You can find wind pressure from Martin’s Formula;
Presure in lbs / sq ft = wind speed squared x 0.004 (in statute mile per hour)
Using the same sail area displacement ratio from my plank on edge (other Phin thread) you should have a sail area of 274 ins sq. My boat is a lot shallower - 100mm draft?, so you may be able to use more ail. However the drawings of Phin seem to show around the same area - 274 in sq.
This style of boat may be very heavy but they have little stability, so I would make sails from plastic bags and experiment a lot
Your idea of sailing at 30 deg is maybe optimistic, I sail at 60 deg and more, the photo shows a normal angle in a light wind, no crew = no worries about heel. Less than this and you are under canvassed.
Intersesting that Ian. I was going to post the the same formula last night but couldn’t remeber the Imperial coefficient and was too idle to calculate it. Only thing is - I call ot Anson’s Formula. Any thoughts?
In the hope of reaching Burton for a race this weekend I have fettled and finished the footy fleet and am in the procees of sailmaking.
I have unashamedly flattered the successful boats from Bournville (I don’t take all those photos for nowt, tha kens) and tried to get a leg up into the ranks of controllable and competitive boats by standing on the shoulders of giants.
(Thinks - to succeed more easily perhaps I should also stand on their boats, too)
So RAV and Litefoot are water-ready, need to finish ZBF and register it (not quite now, thanks Angus)
Dear Agony Aunt
I fear rejection, and that people will LAUGH at me and my (admittedly advanced) ideas.
I am a sensitive soul who takes myself very seriously
How can I cope with the slings and arrows of outrageous footy drivers?
please advise
andrew and darcy
Imperial Formula? It sounds like a great quick march!
I have never been able to forget the the name, or tune, of “the Imperial Echo” which the Light programmmmmme used, I think, to announce for the 7pm news.
I seem to have once heard that it was the regimental march of the (Royal)Paymasters Corps - the kind of rousing factoid that sticks.
I could check all this with google - but illusion is probably better than reality.
I like to imagine a brigade of Paymasters marching thru the defiles of the Pamir Kush on a mission to relieve Fort N’importe d’ou
To PeteSchug, Ian D, Angus R.
Many thanks for your help, and to Pete for the hint. I knew I had seen the info before, and the hint of “Uffa” took me to “Sail and Power” by Uffa Fox, 1950, where I found a chapter upon the very subject. I attach here the four pages and hope you and others in Footydom can read them if the problem ever arises again. The missing page applies only to the rig of the yacht ‘Wishbone’.
I shall get out my testing tank and my weigh scale and get to work. For the interest of those with similar problems, I will keep the Footy forum informed of my much anticipated progress.
Detailed calculations are (of course in footying) essential
but carrier bags come in a restricted range of sizes - unless you create panelled sails!
BTW in my role as resource investigator (radical) I found a promising sail material t’other day.
While scouting through an economy store ( the name will return as soon as I cease to try and remember) there were windscreen covers for 0.99GBP. They were made in a very light nylon (or similar) synthetic, aluminised on one side and blackish on the other - strong, flexible and light.
Havn’t tried one as a sail yet
andrew
As a rough and ready test of whether the material’s suitable; grasp two sides and give a quick hard pull. If the material shows signs of stretches afterwards, it’s probably best avoided. The florist wrap so frequently mentioned will break cleanly before stretching. Your economy shop also probably had plastic gift-wrap, which is also usable.
How offended would you be (please use a scale of 1 to incandescent) if I were to (attempt to ) construct your original bluesky 3-point hydrofoiler?
I would wish to do this:
with you, (and to a degree for you)
To show how easy is is to make a SWOOPY design
To (possibly) demonstrate the lowness of the tech involved - I can see also a mainly-balsa construction
To produce a radical and legal Footy (Note 1)
(as always) to learn a lot in the process
(Note 1)
I hereby declare that I do not know at this point in time how precisely this will comply with the rules. BUT IT WILL, or it won’t be a Footy
I further declare that the resulting creation is intended to within the spirit of the footy class and would be constructed, trialled (and possibly raced) in a spirit of discovery, fun and joie de vivre, not to mention je ne sais quoi.
I have stuck this in public since the original, sad debates were also in public and the effect on you, Trevor, must have been like being stoned to death with popcorn.
… not quite the flourescent ranges … welcome to your public immolation … as you can imagine there is background behind the whole thing … check your PM’s
Now we can drop the conservative facade (bother - can’t find the cedilla!) and drag small yot design kicking and screaming into the Century of the Fruitbat!**
Todays progress on ZBF below - has gone well and the BC is easier to carve that describe
Andrew, ZBF looks very radical! cool! i have one worry: that rudder is not going to give you any lateral resistance, nor very much forward lift. unless old darcy the squid is going to be pushing it from underwater, or, if i have missed some very important breakthrough, i see no way that the boat is going to “sail”. it will run before the wind, but will slide sideways on a reach as it has clearly very low lateral resistance, and upwind work is out of the question. there is no surface to provide any lift…
if i am wrong, please, somebody correct me, but without some sort of “keel” or daggerboard, i fear that the only direction that boat goes is sideways…
Very radical? I never thought of her in that light:D
A fairing of the stalk (or VHE) is intended, but will not be applied until I see how it is faired into the hull and BC - would that make you happier about the side area?
Clearly my view that the hull is a very short wing with rounded tips does not fully satisfy you.
While mulling over the science limericks recently offered I was blessed with a THOUGHT.
Ii was fairly radical, and allows the batteries to be placed anywhere in the universe and (this may be significant) and other universes. (not sure how the wiring would run - detail)
The thought was triggered by the well known topographical limerick:
A mathematician called Klein
Thought the Mobius strip was divine
He said “if you glue
The edges of two
You get a weird bottle like mine”
Naturally I realised immedaitely that this is the answer to the battery location problem, or challenge, or rule.
If a footy hull is made as a Klein Bottle, then there is no inside and no outside, or more accurately the inside and outside are continuous and identical
Hence the rib-splitting advert “Klein bottle for sale - apply within”
So its obvious isnt it? The Klein hull would allow the batteries to be anywhere and you can still claim truthfully that they are inside the hull.
Don’t even START to think about a Klein Footy box!
Stop cruelty to Darcy, are you trying to train him or kill him. He belongs in saltwater not fresh. I personally am trying to harness a duck, but an having trouble catching the same one to train each time i go to pond. So i end up feeding them all :lol::witch:
A couple of years ago Maynard Hill and some buddies built an RC plane within the FAI rules (5 kilo max weight with fuel) and flew it across the atlantic, from Nova Scotia to Ireland. It was equipped with GPS and telemetry gear and reported it’s position and condition as it flew across the atlantic. (It was the third or fourth attempt) It used an on board generator for electric power. It was an extreme case of an unmanned aircraft performing a mostly autonimous task.
I wonder if a Footy could do the same thing? A boat with a small rig, totally sealed, with solar cells covering the deck, with GPS and a computer on board.
Crazy idea, but it sounds like fun. I look forward to reading about it.
I guess I am suggesting an unmanned, autonomous sailing vessel, and the logical starting point for such a device is an autopilot of some sort.
That, at it’s simplest means a boat that knows where it is pointing and knows how fast it is going through the water. The first is simple. Electronic compasses are used in robotics all the time. The second is more difficult. The classic ways of measuring speed through the water are a spinner of some sort, (taffrail log) a pitot tube or a paddle that feels water pressure. All have their shortcomings, but all can be made to work until the first bit of marine growth screws things up.
With that you can point in a direction and measure your motion through the water.
If you add a GPS you can now surmise things like current based on the discrepancy between GPS location and dead reckoning based on speed and heading. If you are operating a sailboat you can also measure actual leeway if you know there is no current.
All this is done with a computer in the boat that decides things like what heading will get you where you want to go considering the differences between heading and course made good etc. The interesting part is adding sailing tactics like understanding how to go to windward and deciding when to tack and if downwind tacking is better than a straight run, all done by measuring actual performance against getting to the next way point.
Weird day dreams from a guy who has yet to finish his first boat, but this is the sort of thing that occupies a lot of the more technically oriented RC fliers these days and why not bring it to sailing?
Imagine the first transatlantic footy race! Or maybe something less ambitious like the English Channel for a test run.
A bit of googling should turn up any number of autonmous sailing endeavours, transatlantic and otherwise … there is an interesting collegiate regatta (this year in San Diego, I think) that pits engineering faculties against each other in robot sailing races … the boats are by magnitudes more sophisticated than what you’ll see on these forums … the lead on the York Univ (Toronto) endeavour was also lead on development of the space shuttle’s robotic arm and it shows (granted, the resources of an engineering faculty are magnitudes greater than an average home builder can deploy)
Well, at least they aren’t doing it with footys! Considering the size of some of the UAV’s amateurs are working on, it should be possible to stuff this sort of gear in a footy.
Maynard Hill’s airplane had enough fuel for a fist sized engine to run for three or four days, as well as the engine, radio equipment including telemetry gear and servos, generator and some small batteries. The GPS was probably twice the size of today’s gear, and yet it all fit in a pretty reasonable sized airplane.
Tinkerbelle, which was probably the smallest human carrying boat to cross the atlantic was probably around four meters, so although I am disappointed not to have thought of it first, I am not overwhelmed that they are limiting the actual race to boats under four meters!
I do think it is possible to stuff gear like this into a footy, but not in time for the race.
I wonder if they will handicap based on LWL?
Hmm… again. It took me about ten minutes to find a reference to Robert Manry, who sailed Tinkerbelle. I left the last e off in my google search. Tinkerbelle was 13’6" That’s 4.1148 meters, so at least their boats are smaller than a human carrying boat, but not by much!
Measure the speed thru the water with GPS, or doppler for the fine detail.
Me, I’m considering training darcy, but there are a couple of problems:
A) she doesn’t want to go to the US
B) the passport biometric data is a little challenging - good grief the “complexion” entry in the passport is difficult for a cephalopod, and fingerprints are always a laugh
I wonder if the Liverpool meeting might qualify as a centipede? Now there is a thought.