Flush hatches and seal compression...

I have almost completed my Night Heron, but I have a concern about the flush hatches and the invisible hold down system.

I followed Nick's book "The Strip-Built Sea Kayak" on pages 118-120 to make my flush hatches, and they came out looking great! On page 154 I followed the instructions on hatch gaskets, and I have installed the invisible hold down system I bought from CLC. Now the hatches are not flush until the foam seal compresses, and I understand that this compression should take a few days to complete.

My questions are:

1. Will may hatches be flush?

2. Should I have put some sort of spacer before glassing the lip into place to allow for the seal?

3. Should I cut some minicell foam on my band saw as I have heard about on the forum?

4. If my hatches will never be truely flush is there something else I can do to help remedy this situation considering I have bulkheads installed and sealed?

I am hoping to get my boat in the water soon, but I also want flush hatches that I thought I would get since I've tried to follow instructions very carefully!

Answers to any or all of my questions are greatly appreciated,

Chris F

7 replies:

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RE: Flush hatches and seal compression...

Here's a pic of what I described!

flush hatch with seal

RE: Flush hatches and seal compression...

pretty hard to tell from your pics what is going on. Also, not sure what you're talking about regarding the "invisible hold down system". I am assuming that may be the bungee hatch restraint system. All that I can say is that I have a chesapeake 18 with flush hatches and using the bungee hatch restraint kit that CLC sells. Kit supplied gasket material. Takes maybe 1/2 hour for the hatches to go totally flush. Maybe longer for the first time but I didn't bother timing it. But I'm really more worried about getting a good seal rather than a perfect flush fit. My hatches are seaworthy and that is what I look for. 

RE: Flush hatches and seal compression...

Ok, here are the clc links that pertain to my situation:




Maybe a few more days will help the seal compress a bit more!

Chris F

RE: Flush hatches and seal compression...

You need to have a spacer between the underside of the deck and the top of the sill piece that equals the width of the compressed foam.  

For now you can paddle all you want and it should stay dry.  If not tty to tighten the bungie cords a bit.  

You can probably cut the sill back to match the hole and then glue a new sill under that.  In one place, I put in a day hatch and ended up cutting the foam a bit thinner since the spacer I used there was not quite as thick.




RE: Flush hatches and seal compression...

I may just have cut my sill out and make a new one leaving a space just like you've suggested...thanks!

For now I've removed the CLC foam, and I've replaced it with some 3/8 inch closed-cell insulation from Lowes that initially seems to be compressing better than the 1/2 inch wide CLC foam.

Thanks for your help,

Chris F

RE: Flush hatches and seal compression...


I followed those same directions. I have hatches from 2 laminated pieces of 4 mm ply and there are (2) 4 mm sill spacers between the deck and the hatch sill. That worked out well for me, but it does take some time for the gasket to compress. If it hasn't compressed in a day or so, Ed's suggestion regarding cutting back the sill (now a sill spacer) and adding a new sill sounds like it may be the way to go. Try increasing the bungee tension first.  My hatches are usually flush (relatively speaking) in less than an hour. 

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