Creating underfloor space
Submitted by Tradewind on Mon, 2013-09-09 22:27
I've been thinking about the possibility of creating an underfloor space for a kill tank, basically a removable fibreglass container - no pumps or drainage
It's a 78 Chivers Thunderbird with Outboard, so no current underfloor tanks or engine.
From the research i've been able to do there's no foam, just air compartments for buoancy.
Has anyone attempted this themselves before?
I assume under the fibreglass floor is wood stringers running port to starboard. If there are is there an easy way to locate them beforehand? ie knocking?
Also will this affect buoancy much by compromising an air compartment?
Thanks for the feedback
Rob H
Posts: 5749
Date Joined: 18/01/12
Ive done it, but on a
Ive done it, but on a Trailcraft not a glass boat so maybe not relevant?
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milsey
Posts: 1462
Date Joined: 22/08/07
Hey Rob, any chance you have
Hey Rob, any chance you have a few pics of how you did it?
I'd be interested in adding some more starge in my Quinny, which i assume would be very simmilar to the trailcraft.
Miles
Rig
Posts: 2925
Date Joined: 27/12/06
seakem
maybe send seakem a PM milsey as he offered to fabricate some underfloor compartments for my old quintrex when I was asking about this a while back. I never went through with it as I decided to upgrade boat but he had done it to his own boat
petermac
Posts: 2946
Date Joined: 03/03/10
i wouldnt do it
brings a tear to my eye you saying you are going to do that please don't do it those old chivers are built like tanks and the best ones are the ones that haven't been molested , to take a chuck of the deck cant be good for her be happy with the old girl as she is and she wont let you down, just get a bigger esky for your "kill" tank
Rob H
Posts: 5749
Date Joined: 18/01/12
a couple of people have asked
a couple of people have asked me but I think the pics may have been on a hard drive that packed up.
What I did was lift the riveted patch over the fuel tank and found a tonne of space.
So bought a 70 litre esky, cut a hole in the patch and put 50x50 ally angle recessed so esky (without lid) sat below the deck. Screwed and glued in place.
Then made a lid from marine ply, fully glassed it with some foam onto it and flush hinged it.
In hindsight Id get an esky, make an aluminium compartment with lid big enough to drop it in and cover.
Then you can lift it out to fillet, don't need a drain etc
Give a man a mask, and he'll show you his true face...
The older you get the more you realize that no one has a f++king clue what they're doing.
Everyone's just winging it.
Vinesh87
Posts: 2751
Date Joined: 02/04/11
How are you going to lift it
How are you going to lift it out when it fills with water if there is no drain ? Siphon when you get home ?
Rob H
Posts: 5749
Date Joined: 18/01/12
you can do the same as with
you can do the same as with kill tanks and run a drain to the transom.
In my case I rigged it to drain to both kill tank and deck wash with a valve, then when diving you could fill it with fresh water and have a proper washoff for yourself and gear before pulling the pick!
But it was a lot of work but Im a compulsive fiddler also
Give a man a mask, and he'll show you his true face...
The older you get the more you realize that no one has a f++king clue what they're doing.
Everyone's just winging it.
Vinesh87
Posts: 2751
Date Joined: 02/04/11
Yeh run into transom is what
Yeh run into transom is what i would do but he said he didnt want to have a drain or pump so was wondering how he was going to lift it out haha
snappermiles
Posts: 2100
Date Joined: 05/11/10
i refurbed my penguin
and got seakem to build me some fuel tanks great job done and well above the standard that i had expected!
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scubafish
Posts: 951
Date Joined: 15/08/12
Floatation
I wouldn't, if you think of it as a flotation area the deck of your boat is a second hull.With air compartments or foam , it still works as a second hull ,if you hole the bottom of your boat and water rushes in it will fill the under floor area ,if your floor is sealed you wont sink and if you have a below deck pump you will be able to pump water out as you slowly moter to shore safely.Air pockets stop a boat from sinking even if it is swamped and rolls over it will still float.Compromise those things and you compromise your safety.YOUR CHOICE .
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Tradewind
Posts: 756
Date Joined: 18/09/12
Thanks Scuba That's
Thanks Scuba
That's basically what I needed to hear regarding buoyancy/floatation.
I'll leave the old girl's undergarments alone and work on solutions for the top deck.
Rob H
Posts: 5749
Date Joined: 18/01/12
that's definitely true,
that's definitely true, however, if your boat isn't able to have a self draining deck (deck above the waterline) then it will not have enough buoyancy in the hull to float anyhow when swamped.
That of course doesn't take into account any buoyancy outside the lower hull cavity under gunwhales etc as on many modern boats
Archimedes Law
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The older you get the more you realize that no one has a f++king clue what they're doing.
Everyone's just winging it.
scubafish
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I don't understand ,what are
I don't understand ,what are you trying to do here. What has a self draining deck got to do with it ?
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Rob H
Posts: 5749
Date Joined: 18/01/12
don't worry bout it, just
don't worry bout it, just getting technical on the finer points of under deck buoyancy.
Give a man a mask, and he'll show you his true face...
The older you get the more you realize that no one has a f++king clue what they're doing.
Everyone's just winging it.
marble
Posts: 773
Date Joined: 03/09/09
The chances of holing your
The chances of holing your boat bad enough for it to sink are so small I wouldn't worry about it.
We`ve got heaps in our boat and are seriously considering a couple of long insulated fish boxes on either side of the existing one on the centreline. Just gotta tow the thing to Henderson to get the work done.
If you want underfloor storage put it in. If we worried about the worst thing that could happen all the time we wouldn't leave the house, hang on we wouldn't live in a house, hang on we wouldn't breath the polluted air etc etc etc.
PMY 25 Centre Console DF300 Suzuki
Paul H
Posts: 2104
Date Joined: 18/01/07
Go for it if that's what you
Go for it if that's what you want/need, Shouldn't make a great deal of difference with bouyancy unless your talking a huge one (as far as percentage of under deck space).
Most boats -particulary with out boards, are stern heavy and if fully swamped the stern goes under and it will then roll upside down anyway rather than float upright (due to the bouyancy in the bottom of the hull). A normal sized kill box is'nt going to get filled with enough water in a swamping case to make a difference (if this was the case you wouldn't want to fill it with ice and water or fish etc). Larger underfloor engine compartments etc. on larger boats (proper game boats etc) with unsealed deck hatches are a different matter, in those cases only a good fail proof high capacity pump system (or having properly sealed hatches) will make a difference.
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scubafish
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Well done !!
Well done !!
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sea-kem
Posts: 14877
Date Joined: 30/11/09
When I did mine there was no
When I did mine there was no flotation to remove from under the deck where I put the tanks, so no compromise. The flotation is in the sides. I drain mine into the hull on the way in and use the bilge to pump out the water. It's not uasually a lot anyway 5-10L tops. And it gives the bilge pump a run. My top deck has the mini type draining scuppers on each side so am seriously considering a deck wash as well.The tanks are awesome clears a lot of deck space for fishing. And thanks Jeff appreciate that
Love the West!
petermac
Posts: 2946
Date Joined: 03/03/10
dont do it
mate your old girl is 35 years old start cutting holes in the deck and I think you are asking for problems (you might find some scary problems below deck you don't want to know about) just leave her as she is and you will get years out of her yet
Paul H
Posts: 2104
Date Joined: 18/01/07
Agree with you Peter cutting
Agree with you Peter cutting holes can find other problems and mean a hell of a lot more work than you planned - that being said if your hull has major issues the question is would you rather know or rather be ignorant of the fact.. I guess the question you need to ask is if you find problems what can you do yourself or how can you afford to rectify it and if not - do you want to be going out offshore in the thing??
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marble
Posts: 773
Date Joined: 03/09/09
Yep, would rather be out
Yep, would rather be out there in a sound hull without rotten stringers that has underfloor storage than something that will fall to bits if you knock it on something.
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petermac
Posts: 2946
Date Joined: 03/03/10
agree
it was meant in jest , I have know a
bloke a in k town that jigsawed there whole deck out when he found problems then gave up on it and it turned into a garden ornament , sure I would prefer to know about a problem but with a 35 year old boat I wouldn't be messing with the structural integetiy of the deck
Paul H
Posts: 2104
Date Joined: 18/01/07
My boats an early 80's model
My boats an early 80's model and I'm thinking of putting in a under floor fuel tank to free up deck space and increase capacity. That's my only concern - what will I find - That being said she's as solid as a rock and I've had it for (in the family) around 20 years - always garaged so pretty confident its all pretty solid. If you look any issues should show in the transom first. If the transoms solid the rest is "most likely" (""= disclaimer) reasonable (depending on the build).
Cheers
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petermac
Posts: 2946
Date Joined: 03/03/10
i agree
the transom probably comes under the most load structurally if its good the rest is probably good provided rot hasent got into the stringers , what is she ???
Paul H
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4.76 sea skipper cuddy - have
4.76 sea skipper cuddy - have only seen the odd one about and mines looks mint compared to the others I have seen which have had unsightly mods. can see it in South Oz Pauls gallery if you care to have a look.
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Moylees Brother
Posts: 48
Date Joined: 19/02/09
I have done a Chivers
I have done a Chivers Thunderbird with an outboard and opened up the floor with the aim of putting in a fuel tank. There are heavy longtitudinal beams running front to back encased in fibreglass each side of the centreline about 500mm apart. There is a cross beam just to the rear of the cabin and another about a metre from the stern.
I did the knock test and found what I thought to be a point right in the middle where I was sure there were no stringers and cut a hole with a hole saw. I figured if I wanted to close it back up I would put a plate behind it and glass it back closed. I didn't as the aim was to put a tank in there. When I opened mine up I found it filled with expanding foam which had a lot of water in it. I thought it was a bit heavy underway but thought it was just old school glass. It had to come out one way or another so made the decision to open it right up. I dug the foam out and found the water had got in through some big screw holes where the previous owner had some seats. I didn't find any exposed timber so realised I had a great spot for the tank. The only downside was once there was water in there it couldnt get to the transom. I created a lid to go back over this and was trying to work out the tank when I did some tests and found the boat behaved better with weight further aft. I think the thunderbirds with an inboard were excellent sea boats so this made sense.
I plucked the courage to open the floor up under the motorwell and found the space where the inboard would sit. This allowed me to get a square tank of 130 litres squeezed under there. I ended up using the big cavity in the centre of the deck for all my dive gear and cylinders but could have resealed it.
Hopefully my trial and error can assist as once the floor starts to come up it is a lot of work depending what you find so think carefully. The best part was I new almost every inch of that hull and it did me well for almost 8 years until it went to a new home.
Scott