Stemhead Question

[whitejw1967]

I am replacing the stemhead as the one that was formerly there was bent. Apparently, the former owner bent the stemhead to fit into the existing holes, thereby weakening the stemhead (and the last thing I want is a forestay to snap loose under sail).

The question. What is in or under the stemhead that holds it tight? I know that there is about an inch or more of glass on the foredeck, but is there a metal backing plate or something else underneath that? I need to epoxy the old hole and drill a new one, but I am concerned that I'll hit metal underneath.

Any suggestions?

John

[Roger]

Indeed, you are correct. There is a metal backing plate with threaded holes into which the stemhead is bolted. Get a new stemhead from D and R marine and remove one bolt at a time and replace it. The metal backing plate is glassed in, but delamination may have occured (doubtful) over the years.

I have pics of the backing plate if you want me to e-mail them to you. roger02@mts.net

[skier]

I'd like to to see a pic of the backing plate.

I made bracket to hold a position light to the bow. I was planning to screw this to the boat next to the stemhead fitting. If I know the shape of the backing plate perhaps I can plan to miss it. Or perhaps I'll want to change my bracket design.

Jeff

[algonquin]

I'd like to to see a pic of the backing plate.

I made bracket to hold a position light to the bow. I was planning to screw this to the boat next to the stemhead fitting. If I know the shape of the backing plate perhaps I can plan to miss it. Or perhaps I'll want to change my bracket design.

Jeff

Maybe you could design the bracket so it would mount to the existing stemhead screws and save you from putting more holes in your boat. That may require obtaining slightly longer SS screws. Brad

[GreenLake]

I've designed a removable bracket onto which I mounted one of these.

[skier]

Greenlake: That's exactly the light I've got. I would be interested in seeing your design.

algonquin: yes, I'm thinking about that possibility...

[GreenLake]

OK, here's the design. I wanted something removable. At the front, there's only the stemhead and that's filled with headstay and jib tack shackles.

I realized that a set of flat prongs could slide between deck and shackles on either side of the upright leg of the stemhead. (The stemhead is an inverted T). Forward of the stemhead is the rubrail, but it's lower, so I added a platform that rests on the rail.

Here's the drawing (click thumbnail for larger view).

[thumb=876]

What's hard to see is that the semicircular platform needs a bit of a notch in its straight side, to fit the part of the deck that projects in front of the stemhead.

This photo shows a top view of the assembled bracket with navigation light attached. The nav. light has a hole that's threaded on its underside. It's rubber foot is supposed to thread into that. I got a bolt with matching thread size and epoxied that into the bracket from below (not shown in the drawing).

[thumb=877]

The yellow bungee is what holds the bracket in place. It's looped behind the forestay and its knot is hooked into the notch. (The drawing still shows two notches, but using a hole on one side prevents the bungee from getting lost.)

Materials: hardwood scraps (oak), glued together with and encased in epoxy for a totally waterproof design.

I've used it for several years now, and it works fine.

[ChrisB]

Greenlake,

I like the removable navigation light bracket. How did you attach the light unit to the bracket. Which light did you use? (Innovative Lighting sells a model with C-clamp, suction cup, and inflatable boat mount).

Chris

[GreenLake]

I think what I got was the one with the suction cup. The cup ends in a bolt that goes into a threaded socket on the base or side of the lamp.

I simply located a matching bolt and embedded it into the bracket with epoxy.

[skier]

After see pics of the backing plate (easily missed) I went ahead and screwed my bracket (already constructed) to the boat beside the stemhead.
Post and pics link in separate post:
http://forum.daysailer.org/forum/viewtopic.php?t=3453

[SUNBIRD]

I have taken a picture of the underside of the deck of my DS II (1979 model) and the stemhead fitting is screwed to an approximatly 1/4" thick bronze (might be brass?) "L" bracket that is secured to the bow with a huge glob of some kind of polyester "goop" (putty, thickened resin, hardened chewing gum??). There is a gap of about 1/2" to 3/4" between that L bracket and the underside of the deck (at least on my boat). I intend to slip some kind of spacer in there one of these days to fill the gap. I can't figure out how to add an image to this post, so I have posted a picture of my boat's stemhead back-up in the photo page.

[GreenLake]

Rod's picture (click image for lager view):
[thumb=878]

(Rod, look under "website info" to see how to post these thumbnails).

What benefits do you expect from filling the gap between the L bracket and the deck?

It would seem more important to worry about cross bolting the other leg of the L, as was discussed earlier in this threa. You really don't want that L pulling free of the "goop" at some random moment. (When out on choppy seas with heavy gusts...)

[SUNBIRD]

My thought is that (for now at least!) the goop is holding, however what concerns me is if it lets go the L-brace will immediately pull up until it hits the underside of the deck, the shockload of that happening would seem to increse the chance of ripping the deck away from the hull. I figure that by filling the gap between hte underside of the deck and the L brace I would them transfer some of the load to the deck and eliminate the shockload if the goop ever let go. If I could, my preference is to find a way to install a strap that would connect the stem fitting to the bow-eye. I have a pretty good backing block on the bow-eye (inside) and even though that is technically on hte wrong side of the load (really need re-enforcement outside the bow) it would still represent a shear load vertically up the bow (stem). There is a 1984 (might be 1983?) DS II that I spotted in Wareham that must have had the stem fitting backup let go......the forward 12" +/- of the deck is peeled back. That boat does have the hinged maststep, mine is still stepped through the cuddy to the deck below.

Basically, I figure that filling the gap between the underside of the deck and the L-brace should hold for a long time since there will then be less cyclical loading of the bond. In retrospect, the ideal would have been for O'DAY to have installed the brace to be in contact with the deck originally.......didn't happen! Also, note the minimal backing plates for the 2 bow cleats...... however, they haven't budged in 31 years! If I was trying for the ideal upgrade, I'd install a single backing plate for all 3 fittings (stem and 2 cleats), but again...... it still looks OK after 31 years.

PS: I already cringe when I hit a good sea! But, no problem yet!

[talbot]

On my 1973 DS II, there is what appears to be a nylon "doughnut" spacer between the L-bracket and the underside of the deck. I wonder if there was one on your boat at one time, and it somehow cracked and fell away.

[GreenLake]

My thought is that (for now at least!) the goop is holding, however what concerns me is if it lets go the L-brace will immediately pull up until it hits the underside of the deck, the shockload of that happening would seem to increase the chance of ripping the deck away from the hull.

The unknowns in this reasoning are the total load at which the "goop" will fail, and also the safe load that the deck/hull joint can handle. As long as both of these are unknowns, there seems to be no sensible way to evaluate whether the "shock load" effect makes any practical difference.

Further, if you do add a spacer, and the goop gives way, but the deck holds, from that point on, the deck is subject to all the loads, but you won't be aware of it. That means you'll be sailing until the day that a sudden gust exceeds what your deck can hold, and you are no better off than you are now.

Contrary to what you write, the spacer would not appear to reduce the cycling loads on the L bracket, because those come from different amounts of tension. On the contrary, once you have the spacer in place, the L bracket will also receive compression loads when you step on deck.

The problem with the way the L bracket is fixed in these boats seems to be that the strength of the joint is highly variable and probably depends on variable condition during manufacture. To get the full strength, the bracket had to have been properly de-greased, bedded in resin without any air gaps and allowed to cure before load was applied.

If, on the other hand, the bracket was placed dry against the cured laminate of the hull, and then merely secured with goop, it's easy to see how it could work loose from the single bonding surface.

If you cringe each time your boat hits a wave, then drilling one or two holes from the bow, filling them with epoxy and inserting a bolt in each should seem an straightforward insurance policy that might restore your full enjoyment of your boat. The shear forces these bolts can absorb are most likely comparable to the design load for the bracket - so no matter what the (unknown) condition of your bracket joint was before, you should be able to eliminate it henceforth as a source of worry.

You note that the cleats, which are pulled along the direction of the laminate, had been held in place despite limited backing. That should give you an idea of the side forces that can be held by a few bolts crossing the laminate. (The backing plate serves two purposes: it may help stiffen the deck, so pulling on the cleats produces less local bending, and it anchors the bolts against the upward pull that derives from the cleat being levered over its forward edge as tension is applied. But you would always expect the primary load to be sideways).