Re-core project advice

[Carl-T705]

Caleb, I've done these repairs several times on different boats. I always go back with Balsa on curved decks for, several reasons, It's cheaper than all materials, with it scored it will conform to the curve of the deck, it's what the factory used in the Pearson's I do. You can used the old decking skin but when you tape all the joints you will loose the factory non slip so I sand it all off and go back with non skid paint. Although my latest job I using KIWI-GRIP for nonskid.
If balsa is kept dry it will not fail. The factory never backfilled holes with epoxy and redrilled they just drilled a hole and bolted a fixture done with some sealer applied,this let water leak in and that killed the balsa.
I've used plywood on flat decked boats (fishing boats) and there is no problem if all through deck fittings are drill oversize ,filled with Epoxy and then drilled to the proper size. I use butyl tape to seal all through decks holes.
I don't use West products. I use supplies from FIBERGLASS COATINGS in FL they are on line. They beat everyone's prices and have everything you'll need for this job, plus tech support. They only sell to businesses so when you contact them have a business name ... like Caleb Boatworks, you don't need any more credentials than that. This work isn't that messy but taking the saw to the decks of your boat is a little unsettling, once you get over that, the job is very straight forward, I've chatted with folks who recored their decks with the boat in the water.
I don't own a moisture meter or vacum bagging system. I find soft spots , do some exploratory drilling to determine the size of the repair and go from there.
There are some little tricks I use like wetting out the balsa over a piece of PVC pipe so that epoxy leaches into the scoring to make little I beams of epoxy to help stiffen the area and help to stop water from spreading if a leak should occur again from failed sealer, but Butyl tape really never fails or drys out to allow a leak. I also drill holes through the deck skin to allow the excess epoxy to bleed out and allow the deck skin to settle into place. Two people would make this work go quickly but generally I work by myself.
I would be glad to offer any advice you may need over the phone. I'm just an amateur, hobby, boat restorer, but I have met with success with this type of work. A lot of this has been discussed on the Pearson Ariel website with plenty of pictures as well. You can reuse the deck skin but it's not worth the effort to try and save the factory nonskid.

[CalebD]

Everyone loves pictures!

First pic is of the lower skin (inside cabin) where stanchion base compromised the laminations. I chiseled out the small square there to for exploratory purposes.

Second pic is of the still wet Balsa core chunks and mush I pulled out of the core, damaged sections of lower skin. It is definitely 1/2" core material.

Pic #3 is also the lower skin farther back towards where the coaming starts. The mildew bloom is evidence of more water intrusion.

Pic #4 is an outside shot of the port deck above where pics 1-3 were taken. I envision needing to re-core from about where the blue tape is just about up to the shrouds.

@Howard
Thanks for the link to Express Composites. They seem to have good prices for core materials. Have you used their honeycomb propylene core material? http://www.expresscomposites.com/honeycomb.html
Any idea if it is compatible with epoxy resin? A single 4'x8' sheet of this should be enough core for both sides for $60. I bet it sucks up a lot of resin though.

[CalebD]

Wish I could figure out how to insert text between the pictures.

[ndutton]

Wish I could figure out how to insert text between the pictures.

You actually insert the pictures between the text. Type all your text, upload your pictures, place the cursor where you want a picture, click the camera icon and click the attachment you want there.

[hcrisp]

Honeycomb core

Caleb, Yes. The polypropylene core is what I used on the last job, applying it to the cabin top from inside or underneath side. The FRP skin cut very well with the Bosch multi-tool and, as I mentioned earlier, I was able to "hold" a vacuum in the other hand as I cut. I prefer to work from the top, though. The owner didn't want me to mess with the top of his cabin trunk.
The stuff is extremely light and strong, and I also used epoxy. It doesn't use as much resin as balsa would as it is covered on both sides with a scrim material. The honeycomb does not "fill up". It bends easily. However, in your side deck application you will not need compound curves.
For that job I used just about a full sheet, but you can buy a half or even a quarter sheet. It is a unique honeycomb structure with three orientations.
Howard

[tenders]

As I understand it, the benefit of balsa over plywood is that the balsa, up to a point, doesn't wick moisture. But it isn't as strong.

The benefits of foam over balsa are even less wicking, less weight, no rot, cuts easily with a box knife, but at somewhat higher cost.

Is there a structural benefit of polypropylene besides weight? It would seem to be the least strong of any of these cores, and plastic (in my experience) doesn't usually adhere to epoxy very well. And the aramid honeycomb core on that website seems to have so little surface area that it would be difficult to adhere to the top and bottom fiberglass skins.

[romantic comedy]

I found some helpful info at:

boatdesign.net

There are different opinions about which core material is the best.

http://www.boatdesign.net/forums/boat-building/easier-way-balsa-core-deck-replacement-7516.html

[smosher]

Fuel Fill balsa

Hi This subject is timely. In prep for my spring launch I wanted to replace the
fuel fill hose as it looked old. In the process I remove the fuel fill and found the balsa, waterlogged all around the area. I dig it out with a screwdriver at least 6 inches around and left it to dry out.

Since I haven't done this before I was looking on the net for tips but couldn't
find anything particulary on the fuel fill area.

My current thought was to block off the hole with a rubber stopper block off the screw holes with tape and force west expoxy through the area with access holes.

Any hints, tips or am I way off as I haven't done this type of repair.

Thanks

Steve

[Mo]

Steve,

I have an idea you may want to consider without tearing the boat apart.

-clean the area out really well.
-get a piece of metal pipe the same diameter as your filler tube.
-place a couple of wraps of heavy plastic around the pipe and put it back in. This should keep epoxy from chemically bonding it to the boat...ensure it is all covered...tape may make it hard to remove..but might work also.
-on the underside of the filler tube / pipe put a bead of silicone so nothing can flow past that...do the same on the top....let that sit a day to set up.
-at this point you should have a barrier around the tube and a barrier to keep your epoxy mix in the dead space as you need....
-next drill holes the size of the tip of a turkey baster.
-mix epoxy with beads to the consistency of a paste that will run ...but barely...not quiet as thick as peanut butter...but pretty close.
-force the mixture into one of the holes until it starts to come out another...I'd keep the holes about 3 inches apart.
-check to ensure it is not running out somewhere.
-if you have a low area don't put a large hole there...just a tiny one so that you may see epoxy weep up and then just put a screw tip in it to ensure it doesn't run out.
-allow to harden a day then remove the tube /fitting...will have to give it a smack.
-sand the small "hole areas" with random orbital and fair it. Cover with kiwi grip or make up some nonskid.
-check that filler tube fits...may have to drill new securing/ mounting holes through new epoxy.
-re-install your tube sealed with 4200. When tightening bolts on the screw ensure to have 4200 in and around those as well. Have someone hold the screws on the top side to keep them from spinning. If they spin the 4200 looses it ability to seal.

That's one method...hope it helps.

[tenders]

Do you have access to the top and bottom of the deck? I've done this two ways, but be forewarned, it is unlikely that the water damage was confined to that six-inch radius and eventually the rest of the deck is going to go bad too. Could be two years, could be twenty.

Method number 1: apply wide strips of duct tape (Gorilla Tape would be better) to the underside of the hole.

Method number 2: finagle a thin plate of "mighty putty," MarineTex, or similar kneaded-epoxy-stick over the top of the hole in the bottom layer, via the hole in the upper layer. (Or apply the sealing plate from the underside, if you have access.) Drizzle thickened West System epoxy over this plate to seal it.

The finishing steps are the same for either method: using just a few ounces of epoxy at a time to avoid setting the deck on fire, pour slightly thickened epoxy into the hole until it's filled. Once cured, redrill hole with holesaw. Clean up underside edge of hole depending on how much you care about it. Then replace the fitting, sealing well with butyl tape. (I've pretty much stopped using polysulfide these days; butyl tape is better in every respect.)

The hard part of the job is the sealing of the hole. If it isn't sealed, or if the epoxy dissolves the duct tape adhesive, the liquid epoxy you pour into it goes absolutely anywhere and everywhere.

[edwardc]

Hi This subject is timely. In prep for my spring launch I wanted to replace the
fuel fill hose as it looked old. In the process I remove the fuel fill and found the balsa, waterlogged all around the area. I dig it out with a screwdriver at least 6 inches around and left it to dry out.

I had to do a similar deck repair around a ventilator collar in my bow a few years ago.

After cleaning out the waterlogged wood and allowing things to dry, I used tape to close off the edges of the hole, as well as the screw holes on the underside.

Through the open screw holes on the topside, I used a syringe with a skinny, curved tip to inject unthickened WEST System G/Flex epoxy into the space.

The curved tip allowed me to start injecting at the points that were farthest from the screw-holes and work back out towards them in order to avoid voids. After the epoxy set, I re-drilled the screw holes and re-bedded the collar with 4200 (NOT 5200!!).

[ndutton]

Follow up on vacuum infusion

Now that I see the magnitude of Caleb's project I agree vacuum infusion will not likely be effective. I have three spots on my foredeck about the size of a CD where it should work well though. BTW, my core is plywood and the last time I cut a section of deck open to repair a void it was rot free, clearly a condition from the original construction.

We tailor the technique to the project.

[hcrisp]

Deck core

Balsa end grain core has to be totally encapsulated to work. And it works great as far as shear is concerned. But, someone will eventually create a hole in the top skin and water will penetrate...
With a poly core the heat bonded scrim promotes adhesion and prevents the honeycomb from filling up with the resin. Actually, epoxy is better than polyester for this application. Now I'll shut up.
Howard

[hcrisp]

We tailor the technique to the project. NDutton

Exactly. And a tip of the hat to Neil.

[CalebD]

Thanks for all of your input, everyone.

The truth is that sometimes more information just means more choices to choose from. My mind has been spinning like a wind vane on a variable day; one minute plywood core, the next minute Balsa. Then the wind shifts again and I want to use a synthetic core.
On another axis I'm still contemplating doing this from below OR above.

We tailor the technique to the project.

So I will see how easily I can do it from below and if that seems impossible then I can always fall back to Plan A and do it from above.

At least I believe I have settled my mind on which core material I will use. Thanks to Howard (hcrisp) who took the time to speak to me about his experiences doing similar jobs and his link to expresscomposites.com I am more or less set on using the polypropylene honeycomb core material. Kudos and big thanks to Howard!

The cheapskates calculus works like this:
Marine grade ply would cost me at least $60 for a 4'x8' sheet.
I can get a 4'x'8' of 1/2" polypropylene honeycomb core for the same price and avoid using wood as a core material.
That is as close to a slam dunk as anything, in my thinking.
I will have some extra core for other upcoming projects to boot.