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Tom Speer's Home PageWelcome to my homepage. Here you'll find information on aerodynamics, landyacht and multihull sailboat design, and hydrofoils. Nearly everthing is theoretical, for the simple reason that I can't afford the testing to get experimental data. Where possible, I've validated these calculations against published results, but if anyone has any relevant experimental data, I'd love to see them. New: A-Class Catamaran Boards presentation from
The Foiling Week Everthing on this site is for educational
purposes only. I make no warranty as to the suitability or accuracy of these
results or tools for any specific purpose. Commercial use forbidden without
express permission of the author. |
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Optimum Planforms |
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Optimum planforms for sail rigs and hydrofoils having a single, planar
lifting surface. |
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Airfoils |
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Wingmasts |
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The basic aerodynamic features of two-dimensional sections that consist of
a symmetrical airfoil with a thin sail extending from the trailing edge. A
simple method for designing wingmast shapes is presented, which does not
require a computer to produce masts with good aerodynamic performance. The
effects of various mast sizes are explored, and the effects of both under-
and over-rotation of the mast compared to the design condition. |
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Rigid Wing Sail Rigs |
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Rigid wing rigs take the wingmast a step farther, and elimiate the sail entirely. A single, symmetrical airfoil does not produce high lift and as a result the acceleration of a yacht so equipped is very poor. So rigid wing rigs typically have two or more symmetrical airfoils hinged so that they form a slotted flap when deflected. This produces more lift than the wingmast/sail combination. The main wing element of these airfoils was designed to a similar
aerodynamic philosophy as the wingmast sections - providing for a smooth
forward movement of the transition point as angle of attack increases, so as
to have robust characteristics at low Reynolds numbers. The NACA 0012
provides a good section for the flap because of its front loading, which
allows the whole flap to be used for the airfoil's pressure recovery. Any
tendency of the flap to form a leading edge pressure peak can be suppressed
by adjusting the slot gap. |
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External Flap Airfoils Theory vs NACA data for NACA 23012 |
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External flaps are separate airfoils that are positioned near the trailing edge of the main wing. They are were used on the Junkers trimotor and several ultralight aircraft. External flaps can provide high lift with low drag and give the designer lots of flexibility. The NACA tested the 23012 airfoil with a 23012 airfoil as a 20% chord
flap, and the data are compared here with the computational method. The
GA30-612 with a GA37-315 flap is used on some popular ultralights, and the
theoretical data presented gives some insight in to how the combination
works. The C506F is my own design, made for a designer working on an
all-metal ultralight. The the key requirements were very high lift, ease of
manufacture, and good handling qualities. |
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Hydrofoils |
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Presentation at The Foiling Week on A-Class Catamaran boards.
See Day 2 streaming video to watch the presentation. |
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Design of three families of sections for shunting proas. These sections have fore-aft symmetry and rounded edges. Complete coordinates and XFOIL computed data are presented. |
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Design approaches and typical results for hydrofoils which must operate at
low Reynolds numbers (small chord lengths and low speeds), as well as avoid
cavitation at high speed. |
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Chapter 1 Cavitation Inception on Foils, Struts and Pods Chapter 2 Choice of Foil System for Optimal Performance Chapter 3 Ventilation Inception of Surface Piercing and Submerged Foils and Struts Chapter 4 Trim, Altitude and Pre-Takeoff Resistance of Hydrofoil Craft |
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Hydrodynamics of Hydrofoil Craft Technical Report 463-1 This is the most comprehensive reference on hydrofoil design I've found. It presents the engineering relationships and typical results for all aspects of hydrofoil design, covering both fully submerged and surface piercing foils. These PDF files are no longer available online. They can be found on the AMV CD-ROM #1 from the
International Hydrofoil Society. |
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A simple analysis of hydrofoil performance and comparison with test data. Included are comparisons with Alexander Graham Bell's HD-4 full scale test data and Hanno Smits' tow tank data. The approximate analysis is also applied to fully submerged T foils and surface-piercing V foils and ladder foils. The lessons learned are: I am deeply indebted to Hanno Smits and to the Bell estate for their
generous permission to use their data in my analysis. |
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Design Tools |
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An executable MathCad model of a landyacht performance with a rigid wing
rig. (requires MathCad) |
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An Excel spreadsheet which can compute optimal planforms for wings, cat
rig sails, and single hydrofoils. Will also compute the lift and induced drag
for arbitrary planforms, including ground or free surface effects. |
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Landyachts |
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Landyacht testbed build by Landyacht Design Interchange Association (LYDIA). (Apologies for the large size of this file!) This was a proof-of-concept vehicle used to try out new ideas in landyacht design and to investigate technical issues associated with the twin wing landyacht concept. The yacht was sailed with both direct mechanical control of the wing and with the wing free to pivot, controlled only by an aerodynamic surface on a tail boom. The aerodynamic control was found to be effective for an aft tail but was
not workable when configurred as a canard. The partial span flap was
effective in providing aerodynamic twist for high winds, but caused excessive
drag due to the abrupt change in span loading which increased induced drag
and caused stalling of the wing immediately above the flap. |
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Wind tunnel test data and performance prediction of the landyacht built by
LYDIA. The tests were performed by Matt Brown, Daphne Marschalk and Ricardo
Camerena at San Diego State University under the direction of Dr. Joseph
Katz. Model components were supplied by LYDIA. The surprising discovery from
this test was the high drag created by the wheels - 30% to 40% of the total aerodynamic
drag was created by the rear wheels alone. Also investigated was the effect
of sealing the gap between wing and body which significantly improved the
performance. |
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HTML version of a landyacht performance model. Not executable, but shows
all the derivation and sample results. |
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Predicted performance for a notional landyacht powered by a rigid wing.
The results are realistic, however reliable data for an actual design are not
available to completely prove out the method. |
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A parametric study of the effects of wing planform on the efficiency and
heeling moment of an isolated wing as would be used as the sail rig for a
landyacht. The study is only concerned with lift and induced drag - airfoil
parasite drag is not included. Interference with the ground is accounted for,
but interference effects of the body are not included. |
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The origin and rationale for a landyacht which is powered by two rigid
wings mounted in an "A" frame arrangement. Results include
renderings of the concept and initial feasibility studies. Compared with a
conventional landyacht, light air performance is degraded, but higher speeds
in high winds are indicated. The twin wing concept has completely different
load paths, which may result in a lighter structure. |
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A parametric study of the effects of wing planform on the efficiency and
heeling moment of two isolated wings as would be used as the sail rig for a
landyacht. This is a companion study to the single wing parametric study
above, and the effects of the twin wing configuration are compared with the
corresponding single wing configuration. |
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Basiliscus |
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Cruising Trimaran Design Case Study |
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This area has been moved to its own website at www.basiliscus.com |
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Comments and questions? Contact me@tspeer.com |
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