VM Madcap sailing on Boston Christian Science pool video

This is a video of my new Madcap just launched a few weeks ago


Just for show and tell. Its a carved wooden hull. Works pretty good.
John Storrow

Hi John,

Great craftsmanship on a good looking yacht that sails very well …congratulations.

I envy your sailing location too… step out the office at lunch time and hit the water !?!

Cheers Alan

Hi John
nice looking boat, could you tell more about dimensioning ?.

At glance, the booms are too far above deck, Center of Effort can be lowered for better lateral stability and eventual increase of sail area.

she’s a Vintage Marblehead (50/800 dimension)
Can’t increase sail area due to VM (Vintage Marblehead) design rule limiting to 800 square inches measurable triangle. Agree though that C.E could be lowered for more stability in certain conditions but I like sailing in light wind which is likely to be the condition at the Nationals later this month. My thinking is grab the breeze from up higher? Does the decrease in stability from doing this offset the advantage from grabbing the wind up high? Just curious, Do you think lowering the C.E would make it look prettier? I’m kindof on the fence with the C.E.

the pool is a five minute walk from my house. Its like the ultimate R/C yacht pond in every way.

Very nice build, John. I would concur that it would have a nicer looking side view with booms lowered a bit (if rules allow).


I understand that the rules will not allow to change the Mast height.
Lowering the sail and closing them to the deck, not only lower the CE for better lateral stability and more active surface to the wind, but reduce a lot the return turbulences that jeopardize the sail efficiency.
The best, is generally achieved, with the Jib when is close as much as possible to the deck.
Unfortunately cannot be done with the Main that make use of the Wang but can be made as low as possible too or eventually widen the main boom as in the past with the real J-Class, remember the ‘boulevard…’.
See attached sketch showing the effects of vortex and return fluxes :


Thanks for sharing the Diagram. I did think of making a more High aspect rig.

I’ve shortened the mast-
here’s another video


Here’s another video from last year that I sort-of like. the people are walking by, and then the boat sails through a 180 degree wind shift and starts to follow them. Like it has a mind of its own. (might have been the skippers.


John Storrow

I used to sail my cr-914 there when I was going to northeastern university. It is a real nice place. The wind can really funnel between the buildings. It seemed like there was always more pressure on the east end of the pool. It was great how the sides of the pool are designed to shed off any waves, perfect for model sailing. No weeds but they had “no swimming” signs under the water you had to watch out for.

The esplanade is also nice, but a farther walk. A short drive out route 9 there is a reservoir that was really nice and big, but not too big, plus it has a path going all the way around. No weeds when I sailed there.

This is not entirely true.

The Madcap design falls under the Marblehead Class rules, as it is the class that governs this class of model yacht. The Vintage Group has it’s own set of rules governing the Vintage era Marbleheads, but it is not a AMYA Class of yacht.
Under the Marblehead Class in AMYA the Madcap design is permitted to carry a maximum of 800 square inches of sail area, same as in the Vintage Marblehead Group. The Madcap can do so in any manner it wishes, utilizing a maximum height of the sail above deck at 85". An 85" tall rig is a seriously high aspect ratio rig.

While an 85" rig is not recommended for the madcap design, as it is too high of an aspect-ratio for a shallow ballasted boat, It’s also not recommended to use the rig set forth on the design plans. The Madcap plans call for less than 800sq inches of sail, and the placement on the yacht is subject.
on Johns model, the boat appears to be extremely well balanced, but really only the skipper would know that.

In regards to moving the booms down closer to the deck, all this accomplishes is reducing the heeling effect of the boat under-sail. Essentially you could move that rig you are using all the way up until the headboard of your main hit 85" above deck (or more likely use a different high-aspect ratio rig), and leave the huge gap below and still be within Marblehead class, and vintage group rules (although you wouldn’t want to do that).
Basically, the answer here is to do what you have done and move the booms down untuil they become aesthetically pleasing. You lose some power from the top of the rig, but this is the limitation of the rig you have.
If you want a higher aspect-raio rig, just build one. You can go as high as 85" above deck.

John, I would recommend measuring the sail area of your sails. You possibly could be the benefactor of a few more sq inches of sail if these were built per Madcap plans. You could also use this as a “B” rig, and build a higher aspect ratio rig that will perform slightly better in liter airs, due to the taller rig. Up to you…

Some other observations are:
The yacht also appears that it could benefactor from a suit of sails with far less twist in the top third of the mainsail. The roach appears to be falling off to leeward and is not providing the most power it could be.
Additionally, in the video atleast it doesn’t appear that the sheets come close-hauled far enough. Your boom on the mainsail should be pointing that the quarter, and the jib slot pointing roughly at the shrouds, with the jib twist matching that of the mainsail.

It’s surely a beautiful Marblehead. Hope to see you in Spring Lake, NJ for nationals in September 2013!