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Alloy Boat Floor - fully welded alloy vs Plywood

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Post Options Post Options   Likes (0) Likes(0)   Quote strx7 Quote  Post ReplyReply Direct Link To This Post Topic: Alloy Boat Floor - fully welded alloy vs Plywood
    Posted: 18 May 2021 at 3:52pm
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Have had a boat with a ply floor for the past 26 years, garaged its entire life from new. I like being able to remove the floor and inspect the hull for any issues.  The pro's I see of a full welded alloy floor is being able to just hose it out at the end of the day and the floation it provides should it turn to custard on ya.

What are other peoples experiences, loves and hates in both ply floors and alloy floors??  very interested to hear other first hand info....
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 18 May 2021 at 4:30pm
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M8 last week was asking me what I thought on his 90s non pontoon alloy 6m.
Couple bits of ply floor getting...lets say 'aged'
 Was thinking either sections checker plate, welded (as your thought on sealed compartments etc) or just lay plate down.

My 1st question was budget?.. didnt want to spend too much..
To get the alloy AND weld in will not be cheap.

Do you still want to store stuff down there?...  Its handy
Being a older boat do you want to check out the hull/ corrosion/ maintenance in the future? Also thinking about future sale.? ... would like to

Which pretty much answered his own question on most counts.

A current issue is the ply can get a bit slippry at times.. hence thinking checker plate.
 Checker plate is noisy.. drop something fishing in shallow water.. fish freeze...
 gets hot in bare feet... so he suggested floor covering
Adds quite bit weight to the boat, and weight lifting /washing out.. plus the floor covering.
Welding down for compartments...never going to get a crack.. water suck in as heats up and cools when parked up.. or at sea..want to run a few more cables/ mods?

Ply.. yep gets slippery, that a few strips and panels of 3M stick on deck non slip work and last well.
Easy, lite and access...thu bit of a change to the current size, position, weight would make far more practical in more than 1 way.
And if boat sinks, good possibility that a few deck ply panels may float anyway, next to the fish and chilly bin

He asked about marine ply.
 Yep way to go, will last another 25 plus yrs if looked after.
 On the other hand, I have used elcheapo construction ply for a boat floor deck.. well sealed up and lasted for many yrs, and still fine. Its washed down, rain gets to clean it more, and drys out on fine days...doesnt sit in water.
And a fraction of the cost of marine.
 Plus marine or std ply.. itwill be bit knocked around when comes to sell, and either may need replacing then anyway.

 Flotation if things turn to custard...
 Well if you have 'jackets...a few spares in a open locker, Epirp on your body, Water proof VHF strapped to the jacket...
Is having the boat floating longer actually going to help anything when think it right thru...?
 And if everything is well maintained, you are not going to break down on a bar you should not be going over, or marginal..
 And if fire is going to be the issue, and often is, you will not be around the boat anyway.

Im not a fan of sealing off access to bulges .. glass or alloy


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Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 18 May 2021 at 5:22pm
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If you get capsized/sunk being able to climb up on a partially floating boat can greatly increase one's odds of survival. If it's upright then you can often get mostly out of the water, and it's always easier for SAR to find a boat rather than a person. 

As Steps pointed out lifejacket, flares and PLB/Eprib can help greatly. 

If it were my boat I'd replace the floor with marine ply, like for like. But if you epoxy coat it, and bond/seal around the edges really good wyou may be able to get some flotation in. Inspection ports for checking. You can also buy some block foam offcuts and fit it in, depending on how it's all set up. I got polyurethane block foam offcuts from an industrial supplier for two thirds of bugger all. (Less than $1 a litre.)
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Post Options Post Options   Likes (0) Likes(0)   Quote strx7 Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2021 at 9:10am
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The floor in our boat is untreated ply, has been covered with a textured slightly plastic feeling fabric from factory (Marco) and we have a piece of marine carpet over it, it is still in great condition.  I don't see any NEW alloy boats these days without a welded in floor and was wondering what the logic behind it was....
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Post Options Post Options   Likes (0) Likes(0)   Quote Titahi Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2021 at 11:00am
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A good friend has aMarco that we would lift the ply floor of every year to clean the inside of the hull of the seasons accumulation of crud from diving for scollops and fishing, we replaced the ply floor one year and recovered with vynal, then continuued lifting the floor eacxh year for the next three years. 
 Eventually the ply started to show its age and he decision was made to replace it with aluminium,  best decision we ever made for that boat, it stiffened up the hull, we never had to lift the floor again to clean underneath it. I advised a friend of our experience who owns a  5 m quintrex, he then had the ply floor replaced with aluminium, he wishes he had done it years ago.
"I love standing by the ocean and just knowing what its for"
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Post Options Post Options   Likes (0) Likes(0)   Quote Kevin.S Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2021 at 11:52am
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Originally posted by strx7 strx7 wrote:

I don't see any NEW alloy boats these days without a welded in floor and was wondering what the logic behind it was....

The sealed chambers in the floor are flotation, and I think just about every boat manufacturer these days sells their boats as "unsinkable" -by which they mean even if the hull is completely filled with water the boat doesn't sink.
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Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2021 at 12:36pm
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Even if it floats upside down, which every non pontoon or upright flotation boat will do. Better than nothing though. 


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Post Options Post Options   Likes (0) Likes(0)   Quote Schampy Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2021 at 6:00pm
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I remember lifting the ply floor of my 5m Quintrex to fix the fuel sender on the underfloor tank - Only to discover cheap 3mm alloy frame members slotted together, a few spot welds and a bit of polystyrene scattered about for flotation. The hull had massively deformed inwards due to water pressure. Pretty bloody horrible. This was a new boat with only 100 hrs. I sold it.
They are not built to handle NZ conditions.
Marine grade ply with a couple of coats of epoxy resin on both sides will last for bloody years for what its worth.
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Post Options Post Options   Likes (0) Likes(0)   Quote krow Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2021 at 9:00pm
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Last boat Ramco 5.5 Ply floor with vinyl that eventually went soft where rain had been getting to it. Salt preserves the ply. I believe "marine" ply and standard untreated ply are exactly the same except for the priceShocked. Went through all the pros and cons with Aluminium replacement. Went with the Ply just because of the weight and easier for me to do on my own. Worked out about the same cost by the time you seal it and then paint with non slip or cover. When I lifted the floor I had 23 broken welds on the frames that I got fixed (and a couple more the following year. 
I now have a 6m Ramco with a welded aluminium checker plate floor. Several of the welds on the floor to the frame have cracked so no longer "sealed". The centre plate is screwed down so can get to the underfloor tank and fittings. Looks ok for what I can get to but who would know if there are any hidden broken welds on the sides. The good thing and why they weld the floor in is structural strength I'd guess. Yes more noisy when sinkers etc are dropped. Temperature not usually an issue.
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Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2021 at 11:33pm
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Having cut up a lot of sheets of BS1088 marine ply you definitely get what you pay for. More layers, more even bending, less/no voids or fills. My Meranti has 5 layers in 6mm, 7 in 9mm. 


But for a deck and in the 18mm thickness it may not matter. 
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2021 at 8:07am
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 Eventually the ply started to show its age and he decision was made to replace it with aluminium,  best decision we ever made for that boat, it stiffened up the hull, we never had to lift the floor again to clean underneath it.

 I dont get the logic.. its not a mater of not having to but rather not being able to....and being able to get into bulges, not just clean but check and repair stuff....espec going on several experienced posts above..

My original, At least 15yrs, center (over the fuel tank) ply panel is non treated, polyurethaned with  warehouse rubber backed carpet....Still solid as...thu has had at least 3 re carpets.
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Post Options Post Options   Likes (0) Likes(0)   Quote kitno Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2021 at 8:44am
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Not 100% sure but I think h3.2 treated timber reacts with aluminum. Causes oxcidization to the aluminum.
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Post Options Post Options   Likes (0) Likes(0)   Quote strx7 Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2021 at 9:47am
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My thoughts exactly steps, the piece of mind of being able to lift the floor up and check for any possible problems far outweighs the 'hard work' involved of removing the floor to vacuum the hull once a year....  Krow's experience on cracked welds etc just reinforces how valueable it is to be able to do this....
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Post Options Post Options   Likes (0) Likes(0)   Quote Titahi Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2021 at 10:49am
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Originally posted by Steps Steps wrote:

 

 I dont get the logic.. its not a mater of not having to but rather not being able to....and being able to get into bulges, not just clean but check and repair stuff....espec going on several experienced posts above..



And  yet the list of boats made with sealed aluminium floors is extensive 

you cant check under the floor on a 
Stabicraft
Lazercraft
kwiwkcraft
southern sports
white pointer
surtees
extreme



"I love standing by the ocean and just knowing what its for"
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 21 May 2021 at 8:33am
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Does that make it good idea?

Much depends on how the boat is constructed, Does it depend on welded floor for structural integrity maybe?.. like a urethaned glass windscreen in a car?

 If want flotation, easy way, is foam up under the gunnels.. Stays dry..no issues with hull corrosion.. and the boat floats up the right way...and the possibility of baling /pumping out.
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Post Options Post Options   Likes (0) Likes(0)   Quote Pcj Quote  Post ReplyReply Direct Link To This Post Posted: 21 May 2021 at 8:49am
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With the talk of sealed floor for flotation purposes .has any manufacturers actually taken a fully loaded vessel and purposely submerged it to back up the claims? My thinking with weight of motor stern would go under and possibly float with a bit of bow up.Dont think you could actually empty water out.
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 21 May 2021 at 9:05am
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Yep...thats where under gunnels comes in, Which is sorta like pontoon hulls
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Post Options Post Options   Likes (0) Likes(0)   Quote Pcj Quote  Post ReplyReply Direct Link To This Post Posted: 21 May 2021 at 9:13am
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Just watched a stabi video of them filling it up on lake.flat calm.now try it in the Firth of Thames in 15 sw.different story I bet. Most people do not get in to trouble on calm days.
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Post Options Post Options   Likes (0) Likes(0)   Quote strx7 Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2021 at 12:22pm
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here is a prime example, welded floor and corrosion issues..

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Post Options Post Options   Likes (0) Likes(0)   Quote Dept Of Fishing Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2021 at 1:47pm
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Hi everyone, so I’m about to go down this road to replace the floor that’s getting soft in my Fyran 580.
I think I’ve decided to stick with plywood rather than change to alloy as that’s more within my skill base.
I’ve been researching old posts etc and I think it’s best to stay away from treated ply as this could react with the alloy? From what I’ve read it seems the best answer is to cover the wood with some epoxy to seal it.
Can I just paint on the resin or do I need some cloth or something too?
And what is the best grade of ply to use? Does it need to be marine ply?
Cheers,
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