Which is faster?

Rcsailing.net General Discussion
1

Ok folks, so this is one of those “in defense of monoslugs” questions:

Which would be faster, a model multi with all the bells and whistles or a model monohull with the same waterline length (twice the length of the cat or three times that of a tri) with all the bells and whistles?

Just thinking that a big scow can roll with a high performance cat that is shorter (In lightish air, I was rolling a hobie 18 in an e scow (28ft)). Could the same be true at the model level? What would the scale effects do?

Graham

2

Way too many variables and unanswered questions hidden within your base concept.

We have had several documented posts of the Mini40/F-48’s “handling” Marbleheads and 10 Raters of similar or slightly larger sail area by owners in informal pond racing - but in your case there are a lot of “it depends” before an answer can be agreed upon.

Let’s use a maxed out 10 rater for example - with a waterline length about 10 inches longer than an F-48. With most other things being equal - and even with a boat with more sail area - a boat with the displacement of a 10 Rater just can’t stay with a multihull weighing 5 lbs. or less all up weight. At a minimum of double (and maybe three times the weight - or more) of a multihull, the monohull requires “Lead” to keep them upright, whereas a multihull uses it’s maximum beam to achieve it’s righting moment - NOT additional weight! I find it hard to argue that a heavy boat will be faster than a light weight boat in light winds, and a properly tuned multihull that stays upright in medium/heavy winds should also have an advantage if it weighs less.

These kind of questions are similar to those comparing a NASCAR oval track racer to a road race car to a rally car. All are fast - and possibly equal in horsepower, weight etc. - but they get it done in dramatically different methods.

While a monohull may have an advantage in windward pointing (Newer multihull designs are crushing that stereotype these days) when off the wind - whether reaching or running - the monohull will generally be limited to hull and/or actual windspeed - while the light weight multihull will be able to foot off, increase boat speed sail a faster course at a faster speed and cover more distance in mid to upper wind levels. In a drifter - while both boats may be of equal speed comparable to the wind speed directly downwind - once again the lighter multihull “should” capitalize on any puff, gust or temporary stronger wind with better acceleration.

Finally - any multihull sailor who gets excited about beating a monohull is not an experienced multihull sailor. That is like a Marblehead sailor who brags about beating the Vicotria ThunderTiger !

Ummm - and a Hobie 18 is not what I would consider a modern, high performance catamaran. Maybe an Inter 20, a NACRA6.0 or a Maarstrom Tornado however ???

Cheers - and my opinion only.

EDIT: Added below —>
[:-graduate] Graham - did some further checking and the E Scow and Hobie 18 weren’t really a matchup…

E-Scow:
28 feet in length
893 sq. feet sail area with spinnaker
3-5 crew
965 lbs. weight
About $30,000 (US) new

Hobie 18 (No longer in production)
18 feet in length
220 sq. feet sail area - no spinnaker
2 crew
400 lbs weight
About $3,500 (US) when new - estimate

<u>NOT</u> even a close comparison ! [:-grumpy]

3

Dick,
Talking about different cars…a rally car will own any F1 in a rally race, so will the F1 do on a F1 track…

I HAVE NO answer which is faster, I have YET never seen a real rc multi…only pics and movies (heard and read) lots of stories…and the only thing which always come to discussion is tacking!

A 10R might be faster in a tacking race?? what do you think?
But then again, I HAVE NEVER seen a 10R…fastest rc sailing boat I have seen is an IOM (but my SW rules them all lol [;)] ).

The bulb and weight might be a HUGE handicapped for the mono…well…wait and see, and I’ll tell you if a mini40 can handle a SeaWind rotfl…

Interesting post! keep up the infos

my 2 yen

Wis

_/ if it isn’t broken, don’t fix it! _

http://wismerhell.esmartdesign.com/index.htm

4

I thought I wrote a report here on my 10R againt the Nightmare a few weeks ago but can’t find it. I sailed the tri and three different friends sailed the 10R. The 10R was about 1 1/2 times faster than the US-1M and the tri twice to 3 times faster than the 10R when the winds were over 5mph. Our pond is 180’ x 150’ and the course is shaped like a W with the top of the W connected and is the windward mark. The bottom right is the start finish. You are tacking or jibing every 150’or less. Most think a tri can’t do this course. I can out tack the US-1M when winds are over 5mph. When the winds go to 10-12mph the tri was three times as fast as the 10R. It was sailing on the front few inches of one hull only and the wind seemed to follow me around the course. I was making my own wind and always seemed to be on a close reach. It was always on the edge and seemed like it would catch the lee amas but never did. I made three laps with the higher winds and took the boat out after being encouraged by the other member so I wouldn’t destroy it. I had enough adrenaline for a while anyway. It had the max 1392"? sail and the 10R which is a new Sterne Viper which I had him design a Stingrig 1490"? for. The first I believe. The 10R is less than 11# the tri 5#-2oz. No one would sail the tri before and now never. They all say it goes too fast. If I finish the MKIII I don’t know who will sail it against MKI. Everyone wants to sail the Viper however.

5

Here we tried the tornado sport against those Whitbread 60 feet monos, As fast upwind, tornado as fast downwind.

If we compare the designs and multihull is always faster than mono by design.

Take a hightech high end monohull like Skandia, morning glory or 18 foot skiff etc and race it against Cogito ( C-cat ). Theres high end sailing machines comparinson for you and theres no doubt wich one is faster. Or compare morning glory ( rated 1.61 ) on round islands with Orange 2 ( rated 2.016) theres no bet against orange 2.

Sure, all catamarans are not fast and neither are all monohulls, so they can beat each other, but for the question wich one is faster, a mono or a multi the correct answer is multi.

  • HJ

“Expertice is gained trough mistakes. However repeating
same mistake is not learning but stupidity.”

6

Skandia high tech what a load of crap, its sloooooooooooow for a 98fter, there is Full Pelt, which is 36 ft, that is waaaaaaaaaaay more high tech, rates way faster than skandia on IRC, the maxZ86’s are faster than skandia, there are heaps of boats faster than skandia. maybe you should have said Mari Cha IV, 140 ft, does 525 nm in 24 hrs, that is the fastest ocean going monohull, the fastest ocean going multihull has done over 700nm in 24 hrs (& 18ft skiffs are old now, they are going one design to, which sucks). Fastest all out over a 500m course is Yellow Pages, 46.52 knots or something close to that (i’m sure a windsurfer would also beat the c class cats because they are only like 0.28 knots slower than Yellow Pages over a 500m course), they will **** on your C Class cat any day. & your ratings, if IRC are totally wrong because Skandia rates 1.614, & if MG had rated 1.61 would have done last years sydney to hobart.

I see said the blind man to the crippled nudist who put his hands in his pockets & promptly walked away.

7

Monohull ratings suck anyway, because they mod the boats to the measurement systems. The rates were there just to give exsample of the difference. MCIV is 1.4 times slower than O2 if compared to 24 hour result. Also I very much doubt that a surfboard can beat c-cat around the buyous. The precious Full pelt, well that boat surely rates high, but does it live up to its theoretical performance on ocean wave enviroment? And the new pelt is practically nothing new, things like those have been racing on lake garda in Bol’Dor for ages.

O and also the surfboard beating almost to the record of YPE2 was a sinker. Sinkers are not fast around the buyous. You could also ask from Steve Clark if they have been beaten upwind by ANY sailboat except the old c-cat Yellow Pages. Comparing one way speeds only is like comparing F1 and a dragster and afterwards claim Dragster is a faster car.

  • HJ

“Expertice is gained trough mistakes. However repeating
same mistake is not learning but stupidity.”

8

Comparing sailboards and the original yellow pages with tornadoes, skandia, mari cha etc is ridiculous. They are all designed for a specific need. I would however like to know what some of them could achieve in 24 hours in perfect conditions, but I wouldn’t want to be on board some of them.

Comparing r/c monohulls and r/c multihulls and wondering which is quicker has problems too. The course that they are going to sail for one. The original question asked for a mono with the SAME waterline length as a multi. Does this this mean adding the three hulls of a tri and two for a cat? I think that you would need to be adding just two hulls regardless of whether they are cat or tri. This being said what you are then looking at is a monohull of 2.4 metres long. They have already been made, and the mini40 in any conditions sail rings around it.

Peter

9

G Walker didnt say whether it was around the bouys did he, no, sorry your are wrong. I am sure, once they get everything ironed out of the new full pelt, it will be faster than a lot of boats, it is more high tech than skandia by ****loads, skandia weighs like 11+ tonnes, theres a 117fter that weighs less than skandia. mmm, skandia is slow yes, it was designed to be at the rating limit for the syd hob (same with Zana), which means they have detuned it. mmm, so a dragster isn’t faster than an F1 car? hmm, I have always thought they were. just remember, G Walker didn’t say anything about going around corners.

I see said the blind man to the crippled nudist who put his hands in his pockets & promptly walked away.

10

For the record, I made no mention of going around the buoys…

Anyway, MY idea was whether an RC monohull with a hull length equal to the combined hull lengths of a multihull (same waterline length…) would still be slower than the multi.

In response to Dick’s comment about a hobie 18 and an E scow being comparable, they weren’t supposed to be. The E scow I was sailing was the same 80’s vintage as the hobie 18 I was sailing against. Both were under $1000 but still in good shape (the midwest is full of good deals).

My idea is something along the lines of “Would an A-scow (LOA = 36’) be able to keep pace with an F-18 (catamaran for those of you about to say it’s hard for a sailboat to keep up with a Navy Fighter)?”

If it were situational, what would the situation be?

Personally, I think in light spotty wind, both designs have drawbacks. A cat would accelerate quicker, but the bigger boat has much more momentum, and when it loads up, it’s not stopping any time soon…

Would a 40 ft M20 be able to keep up with a tornado?

I don’t know, but I like how the discussion is opening up.

It is interesting to note though, that an A- Scow can keep up with 50 fters when the chop is low. A quick scow is just as much an apparent wind machine as a cat…

Graham

11

Ok. Let me clarify something: Multihull is not fast beacuse of its combined waterline lenght. Most of the multies fly 1 or 2 hulls, and then the waterline would be shorter and the boat slower? Multihull is faster because the hull is not a displacement hull with length to width is like 5 to 1 or 7 to 1. Multihulls have much narrower forms, stating from 15 to 1 and to 30 to 1. this practically means that the wave forming resistance wont grow as significantly when the speed. this is what makes it possible to multihull to exsess the so called hull speed. Hull speed is roughly Quadtang of 2 x waterline lenght for displacement hulls, for narrow hulls such formula doesnt exsist, as the wave forming is not the limiting factor on narrow hulls. This is also the reason why modern submarines with equal enginepower both on surface and submerged are faster underwater: they do not drga a wave behind them underwater.

  • HJ

“Expertice is gained trough mistakes. However repeating
same mistake is not learning but stupidity.”

12

Graham,

As a scow sailor, I can vouch for the fact that scows are amazing aparent wind machines.

I happen to have a few numbers at my disposal out of Marchaj for an A scow (38’) and a Tornado (20’). At a true wind speed of 10 knots, the A scow Vmg to windward is 7.1 knots. The Vmg to windward of the Tornado under the same 10 knot wind speed is 6.5 knots. So in a windspeed of 10 knots, the A scow will handily beat the Tornado to windward.

However, the A scow Vmg to windward maxes out at about 12 knots true wind speed. The Tornado on the other hand maxes out at a much higher wind speed. This is due to the righting moment difference between the two craft. The A scow has 5 to 7 bodies hiking off the side. Since the beam of the boat is relatively narrow, this limits the righting moment of the craft. The Tornado on the other hand has a much wider beam and allows one of the two crew members to trapeeze off the side. So the available righting moment is proportionally much higher. This allows the Tornado to continue to remain powered up as the wind increases above 12 knots whereas the scow is starting to depower.

So upwind, under 12 knots the A scow will win. Upwind over 15 knots the Tornado will win.

The data I have does not include downwind performance. The A Scow has a massive asymmetrical spinnaker and is capable of massive downwind speed (30 to 35 knots have been reported by powerboats trying to keep up with A scows going downwind in a blow). The Tornado also has a nice sized asymmetrical kite. I imagine it is pretty quick off the wind as well. I’m not sure who would win, but if I had to bet, i would put my money on the scow…

  • Will

Will Gorgen

13

Will, jut out of curiosity, is the marchaj numbers you have for tornado for the new twin strap-squarehead main-spinaker setup?

Anyway, An A Scow will beat Tornado upwind on light winds and probably downwind too. Actually, A scow is so overrrigged, that it will be hard to beat with any sailing machine under 12 knots of wind speed. However theres other things: My personal opinion is that a boat wich cannot be raced on +1 meter swell and over 12 knots of wind with full power is a freak. Ofcourse something like a scow has the coolness factor way above Tornado, because the sailing requires much more precicion in general. Both boats however require quite amount of precicion to be sailed as fast as possible.

By freak i mean the comparison basis. We raced our tornado on 25 knots gusting to 35. Nothing broke and out of 9 starts we flipped only in 1 because of hot headness. So IF you compare, you should compare boats being able to sail in equal conditions. A freak tornado size multihull wich must be depowered at 12 knots would be faster than the A-scow. Also the freak multi would be at least 3 times more expensive :slight_smile: We have lost to a Dehler 33 on 0 to 4 knots upwind race with Tornado and a Dehler is a slug compared to A Scow.

Ok. If we make a conclusion out of this back to the Model boats, the fact is that you simply cannot sail something as relatively overrigged as a Scow via rc-controls. You just dont have enought sensity and the visual feedback just is not enought to sail something as powered as a Scow. Something as powered as Tornado… well that would at least be easier.

  • HJ

“Expertice is gained trough mistakes. However repeating
same mistake is not learning but stupidity.”

14

A SCOW IN A BLOW http://www.ascow.org/M51storm3.jpg http://www.ascow.org/M51storm5.jpg

15

Love Beachbum’s explanation. It’s on the nail. Just to add to it. You’ll note that a fast cat, flying a hull, is actually sitting pretty deep in the water with the leeward hull. It doesn’t plane as such - quite the opposite (especially if you let that leeward bow bury). That long lean hull just ain’t making waves - just as Beachbum says.

I’d be interested in comparing the wetted surface of a typical cat or tri with a “standard” monohull of similar length. I suspect (but don’t know - 'cause I haven’t looked into it) that multis have quite high wetted surface (all other things being equal) which is why they are a bit sticky in the very light stuff. But give them a little power, and they are away.

I may be wrong with this thought, so I’d like to hear from someone who’s looked into it.

Muzza

16

there are only a few multi’s that plane anyway, well, if you dont include the newer record breaking ones, look at tornado’s, a class, c class, there aint many cats that plane, i am sure you could probably count the ones that do by your fingers. long & skinny has always been faster for cats. i reckon if you could build a model type of over rigged (as beachbum puts it) it would be pretty hard to sail in any sort of wind, probably only under like 5 knots, because they don’t like waves & wind. it would be a cool project though

I see said the blind man to the crippled nudist who put his hands in his pockets & promptly walked away.

17

I agree with all of you that scows are pretty freakish in the grand scheme of things. But to be fair, we do sail them in pretty strong winds. Those pictures that Ed posted were of a freak squall that came through all of a sudden. In fact if you look at the second picture, you can see that the wind has already subsided. A scows will go out and sail in 20 knot winds with no problem. Yes, they do capsize on occasion, but experienced crews know how to handle a blow. Take a look at this ride:

Download Attachment: Ascows.jpg
29.92?KB

Anyway, I think Beachbum is right on the mark that the A scow is much more over-rigged than the tornado which gives it an edge in lighter winds.

I also agree that building a model boat with the same Sail area to displacement ratio of an A scow would be impossible to control. If you built a US1M sized A scow, the total weight (including any sort of moving ballast) would be about 2.6 lbs. It would most likely capsize pretty easily.

I would be willing to bet that the existing, working high performance RC multihulls would beat any existing working RC monohull in any wind over 3 or 4 knots.

(By adding the word “working”, I have ruled out any design ideas that have not been shown to work yet in RC model sizes like hydrofoil monohulls or some freakish scow like design.)

  • Will

Edited to make it clear I was talking about RC boats…

Will Gorgen

18

I ve never given this link…(but looks great):
Broadband recommended:
http://www.sail2fly.de/slideshow.html#

I dont even exist, and you ve never seen this !!!

_/ if it isn’t broken, don’t fix it! _

http://wismerhell.esmartdesign.com/index.htm

19

Pretty cool, wis.

BTW, the foil system on that boat was designed by the same guy that helped DL with his F3 foiler… both boats seem to work pretty well… Fun to watch things go fast like that…

I was not here either…

Will Gorgen

20

Have had some experience comparing r/c multis to r/c monos.

In theory, the multihull should be faster.

But two problems for r/c boats. First, in light shifty air, the multihull has major drag problems and can’t respond to “microshifts”. Basically, the monohull leaves the multi way behind in those conditions.

Second, when the wind comes up the r/c multi has a greater tendncy to flip or pitchpole. You can’t get around a course first if the boat is upside down.

Overall, in r/c boats, if there is consistent, medium wind that the multihull can handle, it will almost always beat a monohull around a course.