Hull Deck Joint

[Nick]

Ive currently got my c28 up on the dry and need to replace the hull deck joint all the way around. ive read a few posts but cant find any definitive answer if I should be using a flexible bond like sikaflex 291 or epoxy bog.the old joint was white , very brittle and cracked all over the place. the screws of the teak rub rail went through the middle of the joint so I don't think screwing into sikaflex is a very good option.any ideas would be much appreciated.

nick

[C30 Stargazer]

I don't know what the approach was with Compass in joining the hull and deck but on a Triton 26 (built 1966) that I fixed, the joint was cracked and had opened and was leaking - found only after removing the old teak toe rail. I had assumed the leaks were from deck fittings and around shroud chain plates. I found once I had bedded new teak toe rails into place (Sikaflex) and bolted through tight - all became tight and watertight again. I ran sika into the joint where it was dry but as a seal, not as a glue. The result is a tight, watertight ship again. I didn't realise, until the old bolts came out, that the bolts through the toe rail were really holding the hull and deck together and stiffening the boat.

[feebz68]

Hi Nic   

          get a diamond saw and hold it on its side, and run it along where the joint is all brittle and cracked even get a picking device that you can pick all the lose bits out , you don't have to cut the boat in half, but make sure you get rid of all the bog that is broken and no longer bonding to anything, even around any screw holes, you can just drill new ones holes once you have re bogged the join.

 once that is done clear the dust out of it  ( MAKE SURE YOU WHERE A MUSK you never know what horrible stuff has been used to make the bog),

  go to coles and buy a heap of no name talc powder, it is pretty harmless to the lungs, ( there are other products around but talc is good,) talc will make a very strong  bog, pour some resin into an air tight bowl with a lid, say  250ml to 500ml, then pour in your talc and mix it up to make a nice bog. Then get yourself a mixing board, scoop out some bog, put the air tight lid back on the pot, then add a few drops of harnener mix it in well,(this may take a bit of practice to get the timiming right) then just simply apply the bog into the opened up groove you have made with the diamond saw, really squeeze it in there, with a flat paint scrapper,       

and she will be rebogged

you can keep a tinnie bit of resin with hardner in it to lightly wet out the join first, but that's getting into the advanced course,

cheers

I hope that was of some help,

mix a couple of practice bogs first for some other minor repairs , that can be easily ground off or out if your bog dose'nt go off till you get the mix right   

 

[Graeme Lock]

Nick;

 

In trying to fix hull-deck leaks on my C28 over several years, I've become very familiar with the hull-deck join.

 

Here's what I did for the caulking:

* Cut out the old caulk using a knife then chew the rest out with a drill bit in a cordless. The Stanley knife blades shaped like a hook worked best.

* Grind the sealing surfaces back to virgin poly. A cordless drill with a right-angle adaptor driving a disk of 80 grit worked  well. An angle grinder is far too harsh, and you will probably chew great hunks out. Bear in mind the top sealing surface is just the 1/8" thick lower edge of the deck moulding curve, so there isn't much for the SIka to stick to, hence the need for careful prep.

* Apply Sika primer to joint faces

* Caulk with Sika

 

The lower part of the join is the hull moudling flange and can flex, so a hard fill like epoxy is likely to crack.

 

Screwing into the joint is fraught and must be done with care, as you are screwing into just a 1/8" thickness of resin. Once the holes are stripped you have a leak point (as I had courtesy of the PO).

 

My experience is that the caulked part is no big deal, but dealing with the stripped gunwale screw holes is difficult. I have resorted to enlarging the holes and building a plug about 12mm deep x 12mm diam using thickened epoxy squirted in with a syringe. Once cured for a few days, this will take a #10 self tapper screwed in very hard, without stripping.

 

Good luck!

 

Graeme

 

On 29 April 2015 at 18:29, Nick <lata...@optusnet.com.au> wrote:

Ive currently got my c28 up on the dry and need to replace the hull deck joint all the way around. ive read a few posts but cant find any definitive answer if I should be using a flexible bond like sikaflex 291 or epoxy bog.the old joint was white , very brittle and cracked all over the place. the screws of the teak rub rail went through the middle of the joint so I don't think screwing into sikaflex is a very good option.any ideas would be much appreciated.

nick

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[Maeling]

Glad the old joint was white, Gunther Heucmer, one of the Compass owners spent a week in the Lagoon at Lord howe with a friend of mine on an early C28.  Attached to an old sailing ship anchor in the waves of 2 cyclones  in 7 days Gunther determined they had to do a better job of the deck joint.  He came up with this fabulous blue asbestos bog. It is fantastic but if you find black/blue bog in your way on a Compass be very careful grinding into it!  Those bogs need to be treated with respect, self drilling screws are a no-no.  You need to pre-drill properly and check below for cracking.
In your case follow the other guy's advice

Geoff Raebel

On Wednesday, April 29, 2015 at 6:29:51 PM UTC+10, Nick wrote:

[feebz68]

Hi

     I really like the way Graeme has prepared his deck join, and I now there is plenty of great new products out there now, and also there is always more then one way to skin a cat, But i'm not totally sold on removing the bog from the deck joint, even if it seems that it is not really doing much, (as it all adds up in Strength) and then replacing it with SIKA flex, and not using a strong hi strength glue (bog). 

 Yes SIKA flex is flexible, and keeps leaks at bay, it also holds things together, but I really think an epoxy, poly or vinyl ester resin bog should be used on the join, weather your an epoxy or poly man doesn't really matter.

Once the joint has been re bogged, Then I would use the SIKA flex, and smear it over the join, and on the back of the new timber rub rail, then screw or in my case through bolt the permanent rub rail onto the hull, then self tap the sacrificial timber rub rail to the permanent backing timber.

Cheers

Shane  

    

 

[Graeme Lock]

Shane;

I agree re the bog, but in my case a fair bit of bog had been removed at the outer edge, so the sika is used just to seal (it obviously doesn't add strength).

I found some of the bog in mine was damp, so it wasn't keeping water out.

I have no idea what Shakti's various PO's did, but there are voids under the gunwale curve, so maybe they overdid the drilling/screwing. If the bog was sound, the screws would have had some grip and be able to keep the water out. Just shows how ham-fisted work can create a very long legacy of grief!

I agree about self-tappers Geoff, but my new screws will be going into the epoxy plugs.

Cheers, Graeme

[feebz68]

Hi  
                  Epoxy plugs Graeme, very nice and professional :)

 I don't  spose there's enough room there to perhaps, epoxy in some timber plugs, to screw into.

Just chucking the timber plugs out there as another alternative, for our group to see

Anyhow Nic,

                     there's a few different ways to play with your Hull & deck joint 

Cheers

Shane

[Nick]

thankyou all very much for your posts.i think her condition is probably worse than I explained in my first post.when I removed the teak rub rail a lot of the screws were held into the teak but moved freely in the joint.i scraped all of the white bog out simply with the side of a chisel leaving a 5mm gap between the bottom of the toe rail and hull flange.the bog on the most part only went in about 3mm and behind was a void no evidence of anything elastic . from memory the dome of the toe rail was solid . looking in I could see back to where the hull flange starts to curve down to the hull and where the deck comes into contact with it.its very dirty so ill have to pressure clean it out first . from inside the cabin  the grp joint running between the hull and deck has also lifted in parts on the upper deck side (which ill grind out and re glass once ive waterproofed the outside join) . The two stanchion bolts on each of the stanchions are clearly visible when I look through the join . ive decided to surgically grind inside the join with a dremel .

based on plans of attack suggested by graeme and shane im thinking of epoxy bogging from the back of the flange to within 2 or 3mm of the outside of the joint then sixaflex the the remainder for waterproofing. when I put the new teak rub rail in screw it in a bit higher so it doesn't go through the middle of the outside hull deck joint. apologies for such a complicated post but I want to make sure its done right while shes up on the dry for what I realistically expect to be 18 months. (transport and crane hire are murder)

[Graeme Lock]

Shane;

I'm sure you could stick timber plugs in,but I wonder why you would want to.

imho epoxy (or poly for that matter) is better because it won't absorb water and rot, and will adhere strongly to the glass and the bog, and is very repairable.

I am driven to this level by the awful mess others have made of the gunwale with the rubbing strip mountings. Main problems are holes stripped, and holes much too close to the edge of the deck mould and hence broken away.

Grizzle grizzle. But  as they say if you can't take a joke you shouldn't have bought an old yacht!

Cheers, Graeme

[Graeme Lock]

Nic;

Sounds like you are getting across the problem well. From my experience of years of living with leaks thru the hull-deck and down via the void and tabbing into the bulkhead, there are no shortcuts. I guess the Rolls-Royce solution would be to glass the joint all the way around. But it seems to me the caulking is the least of your worries, and pretty easy to re-establish. The buggered-up screw holes are the big problem (and that includes stanchions and car tracks, which are next on my list). Good luck, and keep us informed.

Cheers, Graeme

[nick anthony]

thanks graeme hope I havent embarked on a sea dragon type quest 

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[feebz68]

  Hi

         To answer your question Graeme

                                                          

            (I'm sure you could stick timber plugs in,but I wonder why you would want to ? )

 

  The advantage of using  timber plugs, is that the timber plugs will absorb vibration and is less effected by temperature changers. Timber also has a bit of give and take. That's why most rub rails and sponsons are made from timber, plus they add a lot of strength and more importantly look great

  The reason why I mentioned using timber plugs, was just another option available, other than just filling a void with epoxy, then drilling some holes,

Cheers

Shane :)    

[MrSeaDragon]

:-) :-) ah infamy :-) :-)