Designing a 25-30ft boat with a HDPE hull

[mattosmond]

Hi guys and girls,
I have been reading some of the posts on here and have been really inspired with the use of recycled HDPE (plastic milk jugs) and am thinking of desiging a multi-use hull that can be manufactured from this material. This is for a design proposal for one of my final year design projects at uni. I would like to have a 25-30ft hull made that could be sold to many small craft manufacturers to build their own uppers on so that fibre glassing could be phased out a bit, by using a recycled material. where with cars you get many different tyoes using the same chassis, i like htis principal and think that it could possibly cut some costs for small to medium size boat builders. The general jist is that you would have say 1 manufacturer of the hulls in the uk to supply lots of companies at a reasonable cost and save them having to build the hull themselves, thus cutting down production times and hopefully costs, therefore making more revenue for these businesses. Do you think this is a good proposal or just dead in the water? Please give your valued opinions..
Many thanks,
matt

[Figgy]

Well, your first obstacle would be to design a hull that enough people want, to justify production. Frankly, thats what most designers are after anyways. Then shipping, what if I want ten, and I live in Maine, can you get them to me? What about one hundred? UK only? My point is, at what point is it less of a hassle to just "splash" one of yours, and produce my own from your proven design?
It's a good idea, if you can sort out the logistics.
-Figgy

[mattosmond]

this is a problem, but i was thinking more along the lines of uk based only at first, then if it were in theory to take off, then different countries can adopt similar principles. Thanks for your speedy reply, this is a very conceptual idea, but with some real ideas in it..... The hull design would be key...... And would probably be the real sticking point. Do you think the strength of HDPE would be enough..... Maybe mixed with another material or with a spine...

[Figgy]

Well, looking at this site, I'd say probably not. Mabe too flexable, but I dont know alot about the product. You might be able to make it work tho'.
I'll have to do some reading up on it. I know there are a few other members on here more versed on this subject than me. They will chime in soon...

[mattosmond]

cheers Figgy :)

[catmando2]

There are quite a few of these things in Australia polycraft being one,placa or plaka boats being another. Seem to have good reports as far as ride and longevity is concerned, but have a weight issue compared to other building methods eg: light alloy or composite,not sure compared to solid glass.

I am looking at a "polycraft tough tender" 3m as my tender on my current project. I was impressed by the picture of 3 blokes standing on the gunall on one side.

Dave

[marshmat]

Sounds interesting to be sure.
I'm not sure how manufacturers would take to the one-hull, outfit-it-yourself business model. The hull's a significant but not horrendously large part of the total cost, and it's also one of the few things marketing departments can differentiate themselves on (even if all 22' cuddies are pretty similar in reality).
HDPE is pretty flexible, its elastic modulus is only 0.7 to 1.0 GPa. Plus its maximum service temperature is only around 45 C (50 C tops if crosslinked), above that it loses its structural properties pretty quickly. You'd need quite a lot of it to get the same strength as a fibreglass hull, and if it's anything other than gloss white it wouldn't take too well to the tropical sun.

[antonfourie]

So how much do you think that the water cooled machined injection die is going to cost for a 30 foot HDPE mould, considering that you would have to have a male and female mould and be able to move them apart. On top of that machining a monster like that is going to take years not months.

Sorry to burst your bubble but the logistics are scary, also what if there is a fault with the design and you have to create a new set of moulds ...

[mattosmond]

thanks for the input, this is really what i needed. antonfourie: sure this would be mamouth, but i was thinking of the long term.. Are there any other good ways of making a strong hull from a recycled material? This is the main point of my concept.

The boat is going to have a wave piercing hull and be a 30 ft cabin cruiser.... Just to try a different type of hull in this ferocious market!! What do you think or am i being unrealistic? matt :)

[hansp77]

Hey Matt,
I like your passion, and your acceptance of critisism.

I love the idea of basing your design around recycling. In my opinion there is not nearly enough of this done in modern boat building.

I seem to be an instinctual collector, salvager and thinker along these lines. (however most of my thoughts end up impossible or already achieved)

From my limited knowledge on getting moulds made (for glass and plastic bottles not boats) it is a VERY expensive process.

For the size that you are talking about, and the design, I think I agree with Anton.
Very Scary!

Maybe you could look at dramatically downsizing your project to something more universally desired- such as a tender. I don't know.

For the amount of investment that would be required, and the sales required to reach a profit, your project just may never get off the ground.

I don't wanto burst your bubble either...
I'll keep my mind on it, and maybe soon start offering some ridiculous and unlikely alternative recycling materials or methods.

Good luck.

Hans.

[mattosmond]

Cheers Hans, if you see my last project in the student design gallery then you'll see i like to think of the off beat concepts (this was my 1st boat deisgn so it is a bit rough around the edges) :)

[MarshallT]

You could make a boat using HDPE but since it is a thermoplastic material it will require heat to form the shape and that means expensive tooling. Rotomolded kayaks is a good example. At 20-30 ft you would need a big oven and metal tooling that could be rotated and rocked back and forth. In your design you would have to add bulheads and stringers to make up for the lack of stiffness (compared with FRP). Maybe a nice soft hull would make for a smoother ride:)

[mattosmond]

Thanks MarshallT that sounds like a good idea. i will investigate this channel.

[Richard Hillsid]

Boat buyers want shine and more reflections 2 things most thermoplastics can’t offer. After this has been solved fibber reinforced thermoplastics could rule.

[mattosmond]

Richard Hillsid: that's a fair point, but if someone did make one look really slick, then people would jump on the bandwagon i'm sure....

[Richard Hillsid]

Yep.

I have tried painting them and other stuff, just can’t get it right. So aluminium is my game.

If someone gets it right and there are many chemists working on it, imagine milk cartons with a reflection would sell better too.

[mattosmond]

would a recycled aluminium hull cost a lot or not?
Do you use recycled materials?

[catmando2]

I still reckon you'd have to adress the weight issue, you'll need more h/p than a composite design.

Dave

[Richard Hillsid]

would a recycled aluminium hull cost a lot or not?
Do you use recycled materials?

In my humble opinion aluminium is a cheap material to build hulls, and hulls are cheap compared to a finished boat.

Sure do, we recycle our beer and soda cans and every now and the I think one is in the sheet im taking, aluminium recycling is easy, I sell all our scrap, we have seperte containers for it, and I know for sure it gets re used, I have played with the idea of a solar furnace to melt the aluminium scrap into ingots but that would not help producing a new boat as the sheets and profiles have to be of special grade, but all in all aluminium boats can be recycled.

[mattosmond]

Well Ricard i think i will defo entertain the ideao f the aluminium hull, is the right smooth or do you get quite a metallic sound, and sorry one more question, do you need more bhp than a fibre glass hull?

Catmando2: Can you recycle composite hulls or are they just as hard ot re-use as fibreglass.

I have heard in england there is some goverment funded research into grinding the hulls down into pellets to be used as under road hardcore, mixed with normal hardcore.....

[mattosmond]

how about rotational moulding? if it were to be on a largish scale... as i have other style boats i can attach this idea to....

[ersyncar]

i am working on a shipyard which produces HDPE (high density poliethilen) boats as boat designer and naval architect. if u want u can connect me by mail. ersinkar@msn.com is my mail and www.deltaqua.com is our website.

until today i have designed boat 4,5, 8,5m , 10m and 12m boats and we built 109 boat in 2006.

Good luck..
Ersin KAR
DELTA SHIPYARD (istanbul)

[mattosmond]

ersyncar:

thanks for the link to your website, it is very interesting. how much are your boats to buy?
You seem to have some pretty good engine size to speed statistics....

[ersyncar]

To tell a price for boats is not so possible because there lots of changeable accessories and machines.But if you want a very general price just for HDPE boat (not including engines,pumbs or any other accessories). For a 8,5 meter boat selling price is about € 12000, (this includes HDPE plaques and pipes, waterjet cutting,workers pay,and engineering calculations)
this boat's built in about 10 days in our shipyard. and engines and waterjet prices are very very changable. For example we use deawoo,yanmar and volvo engines; american turbine, hamilton waterjets propulsions.
if cheap price is important for you you can choose deawoo and american turbine jet. but if you really want to have high quality and performance i advice yanmar or cummins engine and hamilton jet.
For technical datas you can mail me.
Good luck to you..
ErsynCAR

[alaskamokaiman]

I seen the mould and heard the costs for the mould, a 20-30 footer would be lots of cash and you would need a really large heating unit.
I don't think that the hdpe they use is recycled material but they have a great boat I have owned them for over 3 years held up great. I have had them in cold temps. down to -30 plus have not seen how they hold up in 100 degree plus.
They are very tough I use them as ice breakers in the spring, one boat has over 125 miles of ice breaking time and shows no damage. At 12 feet they do flex.
If you would like to see it...mokai.com.

[ersyncar]

no we used recycled metarials.

[dondelmundo]

Hi Matt,

This is too late for your class but polyethylene modular hulls are manufactured by the folks at www.rotonics.com. USCG approved stuff.

[Man Overboard]

I think there is a need for very inexpensive canoe shells for rental companies that are located on rivers. Rocks destroy canoes and kayaks in a fairly short period of time; customers don't treat rental property with much respect. There is a river canoe rental company down the road from my business; they have to dispose of a canoe after 1 to 2 seasons. If the price was right, a rental company would overlook some of the negatives of a big plastic canoe. HDPE may be an appropriate solution to a low cost shell.

[spyro1123]

I think there is a need for very inexpensive canoe shells for rental companies that are located on rivers. Rocks destroy canoes and kayaks in a fairly short period of time; customers don't treat rental property with much respect. There is a river canoe rental company down the road from my business; they have to dispose of a canoe after 1 to 2 seasons. If the price was right, a rental company would overlook some of the negatives of a big plastic canoe. HDPE may be an appropriate solution to a low cost shell.

Mad river canoe already makes Rotomolded hdpe canoes...they are ugly, a little heavy, but would work for a rental.