Since the website says this was invented over a century ago and to my
knowledge is not in widespread use, I'd be hesitant to believe the claims.
It sounds like this is related to cupped props where tips are cupped...that
is curved a bit but not to the ninety degrees of this approach...I knew somone
with a boat like my prior Matthews and the same engines who SWORE his new
cupped props were more efficient....so I had some reconditioned and cupping
added...just as I expected top RPM was reduced....so the guy who thought he was
"going faster" (more efficient) was REALLY just pushing his engines a bit harder
at cruise RPM (using more fuel for the same cruising RPM) ...going a bit
faster....and losing a bit of speed at rated(top) RPM, just what you'd
expect....but not what the engine manufacturer recommends.
This design may well be suitable for use in special applications....who
knows?? I'd be more willing to believe the claim for 10% to 20% slip reduction if
some TEST data were offered and some specific applications suggested.
If the claim IS true, then a smaller prop would be required. Another way to
think about this would be to say that if slip is reduced 10% to 20% and a given
prop modifed then some reduction in RPM is bound to occur....So sizing a prop
with this design may now become less reliable than traditional prop
sizing...already a bit of an art form...
For anyone seriously considering this, I'd e-mail a major prop manufacturer
first and ask what they say.
Cheers,
Rob Brueckner
1972 Hatteras Yachtfish
Since the website says this was invented over a century ago and to my
knowledge is not in widespread use, I'd be hesitant to believe the claims.
It sounds like this is related to cupped props where tips are cupped...that
is curved a bit but not to the ninety degrees of this approach...I knew somone
with a boat like my prior Matthews and the same engines who SWORE his new
cupped props were more efficient....so I had some reconditioned and cupping
added...just as I expected top RPM was reduced....so the guy who thought he was
"going faster" (more efficient) was REALLY just pushing his engines a bit harder
at cruise RPM (using more fuel for the same cruising RPM) ...going a bit
faster....and losing a bit of speed at rated(top) RPM, just what you'd
expect....but not what the engine manufacturer recommends.
This design may well be suitable for use in special applications....who
knows?? I'd be more willing to believe the claim for 10% to 20% slip reduction if
some TEST data were offered and some specific applications suggested.
If the claim IS true, then a smaller prop would be required. Another way to
think about this would be to say that if slip is reduced 10% to 20% and a given
prop modifed then some reduction in RPM is bound to occur....So sizing a prop
with this design may now become less reliable than traditional prop
sizing...already a bit of an art form...
For anyone seriously considering this, I'd e-mail a major prop manufacturer
first and ask what they say.
Cheers,
Rob Brueckner
1972 Hatteras Yachtfish
