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Old 07-09-2020, 18:56   #1
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Deck/hull joint glassing

Hello. For couple of reasons I want to remove teak toe rail which sits on top of hull/deck joint. The wood is held by bunch of 1/4 bolts through the the joint sandwich. The joint itself is through-bolted by separate set of shorter 5/16 bolts and also glued with some black stuff which is rubbery a bit and in some areas kind of dissolving a bit. I hear there was no 5200 back in 1988, so it's something else. I figure since the joint looks solid, removing roe rail bolts will not affect structural integrity. I plan to glass over the joint from outside with one/two layers to stop most leaks once and for all. Here is the question. What do I do with those bolts that hold the joint? I don't want to touch them. Do I glass them over, i.e. over their tops on the outside? Their tops I can't see since they are under the toe rail. The bolts are very close to the edge of the deck, so I can't bypass them when laying up the glass. Naturally I'd like to keep all the stanchions. On the picture the teak would be replaced with glass strip of same width but almost level with deck. The plan is to go without toe rail for a while and then maybe build either glass-encased wood one glued to the deck or maybe something else. Thanks.
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Old 07-09-2020, 19:55   #2
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Re: Deck/hull joint glassing

Hi. Who built the boat. When. Can you draw a sectional view...like you cut into the joint like a slice of bread.
Can you get to the bolts.
Mark
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Old 07-09-2020, 23:02   #3
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Re: Deck/hull joint glassing

I wouldn't glass over the deck/hull bolts. Fiber-glassing over the deck/hull joint will add very little to the structural integrity. If it is only a temporary measure why not use a waterproof tape?
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Old 08-09-2020, 06:25   #4
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Re: Deck/hull joint glassing

Hello and thanks. The boat was build by a yard long gone. The hull/deck joint is flange and lid type as pictured here: https://captnpauley.typepad.com/.a/6...1dbff7b970b-pi
except mine has shorter deck part and teak toe rail covers the outside. So why would not be advisable to glass over the joint and over the bolts? What is "waterproof tape"? Some of the bolts are not accessible without demolishing interior. That is another reason why I think the teak must go: it can't be removed without damaging i.e. drilling out or cutting inaccessible bolts. Without removing it I can't even apply band-aid onto the joint and bolts.
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Old 08-09-2020, 07:17   #5
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Re: Deck/hull joint glassing

You may find that removing the toerail and glassing the joint over is more of a headache than its worth, and may open up new issues when you expose the edge of the deck and the bolt heads. Toerail replacement of course is no fun either. If your toerail is leaking, but otherwise sound (not wobbling), I'd try to salvage what you have.

I'm in a similar situation with old caulking and leaking toerail, but with a larger hull flange and what was once a rotten plywood deck. I ground a bunch of files into tools to route out the old failing sealant/caulking, creating a very thin (1/16" to 1/8") groove at least 3/8" deep from the outside of the hull.

In my case, the deck side of the toerail joint is filled with thickened epoxy as the new deck is installed, while the outside will either get a tinted thickened epoxy or 5200 injected deep into the groove. This goes along with popping out the old bungs and installing new ones that fit better.

Routing out the old caulking from under the toerail is a lousy day's work, but if you clean the two faces well and go deep enough, your new sealant should last a long time.
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Old 08-09-2020, 09:04   #6
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Re: Deck/hull joint glassing

My hull-deck joint is same as OP's' larger fasterners holding the deck to the hull flange with smaller fasteners holding the toerail through both the deck and hull flange.

My toerail is adequately weathered/worn so as to be minimally serviceable in a couple spots, and I have maybe 6-8 toerail fasteners that leak on a rare occasion. These fasteners are frozen somehow in place where, even if I could easily remove them, the toerail needs to go.

I was going to remove the toerail and glass the joint inside/outside...glassing everything in (i.e. all deck-hull fasteners). With 6-8 layers glass inside and out (a common technique) this does lend structural strength. But I've come up with a different approach that I was to undertake before the Covid stuff came up.

New plan that is easy-ish but not aesthetically acceptable to many perhaps:
-Remove toerail and toerail fasteners.
-Clean-dry holes produced.
-Into holes place flanged FRP bolts with FRP washer over deck/under hull flange with FRP nut. When placing these fasteners, set with quality flexible epoxy (=no way for water ingress about these holes in the future).
-After epoxy is set, grind off the head of the bolt...leaving the flange of the bolt head to maintain capture on the underlying washer.
-Fair-in the top-side FRP washer/bold-head remnant to suit and/or somewhat hide under a new toe-rail solution.
-While I'm at it I'm going to glass 3 layers of the bottom/inside of the hull-deck joint.

Otherwise, I will do some type of "from the outside" reaming/digging of the joint as described by SVQofP...wherein I'll place some quality flexible epoxy. But no glassing of the outside of the joint (a biggie to me).

Importantly, the edges of my deck are solid fiberglass such that I'm not concerned about water ingress from about the hull-deck joint migrating into wood in the deck.

For a future toerail I'm undecided on a few options...but if I go back to having any wood affixed to the deck topside, I'll embed FRP threaded studs into the deck poking up /through whatever wood I use. I really, really don't like metal fasteners around/through this joint (or through the deck in general).
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Old 08-09-2020, 12:25   #7
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Re: Deck/hull joint glassing

Greetings. The method described above by Singularity is very interesting. There are a number of very high tech boatbuilders using reinforced plastics in everything from submarines to small warships. The latest reinforcements are, Carbon and Arimid . I found a review in The Journal of Marine Science and Engineering by Rubino. The method above gets you out of the problem of heat when you’d like to use a fastening and you’d like to cut the head off after.
Very, very unique method. I can think of a lot of applications.
I did one Bruce King Design where drilled through, 316 bolted 3/8” with fender
washers both sides, kept the joint 1/4” open, filled it with 5200 as fast as we could then bolted it down and glassed in epoxy over the top of the flat head bolts. Laminated Teak 4” bullwalk Cap rail on the flat over it. The bulwark was held down by the chain plates and the gammon in the bow. Not a drop leaked because no more fastenings went down into the flange area.
Once you get the teak off everybody here will have a better idea of what you are faced with. You might be able to drill through both flanges, close off the bottom,
Vee out the top and fill it with a composit bolt set in plexus.
If you set your rail in Plexus, it will be very strong.
Please let’s see what it looks like without the teak rail. Till then...Happy trails to you. Mark and the manatees
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Old 16-09-2020, 06:26   #8
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Re: Deck/hull joint glassing

Greetings. thanks everyone for sharing. These are all good points. I'm still not clear on disadvantages of glassing over the structural hull/deck bolts. Since their heads will become really inaccessible, is it bad? E.g. crevice corrosion under the glass/epoxy layer? I doubt it since current situation with sealant and wood on top is not any different. If boat gets into real pounding, I assume hull will flex a bit. Will it hurt/crack the new glass and fairing over the joint? Attached sketch of the plan. If this works, at this point I don't need to decide what kind of toe rail I need if any. In fact, I saw plenty of boats (true, most of them power boats) of comparable size without toe rail at all. Cheers.
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Old 16-09-2020, 06:31   #9
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Re: Deck/hull joint glassing

Some of those boats with no toe rail may have a different style hull deck joint. My powerboat has no toe rail, only a stainless rub rail on the outside. But the hull deck joint is a shoebox joint, so the deck fits over the hull and the bolts go through from the side rather than the top. The stainless rub rail hides the bolt heads.
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Old 16-09-2020, 07:14   #10
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Re: Deck/hull joint glassing

Quote:
Originally Posted by vladkri View Post
Greetings. thanks everyone for sharing. These are all good points. I'm still not clear on disadvantages of glassing over the structural hull/deck bolts. Since their heads will become really inaccessible, is it bad? E.g. crevice corrosion under the glass/epoxy layer? I doubt it since current situation with sealant and wood on top is not any different. If boat gets into real pounding, I assume hull will flex a bit. Will it hurt/crack the new glass and fairing over the joint? Attached sketch of the plan. If this works, at this point I don't need to decide what kind of toe rail I need if any. In fact, I saw plenty of boats (true, most of them power boats) of comparable size without toe rail at all. Cheers.
To start, glassing over the joint is simply a lot of miserable work. On the outside of the joint this requires a lot of fairing work and paint, otherwise adding to expense and potentially decreasing aesthetics if not done right. On the inside of the joint this typically requires removing a lot of cabinetry, sanding/prepping for glassing, a process that can require a partial creative destruction/rebuilding of cabinetry while otherwise making a huge mess with all the sanding work (particularly if the inside has been painted...you don't glass over paint).

With respect to glassing over metal fasteners, it seems almost standard that boats with a hull-deck joint similar to those pictured in this thread were build with at least one side (top side) of the fastener already encapsulated from the atmosphere. So otherwise, in my researching "how to glass over the joint" the universal opinion is just to glass over, inside and out, all the fasteners. Presumably the logic is:
a) the original goop that the factory stuck between the hull-deck provides fastening strength
b) the original metal fasteners, corroded as they may be now or in the future, in the net provides fastening strenght
c) once ~6 layers of glass inside and out are laid about this joint, the net result of the new glass and the above is a joint that 'is not weaker than what left the factory'

That's my read anyway. My idea to use GRP fasteners is predicated upon the idea that...the fasteners used to hold my toerail on indeed go through the joint. I'm looking to avoid all the top-side fiberglass work (substantial), so I reckon GRP fasteners with fender-washers will, in the net, provide adequate strength. Only concern is loss of rigidity afforded by the toerail itself.

Indeed some boats don't have a toerail; all one can say is that such boats were (hopefully) designed to not need one for any structural reason.

On edit: This page shows how I understand glassing a hull-deck joint ought to be done, or something close to it. Clearly not a small job!:
Far Reach Voyages Home Page
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Old 16-09-2020, 08:38   #11
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Re: Deck/hull joint glassing

I can appreciate scope of Far Reach project which is a complete re-build. I would like to avoid such project. The guy is lucky his wife did not bail out. I hear it happens a lot during such fun DIY.
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Old 16-09-2020, 16:27   #12
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Re: Deck/hull joint glassing

A lot of Hull/deck joints fail because of the flexing of the hull. I've bolted mine every nine inches. AND then I have a toe rail capping. Covering up the problem with fiberglass is asking for trouble.

David Pascoe is a yacht surveyor and here is what he has to say.
Deck & Superstructure

Surveying Fiberglass Power Boats

2nd Edition

Chapter 9



https://www.davidpascoe.com/survey_book_chapt9.htm
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Old 16-09-2020, 17:23   #13
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Re: Deck/hull joint glassing

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Old 16-09-2020, 17:26   #14
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Re: Deck/hull joint glassing

If you were going to glass over top as you suggest, you would need to ensure plenty of surface area for the fiberglass to grab. That would mean grinding to bare glass along the top of the hull as well as well into the flat surface of the deck. 3 inches into each ought to do. It doesn't matter then what the fasteners or goop do: six inches of tape along the whole length will hold the boat together. Use some biax; use at least 3 plies; finish with woven cloth. If you add a composite toerail later, you'll want to glass the outside onto the hull anyway. I'd suggest doing the whole project at once so you don't have to grind and fair/paint twice.
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