Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
posted to rec.boats.cruising
external usenet poster
 
First recorded activity by BoatBanter: Jul 2006
Posts: 125
Default Changing from 2 blade to 3 blade prop?


"C. S." wrote in message
...
As somebody else pointed out the answer to the "no vibation" may be
counter balance. There is about one meter of free shaft between the bottom
of the boat and the support in front of the prop. Maybe the shaft flexes
enough to counterbalance the missing blade? But why is there no power in
reverse?

C.S.

I can't think that's the answer.
If the shaft flexes from centrifugal force (and I would hope it wouldn't
flex much anyway), it would be pulled toward the single blade rather the
opposite direction which would be necessary to counterbalance. That's what
probably happens with my saildrive, which can move on the rubber motor
mounts, accentuating the shaking.
I would expect your shaft to be more rigidly secured than my saildrive, and
may not allow this.
I can't explain the difference in thrust.
Under sail, if your engine is in neutral, does the prop open up and spin ?


  #2   Report Post  
posted to rec.boats.cruising
external usenet poster
 
First recorded activity by BoatBanter: Oct 2006
Posts: 10
Default Changing from 2 blade to 3 blade prop?


"Garland Gray II" wrote in message
...

"C. S." wrote in message
...
As somebody else pointed out the answer to the "no vibation" may be
counter balance. There is about one meter of free shaft between the
bottom of the boat and the support in front of the prop. Maybe the shaft
flexes enough to counterbalance the missing blade? But why is there no
power in reverse?

C.S.

I can't think that's the answer.
If the shaft flexes from centrifugal force (and I would hope it wouldn't
flex much anyway), it would be pulled toward the single blade rather the
opposite direction which would be necessary to counterbalance.


Now I don't follow. I think the trust from the single blade would push the
shaft to the opposite side and thus generate a counterbalance effect.

That's what probably happens with my saildrive, which can move on the
rubber motor mounts, accentuating the shaking.
I would expect your shaft to be more rigidly secured than my saildrive,
and may not allow this.
I can't explain the difference in thrust.
Under sail, if your engine is in neutral, does the prop open up and spin ?


It does spin but not very fast so I don't know if it is open or closed or
somewhere inbetween.

C.S.




  #3   Report Post  
posted to rec.boats.cruising
external usenet poster
 
First recorded activity by BoatBanter: Jul 2006
Posts: 125
Default Changing from 2 blade to 3 blade prop?

Comments below.

"C. S." wrote in message
...

"Garland Gray II" wrote in message
...

"C. S." wrote in message
...
As somebody else pointed out the answer to the "no vibation" may be
counter balance. There is about one meter of free shaft between the
bottom of the boat and the support in front of the prop. Maybe the shaft
flexes enough to counterbalance the missing blade? But why is there no
power in reverse?

C.S.

I can't think that's the answer.
If the shaft flexes from centrifugal force (and I would hope it wouldn't
flex much anyway), it would be pulled toward the single blade rather the
opposite direction which would be necessary to counterbalance.


Now I don't follow. I think the trust from the single blade would push the
shaft to the opposite side and thus generate a counterbalance effect.


Actually, I was just considering the centrifugal force involved. Not sure
which way lopsided thrust would go.

That's what probably happens with my saildrive, which can move on the
rubber motor mounts, accentuating the shaking.
I would expect your shaft to be more rigidly secured than my saildrive,
and may not allow this.
I can't explain the difference in thrust.
Under sail, if your engine is in neutral, does the prop open up and spin
?


It does spin but not very fast so I don't know if it is open or closed or
somewhere inbetween.

What I was wondering here was whether your prop has a tendency to stay
folded unless "forward" rotation literally forces it open.. Under sail, my
prop immediately pops open and spins should the transmission accidently be
shifted to neutral. This doesn't necessarily explain why your prop worked in
reverse with both blades, but not with one, unless the remaining blade was
stiff with fouling and didn't have the other blade (geared together on mine)
to force it out.
I don't know. Very strange.

C.S.






Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Unlubberizing the Single Screw Inboard, Part II Chuck Gould General 10 October 13th 06 10:36 PM
A freewheeling explanation Roger Long Cruising 17 June 10th 05 01:39 PM
Changing Prop inwater. (lessons learned) Steve Cruising 3 May 2nd 05 12:08 AM
What are the pros and cons of a folding prop? MLapla4120 Cruising 140 September 9th 04 02:03 AM
Removing lower unit from 40 hp Johnson outboard - Help? Brian Silver General 9 September 29th 03 06:17 PM


All times are GMT +1. The time now is 06:14 PM.

Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004-2025 BoatBanter.com.
The comments are property of their posters.
 

About Us

"It's about Boats"

 

Copyright © 2017