Installing Hatches the Right Way [28]

By Dave Winkworth

Sea Kayaking (I’m talking about open sea paddling) is a bit like flying in a plane — you can’t just get out whenever you feel like it! You have to go home or ashore first.

So, your equipment had better work each time every time. This means that your hatches should all be watertight. Many boats these days are fitted with Valley or VCP hatches and, to a lesser extent Henderson equipment.

I’ve seen lots of boats both “home fitted out” and commercially made with leaking Henderson and Valley hatches, sometimes almost brand new. The purpose of this article is to suggest a method of positively sealing these hatch rims and to show buyers of new boats what to look for.

Before manufacturers jump on me, I must say that quality boats are being made and hatch rims well sealed in these. Unfortunately there are still commercially made boats with pathetic attempts at hatch Rim installation and water sealing just to get the product out the door. Buyers, vote with your feet and go for quality!

Problems with leakage can occur around the hatch lid when it is not fitted properly. This is easily fixed — put it on right!

Water leakage around the base of the rim is more serious. The best way to fix it is to take it off and fit it again! If your hatch rim has been fitted from under the deck, you have a problem! They can be hard to seal long-term.

OK, Valley and Henderson rims are made from plastic. Glass fibrer resin will not adhere long-term to this plastic where there is any flexing or manual pressure involved. By this I mean the forcing of gear into the hatches and the pushing-twisting etc to remove/replace hatch lids. If resin/glass is your only sealant, your hatches will eventually leak. This also applies to Q cells which is a glass fibre filler and various commercially made bonding agents which set hard when cured. A flexible sealant is needed in conjunction with glass fibre and resin.

I have seen hatches secured from under the deck with glass fibre only where the rim could be rotated 25 mm each way. Needless to say, this one leaked!

The very best sealant I have seen is Sikaflex. Nothing else even comes close. This sealant is a purpose designed marine sealant/adhesive for below-the-waterline use. You can get it in black or white, tube or cartridge. It can be a bit messy to use, clean up with turps, metho or acetone and store opened cartridge in the fridge. You can get it at Ships Chandlers and marine dealers. Resins will stick to it unlike silicone sealants. It is the best. Again,…it is the best. Do not use silicone sealants.


  1. All areas of contact for the Sikaflex sealant and the glass fibre with both the boat and the hatch rim should be sanded thoroughly. I use a really rough grit paper and remove all trace of the shiny plastic surface of the hatch rim which will be contacted by the sealant and the resin. If installing rim ON TOP of the deck with bolts, roughen the gel coat area which will be under the rim too. When sanding, go around the rim and deck – not in and out!
  2. If fitting rim on top of deck, squeeze a generous bead of sealant around the sanded gel coat area with a loop around each bolt hole. When bolting down sealant will squeeze out and can be wiped off (although a bit messy) or left until dry (about a day) and cut with a sharp cutter.
  3. If fitting rim from under the deck, you will need some clamps or short pieces of wood to keep rim in place until dry for glassing. For under deck fitting, squeeze sealant onto top of flange generously and lift rim into place through the deck. Secure until dry. Sealant should be visible between rim and deck hole all round. At the edge of the flange under the deck, use your finger to smear sealant flat in preparation for glassing.
  4. When dry, clamps etc can be removed. Now, turn boat upside down on some trestles so; that you can get underneath it. Have a small mirror handy and possibly a torch if your work area is not well lit. Cut some small pieces of glass fibre – 225 gsm or 3OO gsm are fine – the 225 if there are tight corners for the fibre to go around. The pieces should be about double the width of the flange to adequately contact the boat material,
  5. Mix resin and go to work, checking for pieces that have not wetted nut completely with the mirror. If you expect anyone to be sitting on your hatch rim – ie if your hatch is in the “day hatch” area, I’d use 2 layers of glass. When cured, give the underside a good sand to remove dags which could’ puncture your new drybags.

If you’ve done it right and there are no leaking bulkheads etc, you should he rewarded with a hiss of air on a warm day. To avoid this pressure build-up, I’ve heard of paddlers drilling small pinholes in each bulkhead near the top. It’s up to you.

I wish to state categorically that I have received no kickback from Sikaflex Australia.