Hi Kiyack14, 

i have built the shearwater stitch and glue and a number of other designs... and my initial reaction is that that design has one of the best water-proofness of its hatches  (e.g., very tight....no leaking).

that said, there are a lot of little bits to that hatch design and perhaps someting was left off which may explain your problem "getting a good seal'

if you could submit a picture of your hatch and the hatch opening so we can see how you have assembled it, it may jump out to us what the problem is.

on shearwaters, a typical challenge, actually, is being able to compress the gasket enough to allow the hatch to actually get in place under the toggles. 

if you could add a picture or put  a link to the picture that would be great.

 below is a picture of my shearwater 17 ....do the hatches at least look like this from the outside?

  h

You are correct:  I struggle to get consistent compression of the gasket... Toggles might help except I'm not certain how to install them.  I am uncertain how to attach a photo.

Hi Kiyack14, 

it looks like you were successful in attaching the picture above.....which already tells me a lot.  a couple more pictures - take one farther away and another where you have removed the hatch so we can see how you built underneath it would be really helpful.

based on what you have sent so far, its very hard to get a good seal becuase straps over the top like that don't create a lot of down pressure of the hatch into the gasket.  that said, there are way to improve the waterproofness of that kind of hatch and we can tell you more once we see under the hatch.

below is a picture of hatches attached with straps that can work,,,,