Design issues from transat 6.5m

[lascraigus]

I'm new here, but have had a love of sailing for a looooong time. I have always wanted to build my own sailboat, and so have recently been using sketchup to rough out my idea of building a boat, based on the mini's from europe. After sketching out my ideas, I imported the .dxf file into TouchCad to calculate the Center of Bouyancy, Center of Gravity, wetted surface area, etc, etc.........but here's the catch......I want the boat to be made entirely (as much as can be......structural members and hull, SOME decking) to be made out of HDPE (high density polyethylene). This of course not including chainplates, keel support structures, and standing rigging anchor locations. I located a company based out of Toronto Canada and plan to use their product to weld all structural pieces together....(see http://www.powercore.com/ for details). The resulting structure (which I have yet to test in my structural/finite analysis software) would be a singular piece of......well.......fantastic plastic........no need to paint, gelcoat, sand, or fair. It has UV protective properties built into the plastic already. Does this sound like a worthy cause to anyone? I have seen a company in Australia that started making conventional hulls out of thermoplastics, and I think it's perfectly feasible. Any comments/advice is greatly appreciated. Thanks!

Welcome here.

When you use the Forums search function, you will notice we have handled similar attempts here quite several times.

Though not with a real encouraging tenor.

Same is valid for the "effort" of designing you own vessel without a pretty substantial level of understanding the theory behind Naval Architecture and boat design.

In case you do´nt want to waste your time in searching the threads, I´ll say it:


in very short form: leave it............



Regards
Richard

[lascraigus]

Thanks for the welcome and advice! I have been searching the forums for such attempts......let me ask you this: If professional plans where acquired for said sailboat, do you think they would translate well or at all for the type of materials and methods I mentioned earlier?

I doubt there are plans on the market for HDPE (for some good reasons).

The stuff is just not a good boatbuilding material. (well, sufficient for some small craft, as proven in a few cases)

Where would you attach the loads of rig and keel, just to mention two significant points?

Regards
Richard

[lascraigus]

I was thinking something like this as a frame made from steel or aluminum for attachment points:

which fits inside this hull....

[lascraigus]

Yet where others have been successful I realize that failure (for me in this case....) is always an option!

Originally Posted by lascraigus

I was thinking something like this as a frame made from steel or aluminum for attachment points:

which fits inside this hull....

Why? There is absolutely no advantage in such setup. It would be less effort and cheaper too, to build it with proven materials.

So, again, WHY???

[Tim B]

The problem you have with HDPE, as with GRP for a one-off, is that you need something to mould it on. That is going to take time and cost money. Potentially, using a space-frame to take the rig loads and major wave loads is a very good idea. Especially if you can use a thin glass or carbon fibre hull to take the incident wave-loads and to keep the water out. You could end up with a very light hull.

However, this is going to take a lot of work and tooling. I think for a first-time builder you would be well advised to build (or have built) a hull and deck in wood from a reputable designer (preferably one who works near you). Alternatively you could buy an existing GRP hull/deck shell and fit it out yourself.

Remember though, that building a boat that floats and sails is the easy bit. Fitting it out is much harder.

You can also try your ideas at model scale (say 4ft LOA) to find out how well (or not) it will work.

Good Luck,

Tim B.

[fcfc]

Beware of true minitransat. They are real engineering challenges. See http://www.finot.com/bateaux/bilanmini650/amateur.htm for scantlings. 145kg / 320 lbs for hull + deck + stringers in carbon sandwich.

[lascraigus]

Thanks for the reply Tim. I think that a space frame as proposed would certainly cut down weight, and apex1 your comments are noted so HDPE is out....I have a HUGE plotting machine so I can scale a PROTO fairly quickly.....might have some thin lexan sheet to "skin" it with too.......as far as fitting out Tim, I assume you are talking about the interior and all that jazz? Personally I don't care what it looks like inside so long as I can sleep...carbon fiber is pretty expensive, I've looked into Jamestown Distributors however and their fiberglass prices are not bad......

[fcfc]

The price of a production minitransat (pogo2 , nacira, d2 , zero) is around 40 000€, 58 000$ , bare from yard. Around 70 000€/100 000$ ready to sail.

Price from a one off pototype minitransat is around 120 000/150 000€, 175 000/210 000$.

[lascraigus]

Please note my first post.......this idea is BASED upon the mini transat, not exactly like it.

[lascraigus]

fcfc- $210 is definitively out of price range......I could buy a 4500 sq ft house for that price!!! (then again the house would not be made out of advanced materials such as CF or Kevlar)......and probably wouldn't float too well either. But oh to be messing about in boats.....it's a fine thing.

[lascraigus]

Please see this:
http://www.vimeo.com/7260551

[fcfc]

Originally Posted by lascraigus

Please note my first post.......this idea is BASED upon the mini transat, not exactly like it.

For information, the 100 000$ ready to sail production minitransat are all polyester (rule requirement) under infusion, with lantor soric core. (rule forbid sandwich)

The maximum righting moment of these boats (around 1200 m*kg) is at least 4 (four) time the righting moment of a beneteau First 21.7, a typical week end / daysailer of similar length. And they weight less than 2/3 of the beneteau.

I fear you are looking at Formula one race car, saying it look fine but the engine is a bit expensive, so replacing it with a lawnmover engine should lower the cost without changing the look of the car. But you will be very very very disapointed by the performances of what you will get in the end.