Hi all - considering moving from my fixed three-blade prop on my 1989 C34 (M25XP) engine to a Flex-o-Fold. Any thoughts on two-blade versus three-blade and a pitch of 9 versus 10? The recommendation from the sales representative was either a two-blade with a 10 pitch or a three-blade with a 9 pitch. I need to question him further on why the pitch difference between 9 and 10.
I want to improve speed under sail, of course, but I don't want to compromise motoring performance. We cruise and as often as not we end up motoring or motor sailing to get across Lake Michigan before nightfall. The two-blade is significantly less expensive so if the difference between the two is marginal I would probably go with cost as the deciding factor.
Thanks for any input or experiences you wish to share.
I have no idea the difference is between the two and the three, but I have a three blade and it works really well. If I push my rpms I can motor right at hull speed (fairly flat water), reverse is fine (as usual way less efficient than in forward) with a modest amount of prop walk--just about the right amount of prop walk to be useful. I know that a standard two blade has way too much prop walk; I suspect that might be the difference between 2 or 3 blades.
I changed from a three blade fixed prop with 9 pitch to a three blade Flexofold
10 pitch. I love it (Engine M35B)
I cruise at 6.5-7 knots ad will get it up to 7.5 at times with a clean bottom.
The only difference is that I can not get full RPM because of the 10 pitch.
My full speed is about 2600 RPM without smoke. However this does give me the speed.
noted above. and a fuel consumption of +/- 0.8 GPH. (And definitely more sailing speed. .5 kn +)
It is absolutely great in reverse.
I am quite happy with the prop and the service from them when needed; a special zinc that I have not found available at other than Flexofold.
If you feel that you need full 3000 RPM then I would advise getting the 9 pitch.
.
Quote from: claygr on April 10, 2010, 08:05:49 AMThanks for any input or experiences you wish to share.
Clay,
I don't recall detailed discussion on your question in all the Flex prop topics. You might have already done a search on that topic, since there's been quite a lot of discussions about props other than what I lovingly think about as "that bucket I'm always dragging behind us!"
You might also want to add your "signature" so we know what boat, year and engine you have, in order to help you better in the future. See: http://c34.org/bbs/index.php/topic,1506.0.html (http://c34.org/bbs/index.php/topic,1506.0.html)
Thanks for the heads up, Stu. Think I've made the change. We'll see when this posts.
Clay,
I added a Flex-Fold last year. Went from a fixed 3 blade, both at 10 pitch. I've been very happy with it, picked up speed under both sail and power.
Ed
Clay,
Added a Flex-O-Fold 3 blade folder a couple years back and have been pleased with it. I selected the 10 inch pitch based upon FoF recommendation for the M25xp. Regarding 9 or 10 inch pitch you can see my results at the link below:
http://c34.org/bbs/index.php/topic,4298.msg25546.html#msg25546
Kurt
For what it's worth, I recall an artical in Catalina Mainsheet a few years ago describing the performance of the Kiwiprop feathering 3 blade. At that time it was significantly less expensive than every alternative I considered. I have now had it for 3 seasons and can verify what the article claimed-0.5 knot increase in sailing speed, fine motoring and powerful thrust in reverse. You might want to look at this before you buy.
Brian McPhillips
Put the flex o fold in about 4 - 5 years ago. Can't agree more with the posts here. Better sailing speed and the best benefit was less prop walk in reverse.
I checked and my current prop is a 15 x 10. It is interesting looking through some of these older posts the Flexofold used to recommend a 10 pitch for the M25XP engine and now is recommending a 9 pitch. Can anyone explain what difference the change in pitch would make other than requiring more RPMs to achieve the same forward velocity? Or am I worrying about something insignificant?
Thanks for your help. This is a decision I really would like to make just once.
Ed, did the Flex-o-Fold vendor recommend the 10 pitch to you? He seems to have done so for Kurt (and others in posts I have seen) so I am left to wonder why he is recommending a 9 inch pitch to me. Perhaps the prop blades were redesigned? I guess I need to have another conversation with him.
Speaking of props (sorry for high-jacking), my fixed 3 blade is a 15x9 with a big "10" stamped over the top. Do you think the pitch has been changed?
(http://images18.fotki.com/v458/photos/4/31944/8541848/IMG_0508-vi.jpg)
(http://images54.fotki.com/v514/photos/4/31944/8541848/IMG_0506-vi.jpg)
I am a relative newcomer to this whole prop thing, but I don't think you can change the pitch of a fixed prop. The pitch describes the angle of the blades to the boss of the prop. You can't change that angle on a fixed or folding prop. You can adjust the pitch on some feathering props. No idea why they would have stamped a new number over the old one.
I believe you can alter the pitch of a fixed prop slightly (not a lot). There are companies that do that as part of truing and balancing. Not sure if you can go a full inch but it seems likely.
Clay,
Yes, a fixed prop can be adjusted. Had my fixed altered from a 9 to a 10 at a prop shop, based on advice from the Forum. Your Flex supposedly can also be adjusted in the water if you find the 10 doesn't work for some reason. Course I don't know the degree of difficulty....
Ed
Clay,
Sorry, I didn't see your additional question above. The dealer said the spec was a 9 pitch, but that since I had a 10 on my fixed with no problem, he said we could go with 10. Also, as I noted above, he said it could always be adjusted in the water if for some reason the 10 was too much.
Ed
Thanks, Ed. I got much the same advice. I am going to go with a 15x 10 and hope it works. Switching out those blades in our cold Lake Michigan water does not sound too appealing!
Just installed a 2 blade flexofold prop and wanted to note some observations to the board, especially for those that are interested in folding props. I decided on the 2 blade flexofold because of cost/performance reasons - being that it was the lowest cost ($1000) while providing good performance under sail and power. My original prop was a 3 blade fixed pitched to 10". New prop is a 15x11x2 flexofold.
Now for the observations - reverse power = as good or better than 3 blade 15x10x3, prop walk = improved, forward = better, sail speed = better. I believe this prop is very well mated to the M25XP. I showed 6.4 knts GPS at 2500RPM which equates to about 75% power for my boat. Reverse showed less propwalk and is powerful, but takes a bit more throttle to get there. We sailed in light winds and made a consistent 3.7 knts in 5 knts true/7.3 apparent which is an improvement for us.
Now for the bad, slightly more vibration while motoring with this 2 blade vs. my previous 3 blade. Hopefully its not cavitation. I am going to align the shaft this weekend and see if that gives any improvement.
Overall great performance and easy install, the blades are very efficient for power and sail.
I have had a Flex o Fold 3 blade prop on my Mk 2 with M35B for 4 years. Originally purchased the 15 X 10, but found it overpropped. After much discussion with the Flex o Fold rep, I purchased the 9 pitch blades and switched them out. The original 10 blades could not be repitched to 9. Am happy with the 9 and would sell the 10 to any forum member interested.
Want to report on our first experiences with the Flexofold prop. We went with the three-blade, 10 inch pitch. The recommendation from the Flexofold representative was for the 9 inch pitch based on our engine (M25XP). However, based on the input from other owners on the site and the fact that our old prop was 10 pitch, we went for the 15 x 10.
Installation of the new prop was very easy. As promised by the sales representative, the hardest part was getting the old prop off. That required quite a bit of effort with a puller. Once the old prop was off, the new prop went on in about 20 minutes.
The performance under both power and sail is pretty amazing. Under power, we are at least a half knot faster in forward. We can get up to 3000 RPMs with no problem with black smoke or temperature issues. At top end, we're burying the stern in the water and reaching close to hull speed.
The performance in reverse is also very impressive. I can now back in a straight line in relatively low RPMs. I previously would only go sideways until I got a good bit of speed up. It has taken some adjustment, though, because I previously had to steer to starboard to reverse in a relatively straight line out of the slip and now that actually causes the boat to turn to starboard, a completely new phenomenom for me. Imagine that - the boat actually going where you steer in reverse.
It also has taken a bit of adjustment while docking. I previously could count on the drag of the prop to slow the boat in neutral. She just is not slowing the way she used to anymore. I've had to start using more reverse earlier on in so I don't scare the neighbors. Not a problem, just an adjustment.
The performance under sail is exceptional. We were hitting 7.2-7.4 on the GPS in 18 knots apparent from a beam reach. Never seen that before. The sound of water rushing by at the stern was very loud.
So, not to sound too much like a Flexofold salesman, I am very happy with this purchase. This is by far and away the best boat purchase I have made in terms of improving performance under way, and that includes the sails I have replaced and the asymmetrical spinnaker I purchased. Also, if you are interested in this, remember that Flexofold gives a "boat show" discount to C34IA members so that is yet another reason that the membership more than pays for itself.
I have one for many years. Love it but it will wear your Cutlass bearing out more frequenlty; probably because of the additional weight of the hub.
It also has taken a bit of adjustment while docking. I previously could count on the drag of the prop to slow the boat in neutral. She just is not slowing the way she used to anymore. I've had to start using more reverse earlier on in so I don't scare the neighbors. Not a problem, just an adjustment.
Dave, you can also slow by taking the engine out of gear. We coast into our slip from 300 yards out. Little or no reverse needed except for the final stop which uses port prop walk to bring the port side to the dock after a tricky 90 degree turn into the slip. OK, OK, sometimes the wind and current, both normally 90 degrees from the axis of the boat in the slip, can make things interesting. What a neat work: "interesting" 8)
I have had a Flx0fold for about 7 years. So far still with the original cutlass bearing.
What kind of life have you the jury had with that bearing? with a folding prop and with a std three blade?
Hi all,
I'm also going to replace my fixed 3-blade with a Flex-o-fold 3 blade. I replaced my fixed 3-blade with a 2-blade Flex-o-fold on my 1985 C30 and it was one of the best upgrades I ever made, both for sailing and performance under power.
There seems to have been a lot of discussion about the recommended pitch on the C34, with most folks opting for the 15x10 for the M25XP. Flex-o-fold recommends the 15x9 for the M35B (which we have), which to me is a little counterintuitive. Since the M35BC has 10hp more shouldn't it be able to handle a the higher pitch better? OTOH if running the engine at 3000 rpm vs 2600 rpm doesn't make that much difference on wear or fuel consumption, wouldn't the 9 be a better choice for low-speed control?
I know this is an old thread, but I'd certainly appreciate the group's opinions. Thanks.
I changed to a Max-prop. I call it the best sail change I ever made. First set it at 9.2 inches. It worked but felt a little under pitched. I changed it to 10.3 inches the next season (the next adjustment up). Works real well, but if I could would try 10.0.
Yes, slow speed is faster. Need to slip in and out of gear to go slower than 2 or 3 knots. Also, prop-walk is more with the higher pitch. It's not bad, just something you have to work with.
Hope this helps,
Jim
I went for a 15 x 10 and havae no problem with it . I can motor at 7 knots plus if the water is calm. I can not get higher RPM than 2800 however any more throtle just smokes. My fuel consumption averages about .6 -.7 GPH. Love the prop but be surf to change the prop mounted zinc regularly. I tink it is ideal for a 35 engine
Mick - The M35B requires less pitch because the gearbox has less reduction than the M25XP, therefore turns the shaft faster.
Craig
Craig, all
Yes that makes sense. I didnt even consider the different reductions.
I'm going with the 3-blade 15x9. Since I can make hull speed with either the 9 or 10 pitch the 9 makes more sense for my situation.
I'm reading this thread with reckless abandon... ok... let me rephrase that. I'm quite interested in getting a folding prop also. Can I point out that through this entire thread people seem to think that pitch is INCHES.
It's degrees right?? 15 x 10 prop is 15 INCHES in diameter by 10 DEGREES OF PITCH. Correct me if I'm wrong.
Dan and Dar
Pitch is in inches - It's the theoretical distance the prop would move in one rotation assuming no slip.
Just curious.... I've gotten so used to the reverse prop walk with the fixed blade prop that I almost consider it an asset when tight-space turning & maneuvering is required, as strange as that may sound. Does anyone with the folding prop miss or regret the loss of prop walk?
Mark, the flex o fold does have propwalk...very similar to 3 blade fixed, but with more control. This prop, unlike many other folding props, has a real bite on the water. The blades are heavy, have a lot of shape at the leading edge, and a thick chord. This helps give predictable propwalk...and also the ability to power up and get a bite in reverse for steerage if needed. It is actually quite a nice piece of hardware that improves every aspect of performance.
Ha! could be why they call them "screws" pitch on threads is in inches... Thanks for the education!