First 25.7 lifting keel

Right, is the boat in the water or ashore ?

Ashore would make it much easier to sort out.

I don't know the particular boat but I'm guessing she has an alloy toerail; that will have to come off - gently so as to refit - for a start.

Then you'll be able to see what you're faced with, if you could post photo's here there would be a lot of advice - some of it even useful ! - forthcoming,
 
No the deck is only glue to the Hull and over there is a small teak toe rail screwed by parker screws not even bolted.I think that un somes parts thé sealant glue vis missing between the Hull and the deck
 
Youen,

the hull/deck join MUST be bolted; my 22' boat has 72 ( marine grade stainless steel ) bolts accounting for both sides and ends, and a lot of Sikaflex sealant.

You may not need that many, but you must have confidence in your boat the lid isn't going to come off !
 
Which is why French boats have a bad reputation for build quality.

If you take off the toerail and rubbing strake it should be easy to see where to drill through the ' biscuit tin lid ' join so as to attach by bolts; the bolts need to be at least 6mm diameter marine grade stainless steel with two large ' penny ' washers behind the heads and nuts, inside and outside - with Sikaflex sealant squeezed inbetween the join.
 
Seajet said:
They CAN be, used a lot in aircraft inc gliders and the Harrier, Space Shuttle etc to save weight; but bonding material tends to have an age / fatigue limit, a row of stainless bolts around a sailing cruiser not so much.
Click to expand...

The problem with bonded joints is that they require much more care during construction to get them right, probably the cause of the OP's problem, because the builder of a small budget boat doesn't have the gazillions to spend on getting it right that aviation does. Bolting by contrast is a low skill job. Stainless steel suffers all sorts of problems too, from stress corrosion cracking to crevice corrosion & fatigue cracking starting from a thread. I'd say the problems are different, rather than one being better than the other.

If the OP's boat is bonded & it's failed the shape of the joint will determine how practical it is to retrofit bolts. Biscuit tin lid is not the only design pattern.
 
But biscuit tin is the very likely method; and I'd be interested to know the failure rate between stainless bolts in shear v bonding !

I used to photograph the failures and proposed fixes of Harrier GR5 carbon fibre wings - the largest c/f structure in the world at the time, everyone was terrified of the material and bonding - though still primarily held on by 4 big bolts like all Harrier wings .

Stainless steel is not a silver bullet, but it's a helluva lot easier to fix and replace.
 
Seajet said:
But biscuit tin is the very likely method; and I'd be interested to know the failure rate between stainless bolts in shear v bonding !

I used to photograph the failures and proposed fixes of Harrier GR5 carbon fibre wings - the largest c/f structure in the world at the time, everyone was terrified of the material and bonding - though still primarily held on by 4 big bolts like all Harrier wings .

Stainless steel is not a silver bullet, but it's a helluva lot easier to fix and replace.
Click to expand...

Bolts are much easier to replace agreed, but that doesn't help the OP, he doesn't have them to replace.

The most common hull/deck join design pattern is inboard flange according to Sail magazine, but we might be talking about the same thing. True biscuit tin lid has no flange on the hull, just a vertical side. This is a poor design for pure bonding as it's difficult to get clamping pressure on the joint, & the gloop gets misplaced during assembly. It's also weak from side forces. The other lid method is an inboard flange on the hull. The bonding gloop is horizontal & pressure can be applied by pushing down on the deck. Expensive multiparty moulds are required though to make the inboard flanged hull.

As an aside, much better bonded joints are outboard flanges on both hull & deck. These do not require multipart moulds & clamping is very easy, just use a load of G clamps during assembly. The downside is that there is a flange sticking out round the hull, not desirable on most boats, but useful on the centre hull of a trimaran as it's what the trampolines attach to.
 
Last edited:
Which is why I said I'd like to see a comparison of bonding / glued surfaces - especially considering age and work fatigue - compared to stainless steel bolts in shear load...

There's no comparison for strength and reliability, but bonding is lighter and possibly cheaper / easier.

I cannot see a reason why the OP's boat hull and deck were not bolted together from the start - maybe another thread's worth - and especially can't see any reason not for him to do it now, while hull, deck and he are still in contact with us here rather than via a oija board.
 
Seajet said:
Youen,

the hull/deck join MUST be bolted; my 22' boat has 72 ( marine grade stainless steel ) bolts accounting for both sides and ends, and a lot of Sikaflex sealant.

You may not need that many, but you must have confidence in your boat the lid isn't going to come off !
Click to expand...

Rubbish. There are hundreds of thousands of boats with screwed or pop riveted hull to deck joints. Designed by Degree carrying Engineers, if you get my drift.
 
Last edited:
Which planet are you speaking from ?

I'm a qualified engineer too and ' pop rivets ' in this application made me laugh out loud ...

We're talking about SHEAR LOADS on fastenings here.
 
Last edited:
Seajet said:
Which planet are you speaking from ?

I'm a qualified engineer too and ' pop rivets ' in this application made me laugh out loud ...

We're talking about SHEAR LOADS on fastenings here.
Click to expand...

Same planet as you, although obviously my bit isn't as well built as yours.

As a qualified engineer you'd know that there is no difference in shear strength between similar diameters and materials of self tap screws and machine screws. If they're different diameters you'd be capable of multiplying the number you need. And you'd know how to calculate the number and size of pop rivets of a softer metal that you'd need to replace a number of stainless screws to gain equivalence.
 
anoccasionalyachtsman said:
Same planet as you, although obviously my bit isn't as well built as yours.

As a qualified engineer you'd know that there is no difference in shear strength between similar diameters and materials of self tap screws and machine screws. If they're different diameters you'd be capable of multiplying the number you need. And you'd know how to calculate the number and size of pop rivets of a softer metal that you'd need to replace a number of stainless screws to gain equivalence.
Click to expand...

Yes, spiffing; but the OP's hull / deck joint seems to rely on glue - and French built boats are well known to be lightly built, I don't say this with any national bias as unlike in Nelsons' time I rate a French sailor way better than the average Brit.

I've had enough of this typical YBW aggressive response when trying to offer qualified experienced thoughtful help, F888 the lot of you armchair clueless critics. :rolleyes:
 
Last edited:
You must log in or register to reply here.

Other threads that may be of interest

S
Amiable demands for money!
Replies
15
Views
829
penberth3
P
P
Essential pre purchase or even pre survey checks
2
Replies
28
Views
905
Refueler
Refueler
conks01
Hanse 301 Buying Advice
Replies
5
Views
352
stownsend
S

Share this page

Top