STRONGBACK DISCUSSION etc.

[kendall]

I think a lot of the reason the doors are removed is because they make the interior feel smaller.
When I first looked at my triton, both doors were open and it felt pretty spacious, after cleaning it out enough to close the doors, it just seemed to feel a lot smaller.

198 doesn't have the door either, so I don't have any real experience. Though when I was working inside, I moved everything into the v-berth, and draped a sheet over the doorway, which made it feel much smaller.
What I'd like to do is open the doorway up a bit, which I feel would make it seem larger.
To do that though I think I'd have to go with a more robust strongback, and after having both my son in laws stand and bounce on the deck above the strongback,(400+lbs) with no detectable deformation, it seems sturdy enough that I don't want to mess with it just for cosmetics.


Ken.

[ebb]

Been trying to see some progress in the A338 interior. (hopefully some pics in the Gallery soon)
So the anti-compression beam/struts and old ply glued in some time ago came into focus again.
What remaining of the original ply bulkhead: the pieces across the top that match the section of the beam and the skinnied down struts that terminate on the V-berth with the skinny remains of old ply have finally been mechanically connected with 24 #14 s.s. phillipshead screws. These are 316 flathead sheetmetal screws - meaning that the shank of the screw is like a straight lag - not tapered like wood screws. These 1/4" screws are indeed lags. (McMasterCarr.)

Worked out great. Since I was screwing into oak the pilothole could be tweeked a little wider so that the fastening was driven (with the Hitachi hammer drill) without fear of breaking. I'm wondering what kind of sheetmetal these screws would normally be used for?
BTW, would never use 316 screws in an exposed situation. Only bronze or monel should be used in oak. Wet oak eats iron for breakfast.


As back up for the laminated oak beam I choose 3/8" silicon bronze carriage bolts (Jamestown) with the bolthead inside and the nut buried in the deck composite. Drilled in 7 of these bolts along the length.

Began with a 1/4" hole drilled completely through.
Used a 1 3/4" holesaw to cut through the top into the balsa. The little lid popped off easy enough exposing the dry tunafish.
A 1/2" chisel quickly (almost TOO easily!!!) evacuated the wood. Used the same chisel to undercut the surrounding balsa. Put a tiny chunk of 1/4" dowel in the hole.
Then dumped two-part epoxy into the holes. Gratified to see very little liquid get absorbed and mopped it out with papertowels.
Refilled the holes with mishmash and came back later with the little PorterCable beltsander and knocked the hockypucks flat.
Then redrill the 1/4" hole.
Took a Bosch 1 1/8" flat bit with a large screw pilot. This sort of thing will want to take charge and pull the bit into the work. But I was using the screw thingy to center the bit in the hole - and bored down into the new puck enough to take a washer and a jamnut - together only 1/4" in depth. Plus a skoch for the fill to cover.

I'm going down today to the boat where I will drill the hole out to 3/8". I think I will prepare the square recess in the oak, knock the bolt thru, screw on the nut and see if the Fein tool* can pare the end of the bolt off right on top of the nut.
I'll refill the remaining hole with mishmash. let it set (hope the epoxy makes up for the skinny nut), dish it out a bit with the grinder and top it with a little circle of 6oz glass.
Then fair. Should be relatively seamless and never show up in the future.

The main reason for the bolts is that I don't trust epoxy used to laminate the beam. The bolts are not parallel to each other as each was drilled in perpendicular to the curve of the beam. In itself that's pretty strong - even if fastening through the deck, as described, is questionable.

Seems like the structure is locked.
Pity the poor sap what has to take this apart in the future!
If there is ever any question about the beam, it certainly seems possible to add an aluminum plate to the V-berth side of the beam. The plate would be cut to the exact shape of the beam and the coachroof.. Since the load is at right angle to any fastening, they could copy the same 'sheetmetal' screw as above with the plate also glued on with rubber adhesive, isolating the screws as well.
Driving screws into the thin oak laminations, therefore keep the screws relatively short.
If I were doing this again I would cut the beam out of solid white oak like the original. Could vertically laminate together thinner planks and thru-bolt.

AND as FRANK DURANT sez the beam could be vertically cut out of MERANTI HYDROTEC BS-1088 sheet and glued together (TiteBond III?). Could be curve laminated also, I guess. Since solid oak has no short grain like the cross layers in ply, I would definitely make the cross section of a meranti glue-up heftier than the oak dimensions.
BTW, only this plywood - NO OTHER, NO FIR, NO BIRCH - can be used for this purpose. imco

Hope this is useful.
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*Fein tool not so fine. Did nothing on the bolt ends. You can take a Fein to metal, but you can't make it cut.
I got a rant on this tool we'll save for later. Put a little flex cutoff blade in the Makita grinder and cut the bronze bolt ends like it was banana.

[Commander 147]

I have been a woodworker for a long time and one of the magazines I like the best is Fine Woodworking. When I started doing my research for the correct glue to use on white oak I naturally went to Fine Woodworking to see what they had to say. Thought the article I found would possibly be of interest here so here is the link.

http://www.titebond.com/Download/pdf...urGlue_FWW.pdf

[ebb]

BUT FOR DISCUSSION let me throw in some things that imco have to be taken into account for woodwork on a boat.

NEVER USE AN "INTERIOR GLUE" ON A BOAT.

White Oak in lamination cannot be glued with any glue used in the Fine Woodworking test.
Titebond 3 so far as I know has not been tested for white oak bent laminations glued up under tension. Nor in a wet/dry cyclic boat environment.
I have HEARD for years that boatbuilders ("conventional wisdom") will not use any yellow glue because it will eventually creep because it is hygroscopic in the damp. The FW test is primarily for wood joints that will live in a fine moisture controlled frufru situation.
A glaring omission from the FW test is water resistant plastic resin glue you catalyzed with water. It has a long open time, requires clamping, and has almost no glue line. Commercial tillers use it.

Titebond 3 (not yellow but grey) seems to be a different animal, but will need testing for veneer laminations and other wood-to-wood gluing in damp.
The conventional test for glues used for wood-to-wood bonding is a four hour boil test!
There is only one glue that survives this test 100% and that is Resorcinol. This glue requires milled surfaces and pressure clamping, no gap filling, THAT I have always taken to mean very light sanding to deglaze surfaces.
Gorilla Glue has no place on a boat. I have witnessed a number of failures used for furniture. While epoxy is a glue, polyurethane* is not!

I have had my own failure with T-88, and wrote extensively here about my experience with it. My conclusion is that the best off the shelf 2-part STRUCTURAL EPOXY ("tropical wood") is made by Smith & Co.
I have used this glue for white oak laminations (untested) and noticed some starved joints. Imco it is very difficult to squeeze this product out of a clamped joint, BUT it seems to be possible and therefor is not used for bent in form lams.
I have some suggestions which have been reiterated elsewhere. Imco no trustworthy lamination can be made with ANY glue on white oak. Except Resorcinol.
And it may be that the oak must be pre-treated/de-natured to remove tannins.

I epoxy-laminated a white oak beam for A338. I put an epoxy saturated layer of fiberglass between each piece of oak in an attempt to not starve the joints. I also attempted to remove tannin oils with solvent and roughly scoured the faces with 40grit. Years now later I see some tiny separations appearing and decided to bolt the whole damn thing together - which I've described in the Gallery.
I'll always worry about it. Wood will ALWAYS move in a cyclic environment. In my case I have isolated the wood pieces with a hard non-moving material. Doesn't really work. So you see what happens using Resorcinol - there is NO glue joint. Can only describe the phenomenon as a chemical bond - rather than a secondary mechanical bond provided by ALL the other stickums.
WITHOUT QUESTION, it would be much better to bandsaw a new strongback out of solid white oak timber!!!

Ultimately, the best bond/attachment is always made with bolts and screws.
Maybe we should see glue as only in a support role for metal fastenings and as a caulk to keep moisture out of seams.

For wood-to-wood furniture work on the boat my gut feeling is that Titebond 3 can be used.
It is easy to use, there's no mixing, it's water cleanup, and hardly a glue line. Mahogany and fir and plywood, conventional joints like the open joints used in the FW test. Only an assumption.
Would like to see anecdotal evidence on this. [EG, what did Larry Pardey use for the extensive interior woodwork in Tallesin?]

For attaching wood to fiberglass there is also no 'boil test' guarantee that you will get bonding. Therefor fillets and tabbing must be used. And that has to be done with epoxy. Could say this method is an attempt to OVERPOWER the wood.
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*Polyurethane tube rubber is another discussion.

[Ariel 109]

If a wood joint stood a chance of being exposed to constant dampness I don't think I would use anything but an epoxy or resorcinol, as much as I like Tite-Bond III. But cycling between wet and dry states will ultimately destroy any joint, regardless of the glue. We all know that maintaining the varnish or paint helps things last.

Resorcinol has a funny taste if I remember.

[ebb]

Resorcinol has the track record and is the only glue that will take extremes of wet and dry, heat and cold.
Epoxy has very limited exposure outside and has been known to disintegrate even if maintained. See the renovations that had to be done to all those traditional finished cruisers from 20/30 years ago - especially anchor platforms and bowsprits.
Epoxy glue is an interior glue! It can't take heat (it softens) and can't take cycling because it doesn't move. If you seriously have to keep exposed wood together, there's definitely 5200.

[Tony G]

So, er, uh, what are you guys sayin' here? My mast beam is going to fall apart? I haven't noticed anything coming undone voluntarily yet. Is 'yet' the operative word in the works here? Crimony! I guess Ebb's lead in holding the beam together is a fix I could apply easy enough, but, I'd rather think it wasn't necessary...crud. Oh well, one step forward and you know the rest.