Deck-Hull Joint

[Dutch Peter]

Anyone ever did some calculations or tests on GRP deck joints which were only glued and not bolted or screwed?
What's the general experience with this type of joints on the long run?

[mmd]

I have no first-hand experience with controlled testing of non-mechanically fastened hull-to-deck joints, but I do know that several manufacturers of motor & sailing yachts are using advanced adhesives for structural bonding in these highly-stessed areas. I am currently telling several of my clients to use the "belt-and suspenders" method of bonding plus bolting mainly because their products (commercial fishing boats) take a lot of impact loading around wharves, and the conservative fishermen are reluctant to abandon the methods of construction that have worked for them in the past. Basically, no one wants to be the first to risk an expensive bond failure, and my client builders find the relatively small cost of adding bolts to the joint is easier than trying to change an industry mind-set. Personally, I would be in favour of a purely bonded seam in all but large or rough-useage vessels, provided that the shop practices and seam design were properly tuned for the adhesives.

ITW Plexus, an American manufacturer, is very prominent in the US market, and I have spec'd their materials to clients for internal structural bonding. Their website is quite informative, and features some honest-to-god engineering data such as tensile strength, elongation, shear strength, etc.

http://www.itwplexus.com/home.html

[Dutch Peter]

mmd,

Quote: {Personally, I would be in favour of a purely bonded seam in all but large or rough-useage vessels, provided that the shop practices and seam design were properly tuned for the adhesives.}

I agree with you, but have to work with a set of Rules. It is therefor I'm trying to find some data, to support my personal opinion.

Local customer (sailing yachts 35-65 ft) has modified the bolt & adhesive methode. They're using countersunk bolts, no nuts, no washers, and a good adhesive. They cut thread in the flanges of the deck joint for the bolts. There is no laminate added afterwards to seal the joint.
When testing this, the boltheads came of but the laminate remained undamaged.
They're now thinking of leaving the bolts out completely.

Does anyone know what the standard connection is according to for example:
ABS, DNV, BV or GL?
Any other experiences with this type of joints.

[Dutch Peter]

To keep my thread on top, I have to reply it myself. That's a laugh!
I expected a bit more response, anyone????

[Danielsan]

Hi there,

I am figuring out how to build my own boat at this moment so I have been doing some thinking:
1 make a hull-deck-in-one seems difficult?
2 get a male sleeve on the deck part, and get a female sleeve on the hull part
before assembling fill the female sleeve up with a "Sikaflex' PU mastic(don't know if it's the wright word) NOT SILICONE!!! put the two pieces togheter. I did use it a lot
in building joinery because of it's high dynamic strength.
When used as a sort of glue it should just do great.

Finaly you could glass over the joint,...

Please correct me if I am wrong because I am willing to use it that way! :-)

Greetings,

Daniel Peeters

[Dutch Peter]

Originally Posted by Danielsan

Hi there,

I am figuring out how to build my own boat at this moment so I have been doing some thinking:
1 make a hull-deck-in-one seems difficult?
2 get a male sleeve on the deck part, and get a female sleeve on the hull part
before assembling fill the female sleeve up with a "Sikaflex' PU mastic(don't know if it's the wright word) NOT SILICONE!!! put the two pieces togheter. I did use it a lot
in building joinery because of it's high dynamic strength.
When used as a sort of glue it should just do great.

Finaly you could glass over the joint,...

Please correct me if I am wrong because I am willing to use it that way! :-)

Greetings,

Daniel Peeters

In principal, your idea is not to bad, but make sure your sleeves are vertical otherwise it won't work.
Your also right about overlaminating the joint, but that is just the point of my question. We don't want to do that anymore.

[Danielsan]

Yep that is one of my concerns at this moment, how am I going to make those sleeves?

If you don't want to overlaminate the joint you don't need to, the joint will keep it together by itself. It should also give a nice cleen finish.

Greetz,

Daniel Peeters

Originally Posted by Dutch Peter

To keep my thread on top, I have to reply it myself. That's a laugh!
I expected a bit more response, anyone????

what's this than

[Roly]

I am aware of the age of this thread....but
Any updates on load testing a purely glued or filleted and tabbed hull deck junction?
Anybody know of scantling rules for this type construction?

[SamSam]

I imagine the people who sell the adhesive might know a little bit about it. Go here
http://www.proboat.com/
and page through their digital issues (page turning buttons at the top) and then go to their advertiser links and e=mail them.
They might even have articles in the magazine itself.

[Wynand N]

On our powerboats we join the deck to hull with bonding paste sold by Harvey's fibreglass. It has a grease like texture and activated with mekp. It forms a solid bond and never had deck came loose on our boats.
Larger boats we fiberglass the fillet corner on the inside of joint over just to be on the safe side.

[Roly]

Thanks guys.
I am more interested in the fillet & tab method but the adhesive Engineers probably know the numbers for this method as well.
Also I will try the engineers at Hi modulus fabrics.
I guess the weakest link is the secondary bond.
It is too late for an overlap & adhesive/mechanical fixing for me.

The NA's err on the side of accepted practice,(belt & suspenders approach) like most designers where the public is involved.
Can't find anything in ABS either for purely F&T.
Good to hear from your experience Wynand, thankyou.

[tunnels]

Originally Posted by Danielsan

Yep that is one of my concerns at this moment, how am I going to make those sleeves?

If you don't want to overlaminate the joint you don't need to, the joint will keep it together by itself. It should also give a nice cleen finish.

Greetz,

Daniel Peeters

While i worked in Korea last year making match racing yachts we did a nice detailed dech to hull joint i think you are looking for . This is my email address stuartwrcom@gmail.comand i will send you some pictures of what we had . The join was glued all the way round the boat and had no fastenings anywhere at all !! never had one problem with any part of the 8 boats , but i did increase the glueing surfaces from 40mm to 60 to get a little more from what we were doing .

[souljour2000]

My 83' hunter is glue-bonded at the seams only...looks like it is holding up okay but I am strongly considering adding bolts spaced a foot apart or a bit less..looking at adding a toe-rail...but I want to move the genoa track onto the cabin sides or top...out of the way..."the rat-walk" is skinny enough going forward on each side....the track is bolted heavily and is about 4 feet long...it would help the hull stay together in a de-lam situation...so thats also why I want to bolt the seam ....

[Speng]

On a slightly different note, does anyone have experience with using structural adhesives in other parts of the boat such as bulkhead joints etc. I visited the SP factory on the Isle of Wight last year and they were using their Spabond product to do this type of thing. It's an epoxy product basically epoxy thickened with colloidal silica or something similar. They were using it on bulkhead joints on RNLI RIBS so it's evidently strong and their experience that it was at least as satisfactory as normal taped joints but much faster to apply.

So anyone have experience with this or similar products or methacrylate glues in this application?