Propeller drag - myrh or what?

[Sailfree]

A few years ago I was sent a table from a german sailing magazine with actual results recorded. If I find it on my other computer I will post it.

Basically folding and feathering props do give significant improvements when sailing.

Unfortunately people make such unrealistic claims wrt when under way with power of folding/feathering propellors compared to fixed props that it makes all their claims questionable.

I reckon about between 0.5 to 1kts improvement sailing but if fixed prop is correctly sized speed under power will alway be slightly less.

 

[guydickinson]

Thanks, Sailfree, that table would be very interesting!! Will you post it in this thread?

 

[jfm]

[ QUOTE ]
That answers the in gear/out of gear debate.

[/ QUOTE ]

Yes, but only for that particular speed/yacht/propellor combo. It doesn't answer it generically. Even the same yacht and prop will have different answers to the in/out gear question, at different speeds through the water

 

[sailorman]

http://www.helensburghsailingclub.co.uk/dinghyresults/2007_PY_List.pdf


5 LISTED CONFIGURATIONS AND ALLOWANCES
5.1 Listed engine/propeller configurations are identified as follows:
Inboard with feathering/folding propeller IBF
Inboard with fixed two-blade propeller IB2
Inboard with fixed three-blade propeller IB3
Any arrangement that allows the propeller to
be removed from the water, or no engine OB
5.2 Recommended trial allowances for different engine/propeller
configurations are as follows:
from to
OB IBF IB2 IB3
OB 0 +1% +2% +4%
IBF -1% 0 +1% +3%
IB2 -2% -1% 0 +2%
IB3 -4% -3% -2% 0

 

[PeteMcK]

Re Drag:- Fixed v. Folding (or feathering); locked v. freewheeling.

See
http://strathprints.strath.ac.uk/5670/
or full research paper at
http://strathprints.strath.ac.uk/5670/1/strathprints005670.pdf

 

[sailorman]

Sent email PM Re Quetzal