Hatch to wall materials?

[TimC]

I am beginning to work on the frame for the hatch. The wall where the hatch meets is 2" rigid foam with canvas PMF wrapped around the hatch sealing face. The hatch will be laminated cedar wrapped in canvas PMF.

Question... is the foam with PMF firm enough to act as a sealing point with the hatch frame? There will be slight pressure on the foam. Just enough to depress a couple rubber weatherstripping strips.

If not, if I epoxied that area to make the mating surface more firm would that work? Is there a need to add aluminum flat stock here?

I hope these photos help...


The pink foam with 1 1/2 sharpie mark on it represents the hatch profile. There is a 1/2" plywood galley wall that provides a half inch flange to block water penetration. The hatch frame member will mate with the flange with a rubber seal inside. That will be the last blocking of water penetration and will be "tight". The other seals will be on the flat surface of the wall profile and provide some water seal, but will not be under much pressure. That is the area I am concerned about being firm enough to support the slightly depressed seals.


Thanks, Tim

[Pmullen503]

Canvas covered foam will be strong enough to compress a foam seal against.

You should always assume that some water will eventually get past the seals and so design some type of "gutter" system to direct that little bit of water back outside.

[TimC]

You should always assume that some water will eventually get past the seals and so design some type of "gutter" system to direct that little bit of water back outside.

Thanks. It doesn't show well in the photos, but, the galley wall extends 1/2" beyond the foam wall. That area is waterproofed and a rubber seal will be held against the face by a mating hatch frame member. The other two seals will just be applied to the hatch outside of that flange. I hope that qualifies as a gutter. The bottom of that will have some sort of channel to drain water. Hopefully the mud bees won't fill it up for their nest!

[troubleScottie]

The reference to the gutter system by pmullen503 could look like this.



The rational is to create a physical barrier to possible water path.

The drawing is a cross section of a typical method of using a tongue and groove to slow and redirect the water.

The blue area is a build up of plywood layers to create a space A ( 1/8" to 1/4" ), a tongue (1/2" to 2" tall), a space B and another ledge for the hatch to rest against.

The two green seals run the entire length of the hatch. Seal 1 is the first seal. If water gets by it, it is redirected into the space A. With seal 2 in place, the water would flow to the bottom of the space at the bottom of the hatch. For the paranoid, you could add seal 3 as yet another barrier if you think both seal 1 and 2 will fail.

At the bottom of the hatch you need yet another seal ( yellow and grey ) to block water out. Notice the yellow seal will allow water to drain from channel A and B.

Obviously, you need good seals on the wood or other material that form this tongue and grove and along the bottom as they will get wet and possibly see standing water.

Remember, while driving in rain, the TD is experiencing gale force winds. The seals will be put to the test.

[TimC]

Thanks for the feedback. Here's better photos and representation of what I have planned. I did a mockup of the hatch side frame with foam and weatherstripping. Ignore, if possible, the large pink foam piece to the left in these photos. The only purpose is the blue line which denotes the outside of the hatch akin.





1/2" rigid foam skin, cedar strips which I will steam bend and then laminate to follow the wall profile, two soft weatherstripping beads on the face of the foam wall and a epdm rubber weatherstripping inside the "gutter" that mates with the flange on the galley wall. Mockup came out more rigid that I had expected so I think this will be close to a final design.

Back to the original question... I hope the PMF'd wall face (2") will hold up to a little pressure from the soft weatherstripping.

[Pmullen503]

If I understand what I'm looking at, the hatch will be inset between the walls? If so, it looks like you'll have three seals plus a 1/2" lip? That should be fine but I would lose the seal at the side of the hatch to wall. If that Gap is too tight water will sit there due to surface tension. I'd leave a 1/4 gap to make sure the water drains. I'd move the first seal in a tad for the same reason. Make sure you leave a gap at the bottom so any water can drain that gets past your seals.

Be sure to account for the thickness of the PMF when fitting the hatch.

[TimC]

If I understand what I'm looking at...

Let me get rid of the stinkin foam that is just confusing the view. Does that clarify it a bit? Would you still loose a small seal? On the port side view which one are you suggesting? The inside or outside?

Here's the port side of hatch


And the starboard side with a view of the gaskets.

[tony.latham]

If that lip is on the inside of your wall I think you need more clearance on either side of it.

Here's the deail on my last build:





Tony

[TimC]

If that lip is on the inside of your wall I think you need more clearance on either side of it...



Tony

It is inside. I will have to tweak that gap a bit. It is too tight on this mockup. I started out trying to maximize the width of the portion that sits on the wall face. I don't think that is necessary after seeing how rigid the mockup is. It'll have the addition of PMF as well.

Thanks for looking.

[Pmullen503]

Ok, that's why I asked. The close up photos actually make things less clear.

To your questions; the PMF covered foam will be fine against your seals. Mine is similar with no deformation of the foam after many years. The inner seal should be at least a 1/4" away from the flange so any water that gets past can drain.

[TimC]

Ok, that's why I asked. The close up photos actually make things less clear.

To your questions; the PMF covered foam will be fine against your seals. Mine is similar with no deformation of the foam after many years. The inner seal should be at least a 1/4" away from the flange so any water that gets past can drain.

Gotcha. Thamks.

[TimC]

Andy's foamie build is on hold for a few days. Yesterday afternoon we had a sudden storm that took down trees all over town. My utility trailer was temporarily parked in an unfortunate spot. After cleaning up most of the maple tree I discovered that the 60 year old boat trailer conversion was salvageable. Dang. I was starting to look at new trailers...



Said maple came about ten feet from hitting my baby, woodie TD#1