About the hull shape of sailing dinghies

A couple of other factors may be relevant when considering the National 12;the total crew weight tends to be quite light and the wide beam is helpful in this respect.Additionally,they now use quite large, adjustable incidence foils on the rudder to control the stern wave and to resist nose diving.

 

I'd be interested in your review of this video & boat, Dolfiman:


It was posted by Paul Scott at Self righting multihull? https://www.boatdesign.net/threads/self-righting-multihull.59935/page-4#post-951132
Am I correct in thinking these boats are a bit flatter forward than yours?
(Not sure what it has to do with multihulls.)

 

The Hadron H2 looks to be a very good design, well thought out for its claimed program, in particular (I quote) " Quick and exciting but not extreme ». I like the video sequence 9:40 - 9:52, she seems to glide effortlessly through the water. She has « flat and shoulders » sections and the bottom view of the hull shows a flat central area of which shape from bow to transom looks like the one I promote with the deadrise 2° lines.

On the other hand, in the longitudinal view, she shows a quite flat angle of attack, I suppose here is your question. This flat attack is linked to quite a forefoot in the water (at design trim 0°), my personal trend is to put less or even zero forefoot in the water to keep a minimum of attack angle in order to early initiate the dynamic lift taking advantage of the fore sections in U. But this is an interesting issue to debate, I have no very fixed position on that, I try to illustrate the issue in the document attached, with my current pro's and con's for both options.

 

Dolfiman,
Reaching my 70's I have been selling off my boats with a high S/D to sailors age ratio.
Thanks for the fodder for thought.

wet feet,
Over 25 years a 1954 Jet 14' Class sailboat followed me home, peaking my curiosity in the wizardry in Uffa Fox's designs.
Until Uffa's time there were dinghies that planed on occasion, but there were no true planing dinghies.
International I 14' "Alarm" first built in 1935 and Designed by: Uffa Fox. A narrow transom, deep rocker design that performance well, both all-around and while planing.


Jet 14' Class
S.A./Displ 41.79
Displ/Len. 47.17
The International I 14 footer "Alarm" Designed by: Howard Siddons/Uffa Fox was the predecessor to the Jet 14 class.
I ripped most of this from information above from.
History https://www.jet14.com/the-jet-14/history


A broach is always a concern when sailing on small lakes but with a narrow transom I fell like I have a chance for a recovery with out pitch pole. I don't mind capsizing now and then but a pitch pole is much less fun.

 

I think somebody made a mistake with the caption on the International 14,described as a Kirby 4-that is definitely a pre-war boat.I sailed a Kirby 2 a few times and it was cold moulded,with plywood ranks.It needs to be kept in mind that almost 100 years ago,when Uffa Fox was at his peak,the hulls flexed,the centreboards weighed 110 lbs,the cotton sails were less efficient and masts broke more readily.To cope with all these evolutionary changes,the boats have evolved and the speed increase has been phenomenal.I think some of it was spurred on by a realisation that the much more radical Australian development classes were even faster than the International 14 and if it was to reclaim the crown as the eminent 14 footer in speed terms,things needed to change.They did change and now the boats are like missiles by comparison.

Then:


Now:

 

wet feet,
Thank, I did not know but should have that that photo of the I-14 was from the earlier years and not the Kirby 4. My understanding is some I-14s were hot molded hulls as well as cold.
In Wooden Boat magazine #244 May June 2015 is an article about the International-14's: My affair with the International 14. A Personal history by Simon Watts.

Also there is a podcast about classic boat designs and the stories behind them. Hosted by Tom Darling at
Conversations With Classic Boats about the I-14's
Ep 26 - Uffa Fox, Bruce Kirby: The Flying 14s and the Modern Planing Dinghy — Conversations with Classic Boats https://www.conversationswithclassicboats.com/episodes/episode-26

If the seat of your trousers aren't wet, you haven't really been sailing.

 

The hull is made from double skin of diagonal inner planks with outer longitudinal planks/strakes. The fastenings throughout are copper rivets
This one is K400 Dragonfly which was designed and built by the legendary Uffa Fox in 1937
https://www.timeandtideboats.com/k400-i14-dragonfly

 

Fascinating construction ! Thanks for these photos.

 

We have a little Catalina Capri 14.2, a real bucking bronco you can feel the flat hull as you role from one tack to another compared to the Jet-14.


Capri 14.2
Designer: Frank W. Butler Ted Carpentier
S.A. / Displ.: 36.17 Disp: / Len: 65.25 Comfort Ratio: 3.44 Capsize Screening Formula: 3.54 S#: 8.20 Hull Speed: 4.88 kn



Jet-14 Class
Designer: Uffa Fox
S.A. / Displ.: 41.79 Disp: / Len: 47.17 Comfort Ratio: 4.04 Capsize Screening Formula: 2.84 Hull Speed: 5.00 kn


Ready to Finish Strong https://jet14.wordpress.com/2013/09/22/ready-to-finish-strong/

 

I am preparing a new version of Gene-Hull Dinghy which integrates the bottom line approach and the deadrise lines drawing as introduced in the quote #1 above, I still have the User guide to finish writing but the application is ready and I did a lot of examples to illustrate its capacity. All that is for the Forum software but I think the document « Examples » can also be offered here to your faithful attention, here attached.

Compared to my previous « Examples » documents associated with each Gene-Hull new development, I here detailed a lot more my intentions, my thoughts and my guidelines in a long introduction (about lightness, sail amount and sail carrying power, easily starting to planing, intrinsic stability) , and reminded them for each design in addition to the « how to do that » with Gene-Hull, so that the document is more lively to read and for everyone, not only for those who intend to use Gene-Hull Dinghy.

In some way this reflects my personal opinion that you may share or not of course. I try to highlight on the design main options or variants and I strive to provide rationale whenever possible. Anyway, in the examples of this document, as the goal is also to show the overall capacity of Gene-Hull Dinghy application, I covered a wide range of hull shapes including the ones I am not very ease with. And in complement, for the second serie of examples, I generated hull shapes directly inspired by famous historical or existing dinghies.

And also, I give the offsets of each example in a separated document here attached too, so that you can eventually recopy them on your prefered software.