|
Server : Apache/2.4.62 System : FreeBSD fbsdweb2.web.rcn.net 14.1-RELEASE FreeBSD 14.1-RELEASE releng/14.1-n267679-10e31f0946d8 GENERIC amd64 User : www ( 80) PHP Version : 8.3.8 Disable Function : NONE Directory : /domains/daveculp/ayrs/AYRSpubs/ |
Upload File : |
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <HTML> <HEAD> <META NAME="GENERATOR" Content="Symantec Visual Page 1.0.1"> <META HTTP-EQUIV="Content-Type" CONTENT="text/html;CHARSET=iso-8859-1"> <TITLE>AYRS #101 (b)</TITLE> </HEAD> <BODY TEXT="#000000" BGCOLOR="#FFFFFF" LINK="#0000FF" VLINK="#551A8B" ALINK="#0000FF"> <P><A NAME="blot"></A><A HREF="101.html#contents">Return to Contents |</A> <A HREF="101.html#Bruce foiler">Previous page</A></P> <CENTER> <P><IMG SRC="p9.gif" WIDTH="399" HEIGHT="556" ALIGN="BOTTOM" ALT="The BLOT" BORDER="0"></P> </CENTER> <P>(page 9)</P> <P><A HREF="101.html#contents">Return to Contents </A> <HR> </P> <CENTER> <P><A NAME="sampanette"></A><IMG SRC="p10.jpg" WIDTH="380" HEIGHT="539" ALIGN="BOTTOM" ALT="Sampanette Photos" BORDER="0"></P> </CENTER> <P>(page 10)</P> <P> <HR> </P> <P><A HREF="101.html#contents">Return to Contents</A></P> <DIV ALIGN="RIGHT"> <P>Greetwell <BR> Todinnick-by-Fowey <BR> Cornwall</P> </DIV> <CENTER> <P>"SAMPANETTE" ?</P> </CENTER> <P>Material</P> <OL Type="1"> <LI>One sheet 8' x 4' x 6ml Marine (or External ) plywood. <IMG SRC="p11a.gif" WIDTH="157" HEIGHT="50" ALIGN="RIGHT" BORDER="0"> <LI>2" Fibre Glass tape. <LI>Resin Glue and Catalyst. <LI>Broom handle for paddle or oars. <LI>Copper wire. </OL> <P>A friend of mine found a small sketch of this boat (Dory ?) amongst a large pile of old yachting magazines, possibly American or Australian. With the sketch was a photograph of the man who had designed and made this craft, and to prove the concept possible he had paddled it across a large bay of rough water.</P> <P>We projected the image of the sketch onto a screen to approx. 1/4 size, then enlarged to full size and copied it onto brown paper patterns. These were then placed on to a sheet of 8' x 4' x 6ml marine plywood, and cut round, using a Black and Decker jig saw.</P> <P>Holes were drilled at approx. 2" intervals around the edges. The two sides were then sewn onto the bottom, using old electric copper wire, and finally covered with fibre glass tape. This method of construction is, of course, used when building a Mirror Dinghy. The boat was cut out and sewn one day, fibre glassed the next, and painted on the third day.</P> <P>The result was very satisfactory, so much so that as the craft looked not unlike my large 16' Sampan "FU HSING", I decided to make one for myself, and fit it out in the same colouring and design as the larger craft. The result was a delightful little boat, that has been sailed rowed and paddled in perfect safety by a young 14 year old friend.</P> <P>I now tow "MINI FU HSING" behind the big sampan, causing considerable comment and clicking of cameras from holiday folk and yachting types.</P> <P>The greatest difficulty is experienced getting one's grandson out of "MINI FU HSING", causing howls of protest when it is time for him to go home !</P> <P><IMG SRC="p11b.gif" WIDTH="246" HEIGHT="134" ALIGN="LEFT" BORDER="0">Dennis Banham</P> <P><BR clear = "left"> </P> <P>(page 11)</P> <P><A HREF="101.html#contents">Return to Contents</A></P> <P> <HR> </P> <P><A NAME="bandersnatch"></A>BANDERSNATCH REPORT 1984</P> <P>by G.C. Chapman</P> <P>In 1983/84 the same foil system was used, with inverted V feelers controlling the main foil assemblies and hence the incidence of the main foils. Performance was improved over the inverted T feelers used in 1979 which gave a more bumpy ride (and 15.2 knots on the inshore course), but both in 83 & 84 the constraints of the Hamoaze and weather gave much less foil born mileage not enough practice so poorer helmsmanship.</P> <P>HULLS. For 1984 I built new folded 4mm ply hulls to increase displacement and give easier handling at low speeds. To reduce the draught and retain leeway resistance the keels are 4" wide, 4mm thick over the full 14 foot length, the hull sides being fixed 1" inboard thus, >> almost to the bows which were built to accommodate boxes in which the feeler arms slide up and down. At -he sterns there are small transoms. These hulls I find give comparable displacement performance to the deeper Vs of "Bluey".</P> <P>FOILS. Photos show that sustained flight is possible at 12.5 - 13 knots, interestingly foil lift is greater than I calculated. They also show and I knew the sail was not sheeted in as hard as it might have been, indicating a potential for greater speed and stability in that wind strength 15 - 16 knots with practice. The 1983 run (Photos Multihull International No 191. Dex. 83 p304), was faster and steadier but then so was the wind. At present, performance compared with surface piercing foils is disappointing, I have looked for reasons. Although the inverted V feelers work and the anti crash foils just above them periodically come into play, I consider there is still too rapid and excessive a motion of the feelers, and long skis which can span 2 or 3 wave tops would be better. These were suggested long ago by Grunberg (alias Graig) and recommended to me by W.R. Frank.</P> <P>Rework of the basic equations suggest that my foil dihedral could usefully be reduced, and the canard now begins to look attractive.</P> <P>(page 12) <HR> </P> <P><U>SPECULATION DEPARTMENT </U>. At Portland in 1984 "OK SHAPE", alias "LOISIRS 3000," at last showed that a reasonably elegant, seaworthy and beachworthy canard can be built. Earlier canards have failed on those counts and as far as I am concerned gave canards a bad name. OK SHAPE is a catamaran with an arm reaching forward to a buoyant ski about 12" wide by 4' long, with the rudder beneath: ICARUS type foils are carried on the main beam.</P> <P>What attracts me about the canard is the possibility of controlling inverted T foils' incidence in a smoother manner than on FORCE 8 or BANDERSNATCH; though skis may help them. And reducing the feeler lift would help reduce drag, by transferring that lift to more efficient foils.</P> <P><U>DESIGN FOR LEAST DRAG</U>. If a limiting value of the athwartships, heeling component of sail force is a chosen (related to sail area expected apparent wind speed &c), and the weight of the boat and crew are estimated, then for the lee foil by itself to resist leeway and to support the weight</P> <P>(formula)</P> <P>where D is the foil dihedral, F<SUB>H</SUB> the sail heeling force and W the total weight (less any weight taken by feelers or rudder foil).</P> <P>The distance between foils will depend on the height of the CE of the sail, and will be a minimum for a boat with its CG amidships. If the crew chooses to sit to windward (e.g. on a catamaran) then the distance between foils increases.</P> <P>Whatever the beam, at the chosen F H only the lee foil is loaded: at lesser values of F H some of the weight is taken on the weather foil, at greater values the weather foil force reverses and the foil holds the weather side down.</P> <P>Up to the chosen F H the total of the forces developed by the two foils is constant and is Weight/Cos D, and is a minimum in relation to other configurations, with different dihedrals. Therefore for the same <U>foils</U> and relative to other configurations induced drag will be a minimum.</P> <P>Above the chosen F H drag will increase because the total of foil forces necessarily increases, due to the reversal of the weather foil force which in terms of lift now acts against the lee foil.</P> <P>The foils should be of symetrical section to cater for the weather foil reversal, unless you discount that possibility; and their incidence must be continuously adjusted to hold the boat up and upright.</P> <P>(page 13) <HR> </P> <P><IMG SRC="p1415.gif" WIDTH="770" HEIGHT="514" ALIGN="BOTTOM" ALT="Bandersnatch - 3 views" BORDER="0"></P> <P>(page 14-15) <HR> </P> <P>If the foils move relative to the struts, no leeway need be carried. If the foil + strut assemblies are rotated to vary foil incidence, strut incidence can be minimized by careful design, raking the struts forward from the foils.</P> <P>The vertical T foil (FORCE 8) is a very special case and is less efficient because lift and leeway are separated, total foil forces are Weight + F H and therefore rise as F H rises. Additionally, the surface piercing struts which resist leeway are less efficient than submerged foils: wetted surface is greater, as are the structural problems.</P> <P>The above remarks apply to canard and Hook-type inverted T foilers.</P> <P><U>CANARD DESIGN. </U>My suggested optimum canard therefore has:</P> <OL Type="a"> <LI>Lightly loaded ski well forward, carrying no lee forces, and arranged to resist nose- dives. <LI>T foils with dihedral set in relation to expected maximum F~ and the distance apart set accordingly, and taking account of the crew's location. <LI>While overall T foil incidence is controlled by boat attitude in relation to the ski, the helmsman must be able differentially to alter the dihedrals (as in e.g. JACOBS LADDER 111). Structurally it is easier to fix the foils to the struts and rotate the whole assembly, with a very small penalty in strut incidence, load and drag. Purists will move their foils relative to the struts and carry a weight and cost penalty. <LI>The ski forward should carry no leeway force. Steering should be by a fenced rudder right aft, giving normal handling characteristics with weather helm, whether the foils are up or down. </OL> <P>You may therefore have either a monohull with the helmsman in a cockpit (for speed) or a catamaran for greater ease of operation, beachability etc., and dual role as a displacement boat for other sailing and for getting to and from the foiling waters.</P> <P>Even if you adopt the above, at some speeds the weather foil and strut are doing no useful work but are still causing drag. To eliminate that and to exploit fully the drag economy of the inclined T foil you would need:</P> <CENTER> <P><IMG SRC="p16.gif" WIDTH="420" HEIGHT="68" ALIGN="BOTTOM" ALT="Inclined T foil force" BORDER="0"></P> </CENTER> <P>And of course if you can also have an inclined sail............</P> <DIV ALIGN="RIGHT"> <P>G.C. CHAPMAN</P> </DIV> <P>(page 16)</P> <P><A HREF="101.html#contents">Return to Contents</A></P> <P> <HR> </P> <DIV ALIGN="RIGHT"> <P><A NAME="foils & weight"></A>87 Staincross Common, <BR> Barnsley, 575 6NA <BR> 9th February, 1985</P> </DIV> <P>Dear Michael,</P> <P>AYRS 100 is excellent. Interesting from start to finish.</P> <P>One point. Reg Frank, B.Sc. We have lots of B.Sc. holders nowadays. Originally, I suggested to John Morwood that it would be very useful to enquire from members as to their specialties, and to start it off, explained mine. The 'B.Sc.' remains in the records. Please remove. Stands out like a sore thumb.</P> <P>Now this is still a good idea. For example, say someone wants to use titanium alloy foils or other parts, e.g. masts, or carbon fibre, or wants information on engines, or on sails, or on a thousand other matters. There will be one or more members who can help.</P> <P>Probably a better way would be to have a column in every publication. 'Can any member give advice concerning making carbon fibre spars ?' etc. Does anyone know of a high power to weight engine suitable for use in a hydrofoil ? Electronics wizard to help design radio control. All sorts of requirements. After reading George Chapman's letters 'Member wants to locate source of supply of p.t.f.e. bearing pads.' My own most useful service might be when people want gunmetal castings or aluminum castings. Amongst our members there is a wealth of experience and special know how, and with a bit of organization that can be tapped.</P> <P>Joseph Dusek's model. Note the grooves made by floats and hull. Now add together all the water displaced from those grooves, and its weight is equal to the model weight. John Morwood was right. You were mistaken. The really tricky question is what happens with submerged foils. I would bet, that if the water surface could be observed, that there would be depressions and that the volume of the depressions has weight equal to the hydrofoil weight. When you see John, ask him what he thinks about that. Pity Avogadro didn't do hydrofoil model experiments in his bath. Apart from all that, aren't they beautiful pictures ?</P> <P>'Only road rollers need weight.' Not so. Hydrofoils need weight. When the hydrofoil has no weight, in theory, then some foils have to pull downwards to provide balances against wind moments, and those downward pulls generate as much drag as the weight which they have replaced. Of course, if the umpires at Portland would set out a measured distance directly downwind, and organise runs during 50 knot winds, then a hot air balloon, or a helium inflated balloon, floating downwind at wind speed, with a fishing line and tiny foil immersed to comply with the rules, would break all world speed records. A crew is weight, and can provide balance, so in that sense there is no requirement for anything else to have weight.</P> <P>(page 17) <HR> </P> <P>Light weight road rollers, with buoyant rolls, and sails, might sail very fast downwind. People sail in bath tubs. Why not in road rollers ?</P> <P>If you would like any more daft ideas, just ask. But just imagine; all this effort at Portland. And a road roller rolls onto the course and beats the lot.</P> <P>l Survival suits. I once did an experiment. Layer after layer of woolen clothing. Stayed floating during early March until our dinghy was rescued after overturning. Then carried on until 2pm, soaking wet through with cold March wind, and I felt warm. Another test in wet suit in very cold weather. I floated around for twenty minutes, and felt warm. But I had 'oilskins', nowadays plastic, smock and trousers, and some woolen clothes over the wet suit. Felt warm. Another experiment. Woolen Norwegian track suit sort of underclothes. Stood on deck in the Humber, at night, cold breeze, slight rain. Stood for 15 minutes. Warm. Next day, this suit under my normal clothing, felt cold and shivered excessively. Removed the track suit. Got warm. Lesson, lots of layers of woolen clothing and a wind proof and shower proof outer cover. Another query. Why are boats built so that crews have to remain in the open ? Why cannot boats be controlled from inside the cabin ?</P> <P>Enclosed cheque for £25, to pay subscription, balance a donation.</P> <P>If you could keep up the interest, these publications are very attractive. AYRS 100 would sell at Boat Shows. Much more interesting than the dreary repetitions in yachting journals. Professional writers could take any one of these AYRS 100 articles, and expand it into an article for popular consumption. AYRS is a jewel, a collector's piece. Congratulations again to all concerned.</P> <DIV ALIGN="RIGHT"> <P>REG FRANK <HR> </P> </DIV> <P>Grenville Griffiths has been poring over Philip Hansford's book "Theory of Wing Sections", by Abbott & Van Doenhoff. Grenville has opted for simple Ogival sections for his foils and hopes carbon fibre construction will be strong enough <HR> </P> <P>THE NAUTICAL QUARTERLY carries an 18 page discussion on the A.Y.R.S. written by Mike Badham. Super reading. <HR> </P> <P>James Grogono may be getting together with Mike Ellison to discuss a second edition of 'Sailing Hydrofoils'.</P> <P>(page 18)</P> <P><A HREF="101.html#contents">Return to Contents | </A><A HREF="101c.html">Next page</A> </BODY> </HTML>