hull to deck joint separation

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Postby GreenLake » Sat Dec 03, 2011 5:56 pm

Kevin,

without some sort of fiber reinforcement, epoxy isn't anywhere near as strong. Still, not exactly weak, but. So you can understand why I get cautious when someone proposes to pour like that. Also, epoxy heats up when curing, so you really don't want any considerable amount in a compact space.

So, let me get this straight. Your bow forms a V. The inside of this was filled with some goop (random polyester / fiber mixture, presumably) and the L bracket inserted.

Have you removed the goop? If not, and if it is still strong (though lumpy) I'd simply try to get some epoxy there to glue the L bracket into its slot. Then, cross drill afterwards to secure with a bolt or two.

If you have cleaned the V, I'd make a spacer out of wood, by sawing and filing a piece to fit. (Hardwood or laminated from multiple layers of marine plywood.). I would aim for the point where there's about 1/16" of a gap between wood and hull and then I would glue the spacer with thickened epoxy (or SystemThree GelMagic - from the cartridge would be the easiest).

Just squeeze out enough epoxy to coat the V shape that when you press the wood in, the epoxy will fill all gaps. Use the squeezed out epoxy to coat the exposed sides.

I would tend to think that a glue joint of several square inches is strong enough that you don't need to drill through your hull - just be really sure you cleaned the fiberglass to get any traces of wax and grease off of it, and rough-sand it as well. That should hold the spacer.

The same goes for gluing the spacer to the L bracket, but if you want, you can also allow for a screw or two as extra precaution. If you pre-drill those holes, you can use the L-bracket to hold the spacer in place while everything cures.

You do want to make sure that all screw holes have epoxy coating and that the inside face of the spacer is glued to the L-bracket. (If you feel better about being able to remove the screws, give them a wax coating).

You don't need to use wood screws - coarse thread machine screws will be fine, the epoxy will form threads in the wood around the screws. The main load on the screws would be shear.

What could you do to make this even stronger?

You could laminate a few layers of fiberglass over your repair, from one hull side to the other, with about 2" overlapping onto the hull. A two layers of mat, followed by a cloth layer would do. Or, if you want, make it four, alternating, finishing with cloth on the inside. In a pinch, GelMagic will wet out laminate, but normally I'd use for example SystemThree's Silvertip.

Adding laminate like that will further spread the load, prevent the L -bracket from separating from the spacer and, by encasing the screw-heads, will strongly resist any upward movement of the bracket. All without having to drill through your hull.

If you really don't want to work with wood, take strips of fiberglass mat, wet them out with laminating epoxy, and wedge them into the V until you've built it up enough to fit the bracket.

Which approach to choose depends a little bit on the details. If the spacer is really pretty shallow, laminating it in place might work, but if it's more massive working from solid stock (wood) may well be easier.

Hope this gives you some things against which you can test your own thinking. What I've written down is what would be my initial plan on going for a repair like this, but as in combat, no plan survives the contact with the enemy. :wink:
~ green ~ lake ~ ~
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Postby Skippa » Sat Dec 03, 2011 7:41 pm

Greeen~Lake~~
Thanks for the reply, Food for thought, Exactly what I was looking for. My reason for considering the epoxy mold was to achieve the "custom fit" but as you point out, Using the wood block with a dose of thickend epoxy will give me a good fit between the inner hull and the wood spacer. I also like the idea of over lapping the tang with a couple of strips of glass and spreading out any loading.
Thanks again for the advice. I want to make the repair once.
Kevin
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Postby GreenLake » Sat Dec 03, 2011 8:08 pm

When gluing with epoxy you want to make sure you are not starving the glue joint. A bit of a gap is good, as are a few bumps that prevent any part of the gap from closing all the way - and finally, for the same reason, you don't want to clamp an epoxy joint under high pressure (as you would a wood glue joint). So, a rough fit is actually desirable.

Good luck with your repair. Post some pictures, if you can.
~ green ~ lake ~ ~
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Postby hectoretc » Thu Dec 22, 2011 12:00 am

Greetings all,
I'd like to put some closure on this particular topic (at least for me).

Through the course of this discussion, we've ultimately ended up addressing the large inverted L brace that is "somehow" factory adhered in place in the DS bow, to which the stemhead is screwed in some manner.

We've determined that generally the factory method for afixing this inverted L brace to the hull is not satisfactory and they can break loose transfering the full pressure of the headstay and jib halyard to the fordeck, sometimes resulting in deck/hull seam failure.

A possible solution discussed is to drill one or two holes through the long down arm of the L brace and through the bow of the boat, insert a couple bolts and add some nuts to the bolts to insure they don't fall out. The force on the bolts is shear (perpendicular to the bolt path) so there won't be any great stress on the nut itself.

If this modification is performed, it "should" reduce/eliminate the possible stress failure which sometimes results in ripping a portion of the foredeck off the boat when the L brace breaks loose from its mounting.

Is this a accurate assessment of our conclusions? If so, does that mean I can pretty much repair my cracked deck/hull seam in the easiest manner available as it will no longer be a contributing factor to the stemhead rip-off syndrome?

Thanks all - Scott
DS #6127 - Breakin' Wind - From the land of 10,000 lakes, which spend 80% of the year frozen it seems...
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Postby Alan » Thu Dec 22, 2011 12:30 am

"does that mean I can pretty much repair my cracked deck/hull seam in the easiest manner available as it will no longer be a contributing factor to the stemhead rip-off syndrome?"

I think the only way we're going to find out for sure is if someone (hint, hint) tries it and lets us know if it works.

The problem there is that any solution will work, until it doesn't. And that may be a long time down the road, and "it doesn't work" will come suddenly, and probably at the worst possible time, in heavy air.

I'm partial to massive overbuilding because I really can't afford any sudden failures if I want to keep sailing, and I've wanted to sail for something over a half century. I won't stop worrying, but that's just me.
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Postby GreenLake » Thu Dec 22, 2011 1:35 am

I'm comfortable with the conclusion that the deck-hull joint as such is not designed to bear the main load from the forestay. That is the the job of the L bracket, as long as it's correctly anchored in the stem.

To the degree that this bracket bends under tension, there may be some residual loads on the deck. They should be small enough that they don't cause hull-deck separation, deck delamination or gelcoat crazing around the stemhead fixture.

The way I read this, the hull-deck joint is, however, designed to contribute to the overall stiffness of the boat, and that means that there are some loads that it is designed to bear. (And it's supposed to be watertight - and remain so).

For that reason, I would probably not recommend "any" type of repair in the "easiest manner". For one, I'd definitely recommend against using just simple caulk...

Given that the DS hull is not precisely light weight, not much is gained by saving a few ounces of material. Therefore, there's room for what Alan calls "overengineering". My own DS shows evidence of having a strip of laminate applied on the inside between deck and hull. That very effectively seals the hull and adds considerable strength to the joint. Whether this was done in the factory or by a PO, I can't determine.

But it seems a suitable measure to make sure that the joint has enough strength and is sealed against any water coming in when slamming into waves.

There's no need to sit back and wait for further evidence to collect - if you back up in this thread, Bob Cramer describes his successful repair (field tested) here. It matches what we've discussed so far.
~ green ~ lake ~ ~
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I hope this is what it's supposed to look like...

Postby hectoretc » Wed Dec 28, 2011 9:08 am

Greetings all
I installed the "stemhead tang anchor" modification this weekend, and hope this is what it's supposed to look like... (or reasonable facsimile there-of)

1203 1204

I should have thought to rotate it 180 deg. in photo shop before posting, but for those who can't make the mental re-orientation, the right photo is upside down as taken but my iPhone reaching down through the access port in the deck. You can see the two 1/4-20 SS nuts on the screws through the bow. Also I added a flat washer an 1/4-20 nut to the aft stemhead screw to add support in case if decides to strip out the 3/4 of a threaded hole it resides in (just barely hit the tang when drilled through from the top). I couldn't get a washer and nut on the forward-most stemhead screw because a glob of (fiberglass resin?) is too close and won't move. But I'm feeling better about the load distribution at this point anyway. I did not seal or epoxy the screws in yet "just in case" I've done this wrong and need to take it all apart again. Before we hit the water this spring, I'll take them out one at a time and seal the screw hole properly.

Questions... comments... thoughts??
Thanks - Scott
DS #6127 - Breakin' Wind - From the land of 10,000 lakes, which spend 80% of the year frozen it seems...
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Postby ChrisB » Thu Dec 29, 2011 10:09 am

Scott,

That looks like an excellent repair. From the photo it looks like you drilled the holes about 3/4 inch and 2 1/2 inches down from the deck joint, is that about right? I'm taking my boat on a four day sailing/camping trip in May and I want to strengthen this weak spot prior to the trip.
Chris B.
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Postby hectoretc » Thu Dec 29, 2011 10:28 am

Hi Chris,

Your measurements sound right, but I'll check it this weekend and get back to you with exact numbers. I'd installed an 8" access port on the foredeck so I could reach in with my arm and "feel" where the tang starts down, and I wanted to position the upper screw be sure to miss the SS stemhead screw ends. The second, I just wanted to go down a little further, but also to insure I hit the tang not knowing exactly how long it is. There is an obvious bulge inside so that made it easier.
Again, I'll get back with more precise measurements after this weekend.

Thanks - Scott
DS #6127 - Breakin' Wind - From the land of 10,000 lakes, which spend 80% of the year frozen it seems...
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Postby hectoretc » Sat Dec 31, 2011 8:13 pm

ChrisB wrote:Scott,

That looks like an excellent repair. From the photo it looks like you drilled the holes about 3/4 inch and 2 1/2 inches down from the deck joint, is that about right? I'm taking my boat on a four day sailing/camping trip in May and I want to strengthen this weak spot prior to the trip.


I placed a tape up into the lip indent on the hull/deck seam and the first screw is 1 1/2" down from that point, the second is 2" further down or 3 1/2" from the inside of the lip curve.

Please let me know it that's not clear and I'll explain it again or upload i picture. (I'm trying to conserve my photo space right now)

Thanks - Scott
DS #6127 - Breakin' Wind - From the land of 10,000 lakes, which spend 80% of the year frozen it seems...
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Postby Alan » Sat Dec 31, 2011 11:04 pm

ChrisB,

Hmmm. Sailing/camping, you say? It probably deserves a new thread, but I'd really like to hear about your planning and preparation, and later, how it all worked out.

My crew (aka wife, who found me the boat etc.), who's proven twice that she handles the helm better than I do, is a veteran backpacker. She'd like to do camping sails, I suspect, but for now we've agreed to picnic sails until we learn what we're doing in sailboats.

Any info most gratefully received.
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Postby ChrisB » Mon Jan 02, 2012 11:07 am

Alan,

I posted a response to your questions about my sailing/camping trip in the "miscellaneous" folder.

- Chris
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Re: hull to deck joint separation

Postby ldeikis » Tue Mar 17, 2015 6:29 pm

Hello all. This thread's a bit of a zombie but after extensive searching, it seems to be the best thread on the topic so I figured I'd build on it.

Picked up a DSII last fall, excited to put her in the water on a mooring this year. The PO dry-sailed her and said he didn't think she really took on any water to the bilge, but he hadn't mentioned this separation before I drove a substantial distance to see it. The price was right anyway, and I was excited, so I came home with the boat despite the issues.

The boat has clearly had some hull/deck separation anxiety on the starboard side, starting about where the starboard side stay mounts and running forwards towards the bow a good couple feet or so. It looks like someone did a rather sloppy job trying to repair this, and either whatever product they used shrunk, or wasn't strong enough and allowed the separation to continue, or they released clamping pressure before a full cure was achieved, or it was just the wrong product, or I don't know what. My goal is to make it "right" enough to check any worsening of the issue, and safely live on a mooring and be sailed all summer without unreasonable water infiltration, and to not do anything that will prevent a better, more aesthetically-pleasing repair in the future... BUT, I do not anticipate having the time or financial resources to do the kind of gorgeous restoration that I've seen some other members do.

All these shots are from UNDERNEATH, looking up at the joint
Wide-ish shot showing the extent of the damage:
Image

Close up of the "repair":
Image

Close up of starboard side-stay reinforcement--I assume this was the original cause of the separation...
Image

...and a top shot of some stress cracks on the deck just forward of the side stay
Image

I'd planned on sliding her off the trailer in the yard and flipping her to apply an ablative bottom paint to the hull and centerboard, and to touch up a couple gouges through the gelcoat from rough docking or trailering or something... which seems like the perfect opportunity to clean this up and apply a proper fix. My current thinking is to use a carbide cutting tip on a dremel like this:

Image

...perhaps with careful use of a 4" angle grinder, to open up the cracked repair, then apply some sort of product to the crack. I was initially leaning towards 5200, and would like opinions on if that's too flexible? On the one hand, this is MEANT to be a rigid joint... on the other hand, the condition of the PO's repair suggests that some flexing might be inevitable. If 5200 isn't the right choice, I like the looks of the SilverTip gelmagic mentioned earlier (http://www.systemthree.com/store/pc/Sil ... ic-c16.htm).

Questions:
Would love more input on what product to use?
Will using a steel-based grinding tool, like the dremel carbide tip or a regular 4" cutting disc leave microscopic iron residues that will leave rust streaks and drive me to insanity?
After opening the crack and applying product, should I clamp the joint, or leave it at its natural spacing?

Thanks for all input. I'm excited to get this boat in the water and do some sailing, and this is the most major hurdle on my list. I have a substantially pregnant wife and a small in-town yard, so I'd love to achieve a functional repair and not have to launch and retrieve the boat to keep messing with it.


Luke
'74 DSII sailing Haverstraw Bay and the lower Hudson River
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Re: hull to deck joint separation

Postby TIM WEBB » Tue Mar 17, 2015 9:02 pm

Hi Luke,

I recently asked Rudy at D&R Marine about a similar issue on TRW, also a DS2. Had some gaps in the hull/deck joint I wanted to fill in, where the original filler putty had cracked and fallen out, around an area where I had smooched a ramp piling recently, but also in some other areas I had noticed gaps. Nothing as bad as what you're facing. Just an inch here and a couple inches there. He recommended the fast cure 5200, which is what I used, and it worked great. I applied it with the boat on the trailer, and it's not quite thick enough to stay up in there on it's own, so I used some clear packing tape to hold it up in there until it cured, then just peeled that right off. One 3 oz tube went a long way.

Hope this helps, and congrats on the "impending family addition"!
Tim Webb
1979 DS2 10099 The Red Witch
(I used to be Her "staff", in the way dogs have owners and cats have staff, but alas no longer ... <pout>)
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Re: hull to deck joint separation

Postby GreenLake » Wed Mar 18, 2015 1:05 am

While GelMagic has some gap filling properties, this is probably not a job for it. (Nothing against it, it's one of my favorites. It works really well for sloppy joints in wood, or when gluing together panels that touch, but don't fit closely. It's foremost a glue, not a sealant).

I haven't worked with 5200 but understand that it has some characteristics of a caulk/sealant in addition to a reputation for bonding tenaciously. Normally, the latter would be an issue in many sealing/caulking/bedding applications, but the hull-deck joint is really never meant to come apart (or to be taken apart as part of any reasonable maintenance schedule). So, that feature is not the drawback that it would be in cases where you do want to be able to undo the joint.

On my boat (a DS I) a previous owner (I suspect) did reinforce the hull deck joint by running fiberglass tape along the seam on the inside. In the spirit of belt and suspenders, this might be something to emulate around your chain plates. That is, if you have any doubts that the 5200 is up to the job. Alternatively, you could simply add that layer or two of fiberglass on the inside and that would "freeze" the relative position of deck and hull; it would probably keep the water out, too, but not address any of the aesthetics.

In return, the prep would be extremely minimal, amounting to a pass with the sander over the area you wish to bond, preceded and followed by a wipedown for grease etc. You'd want to sand through any paint applied to the inside and roughen up the laminate a bit. You can certainly use GelMagic instead of ordinary laminating epoxy (SilverTip); I'm told by the manufacturer that even though it's non-sagging,it's still sufficiently able to wet out fiberglass cloth (and unless you turn your boat upside down, you might want something that's non-sagging...)

Unlike 5200, the added fiberglass is easily cut with an angle grinder, should you ever feel the inclination at a later time to reposition the deck after cleaning out the old repair. With the 5200, you are pretty much stuck with whatever alignment you achieve on the first try; in that way your situation may be different from Tim's where with only minor gaps the original alignment of was presumably preserved.
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