Repairing cuddy roof stringers

[ctenidae]

The stringers (are they rafters in the ceiling?) supporting the cuddy on my DS1 are cracked in a couple of places, presumably from things like me standing on the cuddy to step the mast. They were built with what looks like 2 inch half-round, probably cardboard (haven't dug into them yet).

The question, then is this: Can I just clean out the crack, fill with resin, and lay a few layers of glass over it? I don't want to create a hard point that just focuses stress somewhere else, so maybe lay a few layers over the whole length?

[K.C. Walker]

Are they rafters? Yeah, good question.

The strongest repair for fiberglass is to grind out the crack. You want to have the ground out part taper 12:1, basically feathering it out. When you build back you want to taper your patch so that each layer is staggered out so that you basically feathering that out, as well. You get the most strength per weight in this situation by running unidirectional tape on the "top" of the stringer. It seems prudent to run one layer of tape the full-length after you do your repair.

KC

[GreenLake]

I wouldn't mess with grinding in this case. My thinking is that, unlike a deck or hull, you don't need to restore the original surface. So "sistering" with a patch should be just fine, except that, if you use more than one layer, you'd want your patches to overlap by 3/4 to 1".

I would watch for the connection of the stringer to the roof. If the "tabs" have cracked off, they should be ground off, or glued back on, so that there's no part of the stringer that hangs in air. New glass should extend 3/4 to 1" over the old tabs.

Roughen the old fiberglass and the roof and make sure surfaces are de-waxed/de-greased. Finally, make sure that the new glass makes no hard bends, round any corners with some filleting epoxy if you have to.

As usual, more focused recommendation would require a better description and or pictures of the actual damage.

[K.C. Walker]

Yeah, Capt. overkill here! GreenLake is the voice of reason here. It is likely somebody subject the cuddy to loads beyond design, like turned the boat over on the cuddy.

KC

[ctenidae]

Here's one of the cracks, right in the middle of the stringer (the dark blob behind is the hole the mast comes through). I have a zillion photos, none of the whole stringer. There are two, and they don't reach the walls of the cuddy. Instead, the ends are sloppy draped glass that's a little flexible.

I'm thinking the best bet is to fill the cracks, and lay a couple of layers of new glass along the whole length, and tie them into the walls of the cuddy.

All in favor say Aye.[/img]

[ctenidae]

I ran out and took some pictures. The goopiness is paint remover that I don't have time to scrape off tonight (yes, I'm prepared to redo it, and yes, it's fiberglass safe).

[GreenLake]

I agree with K.C. that this looks like someone bounced the boat while upside down...

Thanks for the photos. Here my detailed suggestions, try these on for size:

1.) Grind off the paint, etc. De-wax, de-grease thoroughly.

2.) One layer of glass like a band-aid, about 6" wide, running fore and aft, starting at least 2" aft of the wall the stringer, and going over the stringer to 2" beyond the forward side.

(As it can't hurt to reinforce the mast partners, you could make the patch wide enough and long enough that it would cover the mast hole - but leave an opening of course. Or you could trim it around the mast - both should work.)

Mat isn't the worst of materials for that part, it's rather bulky even in a single layer, and its easy to tease out the edges for a smooth transition. Around the crack, the loads go in all directions and having a bit of thickness there isn't bad.

3.) as you suggest, run a strip of glass lengthwise. I would use cloth tape for that purpose, so you get nice and well defined edges and don't need to cut long strips. Width: 4-6" should be enough. I really think you only need to cover the round part and enough of the sides as dictated by the width of your tape.

(You could reverse step 2 and 3 - might give a neater result).

4) don't worry about the 'soft" glass at the very end of thes stringers (last 1" or so), but one of your stringers (the aft one) has very sloppy looking glass for a good part of it. You might want to grind / sand that one smooth and give it a layer of tape while you are at it.

5.) I see only one crack in the photos. (Repeat step 2 as needed for other cracks).

6.) The tabbing of the stringers to the cuddy roof seems intact everywhere

7.) I think that one layer of reinforcement is probably enough, with two layers crossing at the crack - the stringer, after all, does have residual strength. You can always repeat step 3, perhaps the second time not the full length and using a narrower width to get a staircase effect. In that case you'd get long strip, mat piece short strip.

With that, you can then focus your attention on any other spot of your hull, because these stringers will be the strongest points

Actually, while you are at it, you could add similar stringers in front of the cuddy. I've found that the decks there aren't really strong enough despite the glassed in 1x4, and could use a bit of reinforcement. You'd need to create a form from a paper-towel roll or a gift-wrap roll cut in half....

[GreenLake]

Ah, I overlooked the bit about the paint remover. So ignore item 4. The sloppiness that I saw is your paint remover.

[ctenidae]

Ah, I overlooked the bit about the paint remover. So ignore item 4. The sloppiness that I saw is your paint remover.

The glass work is pretty sloppy (not that mine will be any too much better, of ocurse).

Thanks for the advice- glad I'm not completely off my rocker on the repairs.

For the forward deck, the 1x4 is broken clean in half (almost looks like it was 2 pieces butted up against each other)



Could I remove it entirely and replace with stringers a la the cuddy roof? I'm not really planning on racing the boat, but would like to keep it class legal. Not sure there's anything in the rules about reinforcing the deck.

[ctenidae]

(As it can't hurt to reinforce the mast partners, you could make the patch wide enough and long enough that it would cover the mast hole - but leave an opening of course. Or you could trim it around the mast - both should work.)

The edge of the mast hole is pretty beat up. I was thinking of building a sleave extending down a foot or so, as much as a guide for stepping to the screw jack as anything, but could also be a good place to mount some gadget (iPod, compass, disco ball, etc)

[GreenLake]

Thanks for the advice- glad I'm not completely off my rocker on the repairs.

For the forward deck, the 1x4 is broken clean in half (almost looks like it was 2 pieces butted up against each other)

If the 1x4 is broken, I think you are best off replacing it. (There may be some rot in the wood - so far, all the encased wood I've investigated on my DS had rot in it).

The 1x4 also serves as a backing plate to the big cleat in the middle of the foredeck, so you can't simply replace it with hollow stringers.

You can replace it with another 1x4 that you first soak in laminating epoxy (e.g. ClearCoat from SystemThree or the equivalent from West System). When you re-drill the holes for the cleat bolts, make sure that you soak any eposed wood at the same time.

You could encase the wood in fiberglass or paint it. In that location the epoxy by itself should be enough to bond the wood to the roof and to preserve it (there's no UV that can get at it). A strip of 4" fiberglass tape would make the board a bit stiffer, but might not be required, esp. if you add some stiffening to the adjoining deck areas.

For that purpose, I would add two hollow stringers to mimic the configuration on the top of the bow flotation tank. At least on my DS, the deck has a noticable 'give' at the location between the 1x4 and the edge of the deck, which therefore should be reinforced.

I'm not able to give you qualified interpretation of the class rules, but I believe you are on safe grounds (others may want to confirm this).

[K.C. Walker]

Greenlake wrote:I'm not able to give you qualified interpretation of the class rules, but I believe you are on safe grounds (others may want to confirm this).
You could always add rebar just to be certain, and we know that's class legal!

KC

[GreenLake]

How could I have forgotten the rebar?

@ctenidae: what KC is referring to is that ODay buried an actual piece of rebar along the opening of the cuddy. More here.

[ctenidae]

Wow- rebar. Kind of makes the thought of carbon fiber seem silly, doesn't it?

Good point on attaching the deck cleat to the 1x4. Kind of looks like excess stress on the cleat is what popped the board. Maybe a steel I-beam is in order...

[GreenLake]

Actually, I would think that even a square 4x4x1 section of backing should be enough to transfer the loads from the deck cleat, and the full strip should be overkill.

However, the deck laminate is a single layer and not all that strong. With a well-designed sandwhich deck, I suppose a long strip like this wouldn't even have been necessary.

Here are some other ideas (short of an I-beam ).

1. Cut a sheet of 1/4" plywood in roughly the triangular deck shape. Coat in epoxy. Glue to underside of deck. That should be enough to reinforce the foredeck as a whole.

2. Since the deck isn't flat near its edges, you could simply stop short with the plywood by 2-3", perhaps making nice tapered edges with a sander to avoid a hard transition.

3. Make a 4x4 patch of 1/2" plywood, coat in epoxy and glue underneath the deck cleat as a backing patch. That should be enough to distributed the local loads.

4. I think you don't need to add any glass on the underside of the plywood, but if you do, run it over the taper and onto the deck by at least 1". Place the backing patch on the outside of the glass.

You'll have the strongest foredeck in your fleet