What to look for when designing a fast sailing dinghy

Gerry, the forefoot is that part of the very front of the boat that meets at the bottom. That is to say the deepest part of the bow.

If that part of the boat is too deeply submerged and too fine there will be some result. Draw a mental picture of a fin like a centerboard or rudder fixed at the bow. When you encounter a wave that is quartering your sailing direction, the waves force on the fin will cause the boat to turn in the direction that the wave is pushing it. Not good.

That is not the only consideration. You will want to be able to tack the boat cleanly and crisply. The boat will respond to rudder input and pivot generally about the centerboard. That means that the bow of the boat has to skid around into the direction that you wish it to go. Too much vertical surface at the bow will resist the skidding and that will cause a lousy tack. It may even slow you enough to capture you in irons.

Notice that the Javelin has the lowest part of the bottom forward of the middle section of the boat. Most other planing dinghys follow that same general layout. Doing it that way allows the run of the bottom toward the transom to have a minimum angle with respect to the water surface. That is advantageous for initiating the planing mode.

As mentioned above, if you are a very experienced sailor then you can reasonably expect some degree of exiliration from a fast dinghy like Javelin. If not a skilled, experienced sailor you are going to be sorely disappointed. Emphasis on the word sorely.because your body will take a beating.

I heartily recommend that you find a used Laser, buy it for a modest price, go sailing. The Laser will plane and give you a vigorous workout. It will also make you an adequate sailor without spending a ton of money. In the process you will not have wasted a lot of time, money, and passion on a self design that is unlikely to equal existing designs that are already proven.

Peace!

 

Hi messabout,

Thanks a lot for your answer! That's exactly the kind of feedback and information I was looking for. Some basic knowledge of what feature cause what reaction on the boat and it's performance. Without pretending to be a boat designer with tips like this, it allows me to better understand the concepts and what is at stake.
As most of you suggested, I will most likely just end up using the javelin hull without changes and just concentrate in the body and cockpit. Nevrtheless, I find it's great to learn about things like you are mentioning, as it's all part of my learning.

I never talked about my sailing experience, but some of you asked about it... I have been sailing for about 25 years. Did IOR and IMS -A1- racing for many years, and sailed optimists, hobby cats ans 420 when I was younger....So I know where I am going with this project.
I don't want to buy a used boat, because 50% of the fun in this is going to be the building part.

Should anyone else have other tips to give me, or minor tweaks I could bring to a javelin hull, please do!
Everything helps

Thanks a lot again
Gerry