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Re: F16 wings [Re: macca] #219531
09/14/10 10:10 AM
09/14/10 10:10 AM
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pgp Offline
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Pete Pollard
Blade 702

'When you have a lot of things to do, it's best to get your nap out of the way first.

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Re: F16 wings [Re: pgp] #219549
09/14/10 12:17 PM
09/14/10 12:17 PM
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Australia
macca Offline
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stay tuned.... new professional video of the F20 is on the way smile


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Re: F16 wings [Re: macca] #219565
09/14/10 01:57 PM
09/14/10 01:57 PM
Joined: Feb 2004
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Looking for a Job, I got credi...
scooby_simon Offline
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Originally Posted by macca
stay tuned.... new professional video of the F20 is on the way smile


And responses to all the questions above?


F16 - GBR 553 - SOLD

I also talk sport here
Re: F16 wings [Re: macca] #219592
09/14/10 09:21 PM
09/14/10 09:21 PM
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taipanfc Offline
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Originally Posted by macca
stay tuned.... new professional video of the F20 is on the way smile


Is it a lot faster than the old 20? The old one can't keep up with the moth once we get on the foils, upwind and downwind.

Re: F16 wings [Re: taipanfc] #219597
09/14/10 11:42 PM
09/14/10 11:42 PM
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Melbourne, Australia
Tornado_ALIVE Offline
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Moth can not keep up with the Tornado. Don't think the new 20 will have much trouble :-P


Re: F16 wings [Re: Tornado_ALIVE] #219598
09/15/10 12:51 AM
09/15/10 12:51 AM
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taipanfc Offline
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Haha, for the price and size it should! 54sq m of downwind sail v 8sq m is a big difference!

But have to say I am amazed how quick the moth is compared to the cats in singapore in the 8-15knot wind range.

Re: F16 wings [Re: taipanfc] #219599
09/15/10 04:35 AM
09/15/10 04:35 AM
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Devon Offline OP
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How about pre 8 knots wind, last time I sailed with a foiling moth is was below 8 knots and he couldnt get it out of the water, a lot of hard work trying though, but when he did manage it really took off and left me for dead, pity he was 2 laps behind, sadly though the hard nosedives took their toll and split his deck, the boat = writeoff!!

Re: F16 wings [Re: Devon] #219600
09/15/10 04:44 AM
09/15/10 04:44 AM
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taipanfc Offline
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Pre-foiling, cats leave us for dead.

But if you are nose-diving that often, then your foils aren't set up right. Can't prevent nosedives, but can certainly minimise their occurance.

Re: F16 wings [Re: taipanfc] #219606
09/15/10 08:12 AM
09/15/10 08:12 AM
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Cape Town, South Africa
Steve_Kwiksilver Offline
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And this has what exactly to do with wings on an F16 ?
Went out yesterday in 12-15knots, did 26,5knots..on a board. Since it wasn`t done on a winged F16, it doesn`t belong here.. just like F20, Tornados and foiling moths..
Back to topic, my understanding of the rule is that the boat is measured as platform including ONE wing, so if wings are not folding it doesn`t affect the application of the rule ? So a 2,2m platform with 2x 300mm fixed racks, would measure.. Or am I wrong in my interpretation of the rule ?
Some have said the racks can extend aft of the transom, do they not have to fit into the overall platform length ? This could be an interesting way of keeping the nose up downwind.

Re: F16 wings [Re: Steve_Kwiksilver] #219663
09/16/10 02:40 AM
09/16/10 02:40 AM
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Western Australia
Stewart Offline
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One can add aft racks As I read the rules the length is basically waterline length... But I have a feeling hidden somewhere in the ISAF rules there may well be a requirement to have at least one foot on the boat.. This is due to a crew in a 470 or 505 brother combo the crewing brother "hiked" out from his brothers shoulders. Now my memory could be faulty but someone with a younger brain may have the info at hand... This requirement would limit the "usable" aft extension and may not do more than a winger rudder setup.

Steve mozzies do belong here.. Still grandfathered..

Re: F16 wings [Re: Stewart] #219751
09/17/10 02:59 AM
09/17/10 02:59 AM
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Cape Town, South Africa
Steve_Kwiksilver Offline
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Thanks Stewart, I meant that discussion around whether a moth is faster than a F20/Tornado/my mother-in-law on a skateboard does not belong in this thread, since it`s about F16 & wings/racks.
Now I have another question - if this is an ISAF rule (one foot on the boat) then does this not outlaw racks on all classes, how do the I14s, 18fters etc manage this ? What I understand is that F16 is not an ISAF registered class, does this mean they can ignore ISAF rules? This seems contetious as we all sail under the RRS which is administered by ISAF. And I`m still no wiser regarding how racks are measured in the F16 class, is it platform width plus ONE extended rack, even if the racks are fixed, not folding ? That`s how I understand it.
Not that I`m going to put 30cm racks on the Mozzie, just interested in the rule interpretation. I don`t think that it would change much and would add a whole lot of extra hassle, as most have said, wider beams would be the better option. (And higher-volume hulls.. and a taller mast.. might as well buy/build a proper F16 then.)

Re: F16 wings [Re: Steve_Kwiksilver] #219752
09/17/10 03:11 AM
09/17/10 03:11 AM
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taipanfc Offline
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Threads evolve and move by questions and responses. As long as it doesn't fall into a dustfight of name-calling, then we don't need thread police. You never know where the exchange of knowledge may go.

To help equalise the narrower platforms, Taipans/Mozzies can put racks on the sides. These are measured from the leeward hull to the wing extension.

Personally I think these give more righting movement for those with wings. Mainly as i look at the rear view of the boat and the hull/platform/rig is acting as a level 3 lever. Scooby_Simon has a different view, and i am fine with that. Down to how you race 'em on the water.

Re: F16 wings [Re: taipanfc] #219753
09/17/10 03:22 AM
09/17/10 03:22 AM
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taipanfc Offline
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14 Foot skiff rules - "Both members of the crew shall be in contact with the hull, fittings or gunwale assembly. Either, or both, may use a trapeze, individually or simultaneously. Trapezing is not allowed from any point outside the 4267mm length of the hull as defined in Rule 1."

Full rules here --> http://www.international14.org/images/pdfs/march%202010%20class%20rules.pdf

So do the F16 rules have anything in regards to aft wing extensions? And also describe what level of contact one must have with the boat?

Re: F16 wings [Re: taipanfc] #219754
09/17/10 03:37 AM
09/17/10 03:37 AM
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waynemarlow Offline
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I am not sure why we are asking this question re being further back from the transom, the boat would be so unbalanced and ponderous ( butt sitting in the water ) that you would be nothing but slow.

If you are having to go back behind the beam then your boat has to little foward bouyancy and the easiest way out would be to buy a couple of T foils. Also by going to the max spinny pole length and raising it slightly also seems to help lift the bow at speed.

The skiffs step off the back more to raise the bow because of the hull design, on the cats we should never really need to.

Last edited by waynemarlow; 09/17/10 03:40 AM.
Re: F16 wings [Re: waynemarlow] #219757
09/17/10 04:55 AM
09/17/10 04:55 AM
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Cape Town, South Africa
Steve_Kwiksilver Offline
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Wayne, my question relates to having a boat without the forward bouyancy of the modern F16 hull shapes. If you wanted to take a Mosquito or Cobra platform and put a full-size F16 rig on it you would want to be 2 feet behind the transom going downwind in most of the conditions we sail in. With the current 7,3m mast (1,2 shorter than F16) we already have too much sail up downwind, even 2-up, and get a few bus-stops on each downwind leg. Of course I would not want an 8,5m mast and sail areas that the F16 class allows if I can`t have banana boards, it makes no sense when you sail in the conditions we get more often than not. I would even prefer a smaller main and spinnaker for the Mosquito for those 28-35knot days.. ie every summer afternoon in Cape Town.

Re: F16 wings [Re: waynemarlow] #219758
09/17/10 05:02 AM
09/17/10 05:02 AM
Joined: Nov 2005
Posts: 69
Live in Germany, House in UK, ...
DanTnz Offline
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Hi All, I'm not sure what is meant by class 2 and 3 levers (and I have a masters degree in engineering!), but this looked like an interesting problem and I have been helping out a student doing these types of problems, so I thought I'd have a go.

So, I drew a couple of very simplified free body diagrams of a 2.2m beam cat with wing and a 2.5m beam without.

The diagram is drawn at the point that the windward hull just leaves the water and the crew(s) is not trapezing. It is simplified by assuming the heel angle will still be zero and it ignores the difference between the side and centreline of the hull. None of this should matter for comparison purposes. It also assumes that the force generated by the sail, height to centre of effort and crew weight remain constant.

So on the diagram F(crew) is the downward force of the weight of the crew, F(sail) is the sideways force generated by the sail, centred at a height of D(sail) from the waterline.

OK, so taking moments around point (0,0), we see that in both configurations a clockwise torque of F(sail)xD(sail) is generated. i.e. it doesn't matter to the mast what the beam is, the capsize force is the same.

Still taking moments about (0,0) in case 1, the righting moment produced by crew weight is 2.5xF(crew) and in case 2, it is also 2.5xF(crew).

So in other words, a 2.5m platform produces the same righting moment as a 2.2m platform with 0.3m wings.

There will however, be an advantage to the 2.5m platform in that is also gains more righting lever from the windward hull itself, since its self-weight will act further from the pivot.

Presumably the 2.5m platform will have less windage as well, and no wing dragging in the water to leeward. The 2.2m hull will probably lift a hull earlier, so maybe a lightwind advantage if the extra weight and air drag doesn't cancel it out.

So, conclusions? Designing a new F16 - 2.5m beam everytime.

Got a narrow grandfathered design, add wings to get the leverage but check this is actually faster once you've done it!

Attached Files
WingvsBeam.jpg (244 downloads)
Wings vs Beam
Last edited by DanTnz; 09/17/10 07:46 AM.
Re: F16 wings [Re: Steve_Kwiksilver] #219759
09/17/10 05:03 AM
09/17/10 05:03 AM
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waynemarlow Offline
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Its not so much the hull design as simply toooooo much sail area for the conditions, by stepping off the back all you are doing is depressing the leeward hull further which simply is going to make you slower which is simply going to make you more prone to digging the bows in. Bit of a vicous circle I'm afraid.

Re: F16 wings [Re: Steve_Kwiksilver] #219766
09/17/10 07:33 AM
09/17/10 07:33 AM
Joined: Jul 2001
Posts: 953
Western Australia
Stewart Offline
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Western Australia
Steve,
The I14s have done many things in pushing their envelope.. Including flying I14s. I know of one skipper who build a rack behind the hull to trial.. Ended up the rudder foils were quicker..

I would thus suggest using rudder foils rather than an aft rack on a mozzie or cobra..

Last edited by Stewart; 09/17/10 07:52 AM.
Re: F16 wings [Re: Stewart] #219769
09/17/10 07:49 AM
09/17/10 07:49 AM
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Posts: 5,525
pgp Offline
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How many of you guys have sailed a F16 as is? I'm not busitng your chops, it's just that it is a hell of a platform as is.

Talk all you like. It's good that there is interest in the class and traffic on this forum is, overall, good. But for my 2 cents, it (F16) ain't broke and doesn't need fixing.

Cheers! smile


Pete Pollard
Blade 702

'When you have a lot of things to do, it's best to get your nap out of the way first.

Re: F16 wings [Re: pgp] #219775
09/17/10 08:17 AM
09/17/10 08:17 AM
Joined: Jul 2001
Posts: 953
Western Australia
Stewart Offline
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Stewart  Offline
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Western Australia
Im not suggesting modifying the rules.. T-foils are part of our rules..

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