Some days ago I was tilting by 35° one of my RG65 the “Trap” and got the impression that the Deck Sheer line was relatively higher then the Jib Boom. See attached sketch.
I told myself that probably the wind flow, reaching the hull, may deviate upstream and by consequence the lower part of the jib sail may not receive any wind force since hidden by the deck sheer line.
I have also noticed also that any peaked foredeck would not interfere with the wind flow.
My first reaction:
Is eventually that a jib closed to the deck will loose power ?
From the books I learn that the jib should stay as close as possible to the deck as such to contrast the air surface fluxes that tend to move from one face to the other and reducing the sail efficiency.
A nice set of yacht pictures demonstrate this point. Interesting bow of Rambler !
Further in the set of pictures I noticed also that the jib is very close to the Mast, as such that Main and Jib are almost the same sail.
What about the famous “window” of our RG65 models and not only ?
Is eventually useful to fix the jib higher from the Deck to catch more wind and use the peaked fore deck as a “barrier” for the sail swapping air fluxes ?
I do adds a sketch representing my toughs.
Your comments if any ?
Some bows front views !
Claudio:
You know I’m no expert… but have some thoughs:
- Yes, it’s true thw hull is shielding the lower part of jib
- Yes, the lower part of the jib is not being very efficient
- You have to consider the wind is coming from the bow, at 40-50°, not at 90°! This means the effect is not as bad.
- If you put the jib higher, separated from the hull, it would create a hole where the wind would escape, forming vortexes nobody wants.
I just thing it’s the best of two bad things: having the jib low against the hull is not as bad as leaving a hole open. And for the same reason the main should be very low, too!
If you look at some new IOMs, you see builders doing foredecks in a “A” shape. I think this may help a little. Also, I used to sail in an old “Wal” class wooden sailboat (about 8m LOA), and the foredeck was round! I remember it being very slippery! Maybe these are some ways to deal with this problem.
Regards,
Hi Thomas,
I tends to agree by choosing the lower degree of pain.
This is why I’m actually exploring the best peaked fore deck form and height within the limits of the Rules with my Class M “Triss” . see below
I’m also thinking to remove completely the jib boom by increasing the “stiffness” of the jib base + a pivoting lever to drive the sheet clew.
The aim is to lower the Jib base closed to the deck and compensate the “inefficient” surface by resizing the jib.
Me too I have been racing for long time with a Dragon fully restored by myself.
Cheers
Happy New Year !!
There is some shadowing but in experience from big boats the wind refracts slightly as it
comes over the gunnel. also the wind will migrate down a percentage depending on the wind
speed.
Mike