87' 170 Soft Deck Repair. Need Advice!

[tannersjack]

Hi all, I recently bought an 87' 170 that was basically turn key ready to go, with the exception of a soft spot in the deck in front of the console.  I've been taking her out every chance I get but always worried about the deck. So I've decided to replace it sooner than later. I know there is a lot of experience in this site so if anyone has any advice it would be greatly appreciated. I am going to cut the top layer of fiberglass off of the deck and dig out all the rotten wood, then replace it with some T-92 1/2" core and re-glass the cut deck back on. Any fore-warnings or advice welcomed!





This is the area in red that I am replacing with core.. pretty large looking at it from this view.

[RickK]

Welcome aboard!  I have not seen anyone use that approach, which doesn't make it wrong, and I'll grab the popcorn and subscribe to the thread.

[mshugg]

That area of the deck is most likely rotted because of water migration from the screw holes that hold the tank coffin lid down.  It would be worthwhile to pull up the lid and verify that everything is solid and well sealed.  That way your repair will last, and you won't have other areas go soft.

[kurantt]

I did a partial floor replacement on my 17.5 osprey over a year ago, it seems to be holding up well.

[wingtime]

I injected the deck of my 1987 170 a few years ago with good results.  Still rock solid.  I had a soft spot in that area as well.  Most likely caused by the screws holding the console down were not properly bedded (sealed) and were allowing water intrusion into the plywood core.

Here is a link to some videos of how I did mine:

[tannersjack]

So I got the top layer of glass cut off and discovered rotten wood, but what I didn't expect to see is little pieces of scrap wood instead of a solid sheet?




I was assuming it would be a sheet of plywood for strength. I'm also assuming this deck has been replaced before and someone did a halfass job or was just lazy. Any of you that have replaced your decks, have you seen this before?



I got it all scraped out and sanded but the remaining layer of glass is very thin.. I'm wondering if this has anything to do with flexibility in the deck regardless of the rotten wood. It looks like only a single layer of 1.5 oz glass.

[wingtime]

Yup that is actually normal practice and is the original core material.

Remember the plywood core is only there as a spacer. The strength of the floor comes from the tension and compression on the bottom and top layers of fiberglass.

[RickK]

All of the coring in most of the Aquasports floors is 3/8" blocks of end grain balsa.  The little blocks gave the floor better stability than a sheet of plywood.  We have seen some of the boats come off the line with plywood if they ran out of balsa.

[Capt. Bob]

Any of you that have replaced your decks, have you seen this before?

As stated above, pretty much SOP on both Hialeah and Genmar built hulls.



As you can see, the bottom layer of glass is more for sealing the material, thus not as thick but as Wing stated, it works in tension.

Good luck.

[chris0614]

Wingtime, I watched your video and was wondering- do you recall  how much epoxy and cabosil you used to complete your deck injection?

[wingtime]

Wingtime, I watched your video and was wondering- do you recall  how much epoxy and cabosil you used to complete your deck injection?

Hmm good question.  The epoxy was a 2:1 mix I think I used two gallons of epoxy and one gallon of hardener.  I think I used at least two quarts each of the cabosil and milled fibers.  The empty caulk gun tubes hold about 10 oz of epoxy.  I think I started out mixing 8 ox of epoxy and adding three heaping tablespoons of milled fibers and two to three tablespoons of cabosil.

[chris0614]

Thanks I think I'm going to give it a try in the spring and hadn't really found an estimate of materials.

[Capt. Bob]

Light reading.

http://classicaquasport.com/smf/index.php?topic=10525.0

http://classicaquasport.com/smf/index.php?topic=10787.0