20ft Fibreglass boat repairs help & advice needed

Hi.
I purchased a 20ft half cab boat which the floor had been cut out, after i got home i see the floor was rotten especially at the front where it hadnt been removed yet.
I have now discovered that all the stringers are rotten and 90% of them are completely gone.
I decided while the floor was out i will remove the back part of the top of boat and im glad i did as the transom was like paper peices and completely rotted out.

Anyhow i removed the seats in 1 peice from the front cab so i can just put back, also cleared the transom and rotting wood / fibreglass.

its all cleaned now and all thats left is the old left over stringers.
I also noticed the the boat is very floppy as the cross beam is rotten and collapsed too.

I need some help and advice with getting this fixed up.

1. How do i remove the old stringers?

2. i think i need some temp cross braces, where would i put them?

3. Ive out that the stringers are 18mm and will be using marine ply, what would be the best to seal them with and also i was reading about making sure the wood doesnt touch the fibreglass. What exactly does that mean?

4. the boat is sitting on a tandem trailer on skids almost from the front to the back, would this be ok to fibreglass the new stringers while its on them? if not what should i do.

5. The old stringers at the transom was sealed to it which made no sense to me as if water got in it wouldnt have anywhere to go, could i drill a hole big anout to put a tube in and seal around the hole with silicon?

6. I want to put a underground fuel tank in the middle too, can someone give me some tips and ideas?

7. When fibreglassing the stringers how many layers do i need and what about the thickness of the layers as i can only find thickness in GSM.

I think thats all for now and will keep adding photos and details as i go along which hopefully will be of help to someone else.

Thanks all.

 

to the point !

You should have left it where it was and found something else .
But in saying that we all do silly things from time to time its repairable and will be a totall repair and rebuild . its a good example of a bad example of wood under floor frames possibly never been sealled just slap it on and cover over and forget about it . plus you going to have coamngs to remake as well ??

 

hi tunnels.
If you read i do have the coaming as i cut it off to access the transom and stringers.

All i need to do it clear out the old stringers thats almost gone anyway, put in new stringers, put in new transom, then new floor, put the coaming back on and bobs my auntie,.
I do need some advice on how to do some things.

 

Sounds kinda like mine stuee. Mine is torn down and has been on hold for a while, gonna get back to it soon when it cools off a bit outside. Transom, stringers, and a new floor stem to stern plus adding part of a cuddy and hardtop off of another boat

 

Ok so you have one grinding job from hell !reason is it give grounds for new glass to stick properly to the old glass surface so a good grinder and if you can get a big one will be faster and easyer and make a good job . all areas where the new glass goes on the old glass needs to be 99% sanded and cleaned off !!,where the old stringers were ,take it all off ,the old transom needs to be ground totally and the area 150 outside where it was including the hull and topsides etc etc
where the new stringers will go 300 mm wide so you can get a good strong bond out onto the hull both side of the stringers .
post some good inside pics looking from the front to the back so can see the transomans surrounding area ! making and fitting and glassing over transom first will need to be finished so stringers can butt against and then go forward from there .
Transom thickness ??
stringers ! what and how you intend to make ??? and the floor going on top what are you going to use !!
That should be enough to keep you busy for a day of two !! the main grind up is very important and is going to take a while a big grinder will howl through it and get the buld done in a short time then finish all the hard to get to places with a small grinder . remeber new wont stick to old unless it ground and clean 150mm wide every where new glass has to bond . careful with the outside edge of the grinding dics and dont cut through the old hull specially on internal corners
progress before and after pics would be great . and sizes of the stringers . Solid wood is ok and even better with 5mm ply each side solid had a habit of splitting if you hit anything in the water .

All and any bonding to old glass surfaces need to be a minimum of 100 mm so 150 gound surface will give plenty of good bonding . Its a old boat so lets go over board a little and you wont ever have to worry about anything for long time to come . you will get other saying 50 to 80 mm is ok but thats for a newer surface . yours has oxidised by what i remember looking at the pictures !! Good luck !

 

Hey all. Ive had my break and now to get back into it.
I have grinded all the stringers down, it appears there is a filling of dark colour fibreglass between the stringers and the gullys in the hull. ?I did read somehting about not putting the weed direct onto the hull.
Wil it be safe to put on that or should i remove that and put some fresh packing in and what should i use if i do?

thanks

 

Pictures !! post pictures as many as you can if what you go and what you doing !! :?:

 

Tunnels, reading between the lines here, I think Stuee was talking about putting wood directly against the hull (finger slip on the k/b maybe lol), the "packing" I have no idea unless he meant a filler

 

Tunnels:
I will put up some photos tomorrow when i clear the 2ft thick coating of fibredust from everything.
It was also a typo "weed" = "wood"


Wooky:
When i said packing i did mean like a filler between the the stringer wood and the actual hull.


One more thing:
Im not sure what the bits of wood are called, they are the bits that interlock with the stringers that the floor sits on.
What would be the recommended gap between them as im just working out roughly how much wood i need and drawing a rough plan too on the computer.

Thanks guys for all your input, ive given myself till xmas to have this in the water so going for it now

Cheers

 

Stuee, the recommended filler I've read about on here is a mix of epoxy/hardener plus some cabosil or wood "flour" (sawdust ?) added to the consistency of peanut butter, I'm not sure if you mix with the measured resin then add hardener or the other way around (I have some more reading to do as I'm not quite ready to start back with mine yet, economy)

The "bulkheads" (?) to support the floor, I don't know if there should be an air gap, I'm going to fit mine to the hull with the filler then tab (I think is the correct term) them in place. As for the top of them, cured resin on both sides of floor plywood (after cutting to fit) then filler along the bulkheads and tabbed at the outer edges and along the stringers (if this is the wrong way somebody chime in so two of us don't do it wrong). Don't forget to have some way for any water to be able to drain back along the stringers and down to the bilge drain

 

Hi woody.
as the packing resin is in already and would be a pain to remove i was wondering if i could just put on top of that?

For the bulkheads? i was thinking i would seal the stringers with resin first, then sort of tack them in with a few patches to hold them in place, fill and gaps under with the filler mix you mentioned, then make the bulkheads to fit and fiber them all together and to the hull. Is this the correct procedure?

I was also thinking i would cut some holes the same size of conduit in the stringers and first seal them with resin then put in the tube and seal again this way the water has drainage means to the billage drain..

One more question is how high should i make the stringers, i was wanting to make some compartments in he floor so want to calculate the room, i was also thinking of making a custom tank to go under the floor in a sealed compartment with a lid on so i can access if needs be?

As usual if anyone has some comments please add.

Oh i just remembered too.
I have 2 x 1200x2400mm x 18mm marine ply for the stringers, what would the recommended floor thickness be?
12mm
15mm
18mm

Cheers

 

OHH NOOOO My reading is that you use the filler as you are putting the stringers and bulkheads in letting it ooze out of the joints then use a spoon or popsickle stick to smooth and round out the joint then glass and resin to tab them

As for drainage I was going to cut the corners off where the bulkheads meet the outer side of the stringers with no tube, letting it into the bilge at the transom and another main bilge drainway along the keel for the area between the two stringers. I've read that resin is hard to stick to PVC

You got me on the ply sizes, I'll be using 3/4 inch for transom (X2) and bulkheads with 1/2 inch for the deck/floor. 2X8 or 2X10 (forgot measurement) Douglas fir (was recommended) for the stringers to bring the floor back to where it was originally

I've got a brand new aluminum belly tank (came with the boat, never a drop in it yet) and have to make some sort of cradle to mount it with an access hatch

I'm still reading and learning before I start back with mine, I had stripped it down the the economy tanked on us but the boat isn't costing me anything right now as it's long been paid for

 

And off we go again.
Ok i have purchased the wood and its getting delivered tomorrow which i want to make the stringers and bulkheads over the weekend.
Im also picking up a 20kg container of fibreglass resin as i would like to start glassing next week.


I completely cleaned out all the old fibreglass stringers and its ready for the new ones.
I thought i would fill the hull with water to the floor level line to see if there was any holes, there was 1 i did and another where the previous person cut the floor out with a circular saw and didnt quite cut through but close enough for it to weep.
Would filling the cut line with resin then a sheet of glass on top after the resin has set be enough?


When i filled the boat up with water i saw it had sat on the trailer properly again as when i removed all the rotten stringers it seemed to turn floppy and also the hull seemed not to sit on the trailer properly and pivot side to side.
when i remove the water the hull will go back to how it was pivoting, is this ok to just put the stringers in and reset the trailer rollers?

What would be also the best way to join 2 stringers together, please select a number from attached image, personally i think number 1 as number 2 has the ability to slide and move whereas 1 is locked in.

What would be the recommended space between the bulkheads?
the space that is the main floor area is 3m x 1.9m wide then the front cab area but the stringers taper off there and will prob only need one small bulkhead.

When i make the stringers as the wood will be square do i need to make the bottom in the contour of the gaps where the stringers go?


Think thats all for the moment

 

Photos of what you have now !!!

 

The cut you mentioned just filling with resin is no good at all
Resin has no guts and the slightest bit of movment it will break just like a glass bottle and you will have a leak . Needs to be ground out gently and glassed properly maybe a small patch but the surface needs to be a 100mm or more all round the hole !! then glassed
The other thing that need checking is the bottom of the boat , find a long straight edge of timber or something and check how flat anf straight the bottom is !!!! bothsides !! Sitting on trailers changes the shape over time !!! ,it could have a bow up this is called Hook !!
if its bowed down it called rocker !!!
rocker is better than hook depending how much of course !! Hook you can push down and fit your stringers and glass them in place and will solve that problem . rocker if there to much needs to be pushed up and then stringers and glassed and should stay there ok
So before you get doing any work such as stringers of frame work ,check the bottom . need pictures to see what you got now . filling with water is practical but was not a good idea as the inside needs to be 100% dry before you do any kind of glassing what so ever . Plus the surfaces to be glassed over need to be scuffed and ground 99% clean so the new glass will have any kind of a chance of sticking properly and so it will stay and last and not fall off sometime later . What is the glass have to do the work you intend doing ??
How fats will the boat go when you finished ?? just need to get a idea for glass lay ups to make sure its strong enough to take any pounding etc etc .
Whats you exsperiance with Fibreglassing ?? you understand what you are doing or not ?? Just need to know what you know am only asking !!