Another deck re-coring question (or two)

[Wind River]

I have a 1982 Hudson Force 50 center cockpit ketch that I am in the process of removing the teak decks and replacing the entire deck core including the cabin top.

I have removed the upper skin of the starboard side deck the starboard half of the foredeck. I was going to replace the core in sections at a time but after removing the skin, I have noticed that the side decks were cored in 3/4" plywood squares and the foredeck was cored in thinner ply. The thinner ply was dry but de-laminated so the actual thickness is harder to determine but looks to be 5/8" with a thicker glass laminate over the top.

I will be using Coosa Bluewater 26 for the new coring material and there is a price discount for 10 sheets or more so I would like to make the purchase of all the material at one time. My question now is what thickness is the aft deck and cabin top core. I suppose I could just drill core samples and see, but I would rather just remove the skin and prep it all for recoring. The inner skin is very thin (1/16" - 1/8") but there are beams below it and a 3/8" plywood headliner is attached to the beams.

Structurally speaking, is there any reason not to remove all the deck core at one time?

Next question.
When I removed the first small section of deck skin on the side deck, I had intended to run the new glass up the sides of the cabin top and up the gunwale but after reading many of the deck recore threads on this forum, I have decided on leaving a 3" margin of the original deck and glassing to that instead. Now I have about a 3 foot section of side deck with only a 3/4" - 1" margin to glass to. Will this be a problem? The side deck glass is approximately 3/16" thick while the foredeck is 1/4" thick.

I am going to relocate my stanchion bases from horizontal bases bolting through the deck to vertical bases attached through the gunwale. (The gunwale is 3" high to the bottom of the teak toe rail) Since these bases are within the 3" margin, they have to be removed and I will have to put glass up the inner side of the gunwale any way in those areas. Should I get rid of the margin on the gunwale side of the deck completely? This will require a lot of sanding/grinding in an area that is not easily sanded.

I plan to vacuum bag the new core to the inner skin with ArJay Core Bonding Compound as recommended by Minaret. The inner skin is not flat and smooth and will have to be sanded considerably to get that way. Since the inner skin is so flimsy, there will be no weighting the core down with sand bags and such and expecting it to bond well unless it is bagged and the inner skin is sucked up to the new core.
I am not going to try to reuse the deck skins and will use 2-3 layers of 1708 biax glass with two layers of 1.5 oz. chop strand mat on the top to achieve the 3/16" laminate thickness. Another layer of the 1708 on the foredeck should get me back to the original layup thickness with poly resin. The decks will be painted with Awlgrip and non skid when finished.

One last question about Coosa Board. Can it be sanded? Such as when two pieces are making up the core and laid side by side. If one is a little higher than the other can the higher board be sanded fair a bit before glassing over them? I hope this is not an issue for me but I am curious as I have never used it before.

I have read most of the deck core threads on this subject and got a lot of good information about doing this job. Any other suggestions on the best way to attack this huge job and any specific techniques to prep for it would be greatly appreciated.

[chebba]

You can look at some pics of my recore project. It may help you work through your project. Untitled Document

[Wind River]

Originally Posted by chebba

You can look at some pics of my recore project. It may help you work through your project. Untitled Document

Thanks for the pictures. Nice job!

It looks like we are going about this project the same way. It appears you had your decks off and the core out all at the same time, so maybe I am worrying about nothing. I do have a lot more deck than you though and by the looks of it, your sub-deck is wood. Mine is just thin fiberglass and I don't think I will be walking on it without laying some plywood down to span between the lower beams.

[Wind River]

Maybe I was too long winded in my post.

Question 1: Is it a bad idea to remove all the deck core on a boat at one time or should the re-core be done in stages?

Question 2: Can Coosa board be sanded like plywood to finish seams that are not level?

[chebba]

I removed the entire top and core at one time and then totally cleaned the area. My underside fiberglass layer was plenty thick to carry me. I was careful though. I replaced core with plywood pieces that were coated with fiberglass first and then fiberglassed in when still wet and screwed down into the lower underside layer. Many spaced screws. The bonding turned out excellent imho. then built the upper layer with good clothe. very solid sandwich. Beveled the plywood pieces. I was going to put in two layers of plywood with a fiberglass layer in between and staggered joints but got talked out of it by a couple of old salts here. Still don't know why they didn't like the idea other than they didn't think it up. I think the fiberglass bond between the plywood layers would have been stronger than the bond between the layers of the plywood. Kinda sorry I listened to them.
I do not know about vacuum bagging. I did not like the idea. If I were you I would install bottom support in the cabin on each area with cross pieces of 2"x4"s and then use weights on top for compression.
My subdeck was not wood. Just looks like it.

[Cyrus Safdari]

if you're worried that removing the core could warp the boat especially since it is on the hard and held up with pylons, screw in some 2x4 crossbeams temporarily.

This fella had to re core his entire deck

https://www.youtube.com/watch?v=7Pa-FHTK0eI

[Almost-There]

I've used really rough grit flapper wheels on a Makita grinder to shape and level coosa board or to clearance it etc and it works a treat.You can also use chisels and a router. But it will make them dull pretty fast so I only use when I really have too. Then last but least is my secret weapon the sawzall ;-) If careful a sawzall can make quick work of getting it close,for example taking a corner off etc. Then followed by a flapper wheel/grinder is the fastest/cleanest way I've found so far.


I'm not a safety freak but just be warned its not much different then grinding fiberglass as far as safety precautions go........So use what you choose to use for that when cutting/grinding this stuff too ;-)



As far as the deck goes I prefer stages especially when going between cored areas on larger boats.For example if I was doing the deck and cabin top,I'd do them separate for sure. There is just too big a chance for things to move around and even though you'll support it,if you take the rigidity out of the cabin top it will flex and come out wavy. The other thing is you can only lay up so much at a time. I prefer to do it in sections for just this reason the benefits to me outweigh the risks associated with doing it all in one shot.

[Wind River]

Originally Posted by chebba

..... If I were you I would install bottom support in the cabin on each area with cross pieces of 2"x4"s and then use weights on top for compression.
My subdeck was not wood. Just looks like it.

I wish I could do that, but I have head liner that keeps me from reaching the lower skin.

There are 2" x 2" beams under the deck that the head liner is nailed to. I would imagine between those and the bulk heads the structure would be sound enough to remove all the core at least on both side decks like you did.

I think I will still do this in stages as Almost-There suggests. I can leave the cabin top and aft decks intact except for some smaller sections that I will remove the core on just to gauge the thickness of the core material.

[Wind River]

Originally Posted by Cyrus Safdari

if you're worried that removing the core could warp the boat especially since it is on the hard and held up with pylons, screw in some 2x4 crossbeams temporarily.

This fella had to re core his entire deck

I love watching this guys videos. He is very pleasant to listen to and really thinks his projects through, not to mention how "spiffy" they turn out.