adivice on how a sharkcat is constructed, and best way of doing new floor.

[lembo]

gday guys
so got the new sharkcat sportsman and I love it.
its had a big tidy up and looks pretty flash but the floor and tanks are original and in need of a replacement soon. so im going to go all out and put bigger tanks in it. hopefully 180 litres a side (2100 kevlacat tanks) and a pair of 2400 kevlacat pods on the back. also a few bits of timber are soft underfloor so they will be replaced.
so im considering foam filling between all bulkheads and sealing right up, except the back one where pod bolts come through.

so my questions.
the sides of the boat above deck height, is it a single piece of fibreglass or a double skin ?
im concerned about water getting through the seal, finding its way between an inner and outter skin and getting underfloor ? or if its single I can glass floor to the sides of boat so there should be no way of water getting under floor.

any info on the process of doing a floor would be appreciated.
boat has ports into every section underfloor at the moment and its good to be able to inspect, but on the downside I think the ports let water in.

any ideas of how you would do it would be appreciated thanks.

[Noelm]

Not too sure what you mean by a double skin above the deck? Will the tanks fit? I would get some custom tanks made rather than try to adapt something, be pretty rare to find the crossover beams under the floor rotted out, the floor itself is weak as water, but provides no structural strength to the hull, well.... Very little.

[captain rednut]

Hey Lembo didnt somebody post some pictures of that exact boat having the floor done recently and it showed all the glass-timber-bulkheads-bouyancy foam etc

[lembo]

Sorry if I didn't explain to well, but on the sides of the boat above deck height is it just one layer of fibre glass? So if I was drill through the side would it be single layer or two layers ? I thought I remembered reading a while ago that someone said it was 2 layers. I'm concerned about water getting through my seal and dripping down between 2 layers and getting underfloor. But if it's single layer I wouldn't have that problem. Just glass floor to sides and it will be sealed. Hopefully I explained a bit better ?
Thanks rednut il try look some pics up.

[The Woo]

Rednut already took photos and showed you in another thread.

The hull sides are single layer, no core, no foam, just solid single fibreglass layer.

[Master4Med2]

Lembo, as you know I've started lifting the deck on my 560 Shark cat centre console.
I will be replacing all bulkheads, cross members, fuel tanks and at the same time removing the engine wells and installing pods.
There is no internal liner on your cat, and the thickness of the topsides is about 10mm so you need take care when you cut near the edge.

[lembo]

yeah I couldn't tell by the photos that rednut put up that's why I asked.
those pics were very helpful tho. so Master4med2 are you doing all glass work yourself ? what type of timber are you going to use for the cross members ?
is there any chance you could measure the dimensions of the tanks for me mate?
my boat gets some water into most compartments, and I was wondering how it got down there, only way must be through inspection ports. so I think il foam fill all compartments except back two, and get rid of the hatches and it should all stay dry.
thanks for your help guys.

[Flex]

In reference to the construction here's a quote from F&B magazine. It makes reference to an "inner liner". The description is a little lost on me.
"Construction ]Like its forebears, the 18 footer ismassively constructed with enoughʻglass to build a couple of ordinary18ʼ runabouts. As the accompanyingphotographs reveal, it consists of onemassive hull mould, an inner liner,and the deck and cabin mould. Thebasic construction sees the two hullsglassed together over the tunnel, with10 horizontal stringers glassed in toprovide substantial stiffening andresistance to hull movement. Prior tothe stringers being placed, 45 cu.ft. ofpositive foam buoyancy is beingplaced in position from blockspreviously moulded for the job.Provision is made for the twinstainless steel fuel tanks to belocated in each hull. With the tanks,buoyancy and stringers glassed inposition, a marine ply deck is thenlaid, glassed into position, with threefurther reinforcing stringers beingplaced over the forward sections ofthe tunnel.

Then, the deck and cabin mould isplaced in position and finally, theinner liner laid over the marine plywood floor.As other manufacturers havefound, the installation of a marine plyfloor after the stringers is a heavy, butnecessary additional stage, as itbasically locks the sub-frame intoposition, and creates a fair surface forthe inner liner to be bonded against.
Harris originally found it wasvirtually impossible to guarantee agood bond between the stringers andthe inner liner, thus he decided it wasbetter to lay an additional floor ofglassed-in marine ply before dropping[/the inner liner into position. In thisway, he achieved a good chemicalbond between the surface of theinner liner and the sub-floor sections. [/COLOR]





I can provide the link to full article if anyone wants it.

cheers

[Noelm]

Only the very early ones had a liner, the later (from about the late 70's) all just had a standard sort of build, with a hull, floor and flow coat.

[Master4Med2]

Lembo,
I’ll be doing all the glass work myself.
As for the timber, i won’t be using any, I have some material leftover from a previous build.
I will be using epoxy throughout the rebuild, and Coosa 26 for the transom, bulkheads, cross members and honeycomb for the deck.
The tanks are still in place, so i can’t get the size for you for a couple of days.
One thing I was concerned about was having the hull change / distort shape when I remove some of the bulkheads and cross members, so I spoke to a friend that is a boat builder / repairer, he suggested bracing the hulls, as the have a tendency to toe in.

[lembo]

thanks flex I read that article too , hence my confusion.
I wont be pulling out everything underfloor as a lot of it is good. a few of those vertical timbers are cracked and soft also some of the cross beams straight under floor. I will only be replacing whats needed, bulkheads all look good, but never know until floor comes up. I will just be using timber and ply floor I think.
can anyone tell me what type of timber was used in the original builds ?

[The Woo]

Most likely they used masonite.

Why anyone would put timber or a masonite type product back into a boat in this day and age is beyond me. I see the yanks on The Hull Truth doing it all the time and it baffles me. As above there are far superior products available they will never absorb water or rot. Much lighter too.

[lembo]

only reason I was going to use timber was because I'm only replacing very minimal stuff under floor , all bulkheads are solid and I've felt 2 soft cross beams and two soft vertical bits so I would probably have left over timber if I got a 6m length. Obviously I'd do it differently if everything underfloor was getting pulled up , but it's not. I would love a boat with no timber but its a much larger job to do that then the job il be doing. I am considering not using ply for the floor tho. The main reason the floor is coming up is because new tanks are going in. So I may as well do a tidy up job underneath while it's open.
So cost, size of the job and practically come into play.
yes my floor is Masonite , it's very thin and glassed over, noelm mentioned the floor ads no structural strength it's just there for something to stand on. The floor is in great condition , bit ratty but excellent for 25 years old.
i read hardwood was used in the sub floor structure . Anyone know what type of hardwood ?

[Flex]

Cheers Noelm for the info.

Im part owner of the boat with Lembo.So to follow along with his post..Boat had its first test run last week with the f115 yammies finally bolted on! Floated better than I expected.

The boat is under-propped. As the motors where pushing a 6.2KC prior and is a heavier boat.

Top speed is around 75-80km/h with motors easily going above recommended rev range.So might look at changing in the future, but over all it performed great.Easy cruise speed of 30 knots for around 4000-4200 rpm.

The torque is amazing! makes me realise how my old 5.2 KC was with twin f60's was under performing. More power off the back the better and softer they are.

For anyone interested here's bad photo of it floating., plus a couple of others.
http://www.ausfish.com.au/vforum/attachment.php?attachmentid=109435&stc=1
http://www.ausfish.com.au/vforum/attachment.php?attachmentid=109436&stc=1http://www.ausfish.com.au/vforum/attachment.php?attachmentid=109437&stc=1

As Lembo mentioned we are looking at replacing the fuel tanks to get larger ones. There are two beams that run across the top of the fuel tank which will need replacing aswell as the floor since it going to come up.


I'll be first to admit im a total novice when it comes to glassing but im gunna give it a crack. Cant be that hard surely. Ive watched 100 youtube vids and spoken to a few guys in person and no one seems to agree on an exact layup schedule for the beams? any adivce would be great.

[Noelm]

You will be able to get the tanks out by cutting one cross beam, then just fit the new tanks and glass another cross beam beside the cut one, I know guys that have cut a few out to make underfloor storage and years later the boat is still perfectly OK, so, I am not too sure how much strength they add to the hull, or if they were just there for the floor to sit on.

[Noelm]

just thinking about under the floor, the cross beams are only about 3/4" thick and on their flat, so they would provide little strength, but, that said, each bulkhead is glassed (very thinly) to these beams, and have a (usually) bare piece of rough hardwood going from the top to the keel section, then this is glassed (around the edges only) to some ply to form the bulkhead.

[Master4Med2]

If your going to replace the fuel tanks with larger ones, then your going to have to remove both bulkheads either side of the fuel tanks.
Then you'll need to make up new bulkheads and the base that the fuel tanks will sit on. Bigger job than replacing two cross beams.

[Noelm]

There is lots of room in the fuel tank area, to go wider, longer and a bit higher.