra vertical lamination.

[Commander 147]

Ebb

I always appreciate your 2 cents worth.

I will take your advice and use bronze screws to lag the beam together. I already bought some #12 x 2" screws that I had planned to use for the combings. I can drive them in from both sides and they will overlap a 1/2" in the middle.

Did you notice my plan to use a double bulkhead with lumber spacers between in post 288? In the area under the beam ends I will use white oak spacers between the two sides as posts to transfer the load all the way down to the hull.

BTW what were the final width and height dimensions for your strongback?

[ebb]

another half cent.
There have been reports in forums of failures with both resorcinol and epoxy gluing white oak.
Each report does not go into full depth of what happened, Moisture, clamping pressure, actual kind of white oak, temperature, loads, weatherability (UV, shrinking, expanding).
Failures could be due to anything - lousy glue or not carefull measuring of Parts A & B. Resorcinol has a shelf life as well. There have also been many triumphs and total success.

All woodworkers agree that laminations should include redundant mechanical fastening.
Especially horizontal load bearing laminations.

It is the acid in quercus alba that the epoxy doesn't like.
One worker says he has had success rough sanding faying surfaces JUST PRIOR TO GLUING.
Not allowing the wood oils to come to the surface. As we might suppose there may be an adverse oxidation on the wood surface that acts as a debond. This rings true to me - unscientifically.

Your vertical glueup won't pop off veneers when weight is put on it - which is what happened to laminations I've done.
The glue-up pressures in curved veneer lamination can be severe and glue can be squeezed out of the joint.
If you are laminating with epoxy you might consider a layer of cloth in the glue to preserve the glue line. The horz-lam beam in A338 is done that way. The vertical mode won't require enormous pressure.

You will probably be building up a baulk and cutting it out on a bandsaw.
You be able to see the insides of your glue lines to see how well you did.
You also will be encapsulating the beam in epoxy, which will go a long way to stabiliizing it.

For resorcinol you'll want freshly milled surfaces to start and perfectly sustained temps. Lots of clamping pressure.


Why not use trenails instead of screws - expensive screws - to marry the glue-up together.
Drill holes through the completed lamination and glue in white oak DOWELS. 5/8" D comes to mind. Drill the holes thru face to face.
Ebb would skew the holes slightly in various directions so that there would be no way the laminations could come apart. You'd never be able to drive a sharp chisel into a glue-line to see if it would pop loose.
Wouldn't happen. Trenails, better than screws. whatdoyouthink?

Have to turn your own dowels probably. Or 8 side square stock and hammer through a die plate. I think the key to using epoxy successfully on white oak is freshly prepared surfaces and 100% solids epoxy. NO solvents. No solvent prep of the wood.
Since there are so many variables there is no guarantee that it will be successful.

Bronze screws will look better in those coamings!
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Have to add: I glue many pieces of wood together using laminating epoxy.
Saturate surfaces, then wipe them 'dry'. The glue is epoxy mixed with fumed silica. Use the wet out brush to apply the fairly stiff gel. You can get pretty even coverage by smooching it around.
You cover both faying surfaces. When you press them together it is impossible to squeeze out all the gel glue.
You have a glue line and successful bond. In other words you can't glue with plain jane liquid epoxy.

I have never had a failure (but never used it for curved lams) with Smith & Co's All Wood Structural Epoxy. (google this: Oak and Teak Epoxy Glue - You Can Depend On It ---smithandcompany.org) It is a 2-part viscous thick material formulated for gluing wood to wood. There is a Steve Smith style tutorial immediately available on the website telling you how to use his glue. It's probably expensive - don't know about S&H.
Won't recommend System 3 - T-88.

[carl291]

Jerry, The companion way looks great, the hatch handle is a great two function bit of work, handle and splash guard. Thanks again for your old companion way trim it worked perfectly for my Electra, an odd note, all but one screw hole lined up with my original holes.
I seen somewhere you wanted to test the strength of your laminated beam to the tune of 2500lbs. How about the same way the strength of fiberglass layups were tested in the 60's, lay the beam in your driveway and drive your pickup on it and measure the flex. Carl