End grain balsa substitute?

I just brought my 22' Aqua Sports center console home. She has been in covered storage for about 3 years. Before storing her I had discovered the dreaded rotten deck. Last night after I got her parked in the shop, I inspected the damage. The decking has completely dried, but is rotten most of the way around the t-top and center console. I need to replace the core of the deck before I can use the boat again for fear of losing the t-top.

I plan to remove the t-top and center console, then cut off the top layer of the deck in one or 2 pieces. once complete I can remove all the rotten end grain balsa, and replace the core by laminating it to the still in place bottom layer of glass with resin. I will then do the dame with the top layer of glass previously removed. While the deck is opened up I will laminate in new anchor points for the t-top directly to the stringers. This will hopefully stiffen the deck and help keep it from leaking in the future.

Will my plan work, does it make sense?

Would you go back with end grain balsa, or would you upgrade to a better material? I have found a selection of new core materials here:

http://www.jamestowndistributors.co...ls and Foam&categoryId=399&refine=1&page=GRID

I would however try to find a local source for these products to save on shipping. I live in North Florida so this should not be a problem (lots of boats here ).


let me know what you all think, and thanks in advance for the help. I will get pictures up here shortly, if I can find my digital camera.

Tom

Re: End grain balsa substitute?

Your plan sounds fine. Generally it's better to replace a cored panel from the side that's least visible, but since it's the deck and you can't really do it from below, you have a good plan.

End grain balsa is cheap, and if sealed will last a long time, and is strong. You could replace it with something like nidacore or foam, but I think you'd see a difference in flexibility... it would be stronger but flex more.

The idea to reinforce the top mounts is a good one, do the same everywhere if you can.

Be prepared to find that the water has spread more than you think...

Erik

Re: End grain balsa substitute?

IMHO I would cut the whole deck out. I am about to start the same process on my 1973 19-6. I don't know how you would get the new core to be flush with no gaps between the core and bottom layer of glass. Plus if you open it all up you can see if there are any issues under the deck. I'm going to use meranti 1088 marine ply and epoxy. Also it will be far easier to put better supports for your t-top while you have it open. Make sure you use epoxy because of the better secondary bond to the original fiberglass.
If you haven't seen this check out www.classicaquasport.com there is a wealth of knowledge over there as well.
For supplies also check out www.bateau2.com, they are in Vero Beach.

Re: End grain balsa substitute?

erikgreen said:

Your plan sounds fine. Generally it's better to replace a cored panel from the side that's least visible, but since it's the deck and you can't really do it from below, you have a good plan.

End grain balsa is cheap, and if sealed will last a long time, and is strong. You could replace it with something like nidacore or foam, but I think you'd see a difference in flexibility... it would be stronger but flex more.

The idea to reinforce the top mounts is a good one, do the same everywhere if you can.

Be prepared to find that the water has spread more than you think...

Erik

Click to expand...

Agreed, ideally I would like to do this from below, but it really is not possible unless I remove the upper half of the boat. I just don't have the facilities to do that on my own. The next best solution will be to do it from the top and then paint the deck. I am going to try to make all my cuts so they line up with the existing pyramid texture on the deck. If the seems are too noticeable, I am going to paint the whole deck with a good quality grip type coating, although I may need to sand off the existing texture so it does not show through.

I am hopeful that the stringers are untouched. As best I can tell, The t-top was screwed into the deck only. Because of this my hope is that the stringers have not been affected. The boat looks to have been built with about a 1 1/2" gap between the underside of the deck and the top of the stringers. This gap is filled with a caulking type material. So the deck should be totally isolated from the stringers.

I think when I re core, I am going to go with solid resin with filler for about an inch around the t-top mount. I will also install access ports so I can add clamping plates under the t-top mounts to allow the use of bolts instead of screws. Hopefully, this will prevent any further water intrusion.

IMHO I would cut the whole deck out. I am about to start the same process on my 1973 19-6. I don't know how you would get the new core to be flush with no gaps between the core and bottom layer of glass.

Click to expand...

I have been reading a lot over the last few days. The sailboat guys seem to have this same problem a lot. Most of the papers and sites I have read suggest a thin layer of resin be added to the in place bottom layer of the deck. This helps smooth the surface. Then a mixture of resin thickened to a mayonnaise consistency with light weight fill is added with a notched trowel (kind of like ceramic tile). The new core is then laid onto this and compressed to remove all air pockets. Then repeat on the top and so on and so forth.

I appreciate all the info from everyone so far. Last night I started working on pulling off the t-top. I got all the wiring and engine controls unhooked, and of course discovered a few more things I want to fix. I am sure this will turn into a complete rebuild before it is all said and done with, but hey it's all fun as long as I have something to work on. I think I can have the center console off and the deck cleaned and ready to cut by tonight some time. If I bust my *** on this I may actually be using the boat by summer. Probably not, but it never hurts to be optimistic.

The wife stole my camera for the week, but I will try to get pictures up as soon as I can.

Tom

Re: End grain balsa substitute?

Oh, I do have one question. I will be doing this all by myself, so I am going to have to use a slow setting resin, and work very fast. I probably have an area of about 32 square feet to re core. I will probably have to work in about 3 sections as best I can figure. is there any need to overlap the core material, with angle cuts on the edges, or can I simply butt them against each other and make sure the joints are filled with resin?

Thanks,
Tom

Re: End grain balsa substitute?

When I installed my t top I didn't want any thru bolts in the deck, so I glassed wood pads (with blind nuts on the underside) to top of the deck, most of the support for the top comes from the verticals being tied into sides of the console, then I glassed the inside of the console to the deck for rigidity.

But if you're going under the deck anyway I'd just mix up some resin with chopped fiber and cabosil to a mud and make footers of some sort.

Originally my console was screwed thru the deck to a plywood pad beneath the glass deck liner, I eliminated all those screws and sealed it up.

The forces tranmitted by the top is too much for 4 deck mounts. They will work loose and water will find a way.

I re-cored the deck with seacast. The original coring was honeycomb cardboard, I kid ya not.! its a 1974.

I also cored my top with home depot urethane foam sheet , score it with a steak knife and squeegee thickened resin into it, sets up firm and its very cheap. At $20 for 1 inch 4x8 sheets you can afford to test it , peel the coating off one side and score it right through into 1 inch squares, squeegee the mud into it and once you put a layer of matt and resin over it you have something quite strong and rigid.

http://s261.photobucket.com/albums/ii67/jonesg_photos/T-Top/?albumview=slideshow

Just some ideas.

Re: End grain balsa substitute?

If the urethane foam sheet you mention is insulation material, probably it's not a good core choice.

Despite the fact that it seems pretty good when it's first made, eventually the skins of fiberglass will delaminate from the foam. What actually happens is that the foam will shear or snap just below the joint with the resin. You can do a search here for posts by KnottyBuoyz from a while back for his experiments with this, or consult a good reference on composite construction.

This is due to the fact that insulation foam is usually 1 lb/cubic foot or less density, and doesn't have the shear or compression strength to work well as a composite core no matter how it's shaped or prepped.

If you can find insulation foam with a density of 2 lb/sq foot or greater (4-8 is better) then it would probably work well for this, but I don't know where to get that.

Erik