Adding companionway hatch to DS2

[hectoretc]

For the purpose of this question, please simply imagine a 18"x18"x 1/4" sheet of gel coated fiberglass that has been cut in half (now two 9 x 18 x 1/4 pieces), seperated about 3-4 inches apart, and I want to fill in the space between them with fiberglass to end up with a 22" x 18" x 1/4 piece.

For a gash in a hull or large crack, my reading on this forum suggests grinding down the edge of the hole with a rotary tool or sanding disc (or grinder). If that understanding is true, a couple questions please....

1- Is there an optimum angle for this cut? or as wide as it can be done?
2- Do you want to expose or even work hard to expose a more jagged cut so there are original fibers exposed (mat or cloth depending) so the repair has something to adhere to better? or doesn't it care?
3- Most of the comments I've seen suggest building up from the inside so the mess is contained. Would that logic also apply where you have two seperated pieces (again with about an 18" joining edge)
4- Do you need to grind down, or rough up the "inside" of the hull or fiberglass piece before applying a patch?
5- My thinking would be to pre-postion the pieces about 6 " apart on wax paper, build up a 18" x 6" piece of layered resin, cloth, resin, mat, etc. and then to lay each of the two pieces in position on the new material overlapping the edge by an inch on each side. Let it set up, and then start building up the gap toward the final height using some finishing putty or whatever is appropriate for the last 1/16" or so. Sanding and painting as the final finish.

Will that work? (in theory)? If this is simply a non-starter, in other words theres more problems here than space to correct, "It won't work" is an acceptable answer and I won't ask you to give the the thousand + reasons why it won't work.

Thanks - Scott

[GreenLake]

Scott,

the purpose of grinding edges (at about 1:12 slope) is to give enough of an area for the patch to bond to. This assumes a patch that doesn't add any extra thickness to the laminate at the point of the repair. It would merely replace the damaged laminate in place. That's what most instructions assume.

I can imagine situations where you would be fixing something by using a strip of laminate just like a piece of tape - gluing it on top of each side with overlap. If you have enough overlap, then the patch would hold (1" is a bit of a minimum, for some high load applications I'd be happier with 2").

Also, one likes to avoid "hard spots", so let the innermost layer of mat overlap 2", the layer of cloth 1.5" and the final layer of mat 1" - think stair steps.

Finally, your method of repair, let's call it an external patch (in contrast to an integrated patch) does have the drawback of leaving behind an unfilled gap, so you need to fill it. I would not use just filler, because if your repair flexes, many fillers aren't flexible or strong enough if applied at excessive thicknesses.

If you bypass damaged laminate, so that it's no longer relied on for strength, then, in theory you could encapsulate it in place. However, in a boat, any internal void that can collect water will.... keep that in mind. Damaged laminate is like a sponge.

In general sounds much like my repair after a El Toro "gored" our DS. I made an external patch which I applied from the inside of the hull (glued in place with an epoxy glue). However, I also cut out the damaged laminate at a shallow angle and then filled most of the gap with new laminate (some mat, some cloth) and only used filler to fair the repair.

In effect, I did a belt and suspenders job. Having the patch against the inside of the hull helped in two ways. One, I was no longer worried about whether the new laminate in the crack would be up to restoring the total strength - the patch did most of that. Second, I had a nice backing, so my new laminate was kept in place.

Did that answer your questions?

[hectoretc]

Thanks GL,
Answered nearly everything...

I'm assuming it is necessary to also sand, grind or to do something to the inside (non-gel-coated side) of the fiberglass before attempting to attach the patch from behind? this question applies also to the reattachment of the top of my forward bulkhead repair I need to complete (from a different post). Not withstanding washing everything down with a de-waxer and acetone, I assume (perhaps incorrectly) that the currently exposed surface needs to be additionally prepared in some manner for the patch attachment?

I equate this to the minimum requirement of roughing up any finished surface before applying new paint. The inside of the DSII for example "appears" to have been painted in some fashion, in my case looking like a white paint with blue speckles tossed in for color as shown in this inside picture during my porthole project.



That or Oday's fiberglassing process has a remarkably nice natural finish. Given your comment on a 2" overlap, would I also want to sand/grind back a 1:12 bonding edge on the back side for the inside patch?

In this specific instance, this is an intentional cut to separate the two halves and add size to the overall piece so other than the violence of the cut, there is no damaged laminate to cut out.

Finally (this is an additional question), I know from previous discussions that you are a strong advocate of epoxy vs. polyester resin for many repairs. I've read the arguments on the West System site as well, but they sell the epoxy so "maybe" their perspective is a bit biased. Yours I trust more.

You know also from previous posts that I have a fair amount of polyester resin on hand (I was however only joking about the 55 gallon drum just in case you believed me). Is this type of work (adding size to an existing fiberglass panel) equally well served by either epoxy or polyester? or is there a serious benefit/detriment to using one or the other for this type of work?

I think that covers my gaps at this point.

Thanks again - Scott

[GreenLake]

Scott,

you are absolutely correct, sanding will be required even on a bare fiberglass surface, because, once the resin has cured, anything you had can only enter a mechanical, not a chemical bond. (That's independent of the type of the resin).

Epoxy just gives a better bond, that's why there's such a marked preference for it for repairs. However, your design looks like it will have redundancies in strength and bonding area, due to your "backing plate" of a patch.

So, you might be able to do your work in polyester and get away with it. If you had the "backing plate" laid up and well cured (using polyester) you could sand it and then use a bit of epoxy glue to attach it to your gap from behind, then fill the gap with more laminate (using polyester).

If you decide to sand the edges of the gap to a 1:12 bevel, that needs to be done only from one side. The front side, opposite the backing plate.

To get good attachment, you do need to sand through any paint layer, and yes, it's quite possible that you are looking at paint there. I would tend to use a 60 or 80 grit (unless you can find more qualified advice in the technical literature online). Unlike paint, the epoxy glue (or polyester resin) can easily fill the sanding marks and I would imagine sanding with such coarser grit would give you a better "grip". (When gluing with epoxy, make sure not to clamp too hard, or you'll squeeze the joint "dry").

Remember to lay up your backing plate as a step-pyramid, then after curing and sanding, attach it with the wider side. That's to allow a more gradual transition in strength for your repair.

I think I can guess what you are doing this for, and in that case, having a bit of a "rib" on the underside due to the backing strip might give your piece a bit of additional strength.

[hectoretc]

I think I can guess what you are doing this for, and in that case, having a bit of a "rib" on the underside due to the backing strip might give your piece a bit of additional strength.

I think you can guess what it is for too...

I'm in my 3rd or 4th prototype model (depending on how you count them) for the companionway hatch and have elected not to post each test piece because they are just that. Test pieces. Throught the process though, I have decided the shoe box top configuration is truely going to be the best for water seepage control. I won't go into the details of the current iteration too much becuase it most likely will change again, but one thing I've decided for sure is that I want to move the raised lip back about 3-4 inches to use as a cover over the cuddy hatch. Ergo the need to seperate it from the remainder of the hatch cover and fill in the gap.

I'm temporarily away from my computer that lets me shrink my photos down to forum friendly sizes so I can't post them just yet, and I was concerned that specifcs would cause more confusion than value without them for reference.
Appreciate you playing along though...

I'm pretty sure you've made mention of (and even posted a photo) the epoxy in a tube that mixes at the tip, maybe works with a standard construction style glue cartridge gun? That would be really convenient. Can you cite the brand and product? Maybe you've also mentioned that before but I'm not finding it.

Thanks again for the information and support.

[GreenLake]

My preferred manufacturer is SystemThree. Their glue is called "GelMagic". You can order this from their website. I think it's part of their SilverTip series, but I can't recall. (Nicely non-sagging stuff, but it is still liquid enough to even wet out laminate if you must).

West System markets something that seems equivalent as six10.

[jdoorly]

Hi Scott, I was rather alarmed by the term 'patch' and the building up of a center between two old pieces of cuddy roof. What bothers me is that a 'patch' is usually surrounded on all sides by good fiberglass, joining 2 pieces of fiberglass that are several inches apart would need much more overlap than 1 or 2 inches and probably needs a board mechanically fastened to the 2 pieces. I would suggest making a mold of the new hatch out of cheap glued-finger pine, and then laying fiberglass and poly (or epoxy) over that. Or, if you want a curved hatch use some layers of 1/8 ply and encapsulate that in fiberglass. Both, much easier than reusing the hatch cut-out board.

I was surprised at how quick and easy my curved hatch was to make, and if i originally intended to paint rather than varnish I could have made it for $25 instead of $75. Since you already have plenty of poly you won't have to worry about adhering to old fiberglass.

[GreenLake]

Right, there's that. Scott phrased his question as "repair" but new layup would fit his ultimate project better.

Here's another suggestion for Scott that plays into his desire to use fiberglass as material, rather than wood (not that there's anything wrong with using wood).


Soctt, screw the two pieces together with a plywood backing plate. Use Bondo to fill the gap, fair and sand really, really well. Wax, wax, and wax again. Now you have a plug.

Use your stock of polyester resin to make a female mold with some layers of mat. (You can laminate a few scrap pieces of wood as well, so that the form will later keep its shape). Separate mold from plug, wax the inside of mold and now you are ready to do it the right way.

Put down a (not too thick!) layer of gel coat, then laminate your piece to perfection.

Without the detour via the female mold, you could laminate your part directly on the plug, but then you would get a rough outer surface, and can't use gelcoat. In case you are wondering whether people ever go to the trouble of doing the layup for a mold for a single custom part: they do. I once met a guy who did just that to construct a custom fairing for his bike.

It's not as unreasonable as it sounds: the fairing and sanding to perfection is the toughest part of the process, by far. Creating the mold therefore does not double your total effort. I'd expect it would result in 20% more work, but the result can be great.

[hectoretc]

My preferred manufacturer is SystemThree. Their glue is called "GelMagic". You can order this from their website. I think it's part of their SilverTip series, but I can't recall. (Nicely non-sagging stuff, but it is still liquid enough to even wet out laminate if you must).

West System markets something that seems equivalent as six10.

Thanks GL - Am I correct in my understanding that it comes out of the gun (tube) mixed and you can apply it directly to a joint (or whatever) or do you still need to squeeze it into a tray or container and mix before applying. The only reason I ask is because on the gel-magic ordering site, they also offer/suggest mixing sticks on the same page when ordering the tubes of gel-magic.

Thanks,

[hectoretc]

Hi Scott, I was rather alarmed by the term 'patch' and the building up of a center between two old pieces of cuddy roof. What bothers me is that a 'patch' is usually surrounded on all sides by good fiberglass, joining 2 pieces of fiberglass that are several inches apart would need much more overlap than 1 or 2 inches and probably needs a board mechanically fastened to the 2 pieces. I would suggest making a mold of the new hatch out of cheap glued-finger pine, and then laying fiberglass and poly (or epoxy) over that. Or, if you want a curved hatch use some layers of 1/8 ply and encapsulate that in fiberglass. Both, much easier than reusing the hatch cut-out board.

I was surprised at how quick and easy my curved hatch was to make, and if i originally intended to paint rather than varnish I could have made it for $25 instead of $75. Since you already have plenty of poly you won't have to worry about adhering to old fiberglass.

Thanks guys - I really appreciate your thoughts and suggestions, and I may ultimately end up going that way.

To get somewhat current, I'm on my 4th prototype, no point in rehashing 1 to 3 because they weren't satisfactory, and I don't have the photo upload capacity to get into them anyway. For the purposes of clarity, I'm using the term Hatch cover as the companionway cover and door as the normal cuddy bulkhead door (vertical) that lots of people have (in various forms).



This iteration follows the shoe box top concept having milled (using a table saw and router) some 2 x 4 CCA pressure treated stock into a pair of L and inverted L pieces that form the base structure for the hatch assembly.

This structure is taller then I hoped but it is very solid. To finish it, my thinking was to dissemble the pieces and cut/sand a much more rounded outside edge on the wood. The pieces would be glued both together (with pins) and glued (epoxied) to the fiberglass, the screws removed and the holes of course filled, then I would build a fiberglass wrap from the cut edge of the fiberglass panel around the wood curve, down to the deck. I would do it with the hatch on the boat using wax paper is a deck shield to give some sense where the finshed edge would be and to further help match the deck curve. That followed by cut & sand rough hatch cover to deck edge. The water seal and strength comes from the wood on wood (with rubber seals) frames.

The 4" slot I cut in the hatch to move the outside lip back over the cuddy door hinge/seal will be strongly supported by a solid wood frame. My concerns lay pretty much exclusively in the strength I can expect from the existing fiberglass transition to the added fiberglass pieces. There really shouldn't be a lot of stress on that seam that I can envision. If I were dumb enough to stand on the outside edge of anything fiberglass I guess I wouldn't be surprised if it cracked some.

A question is, would there be any benefit in cutting either square or V notches in the existing fiberglass to add attachment surface area for the new virgin material, plus reducing any "shear" pressure from a straight line joint?

Sorry if this was too hard to follow, and if you either tire of, or can't get your head around what I'm talking about and choose to just slowly back away so's not to spook the psycho with the sharp object I'll understand and eventually figure it out.

Thanks

[jdoorly]

PsychoScott, your inexperience with sailing will soon be in the past, and it is of no consequence while 'messing about in boats' since your willingness to use sharp objects round and about your boat shows great commitment and confidence in achieving the successful ultimate outcome. I find that the people I most respect, like yourself and some of the 'beautiful minds' I work with, have no real need of my instruction or guidance and would accomplish their goals simply because to them it's fun.

[GreenLake]

Scott, we know what you'll do is what you want to do...

but looking at your pictures, I would go back to my suggestion of simply modifying your prototype into a "plug".

You would be reusing the most important aspect of the old fiberglass, which is the "information" contained therein, viz. the precise curvature. That's much more useful than merely saving a bit of material.

So go ahead, shave off enough of the temporary wood until the outer dimensions are where you want them, plug the gap from below and fill any rough spots with bondo and sand until perfect(!)

Then use that as described in my earlier post to lay up a new piece from all virgin material. You won't have to worry about strength, as it will be a single piece. You won't need to worry about surface treatment, since you can use gelcoat in a mold, where it will cure properly.

And you won't have to deal with epoxy.

When you are done you'll have a perfect shoebox lid. Nice surface, nice curve, and you can design it a bit more shallow than you would when working with wood

The inner frame you could build with wood and epoxy that to the deck from below. Epoxy treated wood with some UV protecting paint or clear coat will last forever in that protected location. If you paint it the color of your gelcoat, you wouldn't notice it's wood (depends on the looks you are after).

Do up some drawings - too hard to follow verbal design. A photograph of a sketch would be fine - we don't need CAD level design to understand your basic plans.

[hectoretc]

but looking at your pictures, I would go back to my suggestion of simply modifying your prototype into a "plug".

Thanks guys - I truely do appreciate your thoughts and your patience.
I really do get it, and doing some soul searching, I think the reason I'm resisting is discomfort with a process I've never done aka plug and mold and gelcoat and finished piece.

But two realizations come forth, first, since I'm not really destroying anything, so if it doesn't work, the worst that can happen is I can either do it again, or go back to plan... d or e... (whichever this one was). Second... my posts are too long and complicated. So I'll work hard to keep them short and in very small incremental steps.

Step 1 - Plug - My plug right now is way too big. If I used it as is, the new lid would flop around with about 3/4" of play on all sides. I'll need to build a plug that doesn't have to be structurally sound, but rather the exact right size for the outside edge of the finished piece, which should be the outside edge of my opening plus maybe 3/8" all around. That would allow for a 1/4 thick fiberglass edge and 1/8" gap between. (like I'm going be be able to be that precise").
I also need to solve the challange of managing the flare at the back of the cuddy (both the boat side and the lid side). I knew that was coming up eventually, so I guess now is as good a time as any to attack it.

OK... off to make a correctly sized plug...

[GreenLake]

As you build your plug, make sure that the 4 sides are not truly vertical, but just a tiny bit angled. Helps in getting the mold off the plug and later, the piece out of the mold.

In builiding a plug, I've had bits of Bondo sticking to the mold. That stuff can separate - or perhaps it was because I used a liquid release agent, not a wax (and it may have soaked into the bondo). Use a good release was and apply several coats, buff each.

[hectoretc]

Thanks GL
I'm sure I'll be back to ask many questions before i am bold enough to start casting. I still have a dozen questions about the plug but I'll try space them out a bit.
Thanks again,