Futynette - ndc

This is one of my applications of the New Design Concept.
This design refers to the Footy RC and called FUTYNETTE:


The Sail Plan and Righting Moment vs Wind Speed


Your Ester 65 design intrigued me. As well as liked the hull shape… So I grabbed your RG65 Ester plans and patterns and scaled it down to Footy size, so it’s very similar to your Futynette.
At the moment its all framed up, bottom has been glued on.


Big Mistake !!

you cannot scale down the ESTEREL-65 to a Footy Class.
You should remember that volumes are scaled with the cube of the scale so, 65/30.5 = 2.13 scale factor - the cube is 9.66,

Thanks for your concern.
When it was scaled down it was not scaled 1:1. When actual scaling was done, that’s when I found your Futynette. And also found it to be similar to the Futynette.
No big loss if it doesn’t turn out, just a few dollars of wood. Footys are fast and easy to build, so I can always build another different Footy. Will post a picture when the sides are put on.


-I do not quite understand this rule of the cube of the scale :spin:, please, could you explain a little more, how and why?

-Thanks in advance.

Sorry, probably I did not explained myself well, but you should calculate the displacement obtained for your footy before continuing the construction if you scaled down the RG65 of any type !
Certainly will be difficult to manage if the construction is 107g or 120g, knowing that 50% is generally used for the bulb.

Of course as you says, are only few dollars and if the boat is sinking is not a problem !!!

This is “First RULE” in modeling “scaling” activities of any type :

Linear dimension go with the scale factor : follow linearly, up or down, the scale factor
Surface dimension go with the square of the scale : surface (up/down) x scale factor x scale factor
Volume dimension go with the cube of the scale : volume (up/down) x scale factor x scale factor x scale factor


PS: assume to take the Futynette and scaled up to get an RG65 -
volume of the RG65 = 480g of futynette x 9.66 = 4636g, while generally the RG65 displacement stays in the order of 950g to 1150g

Hi Claudio,
Built up a hull scaled from your Ester RG65.
Like you said it may not sail and may sink…built it anyways.
Just another experiment. Had I noticed frame patterns for your Futynette,
would have built…

Thought you might like to see several pictures.

Fine and now ?
Are you going to paint it inside and outside ?
What is the actual weight ?
For curiosity, put inside for few minutes, 480cm3 of water and see at which level is raising, with that you may have a direct vision of displacement achieved. Note that LWL Plan is below max beam edge as visible on post #1

Please remember, this is just a fun build, just to pass some time this weekend. It was not a serious effort to build an actual sailing Footy. I just like the hull design and decided to build one.
There’s enough other Footy plans out there if I want to build a sail-able Footy. Probably going to order two Half Pint Footy hulls for myself and father-in-law. I really want to build RG65’s again.

I will have to weigh it out when I get home after work. Will coat the hull with epoxy and try the water test anyways.
Here’s my website with my other builds.

Fine constructions on your site, what is surprising me is that you have not yet compared dimensionally the one just published with the others !
Anyhow was just an exercise !!

This was a relearning excercise for me regarding displacement, it’s been about 4 years since I built my last Footy. Did the water test and got a first hand look at how the build sat in the water. A bit low, and can see how a wider beam, transom as per your drawing in the first post would remedy that.

Still may just want to build another using your diagram to make patterns from. As I mentioned I do like the hull shape…

Fine then !
The shape BTW was not researched as such or for aestectic point of view.
The shape applied to a Chine hull, is the result of various technical considerations as described on the tread “Narrow Deck Concept - NDC”.
Testing will prove the approach validity, if not, will be a nice try around an idea !
Now, if some one like it, is a plus ! ehehe!!

While Claudio’s point is well taken regarding the effect of scaling on displacement, many RG65 designs lend themselves well to Footys…and vice versa. I placed 3rd in the RG65 nats a few years ago with a Ranger that was basically scaled up from a Footy, and going the other way works, too…but not on all designs.

Paul Risdale scaled down a Jif2 and got a 417g Footy…his build is here http://www.sailfootyuk.com/puma305.html

To scale down an RG65, you could also try .5 x length, .75 x width, and .75 x vertical dimensions. That is likely to get you in the ballpark for a Footy that would fit diagonally in the measurement box, with reasonable displacement. Each design is different, though, so you would be wise to calculate the displacement or do a quick mockup before committing to a full build.


p.s. Claudio, is your Narrow Deck Concept different from what we’ve always known as tumblehome?

Hi Bill,

I totally ignored the ‘tumblehome’ shape until some weeks ago, while I also think that some sailboat designs where developped in the past to ‘cheat’ some 'Rules" too.

My driving idea was simply the potential gain on the hull weight. Some increased strenght could be achieved too and further gain obtained with the tissue selection.
For me, I did not found any justifications to use a wide deck, no lateral stability considered at model level due to the long fin and bulb.

What came out later, during the drawing process at 30°-40° heel, as generally I do, is that with a chine hull shape I could get some benefit to contrast the typical sailing drift by exploiting the ‘vertical’ immerged wall.

Sincerely I do not know yet if this will be a good thing or not. What I’m sure now is that the deck sheer line is far away from the air/water interface when heeled and that the total hull weight is reduced with a narrow deck.

Someone start thinking that is also nicelooking. This principle is actually implemented with Esterel M ‘Diamond’, Esterel RG65 and Futynette, none off has reached the water yet and since I’m busy with a ‘home removal’ it will take time to get more info.