Folding Prop Verdict

[Georgedoyle]

After a Summer and Fall with our new Gori folding prop we feel like we can make some judgements about its impact. First of all there were some advantages that we expected:
1) The prop works great in reverse. No more prop walk to starboard. It tracks straight and is very predictable.
2) The overdrive feature is not a gimmick. It allows us to go faster at a lower RPM in typical Southern California conditions.
3) Our sailing performance has improved. We are definitely faster in all wind conditions.
4) We are able to sail in light wind conditions. The boat now carries speed through lulls and accelerates nicely when sailing in the 2-4 knot boat speed range with the wind blowing between 4 and 6 knots.

Now here are some unexpected advantages:
1) Our helm is now noticeably lighter. The boat steers itself in up to 10 knots of wind. It is an amazing feeling to let go of the wheel and watch as the boat sticks in its groove. I was not expecting this. Previously, it was a constant wresting match with the helm. I guess the fixed three blade really messed up the boat's balance.
2) the boat heels a lot less. When the wind powers up the sails, we get a little bit of heel and then the boat takes off. This is really noticeable in puffs. Before we changed props, we had to be quick to ease the sheets to avoid excess heel. This problem was partly solved with new sails, but the new prop has made sailing in gusty conditions even more comfortable. I didn’t even consider this when getting the new prop.
3) I knew that the prop wouldn't spin when sailing anymore, but I underestimated how much of an impact the lack of prop noise would have. The total silence down below is awesome.

Any one of these advantages would be reason enough to buy a folding/feathering prop. Taken together, it's really a no-brainer. For me the change in helm feel is probably the biggest surprise. I used to depend on the auto pilot most of the time because the boat just wasn't fun to steer, especially in light conditions. Now I prefer manual steering. The helm is very responsive, and the boat easily finds a groove and stays in it. All of this must be from the change in props. Nothing else on the boat has been changed.

 

[sail sfbay]

No advantage for my sailboat in the San Francisco Bay.........so I have a 3 blade fixed propeller.

 

[Ralph Johnstone]

2) The overdrive feature is not a gimmick. It allows us to go faster at a lower RPM in typical Southern California conditions.

I would carefully look at you engine manual's numbers on this one. You may well be getting into a lugging condition. You must be able to achieve maximum engine RPM with this new prop. Heavy torque at low engine speeds is unhealthy for a diesel.

 

[Davidasailor26]

I had a similar pleasant surprise when we switched to a flex-o-fold. With our old fixed prop the rudder would stall pretty easily as wind speed increased. With the folding prop the turbulence in front of the rudder is much less and we can sail in winds about 5 knots higher with the same sail configuration without rounding up.

 

[artboas]

After a Summer and Fall with our new Gori folding prop we feel like we can make some judgements about its impact. First of all there were some advantages that we expected:
1) The prop works great in reverse. No more prop walk to starboard. It tracks straight and is very predictable.
2) The overdrive feature is not a gimmick. It allows us to go faster at a lower RPM in typical Southern California conditions.
3) Our sailing performance has improved. We are definitely faster in all wind conditions.
4) We are able to sail in light wind conditions. The boat now carries speed through lulls and accelerates nicely when sailing in the 2-4 knot boat speed range with the wind blowing between 4 and 6 knots.

Now here are some unexpected advantages:
1) Our helm is now noticeably lighter. The boat steers itself in up to 10 knots of wind. It is an amazing feeling to let go of the wheel and watch as the boat sticks in its groove. I was not expecting this. Previously, it was a constant wresting match with the helm. I guess the fixed three blade really messed up the boat's balance.
2) the boat heels a lot less. When the wind powers up the sails, we get a little bit of heel and then the boat takes off. This is really noticeable in puffs. Before we changed props, we had to be quick to ease the sheets to avoid excess heel. This problem was partly solved with new sails, but the new prop has made sailing in gusty conditions even more comfortable. I didn’t even consider this when getting the new prop.
3) I knew that the prop wouldn't spin when sailing anymore, but I underestimated how much of an impact the lack of prop noise would have. The total silence down below is awesome.

Any one of these advantages would be reason enough to buy a folding/feathering prop. Taken together, it's really a no-brainer. For me the change in helm feel is probably the biggest surprise. I used to depend on the auto pilot most of the time because the boat just wasn't fun to steer, especially in light conditions. Now I prefer manual steering. The helm is very responsive, and the boat easily finds a groove and stays in it. All of this must be from the change in props. Nothing else on the boat has been changed.

Be careful of marine growth on this prop. It can affect the overdrive function . There are many posts on this.

 

[SEMPERAVANTI41]

I think it would have been great if you had taken down actual empirical data such as wind speed, speed thru the water, heel angle, etc. with the fixed prop under varying sailing conditions, so the data could be scientifically compared.
Why on the Gori website is no data given for a test on a Discovery 57 for improved performance under sail? The only result is stated as, "3 blade Gori has less drag (Sailing)". I for one would certainly want the advantages of the folding prop clearly noted for prospective buyers.

 

[Davidasailor26]

I think it would have been great if you had taken down actual empirical data such as wind speed, speed thru the water, heel angle, etc. with the fixed prop under varying sailing conditions, so the data could be scientifically compared.
Why on the Gori website is no data given for a test on a Discovery 57 for improved performance under sail? The only result is stated as, "3 blade Gori has less drag (Sailing)". I for one would certainly want the advantages of the folding prop clearly noted for prospective buyers.

I’ve done that with my Flex-O-Fold.

Blue dots are boatspeed vs wind speed with the Flex-o-fold. Orange dots are the original 3 blade fixed prop. At low wind speed the folding prop is almost a knot faster. They converge as the wind builds, then the folding prop pulls ahead again as the wind builds and the fixed prop was causing the rudder stalls.

 

[Georgedoyle]

We tried to take data under power before installing the new prop, but even on smooth water in the bay, it was really hard to get consistent readings. I guess the current, state of the tide, and even light headwinds affected our speed. I don't think I could possibly recreate the same conditions to test the prop on a separate day. It would be even more difficult under sail. We concluded that the overdrive feature works because we were able to test it on one tack in the exact same conditions back to back with the regular prop setting. We also used it on several trips to Catalina and were able to maintain target speed at a 400 rpm reduction. The steering characteristics were easy to prove. Before we changed the prop, the boat would quickly round up when the wheel was released. Now, it just keeps on sailing with only occasional steering input. Hat is definitely less fatiguing and more fun.

 

[Paul Mermelstein]

I've had the 3 blade Gori for about 10 years. I agree with the subjective findings that George posted. I don't have any real complaints. You have to keep off the marine growth, but nothing more arduous than the typical things we do anyway such as a diver several times a season and a good cleaning during haul out. I did have to replace the rubber bumpers after about 9 years.

I also find that the overdrive works as "advertised". I can rev about 20% lower for the same boat speed but I don't abuse it. I use it only about 60% of the time and usually for longer motoring trips. I have not found any overtly negative impacts on the engine like excessive carbon buildup, smoke, or whatever.

 

[SEMPERAVANTI41]

I’ve done that with my Flex-O-Fold.
View attachment 210851

Blue dots are boatspeed vs wind speed with the Flex-o-fold. Orange dots are the original 3 blade fixed prop. At low wind speed the folding prop is almost a knot faster. They converge as the wind builds, then the folding prop pulls ahead again as the wind builds and the fixed prop was causing the rudder stalls.

David, was the prop free to turn or locked when the test was done?

 

[Davidasailor26]

David, was the prop free to turn or locked when the test was done?

The fixed prop was always left in neutral as Yanmar recommends. With the folding prop we shift into reverse briefly after shutting down to fold the prop, then back into neutral.