Human Power Editorials lar group, first. Other countries are also The technical journal of the having outbreaks of right-wing advocacy International Human-Powered Vehicle Internationalism and violence. There is at present a high- Association The IHPVA is often criticized, per- ly embarrassing war of words between a David Gordon Wilson, editor haps justly, for not being sufficiently in- small minority of public people in Japan 21 Winthrop Street Winchester, MA 01890-2851, USA ternational. It is something we all have and the USA following a disastrous state Phones: 617-729-2203 (home) to work on constantly. All the "higher" visit by the president and a group of 617-253-5121 (MIT) animals are territorial. Mankind easily over-paid auto-company executives. 617-258-6149 (FAX) reverts to this pattern. As I write this, (Why couldn't he have taken some of one of the US presidential challengers is our HPV pioneers - people we could Associate editors trumpeting the call of "America First!" I have been proud of?) Toshio Kataoka, Japan thought that that had disappeared in the These reflections are partly the re- 1-7-2-818 Hiranomiya-Machi Hirano-ku, Osaka-shi, Japan 547 thirties, a time when I remember my pri- sult of another act of kindness by a Japa- Theodor Schmidt, Europe mary schoolteacher hugging me and say- nese friend, in this case Akira Naito. Hoheweg 23 ing "Aren't we lucky to belong to the We were very grateful to him for giving CH-3626 Hunibach best country on earth?" Pride in one's us his paper on HP helicopters in the last Switzerland country and in one's group or team is issue. He was appreciative of the help Philip Thiel, watercraft good so long as it doesn't lead to a dis- we had given in editing the paper. He 4720 7th Avenue, NE Seattle, WA 98105, USA paragement of other countries and has just sent a stunningly beautiful pre- IHPVA groups. In Britain it was only slightly sentation of micro-origami - Parade of P.O. Box 51255 humourous to refer in those days to peo- Cranes. (The folded-paper cranes have Indianapolis, IN 46251, USA ple unlucky enough not to have been wingspans from about 25 mm to 0.7 Phone: 317-876-9478 born in Britain as "the great unwashed". mm, too small when mounted on the Officers A famous London Times headline is re- points of sewing needles to be seen with- Dave Kennedy, president to have stated "Fog in the Chan- out a strong magnifying glass). I hope Adam Englund, secretary puted Bruce Rosenstiel, treasurer nel: Continent cut off' On my first visit to present it to a museum so that others Marti Daily, exec. director to the USA I was entranced at the great- may appreciate the craftsmanship and Paul MacCready, int'l president er interest in and acceptance of people artistry. Doug Milliken, VP water of other countries than I saw in my own I also feel, as I did when Ellen and I Glen Cole, VP land country. Foreigners were treated as peo- visited Japan, that in the face of many Chris Roper, VP air ple having habits that were no so much beautiful and subtle courtesies shown to Matteo Martignoni, VP ATV Theodor Schmidt, VP hybrid power strange as interesting. At the same time us we may have been perceived as we were guilty of appalling racism. We clumsy, even boorish. (No one gave us Board members in the USA have apparently progressed any impression of perceiving us that Allan Abbott in this area so far in the last thirty years way). The point that I want to make is Marti Daily that we feel smug when confronted by that, if we are to make the IHPVA truly Peter Ernst occasional renewed appearances of international we have to keep on our Chet Kyle the guard not to disparage any practices of Gardner Martin throwback movements proclaiming Gaylord Hill need to put the country, or some particu- other groups, but to do our utmost to Dennis Taves communicate. compete and cooperate in David Gordon Wilson In this issue fun and friendship. Human Power is published quarter- Editorials Dave Wilson 2 De-cavitator HPH Mark Drela, Almost DTP ly by the International Human- Human Power has relied in the past Powered Vehicle Assoc., Inc., a non- Marc Schafer & Matt Wall 3 on a network of volun- profit organization devoted to the for its production Letters to the editor 4 teers and of one or two people who did study and application of human mus- Book reviews - Bob Stuart 5 cular potential to propel craft through professional work at well below market the air, in and on the water and on "Paddlewheels" - a correction 9 rates. Drafts and diskettes were shuttled land. Membership information is In search of the massless flywheel from place to place around the country, available by sending a self-addressed John S. Allen 10 sometimes suffering some delays and stamped business-sized envelope to the What is an HPV? Rob Price 13 always surprising the editor somewhat. I IHPVA address above. Aditional copies of Human Power Cycling Science 3/3-4 - a review 18 would never know, until the final prod- may be purchased by members for More on hull shapes for pedal power uct turned up, exactly what the composi- $3.50 each, and by nonmembers for Augustus Gast 19 tor had managed to squeeze in. For this $5.00 each. Advances in flow visualization issue I'm trying the experiment of pro- Material in Human Power is copy- most of it myself. I've bought a a review (Dave Wilson)20 ducing righted by the IHPVA. Unless copy- new, fast PC, Microsoft Windows, DOS righted also by the author(s), complete Wind + HP quadracycle Wally Flint 21 5.0, and Lotus Ami Pro. (If this sounds ar, ticles or respresentative excerpts Tricanter HPV energy modelling may be published elsewhere if full like an advertisement, let me reassure credit to the author(s) and the IHPVA J.KRaine & M.R.Amor26 you that it has a purpose. On the title is prominently given. Richards' Ultimate Bicycle Book page of my last book I printed "Pro- We are indebted to the authors, to a review (Dave Wilson)33 duced on Lotus Manuscript". When it Marti Daily and to Carolyn Stitson, Second int'l HP-submarine race didn't work as advertised, Lotus was fan- whose dedicated help made this issue Cory Brandt 34 tastic. It brought out a new version of possible. Dave Wilson l Uawp. 'in fluurlllrfuuAS-/flLsfU Urt P. V/ Cover design by Bruce adndmore p. 2 Human Power, fall & winter, 1991-2, vol. 913 & 9/4 DECAVITATOR PxjrraPoweredHy'ofoil 27 October91 0 1 2 3 4 5f Figure 2 Three-view drawings of Decavitator, withoutfairings Drawn by Mark Drela requires only a modest anaerobic effort en's racing kayak, with the deck lowered the overall vehicle drag if large-chord for a few seconds. Once flying on the by about 2 inches / 50 mm. A similar wings are used at low takeoff speeds. hydrofoils, the vehicle can be sustained design is employed for the monohull An earlier version of the Decavitator had by a fit cyclist at 9-10 knots / 4.5-5 m/s Hydroped vehicle. Molded composite a rather large takeoff wing of 5", 127 with aerobic power levels. A maximum construction with a hard gelcoat finish mm, average chord, and required exces- effort produces about 15 knots (7.5 m/s). gives very nearly the lowest drag attain- sive takeoff power due to the 2-D wave- Very High Speed. After unlocking a able. Although such exotic pontoons drag mechanism - as clearly evidenced safety latch, the rider has the option to might seem frivolous on a hydrofoil by the dramatic wave train set up behind pivot the large wing up and out of the boat, their low drag is in fact crucial to the wing. Reducing the wing area by water, much like on one of the more re- top-speed capability of the vehicle. nearly half gave a larger Froude number, cent Hydroped variants. The wing piv- the oting is accomplished by accelerating Reducing pontoon drag permits higher and produced a large power reduction the vehicle to at least 14 knots / 7 m/s (a takeoff speeds, which in turn permit despite the higher takeoff speed. fairly hard effort), and then suddenly in- smaller wings and higher maximum A further advantage of higher takeoff creasing the angle of attack of the entire speeds. speeds is that it permits optimizing the wing system via the left lever, which Higher takeoff speeds also have the propeller for higher maximum speeds. drives the vehicle upwards. When the important effect of reducing wave drag One useful feature of a racing-kayak hull upper large wing breaks the water sur- associated with the two-dimensional shape is that it retains its low-drag char- face, rubber cords pivot it together with wave train set up behind a lifting airfoil. acteristics when partially raised out of its mounting struts forward and up into a This is quite independent of the "inverse the water. This permits a very gradual streamlined receptacle. The sequence is ground effect" mechanism of the free and low-power transition to the foil- shown in figure 3. If the high power is surface which increases the induced drag borne mode, where the wings gradually sustained, the vehicle then rapidly accel- of a 3-D lifting wing. As described in lift the pontoons as the speed is in- erates on the remaining small wing to its Hoerner [4], the 2-D wave drag scales creased.