1969 Chris Craft Roamer 46 Refit: Porthole Gaskets II

Getting the boat weatherproof is essential prior to launch. Getting new gaskets in the portholes will leave only a few weatherproofing steps to go.

Ecoflex 00-50 silicone kit and gasket mold are ready to go

The stock gasket profile is 3/8″ x 3/8″, and each gasket requires ~61″ of material. To figure out the volume of silicone to mix up, I converting inches to CCs, which was pretty easy since 3/8″ is roughly equal to 1cm. To fill the mold to the brim should take ~155cc. I want to get the mix exactly right, so instead of relying on my old eyeballs to sight the line on the mixing cup, I’ll use my electronic jewelry scale, which is accurate to 1/10th of a gram. Ecoflex 00-50 has a specific gravity of 1.07 g/cc, and this kit is mixed at a 1:1 ratio. So…I need 83.1 grams of Part A and the same of Part B for each gasket.

Funky looking goop

I transferred equal portions of each component into a mixing cup, then stirred the Ecoflex thoroughly for a solid three minutes before pouring it into the mold. The manufacturer claims no mold release is required so long as you demold the part within a day or so. Pot time is 18 minutes, which is more than enough for this relatively small mold.

Et voilà!

The cure time is four hours, but I poured in the evening and let the material set up overnight. The next morning, I tried to roll the gasket out of the mold but it wasn’t cooperating. I thought of using my utility knife or a putty knife, but I thought the sharp edges might damage the gasket.

Don’t tell the missus about the butterknife!

The butterknife worked great to free it from the mold in the middle. Then, I just pulled it free all the way around.

Nice!

Test fit on the laundry room porthole

That looks pretty good

You can see where a bit of the material flowed over the edge of the mold in the corner. Those pull off easily, leaving a good looking gasket.

Good frame-to-gasket contact

In the picture above, the frame is sitting on the gasket. It’s too light to close any tighter on its own.

Nice seal

Squeezing it tight gives a good seal all the way around

I like it!

The gasket is really soft…like a gummy bear. But I think I can cut down on the volume of silicone and still have plenty of gasket depth for a good seal. With the full-depth gasket, the edges are just a bit ragged from a teensy bit of silicone that flowed onto the surface of the mold. I’ll drop the volume by 10 grams on the next one and see how that works out. It will lose a bit of height for the gasket, but since this porthole stays open by 3″ on the lower edge once the top edge of the gasket contacts the frame, losing a bit of height shouldn’t be a problem. For now, the proof of concept is done.

Now I just need to make 11 more.

Next up in our 1969 Chris Craft Roamer 46 Refit: Aft Stateroom Headliner Prep

1969 Chris Craft Roamer 46 Refit: Porthole Gaskets

Way back in 2013, I disassembled all of the hateful aft stateroom portholes.

OEM gaskets get hard over time

By late 2014 they were back from the paint shop looking very pretty, but it wasn’t until 2016 that I had new glass and screens in them. The last thing I need to wrap up the portholes is gaskets. There are several gasket options that are readily available, and each one has it’s plus and minus points.

WEFCO Square Hollow Rubber Gasket is $1.69 per foot, and I need around 60 feet to do all of the portholes. That’s a relatively  cheap option, but it’s got two downsides: ethylene propylene rubber is a relatively hard material at 65 to 80 durometer on the Shore A hardness scale. This particular gasket is squishy because it’s hollow in the middle, just like the OEM gasket. I suspect it would also get hard over time just like the OEM gasket. The other downside is that there would be four joints in each porthole gasket, and that’s four opportunities to leak.

Then there’s Stop Water Gasket, which offers very nice urethane rubber one-piece gaskets for each style of OEM Chris Craft hatch and porthole. They claim that their urethane is softer than the original gasket material, which is good, but at $41 each it’s a pretty expensive option.

Hardness chart courtesy of Ecoflex

So–and this will come as a total shock, I’m sure–I started looking into making gaskets myself using super soft silicone. I eventually settled on Ecoflex 00-50 platinum-catalyzed silicone. As you can see in the chart above, Shore 00-50 is very soft material. And Silicone retains its its original shape and hardness pretty much forever. So I ordered a 2-gallon kit and set about making the mold while waiting for the silicone to arrive.

2×4 scraps should work for the mold

A few passes over my jointer trued the lumber

Mini Max FS35 jointer leaves a very nice surface on the wood

A super flat surface on the lumber will help ensure the mold is a consistent depth, so the gaskets will have consistent height.

Next I measured the portholes

I sampled several of the portholes. The biggest gap that needs to be filled by the gasket is 5/16″. The stock gasket is 3/8″, which should be fine, but because the silicone is so soft, I’ll add 1/32″ to the mold depth. That should help ensure these things never leak.

3/8″ width will be perfect

Next, I cut all of the lumber to the same width

The first mold cut

Cut 2 makes the width 13/32″

Harbor Freight featherboard was a great buy

If you use a tablesaw, you should have a fingerboard. You can’t buy replacement fingers for $6.99.

Second pass is done

The last pass on the saw

Looks pretty good, but I need to clean up the bottom surface

3/8″ router bit in my ShopSmith cleans up the cuts

Next I varnished the lumber to seal the wood up and then cut the miters at 45°. I used US Composites 635 epoxy to saturate the joint area, then added wood flour to make glue.

Crazy clamps

While I was clamping it all together, it occurred to me that corner clamps would make this a lot easier. Then again, I don’t do this for a living, so I’m not sure I need to buy tools I rarely use. Then again…more tools…mmmmm.

By the time the epoxy cures I expect the silicone will have arrived.

Next up in our 1969 Chris Craft Roamer 46 Refit: Porthole Gaskets II