Deck To Hull Joint

[VIKING]

Any Ideas Of Joining A Polyester Deck To An Epoxy Hull? I Am Trying To Avoid Mechanical Fasteners.

I Have Previously Bonded Epoxy Decks To Epoxy Hulls With Epoxy Adhesive .

I Am Now About To Making A Deck Out Of Polyester And Gelcoat In The Mould So It Comes Out Of The Mould As A Finished Product. (have Perfected My Deck Mould)

The Idea Is To Cut Out All The Fairing Work Needed On The Epoxy Deck

Thanks

[ClarkT]

Plexus and Weld-On should fit the bill well, though I don't see any reason it could not be done with thickened epoxy.

[Thunderhead19]

Plexus is good, I also like Loctite, and SikaFast. SikaFast is new, and seems to be very cost effective. The Loctite (used to be hisol) is really remarkable stuff for peel strength and impact resistance, and Plexus is out-and-out strong stuff, seems to have less peel and impact strength for some reason.

[VIKING]

I Suppose The Question Is Will Epoxy Adhesive Paste Bond To A Polyester Laminate. And So Can I Do Away With Mechanical Fasteners.

[mistral]

no problem with epoxy bonding to poliester; i'd use epoxy adhesive such as SP spabond 345 or similar; in a small/average boat (up to 25 feet) , considering the geometry of deck and hull and with a clever evaluation of the amount of bonding surface, i'd avoid mechanical fasteners and trust in epoxy glue.

fair wind
Mistral

[PAR]

Epoxy will bond well to poly, not as well as an epoxy to epoxy bond, but I'm uneasy about hull to deck joints without metal in them. I've shot down good deals on boats, just because of the spacing of hull/deck joint fasteners not being adequate, in my view. When this feature is advertised in promotional material about a new design, then it's importance can't be just my old fashion way of looking at things.

[henrikb]

I have had problems when trying to apply epoxy to polyester laminate that is "fresh" (less than a year). It is the styrene still coming out of the fresh poly laminate that causes the bond to fail. Best you can do is to try it out before you go for the real thing!

[naturewaterboy]

My '78 Silverton 34C - the deck is fastened to the hull with brass wood screws with some scrap wood backing. Some of the wood is rotten, and some if very hard to get to to replace (I'd have to remove the cabinets in the head and galley for starters). Can I just mix up some epoxy, thicken with Cabosil, and bond the deck to the hull? I figure I can clean out the joint some and just goop the epoxy up into the joint with a putty knife. Will this work or any better suggestions?

[naturewaterboy]

Is there any reason not to bond the deck to the hull on a boat if it was built screwed together?

[alan white]

It can never hurt to add some back-up to the screws. Under extreme conditions, undersize or too-widely-spaced screws can fail. As long as you have access, any reinforcement is at worst added weight and at best makes a much stronger boat.

Alan

[naturewaterboy]

Viking and I would like to not add more screws if the epoxy will be adequate. I seems to me that the epoxy alone would be an all around better way than the best screw or bolt system, or am I missing something?

[SamSam]

Originally Posted by naturewaterboy

Is there any reason not to bond the deck to the hull on a boat if it was built screwed together? I figure I can clean out the joint some and just goop the epoxy up into the joint with a putty knife.

Occasionally it's handy to separate the two halves and screws facilitate that. I assume you are talking about taking off the rubrail and then gooping. You will be putting goop in a joint that is bare glass on the backside of the deck but shiny gelcoat on the outside of the hull, so it might not bond too well, if at all.

[naturewaterboy]

I don't think I'll ever get the urge to unscrew the deck on my 34' Silverton... I hope not at least. I did take off the rubrail - I figured I could run some sandpaper up into the crack and give the epoxy something to bite. I would think that a good epoxy bond has to be better than screws - especially since my screws go into scrap lumber that Silverton used - and that the wood seems to be soft and dry rotting.

[marshmat]

This seems to be a weak point on a lot of production boats.

At the boat show this spring I asked one dealer, who was peddling a remarkably expensive line of craft, how the hull-deck joint on a particular model was done. The response? "Tek screws and 3M 4200". Not even 5200- it was 4200, the temporary easy-removal sealant.

Hull-deck joints need to be strong- and fibreglass does not hold screws well.

My ultimate setup for this joint? One of:
1) Through-bolted at close intervals with decent backing washers on both sides, Plexus or thickened epoxy in the gap, and a beefy rubrail covering the bolts on the outside;
2) Screws used for alignment only, the joint being fully bonded with thickened epoxy, and wide, well-feathered hand-laid glass cloth/tape on the inside to develop the same strength as the hullsides themselves.

Both are overkill, for sure.... but I hate cutting corners.

[naturewaterboy]

I'd put some tape on the inside, but I'd have to do a lot of grinding. When Silverton built my boat, they took the empty hull and glued in carpet first, then built the rest of the boat on top of the carpet. So I'm ripping out the carpet, but they did use some good glue, cause there is a lot of crap left stuck on the hull. Can't imagine anyone buying a new boat with carpet in the anchor locker and inside the cabinets in the head and galley. Guess those who buy brand new boats don't look very close at things like this.