Replacing floor...can I cross support stringers?

[Tmacular]

So my new boat I found full of ice and floor was solid because of the ice..after thawing it the floor is shot. Ripped up all the bad tonight and Im thinking before I put it back together that I would put some cross supports in on the stringers for extra sturdiness. Question is, there are no factory supports going across, only front to back.

My question is can I even do this? Is the reason why they dont put supports in like that because the boat needs to flex? Or is it because my boat is a 77 and they only do that on newer boats?

Anyways just wondering if I can put a few cross supports in without worry and to help have surfaces to screw in the replacement floor pieces. I am loading a pic with red lines representing where I would like to put support beams. Is this suitable.

Thanks for any advice!

 

[jigngrub]

Re: Replacing floor...can I cross support stringers?

It looks like you have some more demolition to do, your existing stringers look like they're rotted and need to come out too... and if you'll core sample that foam it'll probably be saturated near the bottom.

The answer to your question is yes, you can add as many bulkheads/ribs as you want. They didn't install any in your boat at the factory because it was cheaper to let the floatation foam support your deck. Bulkheads/ribs will strengthen your boat and support your deck better. I like this design:

 

[tpenfield]

Re: Replacing floor...can I cross support stringers?

+1 on the rotted stringers, since they are dark in color. The foam probably needs to be replaced as well. May as well check the transom while things are apart.

 

[carribbean soul]

Re: Replacing floor...can I cross support stringers?

I would think of moving the fuel tank closer to the center of the boat too, for weight and balance.

 

[rickryder]

Re: Replacing floor...can I cross support stringers?

Welcome Aboard ! + 2 on core sample of your foam stringers and transom....Yes you can add bulkheads for support and you can move the tank up a bit....keep in mind that with adding a lot of bulkheads and glassing them in you will be adding weight.... more weight means less MPH if that matters to you... Also moving the tank toward the bow will likely slow the getting on plane a bit.... fuel weighs 7.2 lbs per gallon ... don't know how big your tank is but something to consider. What engine are you running?

 

[Tmacular]

Re: Replacing floor...can I cross support stringers?

Ok so to clarify there was a black rubberized paint sprayed on top of the fiberglass underneath. The hot power washer took car of most of it so thats why it looks so dark. The stringers I drilled samples to test in multiple small spots and everything came out ok. They are very solid too with the fiberglass still in tact and not soft anywhere. The foam as well was completely dry. I did think about moving the gas tank up a bit but I also have a storage container that goes in the floor in front of that. I hope to center it at least a few more inches.

Do I have to glass the supports in? I was just going to cross support it mainly to have a nailing surface for target spots on the floor. Support on the hull just a bonus.

 

[jigngrub]

Re: Replacing floor...can I cross support stringers?

Ok so to clarify there was a black rubberized paint sprayed on top of the fiberglass underneath. The hot power washer took car of most of it so thats why it looks so dark. The stringers I drilled samples to test in multiple small spots and everything came out ok. They are very solid too with the fiberglass still in tact and not soft anywhere. The foam as well was completely dry. I did think about moving the gas tank up a bit but I also have a storage container that goes in the floor in front of that. I hope to center it at least a few more inches.

Do I have to glass the supports in? I was just going to cross support it mainly to have a nailing surface for target spots on the floor. Support on the hull just a bonus.

You don't have to glass the ribs to the hull, but they need to be glassed to your original stringers to hold them and to waterproof them.

If you try to screw or nail them you will break the waterproof barrier on your original stringers letting moisture in for rot to take over.

 

[rickryder]

Re: Replacing floor...can I cross support stringers?

If your just looking for nailers for your deck you could notch the tops of your stringers and lay flat 5/4 lumber across....you will have to glass everything together like JandG said to waterproof everything..... If you want to support the hull and install bulkheads I would glass them to the hull. You have to make sure that the wood doesn't contact the hull and there is PL or PB between the bulkhead and the hull. If the wood makes contact with the hull you will create hard spots that will crack the hull over time with the pressure created. Just my .02

In my resto thread you'll see all the info on bedding stringers and bulkheads in PB. I would also fill your core sample holes in your stringers and transom with Peanut Butter (thickened resin) to waterproof them.

 

[Woodonglass]

Re: Replacing floor...can I cross support stringers?

The deck does not need to be nailed or screwed to the stringers. Some don't bother. Tabbing it to the hull is sufficient. If you mark you deck appropriately it will be easy enuf to predrill them to screw into the stringers if you want to. You should always precoat the holes and the screws wth 3M 4200 or 4000. You could put PB on top of the stringers prior to deck installation as well.

 

[jigngrub]

Re: Replacing floor...can I cross support stringers?

The deck does not need to be nailed or screwed to the stringers. Some don't bother

I saw that build on another site, that was the same guy that used latex house paint to paint his boat with.

Not fastening the decking to the stringers would be like only nailing down the perimeter sheet of plywood on your roof joists or floor joists in your house and saying the shingles or carpeting will hold it all together.

 

[Woodonglass]

Re: Replacing floor...can I cross support stringers?

Sorry JNG that is not true for Fiberglass boats. I was not referring to ANOTHER SITE. Aluminum and Steel boats are built to be rigid structures. Not so with fiberglass. I was not referring to ANOTHER SITE.The PRO's on this forum have repeatedly said this to be true. This has some good info... If you do enough research you will see this to be true. Here's just one example.


Marine Surveying : Hull Design Defects - Hull Failure Part I - Boats and Yachts Surveys

If you're building a Large Ocean Speed boat, well then that's totally different

 

[Tmacular]

Re: Replacing floor...can I cross support stringers?

Ok glassing them to stringers wont be a problem. Just did not want to buy a TON of fiberglass as im already starting to lose money on this new purchase. My plan was to make some nailers for the spots in the wood that will now have a seem. I wanted to nail or stainless them in, and then glass the seams all the way around (about 10' long, 5.5' wide). Then instead of glassing the entire floor in, using a gallon of water tite waterproof paint to seal the wood on both sides and the fiberglass. Still ideas for now. Plan for laying the floor will come on Tuesday and will post some pics of what I went with.

Thanks for all the ideas, got some thinking to do

 

[Scott Danforth]

Re: Replacing floor...can I cross support stringers?

dont take shortcuts. glass it in correctly

also, yes, its a BOAT. Break Out Another Thousand. its an expensive hobby.

 

[rickryder]

Re: Replacing floor...can I cross support stringers?

Any job worth doing is a job worth doing right.....Glass the entire deck top and bottom or it won't last:facepalm:

 

[jigngrub]

Re: Replacing floor...can I cross support stringers?

I guess I just take it for granted that everyone understands carpentry and platform/deck framing when not everyone does.

Not fastening the decking to the stringers not only leaves the decking weaker, it makes the stringers weaker too. The stringers strengthen the decking and the decking strenghtens the stringers too. Fastening the decking to the stringers immobilizes the tops of the stringers making them more rigid and stronger.

The only reasons I can think of that would make someone consider not fastening their decking to their stringers would be water intrusion through the screw penetrations in the tops of the stringers, which won't happen if they glass their deck in properly and show their boat the proper care we all have talked about.

... or they're unsure of their build and afraid they've forgotten something or haven't done something well enough that they feel like they will have to remove their deck in the near future, which means they probably shouldn't have started the job in the first place.

 

[tpenfield]

Re: Replacing floor...can I cross support stringers?

I guess I just take it for granted that everyone understands carpentry and platform/deck framing when not everyone does.

Not fastening the decking to the stringers not only leaves the decking weaker, it makes the stringers weaker too. The stringers strengthen the decking and the decking strenghtens the stringers too. Fastening the decking to the stringers immobilizes the tops of the stringers making them more rigid and stronger.

The only reasons I can think of that would make someone consider not fastening their decking to their stringers would be water intrusion through the screw penetrations in the tops of the stringers, which won't happen if they glass their deck in properly and show their boat the proper care we all have talked about.

... or they're unsure of their build and afraid they've forgotten something or haven't done something well enough that they feel like they will have to remove their deck in the near future, which means they probably shouldn't have started the job in the first place.

+1 on this comment about fastening the deck to the stringer system for strength. It should add a lot to torsional rigidity of the structure, which the stringer system alone will not have.

 

[Tmacular]

Re: Replacing floor...can I cross support stringers?

OK so glassing the entire boat. I was slightly nervous not really being a big glass guy but very simple and clean. Got about half of it done tonight. As for the floor, ended up screwing and nailing to stringers, and the cross members, caulked any gaps and screw holes and proceeded to glass them in. floor is very solid without a budge.

I appreciate the help and I know the good old Bust out another thousand as this is my 3rd, but never have I had to do a job on a boat as big as this. Appreciate the advice...pics to come when the fiberglass dries up!

Tmac

 

[rickryder]

Re: Replacing floor...can I cross support stringers?

Caulked?? I hope with PB.....