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Old 31-01-2011, 09:14   #1
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Hull / Deck Joint

as many of you know the hull deck joint on a catalina 27 isnt the best in my vberth i can see many areas where the deck joint is far from perfect my question is i was thinking of fiberglassing in the voids in the joint from the inside with some premix fiberglass resin compound, does anyone have any suggestions or concerns with doing this. i figure will make the joint stronger and seal it up better eventually i want to take the rub rail off the outside and replace with some nice wood. thanks
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Old 31-01-2011, 10:55   #2
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Fiberglass resen is a very btittle material and would most likley crack jn a very short time. It would be much better to use some goop like 5200 or poly sulfide which won't harden and will seal the gap.
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Old 31-01-2011, 10:55   #3
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better to use epoxy with a very light weight filler powder,colodial silica or somthing like that and inject it in with a mastic gun.

polyester resin is too heavy and liable to fall out.

sika flex/5200 works well but expensive
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Old 31-01-2011, 14:01   #4
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If there is a gap then fill it with 3M 5200 or alike. Then you can glass it over with EPOXY + glass cloth (not polyester). If watertightness counts ;-) then start the project from the outside - do not let water in rather than keep it trapped.

Make sure there is something else than 3M and epoxy that holds the whole thing together.

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Old 01-02-2011, 00:28   #5
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The hull to deck joint on your boat needs a gap filling bedding compound, like the polyurethane already mentioned. If you elect to bond the joint, the two surfaces should be clean and more importantly well toothed, if not have all of the gel coat removed for best adhesion. It's completely unnecessary to "back fill" these joints unless you are intending some really serious off shore adventures in heavy weather or you have some other structural needs. I'm not sure what year your Catalina is, but the hull shell/deck cap joint is hard fastened over butyl rubber (early models) or polyurethane (what most have). The hard fasteners carry the load, mostly in shear, though some tension can be expected, in which the fasteners, if on sufficiently close enough centers (approximately 6" on your boat) will easy suffice for 99% of the owners out there. If this, for what ever reason isn't good enough, then double up the fasteners (3" centers) for a nearly bullet proof hull shell/deck cap joint.

You could epoxy it, but the advice of a light weight filler is incorrect. You'll want a structural mix, say 50% milled fibers (we call this stuff liquid 'glass) and 50% silica to harden and stiffen the mixture. Of course, as I mentioned, the bonding surface needs to be clean and well toothed, plus the best bond would be on the mat or fabric, not the gel coat. Personally, this wouldn't be my call, as this treatment will raise new issues and you'll quickly find all the highly loaded areas along the joint seam, which is precisely why they use a bedding compound rather then a fully bonded joint, not to mention the future repair issues with a bonded joint.

In the end, unless you have a real need to marry the deck cap to the hull shell, you'd be best advised to use a bedding. If you need a better looking treatment to the hull/deck cap seam then I'd recommend a lovely piece of cedar instead.
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Old 01-02-2011, 09:52   #6
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The hull to deck joint on your boat needs a gap filling bedding compound, like the polyurethane already mentioned. If you elect to bond the joint, the two surfaces should be clean and more importantly well toothed, if not have all of the gel coat removed for best adhesion. It's completely unnecessary to "back fill" these joints unless you are intending some really serious off shore adventures in heavy weather or you have some other structural needs. I'm not sure what year your Catalina is, but the hull shell/deck cap joint is hard fastened over butyl rubber (early models) or polyurethane (what most have). The hard fasteners carry the load, mostly in shear, though some tension can be expected, in which the fasteners, if on sufficiently close enough centers (approximately 6" on your boat) will easy suffice for 99% of the owners out there. If this, for what ever reason isn't good enough, then double up the fasteners (3" centers) for a nearly bullet proof hull shell/deck cap joint.

You could epoxy it, but the advice of a light weight filler is incorrect. You'll want a structural mix, say 50% milled fibers (we call this stuff liquid 'glass) and 50% silica to harden and stiffen the mixture. Of course, as I mentioned, the bonding surface needs to be clean and well toothed, plus the best bond would be on the mat or fabric, not the gel coat. Personally, this wouldn't be my call, as this treatment will raise new issues and you'll quickly find all the highly loaded areas along the joint seam, which is precisely why they use a bedding compound rather then a fully bonded joint, not to mention the future repair issues with a bonded joint.

In the end, unless you have a real need to marry the deck cap to the hull shell, you'd be best advised to use a bedding. If you need a better looking treatment to the hull/deck cap seam then I'd recommend a lovely piece of cedar instead.


thanks for the information par
what i am planning on doing is in fact getting the boat sealed up then wanting to remove the rub rail, not sure if the rub rail provides any structural integrity or just joins the deck to hull, but want to replace the rail with some nice wood. but as i mentioned i dont want to effect the joints integrity.
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Old 01-02-2011, 09:55   #7
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there is a new flexible epoxy out there that may be worth considering for this task .. if you did not want to go with caulking.
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Old 01-02-2011, 10:25   #8
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Hi Michael,
You are getting lots of good advice but I suggest best not remove the toe or rubbing rail if there is any chance it forms part of the present bonding system.
I am not familiar with the construction techniques on your specific craft, but it is not unusual to have a hull / deck join with fasteners through a toe rail pulling the two part together.
Usually you'd pull them down onto a sealant and again, not unusual to guarantee the join by finishing it off internally with a glass cloth strip to bridge both surfaces.
I'd suggest if everything you have is watertight rather than trying to back fill voids (which speaking from experience you'd find tough to grind back in the limited spaces you have) why not prep both surface areas back for a couple of inches all round inside and apply a cloth tape to cover the join? Polyester resin would perhaps be better if thats what the hull / deck already are.
That solution would presumably give you want you want, and at least provide some added strength to the joint.
Enjoy
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Old 01-02-2011, 11:06   #9
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this is the idea of wood joint im thinking about
Sovereignty, the Catalina 27 - Sovereignty: A Unique Catalina 27 (hull # 65)
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Old 01-02-2011, 18:19   #10
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Michael,

Exactly what this chap did to the hull to deck joint is unclear to me, so I won't comment on that mod.

However, I do hope that you will not follow in his footsteps with the rest of the madness that he has accomplished. His workmanship looks excellent, his judgement is questionable.

Words fail me in looking at this vessel, but terms like overcapitalization, unseaworthy, ridiculous and other unflattering things rattle around in my mind.

I guess everyone needs a hobby...

It is bad manners to criticize another's boat, and I apologize for so doing, but when someone raises the displacement of a stock boat by a factor of about 2 1/2, much of it above the original COG, the stability curve is SERIOUSLY compromised.

The Cat 27 is a perfectly competent small yacht in its standard form, not the best, far from the worst. This owner, IMO, has managed to undo that rating.

Rant now terminated. I hope that you can solve your hull to deck joint leaks, and agree that a sealant such as Sika 291 will likely do the job without major investment of time or money.

Cheers,

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Old 01-02-2011, 22:17   #11
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Lol I agree Jim some of the mods are a bit bizarre for sure but I do want to build a wooden rub rail
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Old 02-02-2011, 04:08   #12
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I didn't bother reading through the Sovereignty's modifications, but the wooden sheer plank and bulwark are certainly doable, but it's not an easy task to do right and insure the hull shell/deck cap seam is tight.

What I see on his hull/deck seam is it's covered, not ground down. It depends on the type of hull/deck cap joint employed and there are generally three different types; the shoebox and the inward or outward turned flange styles.

I'm not sure what style is used on your boat, but a picture of the joint, from inside and above and below on the outside will determine it. I'll bet on an inward turned flange style, as these are common on sailboats, but the shoe box is too.

This joint is a critical one and the extruded rail often plays a role in it's integrity, particularly on the shoe box and outward flange styles.

Polyester resin wouldn't be my first choice here as it's mechanical bond strength is quite weak and the need to remove the gel coat, to get a reliable bond, pretty much means the deck cap must come off.

Again, the hull shell/deck cap joint is mechanically fastened over a bedding compound. The bedding is there to prevent leaks, not to hold the joint together. The extrusion forms part of the fastener system in the shoebox joint and also on some of the outward flange joints, so consider what you're doing. As a rule the elastic compounds will out live the bonded hull shell/deck cap treatment. This is because rigid joint (bonded) will develop cracks from local impacts and other damage, eventually leaking, while the bedded joint will absorb the isolated, impact derived elongation and remain sealed, plus is removable for repairs if the need arises.
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Old 02-02-2011, 08:11   #13
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... It depends on the type of hull/deck cap joint employed and there are generally three different types; the shoebox and the inward or outward turned flange styles.

I'm not sure what style is used on your boat, but a picture of the joint, from inside and above and below on the outside will determine it ...
Hull-Deck Joint Types
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Old 02-02-2011, 10:22   #14
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thanks for the photos gord
from the pictures my deck joint looks just like the shoebox as i have an aluminum track with a rubber rubrail in its groove.
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Old 02-02-2011, 10:51   #15
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I would think taking off on a round the world cruise with the person who modified this boat would be an interesting way to spend two-three weeks.
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