Plate Aluminium Floor

[Tovo64]

Hi all, my first post. I own a Savage Lancer 580 with a 140HP Suziki on the back. Had it a bit over a year and overall extremely happy. Whilst out over the weekend I was chatting to mates about plate aluminium flooring and commenting that it would be good to replace the ply floor in my boat with aluminium. My idea is that it would add rigidity to the boat and of course be much longer/harder wearing. I even thought of an infloor kill tank. I guess the only potential drawback I could envisage (aside from the cost of the job) would be the added weight. I thought it might affect how my boat sits in the water in some way? Does anyone have any input? I'd really appreciate any thoughts.

[ozynorts]

It would be interesting to see just how much your ply floor weighs. It also would depend on how thick the plate is that you put in to replace it.

[PB]

Hi, we replaced the ply floor on a Savage Swordfish with 4mm plate alloy. it worked out great we had to weld in some extra floor stringers to support the plate. this also stiffened the the boat up quite a lot and the owner said it was better on fuel and got another 5-6 knots @ WOT. Well worth doing.

[Tovo64]

It would be interesting to see just how much your ply floor weighs. It also would depend on how thick the plate is that you put in to replace it.

Yeah I think that's the key issue mate, the weight. I can't imagine the ply floor weighs very much at all, certainly not compared to aluminium. On face value it seems a good idea to put in the aluminium deck, but given that the rest of the boat is pressed rather than plate aluminium I'm hoping someone can tell me if it is or isn't feasible. Thanks for the comment.

[Tovo64]

Hi, we replaced the ply floor on a Savage Swordfish with 4mm plate alloy. it worked out great we had to weld in some extra floor stringers to support the plate. this also stiffened the the boat up quite a lot and the owner said it was better on fuel and got another 5-6 knots @ WOT. Well worth doing.

hey PB thanks mate, I saw your comment after I replied to Ozynorts. I thought that extra stiffness would add some speed as well so good to hear. I have found a cracking welder who did some great repairs on my transom (leaking bungs) so I reckon I might ask him if he's keen. Could be a relatively cheap way to upgrade a boat I'm otherwise happy with rather than lay out mega bucks for a new boat. Thanks a lot for that comment, really useful info.

[dnej]

If you have been following a recent post, you would note I completly rebuilt my Stessel.
At the time, I thiught about the idea of an aluminium floor.
However I realised, that unless I screwed it into place, I could no longer get acess to what is under the floor, for maintenance . That worried me greatly, as it is not a plate boat as such, even though I replaced the bottom with 4mm plate.
So I stuck with ply, screwed into place.
Treated the ply with lanolin , both sides, painted it , and laid the carpet using velcroe.
David

[Tovo64]

If you have been following a recent post, you would note I completly rebuilt my Stessel.
At the time, I thiught about the idea of an aluminium floor.
However I realised, that unless I screwed it into place, I could no longer get acess to what is under the floor, for maintenance . That worried me greatly, as it is not a plate boat as such, even though I replaced the bottom with 4mm plate.
So I stuck with ply, screwed into place.
Treated the ply with lanolin , both sides, painted it , and laid the carpet using velcroe.
David

Thanks David, that is definitely worth thinking about. I wonder how under-floor is accessed in plate boats such as Bar-crusher and Surtees? Thanks for raising it, not something I had considered.

[Matt76]

Also bear in mind that a plate boat has an aluminium floor, but the floor is fully welded to the side sheets and therefor the coolness of the water sucks out the heat generated by the sun on the floor. I am not sure on whether or not the floor would get really hot if it isnt weleded to the side sheets.

[theoldlegend]

Hey Tovo,

I suppose you'd have to look at the weight difference between plate aluminium and your existing floor.

I typed in "How much does plate aluminium weigh?" and found a spreadsheet where you just type in certain dimensions and it gives you the answer.

For example, 1 sq metre of 3mm plate aluminium weighs 8.1 kg according to the graph. Then I made the thickness 6mm for 1 sq metre and got 16.2kg.

So, if you could calculate the floor area needed, you could get a calculation of the weight, depending on the thickness. Then compare that with the weight of the ply floor.

But as DNEJ said, you might cut off your access underneath the floor.


TOL

4mm plate weighs 10.8kg per sq metre.

[Tovo64]

Thanks Matt. Another good consideration, I reckon I would put down that tube rubber matting and that would keep my (usually) bare feet from frying. Oldlegend thanks mate. Looking at your weights the total weight wouldn't end up being too much of a problem I reckon. One less fat mate in the boat I guess! Given I rarely go over 3 for comfortable fishing and it's surveyed for 6 should handle the additional weight OK. I will have to think more about underfloor access though. Thanks a lot for doing that bit of research on my behalf.

[johncar]

If you have to access the under floor on a fully welded plate boat then you have to cut a hole in the floor or in such cases as the fuel tank they can have a riveted or screwed down separate panel section. If you were worried then you could have the odd panel riveted.
I saw an ally floor going into a tinnie being modded when down at Origin Boats a while back, it looked to come up good. The owner has done a video log of the whole transformation which is quite interesting to see it shape up.
One of the Boat Vlogs below and you should be able to find the rest from there..
http://www.youtube.com/watch?v=YgO_V1BVe1s

[PB]

the above vid is the same way we did the savage. well worth doing it made the boat. I think for memory it was an insurance job and it was cheaper to do in alloy than flow coated ply.

[Moonlighter]

Re getting access to the under floor areas in plate alloy boats such as the Surtees, the short answer is:

You don't !

No need to, because there is nothing in there to get access to. They are just sealed buoyancy tanks.

They typically have a bilge area at the stern thats separate.

I rarely even open the bungs to the sealed sections that go up both sides of the Surtees. When i do, there is always a rush of air, because these buoyancy tanks are fully sealed up.

So in your case, it will depend on how fully you weld the ally floor in.

It would be worth leaving a central "trench" up the middle like most Plate builders do - where fuel tanks and kill tanks etc are found - and which either have sit-in alloy covers or screwed and sealant sealed down sections covering fuel tanks and the like. At the stern, this trench can be left open for a short distance to create a bilge area for any water thats shipped on board to run to, from where you can pump it out with a bilge pump.

The hardest bit in a pressed boat might be welding around the outside edge to the hull. Fitting it in nice and neatly and welding will be the trick.

And dont forget, if you weld to the hull sides, any paint on the outside where you weld to the inside will be, well, stuffed, from the welding heat.

[Tovo64]

Thanks a heap for the video, gave me a good idea of what is involved. Good point about the paintwork as well Moonlighter, all stuff to take into account. I'd really like to trade on a heavier plate aluminium boat but she who must be obeyed is putting her foot down a bit which for her is rare but I push the patience a bit with my various toys!

[dnej]

I note in the video, that they put Sikaflex around the edges,and dont weld because of the pressed sides. I would be real concerned about not being able to lift the floor if that were the case.
But hey, that is just me. I like to see whats going on under.
David