New structure for fiberglass floor

[cele93]

Hi guys, i'm sorry for my not so good english, i'm italian!
I need a help for the new floor structure of my boat: i bought a used boat and now i'm restructuring it.
under the floor panel the old structure was like this:

I cut and removed the central beam (the wood inside was rotten) and those 4 sleepers (the entire structure was soaked in water and so f*****g heavy).

now i have the "naked" hull and i have to design a new structure (lighter than the old one), my idea was like this:

with a 210cm long central beam and 5 of those transversal panels (i drew only one edge of them) but i don't know the materials, their thickness and if it's a good idea, can anyone help me?
thanks a lot!

 

[jigngrub]

Build it back the way it was, your new and dry material will be so much lighter.

 

[cele93]

it's impossible to reuse the old materials, the wood inside of the fiberglass was rotten, spoiled, and even the type of wood of the sleepers is so heavy. i'm trying to found a new type of structure obviuosly in marine plywood... what do you think about this one?

what about the thickness? the width of the hull is about 200 cm

 

[JASinIL2006]

I think jigngrub was suggesting that you rebuild your boat so the structure looks as it did before, but you should use new materials when you build it. In many cases, it seems the design of the boat is not a problem. The problem is that the materials have rotted (like yours did) either because the boat was not cared for properly or because the boat maker took shortcuts to save money.

There is nothing wrong with using newer, lighter materials. If you look around here, you might find a restoration of a boat similar to yours. That can be a big help.

 

[Woodonglass]

Welcome to iBoats! The longitudinal supports are called Stringers and the transverse ones are called bulkheads. The stringers are important in that they provide flexural support for the hull from front to back so that when waves and wakes hit the hull it wont bend and flex. Same thing for the Bulkheads from a side to side perspective. That's a simple basic explanation. They also provide support for the deck of the boat and some support for the transom. This link will provides some good information on the fabrication and installation of these components and the materials to use. I agree with the others that using new, dry components, will for certain lighten the load and you should attempt to COPY the same structural design that was there in the beginning. They built it that way for a reason. If it lasted this long there's no reason to change it.

 

[cele93]

OK guys, thank you very much for the help, as soon as possible i will post the work in progress photos!

 

[sphelps]

Welcome aboard ! How about posting some pics of the rest of the boat .. Looks like a cool little runabout !
Do you have a motor for it ?

 

[cele93]

Yeah i've got a Magnum Mariner 25HP and these are the images!



we sanded al the hull and the top of the boat, now we have to cover it internally and externally with 2-3 layers of fiberglass, then we'll set the floor structure

 

[sphelps]

Are you planing on painting or re-gellcoating ?
Any reason to fiberglass the whole hull ?

 

[cele93]

we asked to a local boat builder, the existent layer of fiberglass is too thin and the entire boat need more resistence (we found a lot of leaks). naturally we have to re-gellcoating all the hull...

 

[ondarvr]

This is a little late, but you should do all the glass work from the inside, doing it on the outside is a very long, costly and labor intensive way to do it.

 

[sphelps]

This is a little late, but you should do all the glass work from the inside, doing it on the outside is a very long, costly and labor intensive way to do it.

This was my thought . It would cut your fairing and prep work down a lot for whatever finish is going on ..

 

[Corjen1]

Cool Boat, welcome to dry dock!! As others have said, rebuild from the inside. Wood on Glass has a great "how to fabricate" Stinger/bulkheads....same principle applies to the floor.

There are many rebuilds that you can gleen information from.....I suggest you read a bunch of them. Re-gelcoating is not an absolute necessity...you can paint the hull as well. The folks here are more than happy to help. Good luck!!

 

[cele93]

This was my thought . It would cut your fairing and prep work down a lot for whatever finish is going on ..

a boat builder suggested us to remake an external layer beacause the hull has a lot of leak, however the old paint was so ruined. what did you mean with "it could cut your fairing"??

 

[cele93]

Cool Boat, welcome to dry dock!! As others have said, rebuild from the inside. Wood on Glass has a great "how to fabricate" Stinger/bulkheads....same principle applies to the floor.

There are many rebuilds that you can gleen information from.....I suggest you read a bunch of them. Re-gelcoating is not an absolute necessity...you can paint the hull as well. The folks here are more than happy to help. Good luck!!

Thanks!! I will do!

 

[ondarvr]

a boat builder suggested us to remake an external layer beacause the hull has a lot of leak, however the old paint was so ruined. what did you mean with "it could cut your fairing"??

Having leaks makes little difference, doing it from the outside creates a lot of issues that aren't easily solved.

When you sand off the gel coat it creates a rough and uneven surface, then when you add several layers of glass it gets far worse. Trying to sand (fair) the surface and get it smooth again is a big job, sand paper is expensive, and the time involved makes it a major investment.

 

[sphelps]

Whats the gray stuff on the hull? Is that some old paint primer ?
Like ondarvr says , Btw he's one of the few guys here on the forum that does this stuff for a living so I would take his advise every time , to add layers of glass on the bottom.. All of the gellcoat would need to be removed .. You have small holes and dings on the bottom that you will deal with individually ..You grind the old gelcoat away and tapper the glass back around the holes . Then you add multiple layers of glass to the hole with each piece a little bigger than the one you just installed . You will do this all at the same time for an all wet on wet glass lay up .. After some sanding you will skim coat the patch with a filler/fairing compound that you can buy or make some of your own ..
So basically if you install a layer of glass over the whole boat you would need to skim coat the whole boat and sand , sand , sand , sand , and sand some more to get the nice smooth /slick look that is desired .
If the hull is to flimsy for your liking you can add strength with glassing the inside where it will not be seen as much ..
I hope this makes a little sense to ya .. We are just trying to save you some unnecessary work ...

 

[cele93]

mmh ok, then, is right you to know that we have already removed any sign of paint and gell-coat on the hull. our schedule now is to patch all the leaks. and here i've got a question for you: the existing layer of fiberglass is quite thin, how can we repair the leaks with the teqnique in the image (if it's right)???

do you have any suggestion???

 

[jigngrub]

That patching diagram will work, but I suggest patching the outside only. When you are finished patching the outside cover the entire inside with new cloth and resin (layups) like this guy did to his boat that had a thin hull from too much grinding:
http://forums.iboats.com/forum/boat...8-83-lund-sirius-total-gut-and-rebuild/page11
Look at the next 5 or 6 pages to see how he covers the inside entirely with new fiberglass.

 

[sphelps]

What did you use to sand the gellcoat off with ? In the last picture the area just in front of the paper towel roll is new glass ? I am wondering what the gray part is . Was the gell the blue color or was that paint ... If there aren't any bad grinder swirl marks you may still just be able to patch the holes and fair it . Then shoot more gell coat . If you do decide to glass the whole hull on the outside maybe a layer of some fine veiling cloth will help keep the fairing down to a minimum .Idk ..
Have you ever sprayed gell before ? You will need a good plan when you do . I have never sprayed any gell myself so I really can't give much advice on that ..
Hopefully ondarvr can get you going in the right direction ...Painting it may be easier ..