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| The building
of Human Powered Boats is still an art form rather than a science.
As such many things are tried in the name of building a more
efficient human powered machine. Most of these things don't work
too well. On the
IHPVA HPB list, these things are discussed length. Victor
Garza noted that it may be a good idea to list the stuff that
works and doesn't work, as the same questions come up like
clockwork every year or so. |
| Hulls |
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| Keels |
Weight required to keep boat
upright is too high for most HPB use. No clear advantage. |
| Planing hulls |
Humans do not possess enough
power to achieve planing speeds |
| Bidarkas |
Currently untested in HPB
application. May be problem in shallows and weeds. |
| Tilting/pivoting drivetrains |
Works well to allow weed
cleaning and shallow water ingress/egress. Increases
complexity and weight. |
| Hydrofoil wings |
Work well and fast for short distances,
riders cannot sustain flight for extended periods and at
that time they are a liability. |
| Submerged Floatation |
Not practical - very hard to
control floatation/balance. |
| Subsurface bulb bows |
Offers 5 - 25% reduction in energy for larger vessels-
not often exploited with HPBs. |
| Catamaran hulls |
Much more stable than a monohull but will have higher
wetted surface giving it more viscous drag compared with a monohull
of the same displacement. |
| Propulsion
/ Drivetrain |
|
| Air Propellers |
Work well for shallow water
but are easily affected by wind and are bulky |
| Jet propulsion / squid drive |
No, losses too high.
Efficiency probably less than 50%. May be acceptable in a
very shallow water application. |
| Surface piercing props |
Not practical |
| Paddlewheels |
Ok for some applications, but noisy and splashy |
| Variable pitch props |
Yes, if light, efficient and controllable on the fly |
| Folding props |
Yes, if light and efficient |
| Inboard power generation
Converted to electric thrust |
Yes, if conversion is high efficiency,
and a mechanical means of power transfer is difficult. Used
in some subs. |
| Anticavitation plates |
Useful for shallow props
directly behind struts. Efficiency may suffer in other
applications. |
| Weed shedding props |
Maybe in some applications where efficiency losses
tolerable |
| Weed cutting mechanisms for
props |
Good luck has not been had with these, they jam |
| Kort nozzles |
Maybe for perfectly clear, non weedy water |
Right angle gearboxes
|
Light industrial right angle drives are
suitable for HPB drives. There are a wide range of suppliers-
Mitrpak, Zero-Max, Siti, TEA Transmissions. Low cost right angle drill drives have
limited use due to lack of stiffness in the housing. |
| Flexible prop shafts |
It is possible to make curved shafts
from flexible materials. Fatigue life will be a consideration if the
stress range exceeds 40% of yield strength. Torsional rigidity is
important for smooth power transmission. |
| Clipless pedals |
Make pedaling less tiring in the recumbent position. Need to make sure that feet can be twisted
at any point for safety if capsized |
| Flywheels |
Not found to offer any benefit that offsets
the added weight |
| Oscillation foil drive system |
Can be made efficient at cruising
speed for displacement craft. Hobie Mirage is a commercial example. |
| Misc |
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| Engine (human) |
An elite male athlete can generate up to 20W/
kg of body weight for a few seconds. Continuous output for an elite
athlete is around 6W/kg. The corresponding figures for an untrained
but fit person is 12W/kg peak and 2.5W/kg continuous. |
| GPS |
These can be used to give instantaneous speed
and most have the facility to download the track log for performance
monitoring on a trip. |
| Windscreen & fairing |
Useful for wave protection but
HPBs are too slow for a performance improvement. Used on Escapade but not very many others. |
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