Hulls: Aluminum or Glass?

[fast fred]

Like A Gong . Oh Yes they do, like a alu drum. Every time you hit a wave.

[Endeavour]

Rotomolding is good for kayaks and small boats (up to say 10' long). You can't compare a PE boat to a GRP or a Ally boat.

[pathalla]

Originally Posted by Polwart

Roplene is a trade name for a "rotationally mo[u]lded polyethylene" which is the same material most of these boats are made from - in the same way that all "grp" boats are made from glass reinforced plastic. There will be different grades of material - but generally they will be similar. I suspect the problem you describe is not fundamentally with the material - but with the design. Anyone buying such a boat (or indeed any outboard powered boat) should pay attention to the mounting of the transom to the rest of the hull.

Questions also need to be asked about hull thickness. A similar deign of boat typically has a thicker plastic hull than it would in GRP. Cutting down on thickness saves the manufacturer money (particularly in times of high oil price) and he may even say the boat will go faster (as it is lighter) - but has a dramatic effect of rigidity/flexibility.

Some of the manufacturers offer reasonably long garuantees on the hull integrity because they are so sure of the material/design.

Fixings take a little thought - as they would in an ally or grp hull though. If the manufacturer knows where a part is to go he can mould the nut/fitting into the design, if not it needs appropriate backing - and to be fitted in a suitable place in the boat. As the material is "slippy" - self tappers may be even less appropriate than in other boats.

You can repair the material by welding - its is a specialist skill though.

Pathalla there are plenty of under engineered GRP hard boats on your side of the pond - if you saw them you could equally say "never buy a GRP boat". One bad apple and all that...

Thanks for the info on the Roplene Polwart, something I am not really familiar with, This boat did seem somewhat shabby in construction, the components of the center console seemed too thin and the hull looked as if was pulled too soon (while soft) from whatever/however it is built. The slipperiness of the base material did seem to present a real problem in relation to how well it held fasteners, The owner had fasteners constantly working out of the Roplene, I personally think it deforms too readily from it's original shape from stress, if it was a lot thicker maybe not, but I will stand by my original contention, inferior to glass or metal. Just my opinion, and I respect yours and your knowledge on the subject, Merry Christmas to you and yours!

[Rogue Wave]

I drove both Ali ribs and GRP ribs when I was working in the North Sea last year and I can certainly confirm they do be noisy.

I prefer GRP especially for domestic purposess because you can (if needed) repair a hole on a beach and you can carry the repair materials with you in a waterproof tub.
I am also fairly convinced that the hull shape of a GRP plug is easier to refine
so they ride the water better.

Having said that it's difficult to ignore the craftsmanship that goes into an Alli boat. If the boat was to be used as a workboat maybe Ali

[pathalla]

Originally Posted by jyasaki

Logic and Triumph both build boats from Roplene (co-owned companies, I think.)

From the Triumph website: "Most boat hulls are rigid and stiff as boards, creating an uncomfortable, jarring ride. On the other hand, the shock-absorbing Roplene hull of the 195 CC soaks up the impact of every wave. The result? A ride so quiet, soft and dry you have to experience it to believe it."

So, apparently the flexibility is a selling point (though I have also heard that their ride is not all that great.)

The reports of problems from the softness of the plastic and such that Pathalla mentioned are apparently pretty widespread. A buddy of mine has a 19' Triumoh, and is constantly trying to lock screws in place.

Don't know about the comment about low-ish power limits; the Triumph line has a max HP rating of 150 for their 19', and 250 for their 22, which doesn't seem that far out of line.

jky

My buddy's boat which I believe was 21 foot had a terrible ride, harsh. It seemed kind of flat on the bottom for a vee hull, I don't know if it was made that way or if the hull started to flatten on the trailer because it was too soft. Either way not anything I would ever buy or recommend.

[BogMonster]

Originally Posted by Endeavour

Rotomolding is good for kayaks and small boats (up to say 10' long). You can't compare a PE boat to a GRP or a Ally boat.

Quite right

With a PE boat:

- You don't need to antifoul (apparently) as nothing will grow on it
- If you hit something with the hull it bounces off rather than bending or cracking
- No tubes to go pop every other trip by themselves or if you hit anything sharp, or need cleaning all the time

Still unsinkable
Still looks like a RIB (well the one I want does, anyway)
More deck width (on the Mac 570) than an equivalent beam of RIB

It appears that you get to spend more time boating and less time fixing/cleaning which can only be a good thing with 9 months experience of a rib under my belt

There is something sexy about anything made of alli though...

[Limey Linda]

Hi Steven. Has LandRover done a deal with Tupperware ?

[pathalla]

Originally Posted by fast fred

Like A Gong . Oh Yes they do, like a alu drum. Every time you hit a wave.

Fast Fred, Are you jerking Jyasaki's chain? C'mon... I have an aluminum boat and it doesn't make any more or less noise than glass boats do, actually most of the time all you hear from any boat is the hull cutting the waves or the occasional "bang" when coming off a big wave, if it's well constructed that is. What he has is very well constructed, Polaris. Actually, although I like both glass and aluminum as a hull material equally well I do tend to think aluminum is somewhat better because it can be welded, no rot and it is very tough properly put together, I know mine is, very tough...

[Poly]

Originally Posted by Endeavour

You can't compare a PE boat to a GRP or a Ally boat.

Its a bit dumb to say that - it is precisely what people were doing!

Your comment suggests they are either completely diferent kettles of fish (like comparing a 6m rib and a 20m cabin hardboat) or that one is outstandingly superior to the other. There are pro's and con's of both options. (One pro steven missed off his list is price!).

Comparing them is quite logical since they are "marketted" towards similar applications.

Oh by the way I am a rotomolded boat owner - but will probably upgrade to a real rib when funds allow.

Rotomolding is good for kayaks and small boats (up to say 10' long).

you are welcome to try my 14' boat - I think you will find it performs as well as you would expect any similar sized rib (with similar hull profile). I contest that the popularity for rotomolding smaller boats etc is that the cost benefits are much more apparent then.

[Poly]

Originally Posted by pathalla

the components of the center console seemed too thin ...
... The slipperiness of the base material did seem to present a real problem in relation to how well it held fasteners, The owner had fasteners constantly working out of the Roplene,

I recognise with these issues (my console is fine - but the seat/locker lid is too thin (about half the hull thickness) and flexes slightly under my fat ass. I like to kid myself on that it is like a mini ulman - as I bounce up and down on it! I only have 2 self tappers on my boat for this very reason (they hold the bilge pump bracket in place).

[BogMonster]

Originally Posted by Polwart

There are pro's and con's of both options. (One pro steven missed off his list is price!).

Comparing them is quite logical since they are "marketted" towards similar applications.

I found that the price was about the same for what I wanted - the export price for the Mac 570/115hp Yamaha 4/ (5.7m boat) is about the same as the price Jono is offering an Osprey for, for instance, once you take the VAT off. No idea how the smaller ones compare though.

Mac is partly marketed at people who are fed up with the maintenance liability of gelcoat and tubes and can't be arsed to antifoul. That would be me then

No idea how thick a rib hull is but the 570 hull is 18mm thick and the "tubes" 10mm I think. Knowing how tough a wheely bin is (about 3 or 4 mm thick I reckon) that seems to be quite solid to me.

Turning in to an interesting discussion

[Poly]

Originally Posted by BogMonster

I found that the price was about the same for what I wanted - the export price for the Mac 570/115hp Yamaha 4/ (5.7m boat) is about the same as the price Jono is offering an Osprey for, for instance, once you take the VAT off. No idea how the smaller ones compare though.

my experience was Mac were at the top end of this market. (i.e. their competitors were cheaper!) With a new boat the engine is half (or more?) of the cost - so the price savings on the boat are less noticable - but I couldn't have afforded to get a new GRP boat even at the small size I have - so I got a plastic boat (new) for the price of a second hand rib. Might need to add Osprey to my list of potentials then when the time comes - I had assumed it would be more expensive than that.

Mac is partly marketed at people who are fed up with the maintenance liability of gelcoat and tubes and can't be arsed to antifoul. That would be me then

I would agree with that - and previously having owned an old wooden boat - time afloat and minimal maintainance cost was a priority to me. Idiot-proof-ness has been useful (I recon I would have cost myself 100's in carelessness this year with a GRP hardboat)

Turning in to an interesting discussion

Yes - a bit of thread drift - but hopefully useful interesting all the same.

[BogMonster]

Originally Posted by Polwart

my experience was Mac were at the top end of this market. (i.e. their competitors were cheaper!) With a new boat the engine is half (or more?) of the cost - so the price savings on the boat are less noticable - but I couldn't have afforded to get a new GRP boat even at the small size I have - so I got a plastic boat (new) for the price of a second hand rib. Might need to add Osprey to my list of potentials then when the time comes - I had assumed it would be more expensive than that.

Link to Jono's ad on another forum (hope that is ok...!) Thought the price was very good and was quite tempted as I do like the look of the Wipermax but it still has tubes and it still needs to be antifouled.

Compared to that the Mac prices (all inc vat for comparison) Julian sent me were:

570 hull with single console and screen £6867
Underfloor tank £899
Yam F115 4 str £8997
Basic electrics pack £298
Single axle trailer £1692
Total £18753

plus you'd want seats, VHF, other electrickery and stuff on top of that so it would come out about the same price I guess, maybe a little more. Engine is way over half the cost of course, the 90 2 stroke is only £5599 which brings it down a lot but I don't want a lawnmower engine on the new boat.

[pathalla]

Originally Posted by Polwart

I recognise with these issues (my console is fine - but the seat/locker lid is too thin (about half the hull thickness) and flexes slightly under my fat ass. I like to kid myself on that it is like a mini ulman - as I bounce up and down on it! I only have 2 self tappers on my boat for this very reason (they hold the bilge pump bracket in place).

I have seen the smaller boats built out of this stuff and they do seem to be extremely durable, metal fasteners do not seem to like to stay put in it. I guess if they can find a reasonably inexpensive way of welding the plastic parts together without using metal bolts or screws that would go a long way towards curing the problems on boats the size of my friend's Logic.

[Matal Mickey]

My statements are purely personal and if I can assist or guide by them, all the better. I have 25 years experience in this activity, the majority being RIBS. I have operated these boats for the military (worldwide), civilian commercial (worldwide) and leisure. The old addage you get what you pay for in these cases is paramont. It is currently my experience that the financial gap between Glass ribs and aluminium (ali) ribs is closing. On this side of the Ocean, the big scary question of ali is due to the fact that in the range of boats concerned, it is generally a new material to us! There are not that many around, however "watch this space". In my opinion we will all see a vast increase in ali boats in general this side of the Ocean very soon.
From an general operating view, running, cleaning, maintaining, antifouling, prolonging boat life, and resale values, my money is 100% on the ali boat! At the helm, on well manufactured boats, glass and ali, there is no difference. Perhaps the ali boat is slightly ahead regarding maintainance and most certainly performance, due to weights, especially power to weight ratios. Had I the financial resourses and were to allow my imagination to run wild, this would be my ideal boat (RIB). Full aluminium, no question. Approx 10mtr in length. approx 3-3.5mtr beam, full wheelhouse, large single diesel engine around 350hp driven through a decent leg. Not too mush to ask for??? One Company for all to look at is a firm called, Marine Specilaised Technology (MST) Liverpool.
I visited them so time ago (years) and was really impressed with their ali RIBS and general projects. I have since been on one of their vessels at sea and was astounded with the build quality and seakeeping. Hopefully some of this prattle will be of some use. May I wish all on the forum a very Merry Xmas and a sea safe happy New Year.

[pathalla]

Has anyone yet seen a hull built out of sheet stainless steel? They build all kinds of restaurant equipment out of the stuff, if properly ribbed internally I would think the hull skin could be pretty thin so it would not have to be that heavy. I spent a lot of time in a scrapyard when I was hunting for odds and ends for my boat and they had a lot of stainless scrap. I don't know alot about the alloys commonly available but the scrapyard had quite a bit of thin stainless sheet at times, I handled sheets that were very thin yet extremely stiff, seems to me a talented person with a welder could build a very nice, strong hull out of stainless given talent and tools. I have a friend who owns a steel fabricating co. here in Cleveland, they can and do build almost anything out of metal, much much thicker than stainless sheet, anyone ever seen anything out there?

[BogMonster]

I may have dreamed this but doesn't stainless suffer badly from stress fracturing due to fatigue? Just wonder if it could be a problem on a hull... but a whole hull built of stainless would be damned sexy if it would work

[codprawn]

You would be able to travel in time as well......

[jyasaki]

Stainless is not as ideal a material as it appears, either.

It is not typically a very stiff material, requiring some amount of thickness to get a decent structural rigidity. That means weight. Alternatively, you could use closer spaced bracing, I suppose, which will mean weight and fabrication labor.

In a saltwater environment, any crevice that traps water breeds aerobic bacteria. These eventually deplete the oxygen, and anaerobic bacteria begin to breed, the by-products of which consist of fairly strong sulfuric acids. The acid then corrodes the SS in the most out-of-the-way places, leading to failure, usually in places where you want it the least. Ways around this are *really* good quality welding, no unwelded joints (i.e. not much bolting of parts), and/or lots of sealant (not ideal as it invariably fails.)

It would make for a pretty boat, though; at least for a while.

Cod: It wasn't the SS that allowed for time travel, rather it was the energy from plutonium, dumped into the flux capacitor, and coupled somehow with 88 mph. (Yeah, I've seen it a few times.) I still wonder if the mirrors on a Delorean will fold up horizontally...

jky

[Rogue Wave]

Originally Posted by Limey Linda

Hi Steven. Has LandRover done a deal with Tupperware ?

iT'S THE ONLY WAY I CAN SEE FOR THE DOOR SEALS TO BECOME WATERPROOF