to be exact my father doesn’t drink…
but from what i have heard brit doesn’t like to talk about mariner… it would be interesting… i never had a high opinion of te mariner program, and i think part of its problems lay in the hull most definitly, probably 75% of them, but if i remember, [angus you have probably read the book more recently than i,] the syndicate also had issues getting the right sails, ect… so who knows, maybe these immersed transom “leadmines” as brett so aptly put it are the futer of the footy class? let us know how yours sails angus!
And with her distant relative Akela now through apparently effective sea-trials, a toast to poor, ill-considered old Mariner and her inginitely ingenious designer Britton Chance Jr.
There are a few good pics of Mariner’s “fastback” stern in the book “The Grand Gesture” by Roger Vaughn. A pretty good read as well. I’m not sure if the book is published any more, but there are used copies available on the web.
To answer the question about whether the stern shape was slow, all that I know is that after Mariner went into the shop to have a more conventional stern shape fitted, she was quite quick afterwards. If I recall correctly, she was about equal in speed with Courageous and Intrepid and actually won about half the races afterwards. Too little too late however.
With regards to the scale of model, I seem to recall that Mariner was tested at SIT with models in the range of 4-5 feet. The data they got suggested that a full scale version would act like a vessel with a 5-6 foot longer waterline, with no additional drag. The basic notion being that the water would flow cleanly off the steps and there would be a 5-6 foot dead zone of water which would almost act like the “missing” stern section. So yeah, there were evidently scaling problems in the testing. In fact, the misleading data from the models that size were what lead to the 1/3 scale models used in 1977 for Enterprise, and possibly others in that year.
Having said all this, it may be intriguing to see if the concept would work on RC boats, as the 4-5 foot models tested very fast.
Britton Chance was never afraid to swing for the fences. Procyon, for example:
http://www.boatdesign.net/forums/showthread.php?t=10771&highlight=procyon
Cheers,
Earl
Woah, this is an old thread!
I’m told that Brit it really a bit of a genius. That doesn’t change the fact that Mariner was an utter dog. An old worn-out S&S trail horse (i think it was intrepid) cleaned the floor with it so badly that eventually they tried to slow intrepid down. I have always been a fan of the underdog, but Mariner is taking a step too far. There are silly boats (see the tandem keel NZL) and there are dumb boats. Mariner, to my mind, is one of those.
Barrett - Mariner may have been wrong, but dumb she was not. The scaling went wrong but it remains an irrefutable fact that the best instrumented and calibrated yacht test tank showed an absolute reducion in drag of huge proportions. It didn’t scale up, but at tank sizes the effects Chance was looking for were there in spades.
Angus - While i agree with you that that concept looked promising, and perhaps on a four foot model, in a controlled test-tank environment gave untold speed increases, it doesn’t change that fact that the boat was an utter disaster. The team knew this from the beginning! Aussie II could have classified as a “dumb” boat too, Ben Lexan’s wings, which tested as making the boat unimaginably faster in actuality made the boat handle very strangely downwind, and very poorly in slop. In my opinion it was only the “upside down” keel which was a much better way to hang the ballast, and the fact that the aussies effectively turned DC into an insecure madman that they won the cup. The wings are cool, but John Bertrand himself says the the wings were in many cases more trouble than they were worth. I guess what i am trying to say is that, while the idea obviously was sound, and the testing yielded results, it didn’t change the fact that the boat ended up “dumb”. If i had been in the position that the Mariner syndicate was, i would have raced Intrepid. But thats just me. :devil3: lol
420, I have to agree. I guess when I first saw Mariner in Newport that year, the boat was hard to look at. She just did not “look” fast. Weather that played out on the race course because the tank results did not scale up may be so but the mental state of the crew may have also played into it.
I had occasion to be asked to review the steering on US 61. If you think Britt was having a bad day, I can tell you about this one.
Chuck
I sense a story! :devil3:
[i]" For over ten years now we have been pained by more and more frequent references to undocumented accounts… that the towing tank was responsible for the failure of Mariner."
"It is time that we put an an end to this irresponsible hearsay "
“This undocumented impression has been repeated over and over again for years until now the yachting community considers this to be gospel”
“I think it is time that the yachting community stop perpetuating this myth and ,as the man said : let’s look at the fact”[/i]
These are the words of Daniel Savitsky, the man that with his own hands carried out tank testing of both Mariner and Courageous at Davidson Laboratory
THE FACTS
1 - both yachts were tested before the 1974 campaign, at Davidson
Laboratory
2 - each yacht designer was aware of only his own test results
3- according velocity prediction based on these test, Courageous was the better boat on a wide range of wind speed ( mariner was slighty better only at very high speed )
4 - subsequent to the 1974 campaign other tests have been carried out with both 1/8 and 1/13 scale models at 10,20 and 30-deg heel
5 - IN ALL CASES THE MARINER-STYLE AFTERBODY WAS INFERIOR TO THE NORMAL FORM.
The difference was small at the 8.5 - knot speed through the water, appropriate to the stronger wind conditions, and the difference increased in lighter winds.
reference : Marine Technology, Vol 23, No 4, Oct 1986, pp. 320 - 337
" Rik F. Van Hemmen - 12 meter design : state of the art in 1986 "
So much for submerged transoms on big ass boats.
My limited experience with Footies (and few among us has more) is that as they get their get-up-and-go up and going they tend to roll forward onto the fore sections, pushing their bow down and raising the stern. In this case a properly designed submerged transom would no longer be submerged once underway. Since most of you guys designing your boats tend to try to counteract this inherent motion by skewing your hulls to more in favor of a cod shape, what the boat wants to do is thwarted to some degree, and the reward is a steeper bow wave.
My suspicion is that who ever figures out how to manipulate this short boat’s tendency to put her bow down and stern up will change ground rules and outmode all the rest of our collective efforts.
Well, one solution was figured out by Gus Lassel round about 60 years ago:
-
Get the CLR as far aft as you can with a forward-raking fin (his so-called “Finless fin keel” design.
-
Put the LCF (longitudinal center of floatation, the point around which the boat pivots when pitching) close to the LCB (longitudinal center of buoyancy) and well forward of the CLR.
If your juggling comes out right, the mast will be at or slightly aft of the LCF; downward mast pressure on the run will strongly inhibit the tendency to dive. Gus and his buddies got the mast aft on a run using a sliding rig; on an RC boat we have to fiddle with the sail plan to do the same thing.
Boats with wedge-shape waterplanes have the LCF way too far aft, and the fundamental imbalance in such hulls with their corresponding tendency to “gripe” (run up into the wind) must be compensated for by sailplans who have CEs (and therefore mast positions) too far forward, which, with the lack of buoyancy in the forebody, makes all the diving tendencies worse.
If I were to design a Footy (which I have no intention of doing, RG65s being much more to my taste :-)) I’d try and have the mast on the transom.
Cheers,
Earl
Hi Earl -
not to hi-jack a monohull thread, but to point out that in the mid-1980’s a very large (30 feet plus) multihull (catamaran) called “ShotOver” had their mast mounted on the rear cross beam and was (basically) driven by a huge jib/main which when viewed in photos looked like a large Genoa.
Not sure how well it finished in regattas or off-shore races but was an interesting concept that someone tried.
I now return you to the monohull discussion.
A long discussion of aftmast rigs can be found at:
http://www.boatdesign.net/forums/showthread.php?t=623
Cheers,
Earl
Boy - I was only off by a mere 30 feet ! Double the size I thought she was, you can see how small the mainsail is in comparison with the headsails on this cat. (ShotOver) Obviously a “tourist boat” in Australia judging by the number of people and their locations on board, a reefed main in rather flat water conditions, as well as the poorly trimmed jib.
I read the site you referred to about aft masts and had this crazy idea that might be possible in Footys if not in other larger or full-sized boats.
Rod
Its a very interesting idea, and i see in a lot of merit (the cool factor alone is something!) but that big old spar aft of the mainsail looks to me like it does very little but cause turbulance for the air passing off the foil of the sails. My understanding of aerodynamics is limited to allowing me to build shoddy footy sails, sail full size boats, and fly airplanes - i.e. its a “working” understanding - but wouldn’t turbulance on the trailing edge be one of the worst things you could do to airflow on a sail?
:graduate:
The mast would be under very little stress and so could be quite thin. It might even be a straight length of carbon fibre tubing, one size up from the jib and mainsail luff tubes. The sail-plan could be reduced to only one sail, a jib, alone, sloped severely towards the stern. This might provide a significant lift to the bow while running down wind. I will draw out a diagram and attach later.
Rod
Here is diagram. Not completely dissimilar to the Dunedin McRig, but perhaps an alternative.
Rod
Earl,
Can you explain the difference between LCF and LCB? To the uninitiated, they appear to be the same thing. I am guessing that perhaps one or both of them includes the height dimension above or below the water line, as well as the fore/aft position.