Hi All

Now I remember, I was thinking the other night about wave piercer type bows, I wondered if it would be good idea or not, because if one were to include WP bows in their design that was for junior use (I realise other age groups might use them as well) but, having the most forward surface of the bow at basically waterline, there would be a greater chance of damage to others, as opposed to having the foremost part of the bow at the gunwale. I'm sure we probably had our share of mishaps or near misses when we were young, and probably still have them now.

I wouldn't dismiss the idea, but just a thought.

Regards

Hopefully I will have posted an old picture of an Impara Cadet, this would have to have been around 20 years ago. I haven't been able to get to the club to take any photos showing the hull shape bit better. It is very similiar to the Arafura in its rig, however the hulls are rounded tortured ply. Not quite a small mossie, but good little boat just the same.

Regards

Another good reason to pursue this design <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

At the moment I can't see how you are doing this then, the two plots you have presented so far seem to show a near vertical bow combined with non vertical side walls. I know you haven't finished yet but I don't yet see how you can have those two features without a small amount of torturing.

A small amount of torturing is not a bad thing it just makes getting the flat patterns more difficult.

I am keen to see how your design progresses, good luck.

Gareth

I can't see the problem with a small amount of stressing the ply. In fact, I would say it is highly desirable since it induces more stiffness to the design than would otherwise be present plus it looks better! Also, Wouter, I have to agree with Gareth - the sketch you provided indicates some bending of the ply in two directions. I don't see how it could otherwise be made.

The amount of twist is VERY small and developing the shape is very easy indeed. I'm going to make a stiff card model of my second sketch (as amended for Timbo) and see how it works out.

I agree, can freeship, calculate the panel shapes once you introduce twist?

Folks,
I'm surprised at the number of posts that are being entered on this. Just a couple of responses below:-

Phill eluded to a homebuild ply box and rudder here somewhere?

John,
I did and it is dead easy. You could be building the rudder setup while waiting for resin to cure
on the hulls. Just takes a bit of planning. The ply rudder setup will be a fraction of the weight
of a rudder system from a H14 and probably better all round.

How easy or hard this project is to complete in a short time span while not compromising on the final product will get down to well thought out building instructions. These can't be written up in detail until the design is finalised.

*************
"Of course you can have them make the scarf but not glue it together yet."
Wouter, once the ply is tapered for the joint it is extremely prone to
damage even if it does not leave your workshop. There is no way I would ship it at this stage.
There are a number of different ways of tapering the ply for the scarf join.
However anyone not confident in any of these should just us a simple lap joint.

*********************



"I can't see the problem with a small amount of stressing the ply.
In fact, I would say it is highly desirable since it induces more stiffness to the
design than would otherwise be present plus it looks better! "

Janali,
I agree with you on this. Apart from stronger and stiffer the hull will give the appearance of being fairer as well.
********

Regards,
Phill

Just thought I'd look at the drag for the different hull shapes.




Hull1 is a conventinal "blade" design, hull2 is a moth planing bottom design similar to what Wouter and John are proposing, hull3 is a Gcat type Deep V design. All hulls are 12ft long and are displacing 120kg. The slimmer Gcat hull has the lowest drag, but there is not a great deal in it.

With regards to hull 2 this program does not predict planing so if the F12 will plane at higher speeds then there could still be a benifit in going that route.

Gareth

Gareth,

All my designs up till are made with panels that only bend in one direction. All the rest is optical illusion which I'm actually applying to make the hulls look nice !

See here :



Also my bottom panels are significantly more flat then those shown earlier in Johns picture. Afterall I'm trying to achieve some planing properties with this boat. This version has straight sides and a straight bow. The one with the wave-piercer bow is the same but with slightly inward canted sides. The amont of side canting needed for swept back bow is so small that we probably can get that by just twisting the ply inward at the bow.

Work is continuing.


John,



How or where do you see it ?


Gareth,

Can you alter the box hull shape in your drag simulation to have 25 degrees keel panel angle. Meaning each panel moves up from the keel line at 25 degrees ? That is a promising hullshape and it will resemble the red hull much closer in shape and I hope in drag so too. while still presenting a relatively flat keel that hopefully allows some planing. Not full planing but just a little amount so that 2 or 3 knots can be added to the top speed.


Thanks you all it really helps when other people do portions of the work.

Wouter

From the cheap seats.



I'd strongly suggest keeping with the wave piercing bow to give this boat as much a modern look (within homebuild reason) as possible,
or as Phill said, "It will look like a bicycle with training wheels".
And also per Phill, if it's deemed an issue add a layer of glass

Looking at the sketch you provided:



Where the panels join at the bow and along the chine each side, there is undoubtedly twisting of the panel(s). The same could be at the stern but it is difficult to tell from a sketch like this.

The sketch is exacerrated at the stern to show the make up but truly all panels are flat in the real life application with the exception of being bend in one plane.

If you bend two non parrellel panels in their own planes and have them intersect with eachother then the resulting intersection line (the chine) will be curved in two planes. Because this line HAS to lay in both planes ! But each plane itself is still only bend in one plane and therefor not stressed into to compound curve (? right word for it ?)

Do this mind experiement.

Use a flat plat to make yourself a cone. Cut the of at a right angle so the cone is like a round pyramid shape. Now intersect the cone s little below the top with a flat surface. You end up with a circle as a crossectional shape. Now bend this top plate and again make its intersection with the cone. Now the crosssection will be an round but irregular shape. It will not be an ellips although it will appear to be one. No just rotate the top plate. The crossection and chine will be curved and angles in more then one direction but the shape and chine are still the result of only two flat panels bend in only one plane.

My point ? It is extremely hard to tell from chines or crossectional shape whether a shape is made out of the intersection of flat plates bend in only one direction or by stressed plates bend in more then one direction.

Wouter

If it's a boat for kids it needs to look like a boat for kids. There is a reason why things look like they're made for kids when, in fact, they are. An opti doesn't exactly look like a modern high performance speedster.

This is, of course, if you aren't expecting to market the boat to adults unless you expect to first sell to the adult in order to get them to build it for the kid, and then you've created the same circle we're in now.

65 kg (143 lbs) crew is a rather developed "kid", maybe claasified as a young adult? The boat can also appeal to an adult. Could also be two 32.5 kg kids, or there abouts.

Paint scheme can make the kiddy look. Looking at the photos of the Cadet's, some looked like Dad trying to make a "proper" boat and then there was this one Demon

true...
One could just get brett to build lots more hulls...

Another 12 footer that could be reconditioned is the kittycat..

Another idea non flexable pvc tube... Such as used in electrical cabling..
Its cheap...

The design stuff coming from the group of guys working on it is impressive. (I'm learning a lot)
I'm concerned that you haven't identified the:
What
Why
How
and When
very clearly yet.
Your doing well with the How , but the what and why has been
skimmed over. (IMO)

There is nothing more difficult than designing something simple.
I know it's in design stage but there has been discussion about differant rudder assemblies, differant size sails,larger hulls for bigger guys and I think the word carbon was even used.
This sounds like a broad based formula that may not fit into the What .(your really trying to do)

Are you trying to prove you can design a new simple boat or increase the number of youth sailors? ? ?

I know from doing a lot of project management that keeping a group of engineers on point can be like hearding cats.
I get the feeling that Flatlander(John) the customer in my mind and Wouter, the engineer are not on the same page.

We really don't need a 10 boat world wide F12 class.
It also seems there is a lot more interest from abroad than in the USA.

Just my opionions and observations, Nothing personal.

As for the why, you might need to read back to the beginning of this thread.... But most people posting in this thread see a need for something that is different from what is being offered for sale as a way of enabling youth participation.

I for one, as an American, have been looking for something like this for awhile in the interest of enabling youth participation. I believe the ability to home build it as very important because:

1) I think you can come up with a better boat for the purpose.
2) the creation of the boat between the parents/clubs and young sailors will help get them into it.
3) It does not have to economically viable for a company to produce it.

The last part is the important part - this means the design can live on, and people can have one or many in the future long after any company may have given up trying to make a profit and killed it. And, if there are only 10 boats in the world so what. Hopefully those 10 boats are being put to good use - maybe they exist only in one club, but then I'd say the mission is still accomplished. If at some point in the future another club builds 10 more, and then it takes off in a region, well, who knows. If it never becomes a racing class but a handful of families build them for their kids, mission is still accomplished.

Point is, I don't see that happening with any of the current boats available from a manufacturer, new or used, at least for the racing part. This has been an interesting exercise if for no other reason than some of us have been exposed to small buildable cat classes we didn't even know existed. If this fails, I've seen enough that I would try one of those designs for a youth program.

Agree on the need to keep it simple and reduce the exotic materials as much as possible. But, in some cases it might make things easier and cheaper, so the use/elimination should be considered wisely.

For the general thread:
On the needs to look like a toy thing - I think this goes both ways. You may want a toy look for the really young, but once other boats start to look "hot" the toy look will work against you. I agree with the idea that the paint job can suffice for the toy look for the young. Go for a platform that looks good as racey boat, not a toy. Apply paint schemes to make it enticing to the Spongebob set.

On sails - I believe something like this can be done such that a simpler smaller rig goes for the younger kids, and for the older kids a more powerful and interesting rig to keep them going. The same platform should suffice for both.

On the bows - the overriding factor here should be what is considered safer for the purpose of the boats - kids. If parents think that a potentially higher speed boat with a pointy end might endanger children who haven't learned the finer points of boat control, well, adoption of the boat may suffer. Those of us who have put kids into sailing programs can enlighten us as to what the prevailing mind sets are...

Just my thoughts...

If you build it they will come. <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />

Seriously, my nephew-in-law races Highlanders and has several grand-children getting up towards first sailing lesson age. I'm definitely going to keep him abreast of this as it evolves. To me, it would be a great to have something like this if you have young ones you want to get into the sailing.

I'm structuring the project as we speak as I too felt like the project was potentially going off in too many direction.

The vision I have for this F12 is as such :

First your points :

What ?

A good looking sailboat for lightweight crews 45 - 75 kg (optimized for 65 kg) that has its main focus on being really easy and quick to rig and de-rig (incl. transport) for a budget of at max 3000 US$ but preferably less. (Vanguard optimist is 2550 USD)

Within these limits, I'm trying to get maximal performance out of the design and it looks like that is developping rather well.

NOTE : IT IS NOT A PURE KIDDIES BOAT ! More on this later.


====

Why ?

So responsible older children, teenagers and the smaller adults can sail a high performance sail boat that is really fun to sail in these "instant thrill seeking / no hassle" times but that can also be a ladder to truly performant boats like the A-cat's, F16's, F18's, and Tornado's although the last is not a major consideration in itself. With this I want to have a good tool to build up a more young participation in sailing and get kids aways from TV's, computers and obesity by showing that actually doing something in real life is more fun then simulating such a life by a computer game or TV.

The second reason is to give active adult sailors like myself an enjoyable sailboat for the little hours of free time that are too small to rig our normal boats. Like evenings or the two hours before wife wants to go to your in-laws.

The real youngsters are best served by something like an optimist.

====

How ?

But combining all the smart idea's found on other sailcraft (like landyachts and skiffs) to cut down on complexity and cost while keeping impressive performance.

Sadly this is something no builder like Hobie or nacra is doing. They pretty much only scale down a large racing beach cat to 14 or 12 feet and make it out of rubber. That is neither inexpensive, not simple or performant.

But also by having a design of which by far most items can be home-build. This will cut down on operating cost but also will be another life experience for those who decide to go down this route. For several of us like myself it means we can have such a small boat on the side very cheaply by using components of our larger cats. This requires a formula setup.

Also the formula setup allows these adults to make a hull that will carry their weight reasonably well without having the lightweight crews forced to sail hulls that bounce over the water with each wave. Therefor different hulls for different crews => formula setup. will equalize racing between these crew better as well.


===

and When

That is a good question.

I've just come to the realisation that while I personally have the capacity to do jobs with respect to developping this F12 I don't have the time to do it nor the resources to make this a proper launch. Afterall I still have responsibilities in other area's. And because this design needs all the smart stuff of other design/boats it is pretty much a fundamental conflict if one or two persons need to investigate and cover all things.

I want this design to be prototyped this summer at the latest and have 90 % of the development completed by summer 2008 when the final FORMULA class rules will have to be fixed. And at that time I want a serious launch of the class, but those are details I'l cover later. There is absolutely no way 1 or 2 persons can do this. So we need all interested persons to contribute what they can. Often not so much in hard core design work but in making 3D technical drawings, testting setups, gethering info on materials and availability in local area's. And I'm begging for a person to build us a website and a wiki. Alot of it is fun stuff, the truly boring math and such can be done by myself and another person.

Large parts of the design are already in such a state that imaging, testing and develloping can start.

So "when ?" Is now

"When finished ?" dependent on the help we get.



I'm working out a document detailing this all tonigh and will post it so you can all read it and comment on it.

Wouter