Lumenier RB2205C-12 2400KV SKITZO Ceramic Bearing Motor
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Old Nov 29, 2012, 12:15 PM
hiljoball is online now
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Originally Posted by The Tug View Post
Oui you lot,i am searching for the rule where the lower mast band has to be above deck betwene a specific measurement max is 90mm to memory i want the min.Looking through the new IOMICA rig measurement form i have'nt seen it however it was there on the previous tick the box sheet.i want to expirement with lowering my A rig to the minimum.
The spec for the deck limit mark to the lower point is in Part C of the rule and so is not checked during measurement. It is one of the items to be checked at regatta measurement.

I looked at the previous version of the Rig Measurement form and could not find it there either - and it should not be for the reason above.

John
Last edited by hiljoball; Nov 29, 2012 at 12:55 PM.
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Old Nov 29, 2012, 03:13 PM
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Is it better to have your jib boom high so it doesnt hit the water downwind and cause you to nosedive, or is it better to have it low as possible for slightly better performance? Depends on conditions? Design?
Old Nov 29, 2012, 03:29 PM
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Is it better to have your jib boom high so it doesnt hit the water downwind and cause you to nosedive, or is it better to have it low as possible for slightly better performance? Depends on conditions? Design?
My thought is to have the jib as low as possible to gain end plate effect with the deck at close hauled.

The lower the jib, the lower the COE of the sail, reducing heeling and reducing the possibility of nose diving.

I don't see a low jib as causing nose diving. The main cause is a gust hitting the tall main and pushing the top of the rig forward driving the nose down before the boat can accelerate to stay under the main.

John
Old Nov 29, 2012, 03:43 PM
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Ok so the bow goes down in a gust and it keeps going down until suddenly the jib hits the water, the stern goes out of the water, the rudder goes out of the water, the boat twists around, the mainboom hits the water, and your pancaked!!
Old Nov 29, 2012, 03:54 PM
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Ok so the bow goes down in a gust and it keeps going down until suddenly the jib hits the water, the stern goes out of the water, the rudder goes out of the water, the boat twists around, the mainboom hits the water, and your pancaked!!
Yep that is what happens. But the jib boom being low is more efficient, look at Lester Gilbert's wind tunnel test results:

http://www.onemetre.net/Design/WindH...indHanDeck.htm
Old Nov 29, 2012, 03:59 PM
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You're welcome !
Just tell me if your boom is not too much in the water when reaching.

My Britpop has the main boom as low as possible (just over 60mm) on my B rig, we don't have reaching legs over here in the USA so it has not been a problem. Reaching around before the start I can see how on a reaching leg it could be an issue though. My A rig has the bottom of the band just above the deck, I don't recall the measurement from the deck to the band. No problem with that either.

I cut down the Bantock goosenecks to get the boom down.
Old Nov 29, 2012, 04:10 PM
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How low do you go with your main boom? low as possible? I see reaching would be a problem.
Old Nov 29, 2012, 04:21 PM
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How low do you go with your main boom? low as possible? I see reaching would be a problem.
Read my post again, we don't have reaching legs in the USA (just windward-leeward courses). And as I said, it looks like it may be a problem from my experience reaching before the start....but I don't know how it would be in a race with a reaching leg.

Low as possible means it is at the legal limit of 60mm from the band to the deck mark.
Old Nov 29, 2012, 04:51 PM
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You mean all of you guys are going to jump on my top secret experiment lol.Mast is now 20mm shorter,looks good with the boom down in the boat but the real test as Olivier has said will be the boom dragging and wiping you out,but if this thing can go upwind faster than it already does whow.These french goosenecks from Pierre are quite nice and very well made i got some stuff off him at the worlds and had'nt used it, the gooseneck body has two threaded holes that is bolted right through the mast requires precision drilling though but you're not going to rip that puppy out..
Last edited by The Tug; Nov 29, 2012 at 04:57 PM.
Old Nov 29, 2012, 05:07 PM
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Ok so the bow goes down in a gust and it keeps going down until suddenly the jib hits the water, the stern goes out of the water, the rudder goes out of the water, the boat twists around, the mainboom hits the water, and your pancaked!!
Time to change down to a smaller rig.

We run a reaching leg 50% of the time and trust me my main and jib booms are as low as they can get and I have never had a problem with the booms in the water. My main is the legal limit off the deck and the jib is about 10mm I can't go any closer due to the jib attachments and the knot in the string.
Old Nov 29, 2012, 05:20 PM
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Sorry, new in rc sailing and this was asked before I am sure but
where do I get one of this sailboats please?
Thanks
Robert







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Originally Posted by Robert May View Post
A hull capable of being fast to windward normally means it fast downwind too.

Rather than sort out what that problem is and bury the discussion in this thread. That would make a fanstastic and interesting thread in its own right.

Who knows the thinking behind skiff style designs and why are they so popular? It strikes me that if IOM courses do not have reaching legs (as someone pointed out earlier in this thread) why have a planing hull form on a displacement yacht? Does anyone have photos of model yacht (any class) planing?
Old Nov 29, 2012, 05:26 PM
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If you are sailing downwind in the top end of the rig and take a sudden gust you are going to dive irreguardless of where the booms are.It's time to change down,however a lintel can carry the rigs farther than most other boats.
Old Nov 29, 2012, 05:29 PM
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ok so i can get my main as low as possible without any problems?
Old Nov 29, 2012, 05:40 PM
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ok so i can get my main as low as possible without any problems?

Low as possible within the rules, yes. BUT, there may be other things that get in the way, such as the vang hitting the side deck, sheet lines, etc. On my Britpop I had to get the wheel off the vang adjuster to clear the sheets. Just be aware!
Old Nov 29, 2012, 05:41 PM
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Originally Posted by BrushlesHeaven View Post
Sorry, new in rc sailing and this was asked before I am sure but
where do I get one of this sailboats please?
Thanks
Robert
Are you asking where to get an IOM or this design boat shown in the picture?


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