Fixed vs folding prop - SailNet Community
 2Likes
Reply
 
LinkBack Thread Tools
post #1 of 21 Old 03-25-2012 Thread Starter
Member
 
Join Date: Mar 2012
Posts: 67
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 4
 
Fixed vs folding prop

Any guess as to the speed advantage of a 37' boat with a saildrive fixed vs folding prop. The fixed blades have a surface area of 35-38".(each blade is 7" x 3" +/-) What do you think, reaching 12 knots of wind... Fixed is 6.7knots on the polars.
Greyhound37 is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 21 Old 03-25-2012
Junior member, rest old
 
msmith10's Avatar
 
Join Date: Feb 2009
Location: Columbus Ohio
Posts: 497
Thanks: 3
Thanked 0 Times in 0 Posts
Rep Power: 7
 
Re: Fixed vs folding prop

Not a simple question and as far as I know there's no simple answer or formula. Folding prop will be faster, that's about all you can say. 2-blade, 3-blade? Wind speed?
At hull speed it won't make any difference. In light air it will. If you spend most of your time racing, you'll want the folder, but then again if you race a lot you probably have one already. If you race occasionally but have to motor 3 miles up a river against 4 knot current to get back home, you may just decide to eat the speed loss. If you'd prefer to motor than sail when the weather gets rough, go with the fixed blade.
If I recall, PHRF gives you 8 seconds per mile for a 2 blade folder over fixed, 12 seconds for a 3 blade. It will cost you more than that, otherwise every racer would have a fixed prop.
If I had the money for a saildrive, though, I'd definitely spring for a feathering prop (slightly more drag than folding but better performance).

Mark Smith
1977 C&C 30 Mk 1 hailing from Port Clinton, Ohio
msmith10 is offline  
Quote Quick Reply Share with Facebook
post #3 of 21 Old 03-25-2012
ASA and PSIA Instructor
 
Join Date: Apr 2000
Posts: 3,590
Thanks: 7
Thanked 25 Times in 25 Posts
Rep Power: 16
 
Re: Fixed vs folding prop

Half a knot.
msmith10 likes this.

Certified...in several regards...
sailingfool is offline  
Quote Quick Reply Share with Facebook
post #4 of 21 Old 03-25-2012
Junior member, rest old
 
msmith10's Avatar
 
Join Date: Feb 2009
Location: Columbus Ohio
Posts: 497
Thanks: 3
Thanked 0 Times in 0 Posts
Rep Power: 7
 
Re: Fixed vs folding prop

I was wrong. There is a simple answer, as good as any.

Mark Smith
1977 C&C 30 Mk 1 hailing from Port Clinton, Ohio
msmith10 is offline  
Quote Quick Reply Share with Facebook
post #5 of 21 Old 03-25-2012 Thread Starter
Member
 
Join Date: Mar 2012
Posts: 67
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 4
 
Re: Fixed vs folding prop

8 seconds per mile or .5 knot, either way that is plenty. I was trying to decide if i want to replace the fixed prop now and guess i better.
Greyhound37 is offline  
Quote Quick Reply Share with Facebook
post #6 of 21 Old 03-25-2012
Junior member, rest old
 
msmith10's Avatar
 
Join Date: Feb 2009
Location: Columbus Ohio
Posts: 497
Thanks: 3
Thanked 0 Times in 0 Posts
Rep Power: 7
 
Re: Fixed vs folding prop

After replacing my 2 blade fixed with a folder several years ago, I went from 2nd-3rd place finishes to consistent 1st-2nd place in our club races. The folder doesn't back well, and it doesn't drive well in a chop, but I'd rather sail with rough seas anyway. It was worth the sacrificed performance under motor.

Mark Smith
1977 C&C 30 Mk 1 hailing from Port Clinton, Ohio
msmith10 is offline  
Quote Quick Reply Share with Facebook
post #7 of 21 Old 03-25-2012 Thread Starter
Member
 
Join Date: Mar 2012
Posts: 67
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 4
 
Re: Fixed vs folding prop

Wow that is impressive. The Flexofold has cruising folding blades or racing using the same hub. I noticed that is the prop on several boats hauled near my boat Mumm 36, J-111
After spray applying VC offshore, would not be practical to be dragging a bucket under the boat. I hope to do 4 races this year but mostly cruise (as fast as i can go)
Thanks for the input!
Greyhound37 is offline  
Quote Quick Reply Share with Facebook
post #8 of 21 Old 03-25-2012
Just another Moderator
 
Faster's Avatar
 
Join Date: Sep 2005
Location: New Westminster, BC
Posts: 16,567
Thanks: 110
Thanked 320 Times in 305 Posts
Rep Power: 10
     
Re: Fixed vs folding prop

We recently switched from a 2 blade fixed to a 3 blade Max prop.. the difference is remarkable and percentage wise much higher in the light air 3-4 knot boatspeed range than the powered up 5-6+ knot range. We probably reach our optimum upwind speed now in 5 knots less wind than before, and can ghost along at 3-4 knots where 2-3 would have been it before.

The feathering props do away with the folders' reverse issues, and 3 blades is much less vibration under power too... but at a cost, of course ($$$)

Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
Faster is offline  
Quote Quick Reply Share with Facebook
post #9 of 21 Old 03-25-2012
Senior Member
 
Join Date: Jun 2004
Location: western LI sound, L.I., N.Y.
Posts: 512
Thanks: 1
Thanked 15 Times in 15 Posts
Rep Power: 12
 
Re: Fixed vs folding prop

Simple answer of 1/2 knot seems about my experience with my
Flex o Fold, but as stated above by Faster equal advantage is
sailing in light conditions.
Have cruising blades attached to saildrive very good forward speed
and no apologies for reverse, can and have stopped on a dime.
If you go flex-o-fold make sure you or your installer, properly
installs "tab washer" (simple but important).
Also I used red loctite on my install, I will have to heat things up to remove, but hopefully will not be telling any stories about the
time I lost my $1000+ prop in the middle of nowhere.
HUGOSALT is offline  
Quote Quick Reply Share with Facebook
post #10 of 21 Old 03-27-2012
Senior Member
 
blt2ski's Avatar
 
Join Date: May 2005
Posts: 6,884
Thanks: 0
Thanked 30 Times in 29 Posts
Rep Power: 12
   
Re: Fixed vs folding prop

If racing, the credit of 9 or 15 secs locally for a 2 vs a 3 blade prop is NOT any advantage, you lose more than that, and gain way more speed with a folding/fixed prop than the credit is worth. .5-.75 additional speed seems to be the norm in speed gain. As faster said, you hit X knots in less wind etc etc.

Marty

She drives me boat,
I drives me dinghy!
blt2ski is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Feathering Prop vs. Fixed Blade Prop Benevento Pacific Seacraft 70 02-11-2011 07:52 AM
folding to fixed prop Gulfislander Gear & Maintenance 8 08-03-2010 07:49 PM
Fixed vs Folding Prop doons60 Gear & Maintenance 11 07-29-2007 08:27 PM
Fixed vs. Folding Props: How Much Difference? SEMIJim General Discussion (sailing related) 16 07-15-2007 01:51 PM
Inboard fixed vs. folding prop & ratings mikehoyt Racing 6 06-06-2004 10:07 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

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

 
For the best viewing experience please update your browser to Google Chrome