Making an oval hole round...

jarcher · #1 (**permalink**) 04-25-2009

Hi All...

So the new solar vents from Nicro would not fit where the old passive ones were, so they had to move over, about an inch or so. So where there was a round hole, there is now an oval hole.

That means when the new one goes in there is a big gap between the deck and the vent, on one side of the hole.

I'm thinking of just filling the new gaps with Marine Tex, but id there a better way?

sailingdog · #2 (**permalink**) 04-25-2009

I wouldn't just use marinetex. Ideally, you should re-glass in a repair for the section of the "oval" that you're not going to be using.

One way to do this is to cut a section of "deck core" material that is the size and shape of the oval in question.

Grind back the glass to a 12:1 taper on the outside and inside, just around the edges where the "replacement" is needed.

Tape the core material "oval" in place, using masking tape or duct tape... on the side where the nicro vent is going to go.

Fill the gap between the edge of the oval and the existing core with thickened epoxy, just on the side being replaced.

Now, layup new fiberglass over and under the area that needs to be "replaced, overlapping the cutout area for the new Nicro vent a bit.

Let it cure.

Now, use your hole saw or jig saw to re-cut the opening for the Nicro vent... through the fiberglassed edge of the hole only...

Take the tape off and remove the "hole" from the cabintop.

Now, you should have what resembles a hole through a normal cored cabintop, and can basically proceed as if you had just cut a hole... with a few small modifications.

Use a router to remove the core material from between the two new layers of laminate...and fill the space with thickened epoxy.

Fair and sand the patched area and either paint or gelcoat.

Drill and pot the fastener holes... Don't forget to countersink the hole for the vent and the fasteners, so the sealant has a place to form an "o-ring".

Then install your Nicro vent—bedding it with whatever is recommended, depending on whether it is plastic or metal.

jarcher · #3 (**permalink**) 04-25-2009

Okay, I can do that...

I am thinking I'll have to cut the hole bigger in order to have room for the new fiberglass to adhere, and then not cut the new joint. Here are some pictures of the original hole:

Jims Scampi 30 - wierd chainplate covers
Jims Scampi 30 - wierd chainplate covers

After I widened to round hole to make it oval:

Jims Scampi 30 - wierd chainplate covers
Jims Scampi 30 - wierd chainplate covers

Some test fit pictures:

Jims Scampi 30 - wierd chainplate covers
Jims Scampi 30 - wierd chainplate covers
Jims Scampi 30 - wierd chainplate covers

That core material between the top two fiberglass layers is very hard plywood. I'm not sure the bottom layer is actually fiberglass, it seems like some kind of thin plastic liner.

Originally someone apparently did remove some of the plywood and replace it with epoxy. In the event that I can't grind the bottom layer, is doing just the top going to be strong enough?

EDIT: When I use the IMG tag (with the square brackets of course) nothing shows up. How do you guys post images inline with your posts?

ambianceack · #4 (**permalink**) 04-26-2009

Dude-

That is one ugly hole. I agree with SD you need to fill in. I would actually fill the entire area with epoxy and wood core, then use the appropriate sized hole saw for the unit you are installing. Think like a water bead.

Joe

hellosailor · #5 (**permalink**) 04-26-2009

MarineTex is epoxy putty, it is perfect for the repair. A lot less fuss than fiberglass, totally compatible, perfectly stable and at least as strong. You can make a more complicated repair, you can make a more expensive repair, but I doubt you can make a better repair for this job.

jarcher · #6 (**permalink**) 04-26-2009

Quote:

Originally Posted by hellosailor

MarineTex is epoxy putty, it is perfect for the repair. A lot less fuss than fiberglass, totally compatible, perfectly stable and at least as strong. You can make a more complicated repair, you can make a more expensive repair, but I doubt you can make a better repair for this job.

well if I do it that way instead of regalssing it, how do I get the MarineTex to adhere? Would I remove some of the coring material back maybe half an inch then fill from there? I am not familliar with core material, but this seems to be plywood and it is EXTREMELY hard

I was thinking wax paper around the trim ring, then fitting the trim ring into place, would define the gap that needs to be filled.

Yes, it is an ugly hole. The diameter of the vent body exceeds the hole at the hole's widest part, which means I can seal the vent down with butyl tape or 3M 101 or 4000UV, and it should be water tight. I mostly think the hole needs to be closed because I want to screw the vent down to the deck, and one of the 3 screw holes would be over the void.

As for the inside, that is a cosmetic issue. I can make a plastic donut to extend the flange of the trim ring to hide the putty from below.

I have not decided how to do it yet...

DwayneSpeer · #7 (**permalink**) 04-26-2009

I think I'd be tempted to make a teak ring large enough to cover the entire new hole and overlap the edges about a half inch. One for the top and one for the bottom and install the new vent thru that.

jarcher · #8 (**permalink**) 04-26-2009

Quote:

Originally Posted by DwayneSpeer

I think I'd be tempted to make a teak ring large enough to cover the entire new hole and overlap the edges about a half inch. One for the top and one for the bottom and install the new vent thru that.

And just leave the void in between?

kaluvic · #9 (**permalink**) 04-27-2009

Maybe instead of teak, make some fiberglass rings/washers and just epoxy them in place...the void between could be filled if necessary.

sailingdog · #10 (**permalink**) 04-27-2009

I wouldn't use teak. Adding a teak ring really doesn't do much to fix the structural problem of having a big gap in the area around the vent and adds additional maintenance, since the teak is higher maintenance than fiberglassing in a repair properly.

I also wouldn't recommend using just MarineTex. While it is excellent for smaller repairs, the size of this repair really requires reglassing the area. Also, marinetex would have a fairly weak bond, as repairs go, since the only area it would really be adhered would be along its perimeter... If someone accidentally stepped on the vent on the side with the MarineTex it might not hold.

You don't have to grind away too much fiberglass... a 12:1 taper for the thickness of the laminate skins is all that is required. If the skin on top is 1/4" thick, then you only need to bevel/grind a 3" radius away from the edge of the hole. Same thing on the underside.