How Do I Do This And Make It Pretty

[Dave, 397]

I've A problem rolling around in my empty skull that won't quit...every possible solution i come up with just sounds worse and like more work than the last. Maybe someone here can help.

As is to be expected, my deck beam leaves a bit to be desired. Ditto the vertical and diagonal supports. To begin with, I'll get out of the way my belief that the vertical and diagonal supports should be 'glassed to the new bulkheads, which are going to ultimately be painted white. The beam and the new supports? Well, I happen to have a little stash of ironwood laying about, a lot of poly glue, and plenty of clamps. Planned on making all the bits from nicely laminated ironwood (go ahead! rot! flex! ha!).

Here's the conundrum...I'd like to have the ironwood look like, well, wood against the white bulkheads and interior surfaces, but i'm not sure how i can do this and still 'glass it all in. Is there a special magic Hinckley technique to help, or is this just going to either look funky enough that it ends up with paint no matter what I do?

Help?

dave

[Tim]

How about planning on a faux finish on the glassed wood beam? If you're gonna tab the beam and vertical supports in, I don't know how you can avoid having the tabbing, at least, be painted. But a good faux paint finish can be as convincing as real wood, if done correctly.

Alternatively, here's another thought. Decide how much overlap you want your fiberglass to have on the wooden members--1", 2", whatever. Mark a clean line on each piece before installation and apply heavy masking tape to the areas outside the line. Then, glass the members in place as you normally would, not worrying if you get some glass over the taped areas. Then, when the glass has kicked to the semi-flexible stage, take a sharp utility knife (extra blades, please) and cut along the inside of your tape line, leaving a clean edge, and peel away the tape. This is the critical part if you want a clean edge--you have to catch the glass at just the right cure so you can cut it cleanly with a knife without pulling, and so that the resin is not so hard that the knife won't cut through. How long it takes to get to this point is dependent upon temperature, the resin, etc., so you'll pretty much have to babysit it to ensure that you don't miss the opportunity.

Done correctly, this should leave you a neat, clean, sharp demarcation between tabbing and wood, after which you can finish the wood to your heart's desire.

[Figment]

Depending on the weight of cloth and type of resin used, you might actually be able to pull this thing off. Using System Three's Clear Coat resin (see "epoxy" thread) I've been able to get 12oz of cloth (3 layers of 4oz) to go totally clear. It just looks like a really really really deep varnish job. The telltale left over would be the necessary fillet at the joint.

But I gotta ask.... why so intent on glassing the beams to the bulkhead?

[Dave 397]

By glassing the beams to the bulkeads and hull, and by tabbing in the bulkheads well, one increases the strength of the entire assembly. The goal here is to eliminate as much differential motion as one can.
Flex=Differential motion
Differential motion=More Flexing
More flexing=Enhanced failure potential

The hull, of course, flexes...not much to be done for that except to 'glass in a rib or two in the flexiest areas to keep it down to a dull roar. How much does the boat flex? Here's a way to get a picture of the fore-and-aft flexing of even a stout hull:

Carefully set up a laser level back near the companionway, firmly affixed so it can't go anywhere(double-stick foam tape and a bit of duct tape will usually do...make sure it's attatched to something that can't readily move). Set the laser so that its' beam hits a point on a board temporarily fixed vertically at say, the chain locker bulkhead. Mark the spot the beam hits. Sail the boat hard to windward in 20 or 25 knots...crawl up there and make a new mark where the laser's hitting now. This can really surprise you. We have found that tabbing everything imaginable into the boat structurally diminishes the overall flex of the hull as is measurable (albeit crudely) by the above method. The other benefit is a more solid-feeling boat, slightly increased pointing, and slightly sharper response with more stable and constant rig tension under sail. The two guinea pig boats, if anyone is curious, were a Pearson Renegade and a Yankee 30.

Best,
Dave

[dasein668]

Dave,

I'll just toss this out there.... When I got my boat, someone had tabbed in the mast beam, but the inherant flexion that you described continued anyway, and the tabbing ended up just detatching from the beam. Obviously that may have been due to poor technique.

I ended up not glassing the beam in after much consideration, but I did use super-thickened epoxy to "bed" the new beam. 'Taint gonna come out easily! But I figured my new beam ought to last the life of the boat, as it is an oversized laminated beast, and the old P.O.S. beam lasted 40 years....

Just something to consider. I suspect that by bedding the whole beam in epoxy I went quite a long ways toward stiffening things up, as you are hoping to accomplish. Plus, then, I have the nice wood showing without the tabbing masking it.

Good luck, whatever you end up doing!

[Dave 397]

Nathan--
I agree as to the tabbing of the mast beam itself---as long as the fit is really snug as you describe, the compressive load from the rig should hold it quite solid. I was mainly speaking in reply to Figment's question as to why I would want to 'glass the vertical/horizontal supports to the bulkheads, and on the issue of tabbing everything possible in as well as one can...Pearson's tabbing jobs were enough to hold things put and not much more---you can usually poke thru 'em with a screwdriver...other things aren't tabbed at all.

As to the mast beam itself, the only really major improvements I can imagine are to lay in the new one as you did, and to eliminate any coring under the step.

Best,
Dave

[Tim]

Pearson's tabbing jobs were enough to hold things put and not much more---you can usually poke thru 'em with a screwdriver

My recent experience in dismantling #100's interior bulkheads indicates otherwise. The tabbing is extremely thick in most areas; the only places it's thin are where it is, by design, intended to just hold things in place, and where anything more extensive would just be a waste of material. Despite the "rode hard and put away wet", tweaked-to-the-max race-till-the-boat-dies nature of Triton #100's previous life, none of the critical interior tabbing or structural members were remotely compromised. (The deck and hardware is another story, of course.)



Every boat is different, but in the boats I have seen, the thickness and solidity of the tabbing on the important structural members--the main bulkhead chief among them--is impressive , and does its job adequately. Let's also not forget that the hull laminate of the Triton was engineered to be stiff enough to support the entire weight of the boat on any single square inch of the hull, with only minimal deflection (I forget the exact specification). Source: Ev Pearson, in 1977

Sometimes overkill is prudent. Other times, it's just overkill. Beware of over thinking, or over engineering, things that don't need to be.

[Figment]

I'll back Tim on the tabbing thickness. In my bulkhead demolition, the typical tabbing was 1/4", with some spots as heavy as 3/8" thick. Severe overkill.

For an alternative to tabbing as a method of rigidly fixing post to bulkhead, I'd suggest buttering the back of the post in thick epoxy, securing in place with screws (like original installation) and then epoxying dowels into the post from the forward side of the bulkhead on staggered 4" centers. This would leave the pretty side of your wood untouched.

For my own reinstallation, I was just planning on screws on staggered 4" centers. I'm hearing that this might be insufficient.......?

[dasein668]

Mike,

I doubt it would be "insufficient." Although I guess that would depend on what your definition of sufficient is, in this particular case. I for one, if I had the whole mast support thing to do over, would have laminated a new beam that was the same size or even perhaps a bit smaller than the original.

As far as attachment goes, I probably would have just used screws for both the beam and the compression posts. Yes, it probably would be a bit less stiff, but I'm not convinced that the boat really needs the additional stiffness that would be gained by this--at least not for daysailing and coastal cruising. Said stiffness certainly wouldn't hurt, of course. Until such a time as for one reason or another you needed to remove something!

Which is why I go back to saying it all depends on your definition of sufficient. If you are concerned about stiffness, as Dave is, then screws probably are insufficient. But Dave is planning to move aboard with his family and do extensive, and possibly blue-water, cruising. Extra concern about stiffness may well be warrented in his case. Is it warrented for you? Only you can say...

As for me, I waaaaay overbuilt when I did the mast support reworking. My mast support is probably so overbuilt that I could snap the boat in half tensioning the rigging before the mast would come through the deck. But I built the thing before I had sailed her, and after looking at a pretty scary mess of a mast support structure. In the absence of experience or an engineering degree, I just threw more material at the problem. My new beam looks nice, but is way more beefy than necessary.

Phew! We sure are wordy on this forum, aren't we?

[Tim]

Mike,

I don't think that recreating a basic construction design that, except for the moisture that extreme neglect allowed to creep into your bulkhead, has worked well for 40 years could possibly be called insufficient.

Epoxying the vertical compression posts to the bulkhead would tie the two structures together and allow the bulkhead to better share the loads from the mast compression, I suppose. That might be a worthwhile endeavour, though hardly necessary. Still there's the "might as well" factor involved here.

I did not have to replace my mast beam or compression posts on Glissando. Therefore, I did not replace them. The basic structure probably could/should have been better engineered at the onset (original time of construction, that is), but it does work despite everything that seems to be working against its success!

[Figment]

I guess it's worth mentioning that my mast beam has become mostly cosmetic..... It's just a chunk of wood there to conceal the 1/4" steel plate that's going to be thru-bolted to the bulkheads. I suppose it also contributes to the bearing surface of the mast step onto that steel plate, but that's secondary. I know.... I would've preferred bronze, but I found it impossible to find a local source for bronze plate.

Because of this really stiff step-to-bulkhead transfer, I'm considering the compressive forces on those posts to be negligible. They're really just there as stiffeners for the bulkheads. I've waffled quite a bit on the decision of screwing in place vs. epoxy. I settled on the screws because I just can't fight off the feeling that someone might need to take this apart again someday. But then.... I'm not planning on bluewater voyages. Of course your situation is a horse of a different color, Dave.

I did manage to salvage the forward chunk of the mast beam.... the piece with the hull number stamped into it. It's all varnished (except for the numbers, of course) and waiting for reinstallation.

[dave,397]

Judging by the pics and descriptions you guys have posted, I have to conclude that they did mine at 4 PM on a Friday.