3mm or 4mm bottoms difference?

[devocean]

Been lookn at plate tinnys. Was keen on a tabs but the new ones have 3mm bottoms whilst the older boats (second hand) have 4mm bottoms. Do anyone have an idea why they dropped and the difference between the 3 & 4

[Jarrah Jack]

Don't know why but the difference is 1mm. Perhaps they have more framing. What size boat are you talking about ? Sorry about the joke.;D But the difference is really 25% which is a lot.

[Mike Delisser]

It's only a guess but I recon as there was a big increase in the price of plate aluminium a while back they may have gone from 4mm to 3mm to avoid a price rises across their range, very tough time in that industry at the moment. But as I said just a guess.

[tunaticer]

Aint no rules as to how thick they gotta be for bottom or sides, just comes down to the builders desires.
Treat any plate boat hard enough and they will dish in between the stringers, be it 2mm or 6mm.

What size platey are you after?

[cormorant]

Grade of alloy makes a huge difference. I doubt this in this case but just throwing it out there.

[devocean]

Looking at a tabs 5.45 territory pro

[business class]

depends if its 5083 plate or just normall 5005 aluminium. also depends on underneath the floor if its full height frames and so on or just box section throughout. 4mm and 3mm is obviously a little bit of difference but in saying that its not going to be the difference between your boat banging and not banging.

[Dan5]

A 5.45 with only 3mm bottoms sounds a little light on to me......IMO.....anything over 5mtrs should be atleast 4mm.........lots of surface area on a hull that size....3mm would be asking for fatigue cracks.If looking at new i'd be asking the question about an upgrade to 4mm if possible and then you could decide from there which way you went.

Dan

[mojoe1]

mate not to sure but maybe the 3mm is pressed i think u can upgrade to the 4mm not sure if that one is pressed. the new ones look like a pressed bottom to me just like there seascape i think thats why the older ones in 4mm are built like a plate bottom boat(not pressed) cheers

[Jarrah Jack]

I wouldn't go near a boat that size with a 3mm pressed bottom. Had a very expensive experience with that once. TABS are a well regarded boat. It might pay to ask them about the engineering Devocean.

[rabbi]

I had a 5.2m cuddy pressed aluminium hull and it had 4mm bottom.
Wont go there again, It started cracking after 5 years and was a pain in the arse with cracks appearing every third trip out from here at ballina.

If I did it again I would have a heavy gauge plate hull as they seem to take a pounding a lot better.
cheers, steve

[propdinger]

i use a seajay pressed boat in 3mm CC with a 60hp and its been in some pretty rough stuff in the deep stuff and used in shallow creeks its 12 years old and no cracks or broken ribs but have seen the same hull with cracks depends on TRAILER SETUP aswell not just what sort of seas your in

[devocean]

Got in contact with them and you can upgrade to a 4mm bottom but I just can't believe that they can be regarded as a plate boat with 3mm bottoms. I also agree with the above statements that 3mm is way to light for a 5m.

[Aussie123]

A mate of mine who works a lot with alloy made a remark at the recent Brisbane Boat Show about the various companies selling 3mm boats as plate boats.
He mentioned that 3mm is classed as sheet and 4mm and thicker is classed as plate.
So if he is correct in reality a boat made from 3mm is not a plate boat.

[business class]

A mate of mine who works a lot with alloy made a remark at the recent Brisbane Boat Show about the various companies selling 3mm boats as plate boats.
He mentioned that 3mm is classed as sheet and 4mm and thicker is classed as plate.
So if he is correct in reality a boat made from 3mm is not a plate boat.

Thats rubbish, there not classed as plate once it hits 4mm, you can still get 3mm and 4mm in pressable light sheet material. Plate is in strength which is 5083 grade aluminium. just becuase you can get 3mm light grade sheet (as you refer too) doesnt mean your boat is now PLATE because you went to 4mm of the same material. Some companies specialize in plate boats such as AMM, Origin, Blue water just to name a few, and you check out there material and build specs there true PLATE boats hense the massive price difference.

[PB]

Yep I would put money on it that they will be using 5052 and not 5083. and if it doesn't have at least a 5mm bottom and 4mm sides its not a plate boat.

Cheers Pelagic

[Squidlet]

Yep I would put money on it that they will be using 5052 and not 5083. and if it doesn't have at least a 5mm bottom and 4mm sides its not a plate boat.

Cheers Pelagic


5mm bottom and 4 mm sides its not a plate boat ay? if this is true then their are alot of "fake Plate" boats out their, totally disagre with that call i dont build boats but that sounds like shit to me.
Cheers Chris.

[devocean]

From all my research there are in fact a lot of plate boats out there which are not plate boats at all. They are all claiming to be but when you stack them up against each other there are some vast differences
I went for a run in a Vindicator 550 the other day- 5 mm bottom 4 mm sides and 4 mm and the high end aluminium- this thing was a real plate boat it had no slap at all in 20 knot rough chop - I just wish I could afford one!

[robothefisho]

5mm bottom and 4 mm sides its not a plate boat ay? if this is true then their are alot of "fake Plate" boats out their, totally disagre with that call i dont build boats but that sounds like shit to me.
Cheers Chris.

Pelagic isn't wrong. There are heaps of boats out there which arn't true plate boats. If you went for a run in a proper one and then somthing along the lines of anything with 3 or 4 mm bottom sheets you would notice a huge gap in ride.

[PB]

Squidlet please dont take offence but, just a guess from our reply I would say your new boat has 3 or 4mm bottoms?
But you are correct in saying there must be a lot of fake plate boats out there, because there is, quite a few in fact and it will show on the price tag. I was probably a little harsh saying what I did as you can get 5083 plate in 3mm, but 5052 is not classed as plate its classed as Sheet alloy.
But if you’re going to build a plate boat do it the right way, build it tough and build it so it can be put into survey.

[Squidlet]

Pelagic isn't wrong. There are heaps of boats out there which arn't true plate boats. If you went for a run in a proper one and then somthing along the lines of anything with 3 or 4 mm bottom sheets you would notice a huge gap in ride.

Took a test run in a blue water boat,wich i am haveing built it has 4mm bottom and handles like its on rails and built to withstand heavy seas!

[tunaticer]

I am now thinking that most people on this thread think that a real plate boat gives a fantastic service. That alone is a pile of shit, it is the design and shape and construction of a boat that gives it that special characteristic. The thicker the material does not necessarily mean it is a better boat.
From a builders point of view, 3mm and under thicknesses are bought as stock sheets, 3.15mm and over is bought as plate stock as it is defined in the sales catalogues they purchase from.

There are both good and bad hulls made in all thicknesses and combinations and material types, every single time it will be a design difference that will make the biggest character difference between them.

Sure thickness can and does usually help maintain the shape of the hull, but thickness alone will not make it any good at all without the right design to support it.

Take a trip down to the Maritime Museum at Southbank and have a good look at the little ally boat out the back and appreciate its achievements even though it is the worlds ugliest rendition of a floating metal object ever created. It is a mind blowing story and well worth the time to investigate to appreciate.

[robothefisho]

Took a test run in a blue water boat,wich i am haveing built it has 4mm bottom and handles like its on rails and built to withstand heavy seas!
I assume its one of the smaller models, because they normally use thicker stuff in the bigger ones? But anyway now we know why you got a bit P oed. Rest assured these comments wern't aimed at a manufacturer like bluewater, they build a fantastic boat and you won't be dissappointed. They were one of the brands i was considering suggesting to ride in to guage the difference.


The primary difference after design etc is simply the weight thicker material has. Heavier boat = better ride.

[PB]

I assume its one of the smaller models, because they normally use thicker stuff in the bigger ones? But anyway now we know why you got a bit P oed. Rest assured these comments wern't aimed at a manufacturer like bluewater, they build a fantastic boat and you won't be dissappointed. They were one of the brands i was considering suggesting to ride in to guage the difference.


The primary difference after design etc is simply the weight thicker material has. Heavier boat = better ride.

Well said.

Regards Pelagic.

[BenAllen82]

Thats rubbish, there not classed as plate once it hits 4mm, you can still get 3mm and 4mm in pressable light sheet material. Plate is in strength which is 5083 grade aluminium. just becuase you can get 3mm light grade sheet (as you refer too) doesnt mean your boat is now PLATE because you went to 4mm of the same material. Some companies specialize in plate boats such as AMM, Origin, Blue water just to name a few, and you check out there material and build specs there true PLATE boats hense the massive price difference.

I completely agree, 5083 is the marine grade PLATE aluminium, H116 is a sub grade which most builders use. I saw 5005 mentioned in an earlier post, although 5*** is classed as marine grade specs 5005 is too soft and is not reccomended for marine use. 5052 is the usual grade most builders use in their pressed boats and is very versatile.

As for 4mm and 3mm bottoms, if they are plate then they do not require pressing, a builders ribs and stringers offer the necessary support and are usually welded to the hull with little deforming of the plate for the hull, 5083 does not like to be pressed and can crack, most builders opt for roll forming in this case. If however the hull is 5052, it will have to be pressed to a certain degree to reduce "HOGS" and too much "ROCKER" in the sheet which can cause a boat to ride on its nose or porpoise. Then ribs and gussets are added to hod the sheets firm in the vee shape. The pressing shape in a bottom sheet is to add strength, however can also be the source of problems, if the die used to press with is worn or damaged, it can affect the way the sheet is drawn when pressed and lead to thin spots and damage the structure of the alloy. With incorrect trailer type (multiroller eg), trailer setup, or people just flogging their boat, these thin spots, and stress marks can break and crack. This of course is not so much the aluminium, but the way it was constructed. Dont knock a hull if it is not plate, a 3mm bottom boat with the right pressing can be just a tough and withstand a hell of a beating, and being less material means your boat is lighter. lighter boat means whatever flotation fitted to a boat can support more added weight (motor, gear, YOU) in event of flooding or sinking, and more economical and lower horsepower requirements.

Some builders refer to plate sides in tinnies, however they are not plate. Most builders use 1.6 or 2mm 5052 that is pressed to offer strength, and then ribs are placed along the sides in desired places to keep shape and strength. Some builders however use 2.5 or 3mm 5052 with one pressing top and bottom to reduce warping when welding to chine and gunnel. They look great and offer more resistance to bumps and dents, but add to the overall weight of the boat and most times you will find extra ribs used to reduce bubbles in the sides from lack of pressing. These are not PLATE (5083) sides so be careful when advertised as so.

Hope this helps!!!

Ben

[jewjackjaws]

1mm thickness

[Daisy Burnett]

I have 5.7 Tabs and I enquired about the type of ally used at time of manufactor. I was informed that Tabs used 5083 grade. That was the 4mm hull. I assume they would be using the same grade all round. That was only in 2010 so hopefully they have not gone downhill since then.

Cheers
Daisy

[fishing111]

I completely agree, 5083 is the marine grade PLATE aluminium, H116 is a sub grade which most builders use.



I just had a look at the difference between H321 and H116 in "Plate Alloy Boats 3" and there properties are basically the same. Why is H116 a sub grade Ben?

[BenAllen82]

I completely agree, 5083 is the marine grade PLATE aluminium, H116 is a sub grade which most builders use.



I just had a look at the difference between H321 and H116 in "Plate Alloy Boats 3" and there properties are basically the same. Why is H116 a sub grade Ben?

Hey Paul,
When reffered to as a sub grade i was referencing to the grades of 5083 eg. In aluminium you have 5083, 5005, 5052, 5251 etc, in 5052 you can get H34, H22 etc, so in 5083 you can get H116, H321, H302 etc.

There is nothing "sub" about H116, in fact it is one of the most sought after plate alloys. In my experience I found H116 to cut nicer, have a cleaner weld and less susceptible to warping when welded. I have used a 3** series plate and it could have well been H321, and found it to warp with less heat, and did not have such a clean weld when tigged. We did rule out contaminated gas and gear. It was not a "bad" weld, just not the same result as using H116. Apart from that the boats are still on the water, and show no signs of problems. I have heard of but not confirmed of a "pickled" 5083 Plate designed for Aviation use, aparently it is not nice to weld also but usually does not pose a problem as most of their stuff is riveted... Anyone else hear of this??

Other boat builders I have spoken too have also agreed H116 is a preferred grade but it really depends on the supplier and what they have in stock.

Each to their own I suppose. Anyone had experiences with these or any other materials or dramas??

Thanks, look forward to hearing from you!!

Ben

[fishing111]

Sorry Ben, completely misread what you were saying.

[Stuart]

I built my own plate alloy boat and I can testify to the fact that this was an eye opening experience. Dealing with a good naval architect was a learning experience that overturned many old wives tails.
One issue that I always believed in was the structure in the hull determined hull strength more than hull plate thickness.
Most people seem to rattle on more about the virtues of having thicker hull plate and never do you see the structure that the hull relies on to keep its shape under extraordinary pressures.
Off course thicker plate such as 5mm over 4mm is going to have a bit more impact resistance but not heaps more. Plenty of good structure to support the sheet such as close spaced frames and plenty of stringers will see a hull made from even 3mm resist high impacts over a more sparse hull structure using 4 or even 5mm bottom sheets. I have seen enough plate alloy boats in all sizes with Bowes in between the frames. Most of the owners said the same thing, the plate isn’t thick enough, but on just about every boat this happened to the frames where to far apart and there simply weren’t enough stringers to support the pressures.

I happened to be driving a plate alloy when this very thing happened, upon taking the boat back to the factory they dropped a frame straight in to the spot where the hull had bowed in after much manipulation. It spun me out because they had a frame in stock that would fit that very spot in the hull. I did a bit of asking around and found that was a fault with that brand of hull and design.
It seems any hack can start an alloy boat company these days with next to no experience building boats or even fishing. Some of these guys I have spoken to don’t fish or neither have they owned a boat previously. It seems nuts that this can happen in this day and age.
Some poor guy goes out and buys and XYZ boat but unawares to him and his family fishing many miles offshore that the thing is a potential lemon and they loose there lives.
It’s happened before and unfortunately it’s going to happen again. In my experience there is bugger all good plate alloy boat builders around that I would trust, hell that’s a major part of the resone I built my own boat, built like a brick crapper and heavy.
For a 7.3 meter centre console the bare hull weighs 1.5 tonnes then I have the engine and another 700kg to drop in it. Why people want light weight boats for offshore work is beyond me, weight always means softer.

Stu

[BenAllen82]

For a 7.3 meter centre console the bare hull weighs 1.5 tonnes then I have the engine and another 700kg to drop in it. Why people want light weight boats for offshore work is beyond me, weight always means softer.

Stu

Yeah absolutely, weight does help with the ride of a boat and structure of the internals as well. But really if the design of the hull is done right, structure is sound and not skimped on you really shouldn't have any problems. Weight will always make a hull work better, it gives you more momentum to drive the hull shape into and through the water.

Weight can have its inherent problems though, usually requires more horsepower which increases the setup/maintenance costs. More running costs with fuel etc.. Four-strokes are a good alternative for fuel usage reduction but power to weight becomes and issue, especially when the likes of evinrude are getting very good at what they do with emissions and 300H first service intervals. Other dramas can be the weight "setup" in the boat, put your weight in the wrong place can change the whole dynamic of the boat and the way she handles, especially if you get in to some dramas in some big swell, 2T of boat has a fair bit of momentum when it starts to rock and roll. I've heard of people say "oh shes got 400L of fuel and 200L water in the hull...." thats like an extra 600kg of weight. Sure but after being out on a weekend trip how much is really left, and coming home in a following sea is the worst time "NOT" to have that weight there!! If your boats riding higher in the water shes got more chance of rolling. I reckon Surtees "locking flood tube" is such a great idea for that reason.

Stu I gotta take my hat off to someone who really sets out and builds their own boat the way they want mate well done!!. 7.3... that's no easy task!! Did you get it in kit form or start from scratch?? Have you got any pics mate, i'd be interested to take a look.

Ben

[Stuart]

It was a big job on my own, seems a bit of hard work and my list of freinds vanish. The boat wasnt a kit, although it did turn up on a flat pack but then all plate alloy boats do. I payed a naval architect to design the hull, once that was done it was a matter of back and foward untill it was just perfect for me. That took around 2.5 months to get just right and then the CAD designes where sent to me and the cutting file off to the alloy company to be router cutt. I have since changed a few things to better suite my needs, as the build progresed It become more apparent for a few changes, not to the hull but inbuilt eskies and a 2 seat passanger seat at the front of the console which also doubles as a 150 ltr eskiy. Im spraying it at the momment but I intend on putting up some pics when done. Would I do this again, hell ya? And the first question many ask is do you save any money doing this yourself...Yes, plenty.

Stu

[BenAllen82]

Yeah it is a bit easier if you've got the help of someone who's being doing it for a while and have access to the gear required, were into a build on a 6.2 M Platey at the moment with a new hull, should be interesting to see the results...

Ben