Steve,
In your side by side sloop v unirig in F-16 post (top of pg.4) is not the jib added area to the unirig main, i.e., the 2 boats have the same mainsail?
Indeed, both sailboats have the same size sail area. Note that is not cheating by giving one boat more total sail area then the other, even when indeed one but has more then the other.
The point of contest here in the M32 thread is about what is best for a new design performance wise. As it is a new design altogether, one can set its max sail area limit at ANY level. Of course their will be levels where not all sail area can be put in the mainsail, either practically or efficiently. With the F16's the mainsails are pretty much at the max area you can get in there while maintaining an acceptable aspect ratio (efficiency) and control.
Back to out topic. A completely new M32 design. The experiment that can be had with the F16's that relates to the M32's is this. Given the M32 the largest mainsail it can have efficiently or practically. That will be our uni-rig. Now make a second identical boat (same mainsail etc) but a 30% jib is added to the setup. Afterall, you can ALWAYS add a 30% jib to any conventional catamaran setup. Any problems that are encountered can be adressed by bridle foils and other simple solutions.
So the choice or rigs is not limited to either a sloop or uni-rig of the same overall area, but rather between a uni-rig and a sloop with 30% more sail area while using the same size mainsail.
It is this comparison that can be easily tested using F16's. As both setups, F16 and M32, are very similar in overal design the result can be expected to hold for both classes. In the F16 class we found the jib makes the boat faster, even on upwind legs. You point lower but move sufficiently faster to arrive at a higher VMG; and that is what everything is about. Brute force (=speed) winning out over efficiency (=pointing).
High lift yes, high drag not necessarily.
The thing to note about the sloop rig versus the uni-rig or even a rig consisting only of the jib is this :"When the two sails are set right relative to eachother, they mutually influence eachother in a positive way".
Because of the close proximity of the mainsail the jib is "supercharged" and is producing a whole lot more drive then this jib sail would produce without a second sail directly to its rear. Interestingly enough the jib will also operate at much smaller angles of attack while producing this disproportionally high drive forces because of the interaction with the mainsail. The mainsail itself produces less drive with a jib in front then when it would by its own, but the loses are smaller then the gains made by adding the jib. Also the flow of the mainsail is smoothed out and it is far less suseptable to stalling (losing attached flow). Its drive had become alot more dependable and it is easier to have it ride the groove constantly. This is the positive effect of the jib on the mainsail.
The net result is that significantly more drive is produced by a sloop rig (using same size mainsail) then a uni-rig whithout losing too much pointing. Actually the loss in efficiency per sq. meter and loss in pointing angle are overcompensated by the increase in speed due to having more sail drive. Ergo, the boat points lower with less efficiency per sq. meter but it still attains a better VMG and reaches the A-mark sooner on upwind legs.
In this role it is not to similar to the article you provided. It is however on course with high angles of attack. These course are reaching legs and broad reaching legs without spinnakers. Here the jib acts in much the same way as the slats and flaps of an aeroplane. These devises are used on a plane when the planes travells very slowly (landing / tak-off) and flies with large angles of attack. Here it needs to provide alot of lift without risking the wing stalling. This is similar to what a sail boat encounters on reaching and broad reaching legs. On these legs rig drag is not a major consideration as only a smaller portion of the total is acting along the centreline and limiting boat speed. The other portion is acting prependicular to the centreline and only loads up the daggerboards. The deeper you go the less rig drag is holding you back. Actually on a pure downwind leg it is actually the rig drag that is propelling you forward. So somewhere halveway there is a point were all rig drag is acting perpendicular to the course travelled and rig drag become an totally unimportant factor.
Here the jib makes the boat significantly faster then a pure uni-rig (no spi) by being able to produce maximal saildrive (30% more due to having 30% more area) at significantly larger angles of attack (= sailing deeper) while also delaying the stalling of the rig. Where some of these factors worked against one another on the upwind leg, limiting performance gains there, they are all working together to maximize performance on the other legs (reaching and broadreaching). On the pure downwind leg sail area is all sail drive is drag related here. Goosewinging the jib increases the area by 30% and results in 15% speed increase for that fact alone. Goosewinging is setting the jib to the other side of the boat then the mainsail is.
I'm just trying to understand, and I thought this article applied in principal. I remember Randy Smyth pulling to shore and removing his jib in a Worrell when it was blowing hard and it helped. He won that leg, but of course there was a lot more going on.
It should actually work the other way around in these windy conditions. A jib adds alot of drive low in the rig. Meaning it can add 30% drive for only 10% increase in heeling moment.
Do this mind experiment, Say both a uni-rig and sloop rig are 20% overpowered when sheeted tight. The uni-rig needs to loose 20% of the saildrive to stay upright. The sloop rig (with same mainsail) can remove the jib and 20% of saildrive and effectively become the uni-rig. But it can also depower the mainsail to 70% saildrive (30% loss) and use the addition 10% loss to gain back 30% drive through the jib, coming out at a 120% of the saildrive of the uni-rig.
Which one of the two do you think will be faster ?
An added drawback of the un-rig is that it depowers mostly by twisting off the leech and this impacts strongly on its pointing ability. So it looses both power and pointing by having to depower the rig. The sloop was already sailing lower then the uni-rig and the drive produced by the jib is totally UNAFFECTED by any mainsail leech twist. Basically the sloop can keep pointing the same as it was before while the uni-rig has to come down.
And it seems to me Hakan is talking about a unirig w/ genaker setup vs sloop w/ genaker.
He is, but even in the setup we have found that a sloop F16 is faster upwind then a uni-rig F16 when sailed by the same crew.
Interestingly enough we also found that we need to add another person to the sloop F16 is bring it down to the uni-rig performance; this is reflected by the 1-up F16 (uni-rig) being just as fast around the course as the 2-up F16 (sloop).
Surely, having one person extra on board is a performance hit. The jib is the element that adds enough drive to speed the boat back up again.
This goes directly against the commonly "accepted" A-cat wisdom where jibs are regarded as nothing but trouble. Some even believe that adding a jib will actually make a boat slower. Of course these persons overlook the fact that there is no physical requirement to take the jib area out of the mainsail. You can always just keep the mainsail area and just add a jib (+ is area) to it (the total).
And this is where the M32 design will fall flat with respect to its competition, just as the M20 design does.
Also it seems to me that most of the vessels you cite cannot reasonably be used to establish anything relative to beach cats or even this M32. Hydroptere is a large hydroplaning cat, at least some if not many of the others are monohulls
Longshot and the hobie trifoiler, as suggested by Hakan, are actually full foiling craft as well. The windsurfers being fully planing craft and the C-class cats use a solid wing as a sail.
Why can he make such comparisons between widely different craft to argue his case and I can't ?
I just showed the uselessness of his examples by producing similar counterexamples.
Having said all this I invited everybody to do their own experiments. It is very simple.
Get two identical sloop rigged boats and find a crew that has a similar skill level as yoruself. Remove the jib on one boat and race against one another in different conditions while swapping boats and possibly the sails. Your findings will most probably be that the sloop is faster, even when going upwind.
Ergo ADDING a jib (not cutting it out of the mainsail) makes a sailboat faster. So if you make a totally new design where you can set all limits yourself, will you decide to make it a un-rig or a sloop ? And that is the M32 & 100.000 Euro question.
Wouter
P.S. anybody wanting to read more about mainsail and jib interaction or looking for scientific sound proof; read the articles written by Arvel Gentry. He was the first to make his proof scientifically sound when the rest was still acting on "believes" and gut feelings.
