The only objections that I can see are the meaning of the words ‘within the hull’, and the definiton of the word ‘hull’.
Otherwise, fascinating!
Thanks for the reference Andrew. That rig is devilishly clever. Now the wheels, in my head, are turning faster.
A very long time ago when I was fresh out of engineering school, I probably did not understand much about the engineering discipline. I chanced to buy a book titled: The 40 Knot Sailboat. by a navy commander named Bernard Smith. Smith reasoned that we have spent 100 years or so making small improvements to boat speed. He further reasoned that the crux of the problem was that the hull was in the way. So get rid of the hull. Foil borne craft was his proposal. Contemplating that manner of thinking gave me a new insight into the problem solving process.
Brett has used the Smith principle, or perhaps his own open minded method, to noodle up a better, or at least a very interesting sail worthy of exploitation.
Footys and marbleheads and other developement classes seem to attract thinkers. I admire thinkers and like to jaw bone with them.
A: part of the country…Lakeland Florida
B: I have a drawing board with several preliminary Footy designs. None are complicated. There are scows and double enders. All these have what would appear to be too much rocker. That’s because the boat will surely sail in heeled position on all points except downwind. By my reckoning the fastest boat to windward will be the hardest to beat around a three cornered course. I’m kind of hung up on section centroid connecting lines. More about that later if anyone cares to explore the technical aspects.
Fair winds
Its my belief that Brett is a student of William of Ockham, and has not complicated the device more than is required. But a genius too.
Messabout - footys certainly attract giant thinkers and erudite discussion using lots of nautical language way beyond me.
It is also true that at the moment there is an honourable place for fun, cute and scaleish boats
What kind of constructor are you? Balsa-basher or high-tech molder (or slm?)
look at Rod - light blue touch-paper and away he goes and voila, a footy!
my ZBF should reach the foam stage this weekend, if I can just oil the wheels in my head
andrew
Andrew,
I am interested to see the outcome of your project… it looks interesting… to say the least!
i only have a few questions.
-
are/how are you planning to end plate that rudder? or is it just not going to be end plated, and loose a little efficiency?
-
by adding that big bulbous “hull” beneath the water, you are adding a lot of wetted surface, and therefore, i think it is reasonable to conclude, a lot of opportunity for drag… are you planning on making the rig so large that it is powerful enough to over come that? lol, “when in doubt, power up!”
-
from my first glance at your design brief, it looked to me as though you were proposing a large sculpted combined rudder/keel foil, very close the the stern of the boat… you also seemed to have the rig rather far forward… this would create an almost un-sailable amount of weather helm… have you thought about putting a foil further forward to help with that?
anyhow, just some things that popped into my head!:graduate:
looks like a great project, best of luck!:zbeer:
420sailor,
this is, I think a project that will have a digital result - either a 0 or a 1!
Thanks for your views -
the rudder is conceived to be MAR ( as in Mission-Adaptable Wing) in other words integral surface which deflects without pivot or hopefully too much drag. whether I can do this is another thing, but my mind is running down the thin silicone rubber/ old-escapement-bent-wire-operator route.
The rudder is also imagined to be a roll compensator, as it can be in two bits which can seek to roll the ZBF upright like an aileron!
Wetted surface, yes, but bow wave, no. Truly no idea; but worth a try
Will certainly out psych the opposition yet.
Foil - yes combined with the rudder and oh, so thin. Having looked at the keels of Gary Sandersons footys the keel has got reduced to a vestigial member holding up the bulb - and I have the inmpression he is going further in that direction. In the words of Linus “nobody argues with a straight “A” average”
So yes the vertical hull extension (not keel please or foil, its part of the hull whic itself is definitely not a keel or bulb (or ballast)) is the fixed part of the MAR rudder. If there was another vertical thingy at about the mast location this would be convenient for mast support and praps help with the balance you mention.
I dunno, really - easier to try than calculate
Anyway, assuming I make it with a foil and mast pivot essentially in line vertically.
In mild airs the buoyancy compensator would be very small and virtually circular (no geat nose-dive or heeling tendency) so how would the driver know which way the footy was going? - no wake either!
BTW I have been thinking carefully about the buoyancy Compensator (BC) - I think that the ZBF should be ballasted to about +10gm (1/2 oz) of negative buoyancy so that the BC is providing just a little lift, and is submerged a negligable amount. In a blow there will be lot of the odd list (pivoted about the hull centroid) so the BC needs to counter this and nose dive downwind.
So the BC should perhaps be inflatable either on the bank to suit the conditions or automatically.
Thinks: do squid suffer from flatulence at all?
I can give this up any time I like
andrew
Studying Andrews sketch, I think I want two of whatever he is drinking also. Andrew describes the project as a digital one but I think there are possibilities that lie between abject failure and total success.
420sailor: as drawn, the boat will have lee helm not weather helm. I agree that wetted surface may be an issue.
Other difficulties are more mechanical than conceptual. Like making the hull joints sufficently water tight and making the hull extension/fin stiff enough without making it too wide. I’m wondering, too, about pendulum effect and its’ relationship to the bouyancy compensator.
2Cents worth: Make the hull in the form of a NASA section such as 63 series with the maximum camber at about 50%. Move the extension to the center of the hull and make some SWAG estimates for sail balance. I think you will have to use a different rudder layout. Maybe a rudder that is mounted to a boomkin extending aft of the bouyancy thing. The purpose is to avoid the lift that will be involved when the rudder is hinged from the fin. That’ll work like aircraft flaps and induce heeling or counter heeling forces. Anything that creates lift also creates drag. more than that, I think the sketched layout will produce a boat that is difficult to maintain direction. Moving the rudder to the boomkin will also eliminate the leakage problem caused by the underwater pushrod or whatever moves the rudder.
I work in whatever material seems appropriate. Balsa, GRE, CF, or whatever the current brain fart dictates. My peers accuse me, rightly so I fear, of over building. On that account I gotta mend my ways so as to keep the footy light enough that it might not sink. When messing with Marbleheads or 23 pound EC12s, a few grams here or there will not make much trouble. On 15 ounce Footy it is a different deal.
You sa- ay lee helm
I sa-ay weather helm
You say lee helm
I sa-ay weather helm
lets call the whole thing off
Sorry; it reminded me of a song - nearly everything does
NASA section? Swag? Not a tla I am familiar with!
Messabout - my background includes FID competition - microfilm aircraft 24 inch span with min weight 1 gm. Build lite!
Pushrods and projections are streng verboten
Race you to a weird result?
andrew
Sorry; I can’t share what I’m on - I would fear invasion!
Perhaps he was referring to a NACA section? This site will let you generate custom sections
http://www.pagendarm.de/trapp/programming/java/profiles/NACA5.html
NACA predated NASA & is the repository of many airfoil profiles going back to the early days of flight.
Thanks Messabout… i dunno how i got confused there… it was late!:dunce:
thanks for setting me straight…
OH NO!
I have commenced construction of ZBF - the Hull turns out to be 40mm diameter at the girthiest - no worries.
Prototype will be glass with strands of carbon and Kevlar as required
Total stoppage! No room for the on/off switch!
Also it will be in the hull, so submerged 12 inches deep.
The (static) pressure there would be … thinks… calculates…
about 12 inches of water
What to do?
O that such a promising and silly footy should be brought low by such a thing
drill a hole, run the switch wires up the foil, and put the switch on top of the float. it’ll be easier to use anyhow?
otherwise, you may have left yourself no choice but to get out the bizzo saw and do some “modifications” lol.
good luck!
Thanks, 420sailor, that would work.
t’would require some more stuff in the foil, or as I like to call it vertical Hull extension (I don’t want any of these salt-water lawyers thinking wrong about the components)
BTW have you ever stripped a mouse? The corded mice have a great cable with about 6 cores of very fine wire inside (much used by the micro-flying community)
My mind was also running down the reed switch route - but worrying, of course about what would happen if I got stuck in real reeds.
Following your suggestion I might be able to, or might have to, use Sanderson-water-proofing!
tks, andrew
Hull of ZBF will be blue foam, and since it entirely circular in section (the mark 1, that is) I need a sorta hot-wire turning lathe to make it easily.
I will probably hot-wire cut in 2 axes, then take off the corners by hand - then wrap in clingfilm and glass cover. I’m not sure if rolling tape on or draping one half at a time will be the best bet. Leads me to wonder how I will hold it for this process!
This means that I need to add a thin bit of ply at the guessed mast location so I can hold it on the workmate - then if I need to add a foil at or near this location I’m ahead of the game.
We’ll see how this weekend goes - it would be good to have at least all the parts visible
andrew
i would not try to wrap it with tape. one, because FG tape tends to be a of heavier weave than cloth, and i think you probably want to keep weight down. two, because as you mentioned it will be easier to hold. three, it that it is easier to sand one seam of doubled glass along the edge of a part than it is to sand fair a spiraling wrap edge all the way around the boat… its just less sanding.
are you going to “lose” the foam on the inside at somepoint? its going to be pretty hard to make that thing ballast out to zero bouyancy if its full of foam…
<<are you going to “lose” the foam on the inside at somepoint? its going to be pretty hard to make that thing ballast out to zero bouyancy if its full of foam…>>
Yes, and yes, and in that order. Mind you I HOPE that when I take out the foam it will be replaced with air rather than water:p. There will be quite a slug of lead along the bottom, too. Moulded so as to be blended in (naturally)
Current high tech thinking is to make a joint around the largest diameter (where the batteries live) and seal with either an o ring or similar or (just possibly) heatshrink seal.
Now I wonder if I need a bilge pump, or shall I just train the squid better?
andrew
Status at 11 Dec 07. The “lost foam” method, also known as “dug out foam”, to make room for the electronics
Rod,
Now that IS swoopy and radical. Please keep us updated
I must get to the foam lathe
andrew
Rod - Looks less like a scow and more like a tunnel hull trimaran. I’ve have something similar in the drawing phase. Its been sitting for a while but now I’m inspired to get back to it.
Niel
I haven’t been able to figure out how to make a pure-bred scow remain upright. Possibly a conventional blade and bulb keel? If model sailing galleons can have one, a scow should be able to have one too, without violating all the proprieties of naval terminology.
I’ve been contemplating Phinn. I have some Formica sheet pieces, which could be assembled, perhaps, by sewing the edges with braided fishing line, a la Peapod, as in “U.S. Boat and Ship Modeler” of Winter 1988. Might lay to rest the questions about bouncing over the waves vs. cutting through them.
I’ve pretty much decided that the experimental part of Footy building requires than hulls be built to suit the existing rigs. I’m tired of making more masts and sails.
If you guys are using styrofoam (blue, pink, or white) for your plugs and epoxy to make the shells around them the easiest way to remove the foam after the epoxy has cured is by pouring a bit of acetone onto the styrofoam. The foam melts away and the gooey remnant can be removed carefully.
Also, if one is trying to cast a moncouque hull (hull and integral deck) then I recommend this method for holding the plug. First groove the centerline along the deck to accept a thin plywood fin that runs the whole length of the hull. It should probably overhang the ends a bit. It should be tall enough so that the plug will be easy to handle during the layup process. After the plug is waxed or has some other release agent on it you begin the layup by aligning the glass cloth with the fin edge. Wet the cloth out as you go around the plug. Make sure that it is a “dry” layup to start, if the cloth is too saturated it will tend to hang loose because of gravity. Once you are on the other side trim the cloth along the fin so that it sticks tight to the form. Once you have removed the new hull from the plug the seam can be joined with fiberglass tape.
A more involved method is to make a pair of plywood forms that follow the shape of the deck along the fin. In this case the fin and forms should not be more than 3/4 of an inch tall. With the plug upside down in a vise held by the fin, drape the cloth along the centerline and wet out as far around the plug as you can get. Remove the plug from the vise and continue to wet cloth out up to and a bit beyond the point where the fin starts. The two ply forms can then be placed on either side of the fin to clamp the glass snug to the fin and the deck contour. I use clothespins to clamp the forms in place. If the glass extends slightly above the forms you might be able to tighten the layup by pulling on the glass. Once the hull layup is cured the hull can be removed from the plug. There will be flashing from the glass that cured along the fin. I use this flashing to clamp the seam together so that I can join the two halves with fiberglass seaming tape. After the seam has cured the flashing can be cut flush to the deck.
Best of luck!