Sealing new portlights on O'Day 25

[Mad Dog]

I posted this on the Ask All Sailors forum, but hoping I'll get more response from fellow O'Day owners.

I am replacing the Pyhi opening ports with Beckson 414s on my 1978 O'Day 25. I am concerned about a possible error in my work so far. Having removed the old port, I dug out about 2 inches of balsa core all the way around the opening. In my concern to waterproof this area, and forgetting that the wood also acts to prevent flex, I proceeded to coat the opening with 3M Marine Premium Filler (it's all the chandlery had available). This stuff is pretty thick, trowels on easy, but doesn't exactly fill large voids. Just tooling it into the gap probably got me about 1/4 - 1/2 inch of depth all the way around instead of the 2 inches that I removed.

Is this sufficient to give the area rigidity? The through bolts likely will go through the air gap and not pass through the filler. I'm hoping I don't have to grind this out and refill the gap before proceeding. Any and all advice is greatly appreciated.

Matt

 

[Hydro Therapy]

I've used that product to fill gelcoat cracks and gouges. It's a great product but I don't think it's designed to fill large voids. Maybe someone else has used it for that purpose and can comment.

 

[Ritdog]

I might be wrong, but I think you are gonna have to get that stuff out, and epoxy in some more core.

I have to replace mine too (crazed) so am interested!

Am curious as to why you took it out at all...??

 

[dparilla]

Hate to say it, but you do not want an airgap in the core between your fiberglass. You definitely want to build out with core material or thickened/filled epoxy to create a dense enough structure to bolt to, otherwise you are going to end up with a very weak structure around the ports (translation is leaks and cracks). Is the gap in between the filler that you used and the original core, or is it just that the filler sank in and left a gap?

 

[Golden Road]

Wondering why did you dig out the coring? Was is rotten, or???

 

[Mad Dog]

Thanks for the replies. I dug out the core because it was soft. Not rotted completely, but soft and punky, and it looked like it was disintegrating.

Dan - you are correct. The gap is between the filler I used and the core. Here's a picture showing the cutout. You can see the filler has sealed off the gap between the hull and inner liner. The filler probably extends 1/4 - 1/2" down into the gap. I probably took out about 1 - 1.5" inches of core, so that's where the air gap is. This morning, the folks at Beckson said it's probably fine the way it is, as the filler should add sufficient rigidity to the joint. I'm not sure. Part of me wants to grind out the filler and fill 'er up properly.

 

[dparilla]

You could always back fill it. Drill small holes and inject epoxy to fill the gap.

 

[Mad Dog]

You could always back fill it. Drill small holes and inject epoxy to fill the gap.

Good idea, Dan. Along the same line, what about drilling and filling with closed cell foam?

 

[Golden Road]

It is always best on any cut-out thru a cored hull/deck/cabin to cut back the core some and seal off with either a thickened epoxy or polyester. You could inject but I've found that to be slow and potentially messy, esp if the space is large. The foam you might inject is quite soft so it will do little structurally.

 

[Brian S]

The question for me is "What are the structural characteristics of that 3M Marine Premium Filler?"

We know that a reasonably thickened polyester or epoxy resin is strong enough to through bolt and support the compressive loads. Is that 3M stuff similar? And also, is the 3M stuff cohesive enough to withstand the flexion that a cabin side would be expected to encounter?

Perhaps a call to 3M is in order.

I think that if the 3M stuff is up to the task, if the new holes you must drill are all through solid filler, then you might be fine.

 

[Golden Road]

Since you say you've gone back 2", If that 3M filler is not too tough to get out, the ideal would be to get some balsa coring, sand to ideal thickness, dip in a thickened resin and push in. Or some rigid surfboard urethane foam (easy to shape), or Airex foam coring.

 

[Golden Road]

But I also agree with Brian S.

 

[Mad Dog]

Answer from 3M

Since I work for 3M (not for the Marine division), I figured I'd call the help line to inquire. Turns out the 3M filler is fine for waterproofing the gap, but not as a structural filler . So I think a reasonable course of action is to drill a number of holes into the filler and inject epoxy until I see it coming out of an adjacent hole.

Oh well, I suppose the first one is always the steepest learning curve. The next 5 ports will (hopefully) go a little faster!

 

[Ritdog]

Reference mad dogs injection idea, I think that is the way to go - My rudder had a void along the whole length of the submerged part of the blade. I drilled a 1/4" hole at the top and bottom of the void, used a west system fillable caulking tube, and filled it right up with thickened epoxy - it's solid as a rock now.
Note that you want to inject things like this from the bottom, so as to leave no voids in the epoxy!

 

[Mad Dog]

Today, I ground out some of the marine filler to get an idea of the cavity depth. It is about 3 inches deep all the way around the port opening, and the gap between outer and inner is 1/2 inch. I think the epoxy injection is the way to go. Now, I do remember a warning that large amounts of epoxy will give off a lot of heat. West Systems even says "do not inject into confined spaces". If the port is 14 x 4, and the air space is 1/2 inch wide x 3 inch deep, that's a LOT of epoxy. Should I be concerned? I'm sorry for the stupid question.....clearly a noob at this.

 

[dparilla]

Go slowly, I would not expect to fill the whole thing at once. Fill the bottom of the port, and let it setup. Then do the sides, the finally the top. Epoxy does give off heat, but in using a filler with the epoxy to thicken it, you are reducing the absolute volume of exothermic material. The heat is surprising, but not excessive, and won't damage the boat. I filled in 4, 2 inch gaps in the core in my deck and it worked just fine. It will however melt red solo cups pretty quickly.

Grab the book, "This Old Boat" by Don Casey it is a great resource for projects like this.

 

[woodster]

It will however melt red solo cups pretty quickly.

Grab the book, "This Old Boat" by Don Casey it is a great resource for projects like this.

use a Glad storage plastic bowl to mix it in ..it will not melt and when it is set up you can peal out the hard mix and reuse the bowl again and again

 

[woodster]

Today, I ground out some of the marine filler to get an idea of the cavity depth. It is about 3 inches deep all the way around the port opening, and the gap between outer and inner is 1/2 inch. I think the epoxy injection is the way to go. Now, I do remember a warning that large amounts of epoxy will give off a lot of heat. West Systems even says "do not inject into confined spaces". If the port is 14 x 4, and the air space is 1/2 inch wide x 3 inch deep, that's a LOT of epoxy. Should I be concerned? I'm sorry for the stupid question.....clearly a noob at this.

cut some 1/2 in marine plywood filler pieces to take up some of that 3 inch deep gap no need to make it solid glass...it will bond when you pack the thickend epoxy in there

 

[Mad Dog]

cut some 1/2 in marine plywood filler pieces to take up some of that 3 inch deep gap no need to make it solid glass...it will bond when you pack the thickend epoxy in there

Exactly what I did this weekend. Then I popped the new port in there, drilled the holes, and sealed with Dow 795. The prep was the hardest part....putting the new port in took 20 minutes.

Thanks for all the help, guys!