Effectively sealing forward hatch

[Petar]

Hi,

I have noted a small leak on the corner of my forward aluminium frame hatch on my Dufour 31 sailboat dripping onto v-berth. Trying to figure out where the leak comes from was not an easy task as marina management have shut the water off for the winter (although we did not have a single freezing day but a lot of rain)so I have decided to take it off, clean and re-insatall back. When I removed the complete thing off I noted that the sealant used was (most probably) similar to 3M 5200 although hard to say whether it was original (boat is built in 1979,or removed and re-sealed sometime in past. When I have scrapped off the remaining bits of the sealant, the deck surface seemed very smooth with small cracks around the holes for SS screw used to secure the hatch in place but no major damage or reason for water to find it''s way into the boat. Now I have cleaned & polished the aluminum hatch, replaced the neoprene rubber gasket between the lower and upper part of the hatch and am intending to put it back in place. I would appreciate some advice if I should only use 3M 5200 marine sealant between the deck and the hatch or I should also insert some sort of gasket made from rubber or even cork (rubber sheets not easy to find in this size).

Regards

Petar in rainy Vancouver

[roddandcara]

DO NOT use 3M 5200! You might actually need to get it off again in the future. I use 3M 101 bit it''s getting hard to find. I''ve never had a leak due to failure of the 3M 101 and it comes apart much better than 3M 5200 or 4200 (I had 4200 tear up gel-coat once when removing a winch) it sticks less but not much less. Another good option is the new 3M product called UV 4000. I have had bad luck with the Boat Life (mostly drying out, dis-coloring and leaking after a couple of years due to lack of flexibility after exposuire to UV) products and I don''t allow either 5200 or Silicone on my boat. I''ve only bedded two items with the UV 4000 but it seems to be working OK.

12 years ago I did a Catalina 30 complete re-bed (everything from winches, stanchions & ports)with 3M 101 and that boat is still leak free! I would not use anything other than the sealant on your hatch and you can counter sink those holes very slightly to prevent the cracking you mentioned. By counter sinking the hole slightly you also create an o-ring of sealant around the head of the fastener. I was taught this by a one of the guys at Hinckley Yachts...

[sailortjk1]

Acoustic:
Do you or does anybody else know of a product that will aid in breaking down the 5200. My deck plate for the head discharge needs replacing, the cap was cross threaded at one point and the threads are stripped.

The plate is simply screwed to the deck with three screws. But the bigger problem is the compound that was used, after removing the screws I still can not remove the plate. I have removed the hose and clamps from below and the only thing I can see that would be still holding it in place is the sealant/adhesive.

I was going to carefully try a heat gun and a putty knife. Carefully so as not to damage the deck, trying to heat the flange than use the knife under the flange to break the seal.

Any other suggestions or any other product you might know of to aide in my project?

[RichH]

To remove cured 3M 5200 - use a product called "Debond" sold at many ''good'' chandleries or online from http://www.jamestowndistributors.com/decoder_debond2000.jsp

[sailortjk1]

Thanks for the recomendation.
I am fimaliar with Jamestown Dist.
I will place my order at once.

[hamiam]

a product called anti-bond 2015 will remove 5200. its readily avail online or in your favorite boat store.

[Petar]

Acoustic,

I have checked and local chandlery has both 3M101 and 3MUV4000.
By countresinking holes did you mean holes on deck or on the rim of the hatch? Ones on the hatch are already countersunk.

regards

Petar

[roddandcara]

On the deck is where you want to counter sink. It does two things 1- it feathers the gel-coat away from the threads of the screw so as to prevent crazing and cracking of the gel-coat around the hole. 2- It creates an o-ring like seal around the stem of the screw and forces the sealant to become a custom fit o-ring as you tighten the fitting/hatch.

Using this method it''s ok to tighten the hatch all the way on the first installation. By tightening just a little and letting the goop cure to create a "gasket" you create leaks at the screw holes when you tighten after cure. Many people use the tighten after cure method only to have soggy decks. Think about it if the sealant has cured around the screw and you turn the screw you break the seal!

You dont need to counter sink a ton just enough so the threads don''t grab at the edges of the gel-coat.

Using 101 and the countersink method I tighten the fitting all the way and use a putty knife to scrape as much "squeeze" as I can. Then I use denatured alcohol to clean the surface. Don''t get the rags drenched with alcohol or it will soften the 101 under the hatch but you want it wet enough to clean the area.. hope this helps!

[Silmaril]

Anti-Bond works to some extent, but with 5200 it usually takes a knife edge or piano wire to physically break the bond. Then use Anti-Bond for clean up.

When re-installing, make sure you use a liberal ammount of caulk. I would avoid tightening the fitting all the way. That will force the majority of the caulk out of the joint. When the caulking shrinks (it all does) you will get a leak again. The traditional method is to tighten the fitting just enough to BEGIN to squeeze out some of the caulking. Then wait until it cures (read the caulk lable, usually 1 to 7 days) then snug up the fasteners the rest of the way. This resuls in better adhesion and more of a "gasket" affect. Then you can trim off excess with a sharp knife.

Wherever possible, you would prefer to through-bolt the fasteners, as opposed to using sheetmetal screws, but that may not be practical in your case.

[Petar]

Guys,

Thanks a lot on your suggestions. I have bought 3M101 last night although they do not have it in clear but only in white and have sealed the lexan back to upper/hinged part of the hatch.Countersinking holes on deck seems a good idea which I will do during the weekend if rain abates as it is misserable last few days. Through-bolting the fasteners is another good idea I also had but I would need a nice piece of wooden frame as right now it would not work and would look ugly from inside. I will certainly entertain this idea if it proves unsucessful with planned refitting. I guess I will find out soon enough if rain continues like this for another few weeks.

regards

Petar