1976 Seacraft 23 IB - Rear Deck/Hatch Core Replacement

[aldo]

I'm sure that will work but all that plywood & fiberglass may make for a very heavy floor.
When you price out the nida core vs marine plywood it might not be much different in dollars, but much lighter. Good luck either way.

[John3325]

Thanks Aldo.

I picked up the marine ply today. Decided to go this route since I have used it before and comfortable working with it. It may be a little heavier, but I also don't plan to move this hatch around that often.

I am still weighing whether or not to just go with a single sheet of 3/4", or if I should double it up with another 1/2" sheet or 3/4" sheet. Either way, it's definitely going to be lighter than all that saturated bulsa core I pulled out.

Looking into heating options for the garage, I'd like to be able to startin glassing and getting this done.

[Mshugg]

Originally Posted by John3325

I am still weighing whether or not to just go with a single sheet of 3/4", or if I should double it up with another 1/2" sheet or 3/4" sheet. Either way, it's definitely going to be lighter than all that saturated bulsa core I pulled out.

You won't go far wrong if you use the same core thickness as the original.

[John3325]

Yeah that's what I keep going back too, probably what I will end up doing (even considering the extra weight.

Located a torpedo propane heater out in the garage today. As I started stripping a hatch down from the boat (also to replace core), I conducted a heat test. Took the picture a few minutes after I fired it up, I think it got up passed the 60 degree mark so I should be good to go.

Next step is to start cutting up some marine grade and fitting it to the deck.

[John3325]

Took my first stab at stiffening up the first layer in those few first spots.

I decided to let the first few batches cure up overnight, and then add more to fill the holes to the top as needed tomorrow. Even though the holes are not filled to the top, major difference in how firm those small sections are that felt a little soft.

If I have time, I'm going to finish up syringing the holes and get my core pieces cut up.

I do have a question for the group. How would you cut the pieces for the core? Should I fit them tight to the lip I left and squeeze them in as best I can? In doing that should I then fill the void between the lip and the new marine ply with resin?

Should I get rid of that angled lip all together and not worry about filling it in perfectly where the core was before? (Not exceeding the footprint of the old core to avoid clearance and fit issues).

[John3325]

Good learning experience thus far. Think I am done injecting resin into that first layer, the small soft spots I felt are solid now.

I decided it'll be to much to try and fit the core pieces under that big lip, so I trimmed the lip down to about 3/4". I'm going to start dry fitting the pieces hopefully this weekend, and if I am lucky start glassing.

[Outrageous]

3/4 will be plenty strong as compared to the original coring. I redid all my floor with marine plywood and it is rock solid. Just build up the areas that support the hatch where it sits on the stringers so you are not spanning more than the with of the fuel tanks or center section where the muffler resides.
hard to tell from the pics but the exhaust hose looks like it has a few hours on it. If questionable replace it as it is below the waterline and a blow out here will have you headed for the bottom in a hurry. Use some good clamps like Awab and double them up.

[John3325]

A lot more progress today, got the 3/4" core in place with tons of weight on top to sandwich it good.

[John3325]

Just to recap the progress so far:

1. Cut/chizeled/pulled/pryed out the old core.
2. Stiffened up the first thin layers that makes the surface or skin of deck by injecting resin directly into drilled holes.
3. Epoxied the area I put the 3/4" marine ply into for new core (and also put a layer on the side of the ply that went in). Drilled a few holes in the marine ply to let air escape and find its way out the top.
4. Used syringes to inject resin into the seems and around the sides of newly placed core. Found as many heavy things as possible, and put them all on the hatch to sandwich that thing good. It does make a difference, you could see air bubbles escape along the sides and through the holes of the marine ply.

After going back and forth on how thick to make the new core, I am happy with keeping it to 3/4". Only thing I may look into, is putting one more 3/4" peice the width of the stuffing box/tranny hatch/gas tank retaining walls so that the middle of the hatch will have extra support along those retaining walls once put into place. Contemplating the idea, I think leaving it as is would be just as fine too.

My friend had a good point, it was solid as rock even with a saturated core so anything better than what was in it is overkill now.

Plans moving forward:

1. Let the core cure really well.
2. Epoxy resin the topside of the marine plywood, and layer some 1708 mat on top of it. I have something very similar, actually heavier than 1708 I plan on using.
3. I will mix up some West System 403-410 as needed to fill the voids between the new core and the existing lip I left.
4. Sand her down, paint her up.
5. Move onto the other hatches.

[John3325]

The core cured great, and I got the first layer of fiberglass mat on.

I had some West system 407 that I mixed up and used it as a putty to fill the voids between the pieces of marine ply. Worked great leaving it a little runny to let it run down into the voids.

Got the mat on today too, letting it cure and dry now.

I threw in a picture of the front hatch I am doing as well, which has undergone the same process.