Folding Versus Feathering Props

[jeremiason]

Originally Posted by micah719

Feathering includes variable pitch, or no?

We were fortune enough that my wife quit the corporate world worked in a boatyard five years before we left... With her discount, we purchased th Max Prop VP, which allows you to change the pitch in water by turn a ring just forward of the blades.

We had a fix three blade 21" prop for two years before we converted to the Max Prop Feathering Prop four years ago.

We gained almost a knot of sailing speed with the feathering prop. We noticed no additional fuel consuption and the prop walk remained the same.

I believe folding/feathering props are like anchors, everyone has there favorite and each prop has its pluses and minuses.

I have driven other boats with with folding props, which work well in reducing drag, but in my opinion in general suck in reverse. Some people can live with that, but not me.

The other thing I would recommend against is the Gori Folding Prop with overdrive, unless you are the only one ever driving your boat.

This is because you have to shift from forward to reverse to forward again to step into the overdrive mode. I know two boats that had to replace transmissions due to overzelous shifting.

With that said, when properly used the Gori Prop does as advertised and gives you more speed at lower RPMs.

Again it is all a matter of choice and I believe in my situation the Max Prop is the best.

[carstenb]

Thanks everyone. I do need to do something with this prop. I can handle the prop walk and generally I can use it ot my advantage. But the lack of good reverse is a serious issue to me. While we cruise a lot and do anchor, we also enter marina a lot. Her in Denmark, they are overcrowded during the summer and frequently space is very tight. With a 20+ knot wind blowing, no reverse (or very inefficient reverse) means trouble. So far I've been able to avoid it, but sooner or later, I'll end up smacking into something.

I anyone else has ideas/personal experience I'd like to hear it.

[Curmudgeon]

Well, I have a Luke feathering prop and like it. It has slightly more drag under sail than a Max Prop, but is better under power, including reverse. It's also considerably less expensive than a Max Prop.

I had a Max prop on my prior boat and liked it. But overall it wasn't any better than the Luke.

[barnakiel]

I used all sorts of folding and feathering things too and I liked most. My own boat has a fixed 3-blader and if I run into a deal on a feathering prop I will probably go for it.

Older 'primitivier' folding props were pretty horrible (vs. fixed ones) but the newer designs are way better.

My friends' boat had a Brunton and they went neatly into a marina dock (the prop did not engage properly in reverse (such things happen to all folding/feathering designs, especially if there are any floating plastic bags, etc.. where you sail). But it is a nice design and now it has some competition from the other thing (eco-prop eco-drive? whatever) too!

I say if your folding prop p(....)s you off, get a nice feathering thing and you may be very happy with it.

b.

[siroismi]

Had a Max Prop on my previous boat.

Replaced the original fixed blade on this one by Autoprop, but had vibration issues at around 2700 rpm and above from new. I could not solve (and distributor of not much help) after making sure alignement, cutless, engine mount checked by mechanic. Finaly replaced with Variprop and very please. Have 4 seasons and about 8000 Miles with it and very please so far. I feel its better design and built than the Max prop I had before on my previous boat.

Cheers,
Michel

[Bash]

There's a world of difference between how a two-blade folder works in reverse compared to a three-blade folder, especially if you compare a geared folder to the racing props that just work off centrifugal force. I have a three blade flex-o-fold, and it works great in reverse. Used the same type of prop on my previous boat, and was impressed enough with the results that I didn't even consider switching to a different prop for the present boat.

[Ex-Calif]

Depends on the type of folding prop.

We changed from the stock volvo folding prop to a maxprop feathering unit. Second best thing we ever did to the boat. (the first was Autopilot)

We went from 3.5 kts forward, weak stopping and 1 kt in reverse to 5.5kts forward and too scared to floor it in reverse. Stops on a dime.

Our folding prop used centrifugal force and weak blade angle for reverse. More rpm tended to fold the prop due to hydro effects, low rpm gave weak thrust. It took time to build the reverse speed.

[capngeo]

Once you go Max, you never go Bax!

[CarinaPDX]

A slightly incorrect statement on the first page: it is not true that ALL feathering props have flat blades and are inefficient under power as a result. The Luke has blades with the appropriate helical shape as found on fixed props. The result is slightly more drag under sail (but still a lot less than a fixed prop) and improved performance under power. This is a very simple, old feathering design from pre-WWII. The stops are machined into the casting, not adjustable, with no cushions. It is very robust and reliable. Propellers

Even among the other, flat-bladed, feathering props there are significant differences in performance (speed and efficiency). Search around on the internet for comparisons.

The Autoprop sounds fantastic on paper. Some people report fantastic results. Others, including friends of mine, had poor results. The problem is that the prop needs to match the boat/engine; if the prop received is not correct then performance suffers. In the past at least it was not possible to return the prop for a different size at no or little cost. So the manufacturer makes their best recommendation, but if it is wrong the burden falls on the customer. I hope this has changed since then. Check first.

Greg

[Nicholson58]

Originally Posted by Jim Cate

This has been discussed before at length, but please be aware that feathering props are inherently LESS efficient than either fixed or folding props of good design. This is due to the blades of feathering props being flat (ie not having any twist) so that they will work in both forward and reverse. This is true for ALL feathering props.

The result of the efficiency loss is it takes more horsepower (and hence more fuel) to generate a given amount of thrust.

Personal data: changed from a Martec Elliptic two blade folder to an Autostream three blade feathering prop. While the feathering prop generated lots more thrust in reverse, our overall fuel consumption rose by about 25% due the the flat blades. We were not happy with this, and so chose a Flexofold 3 blade for our new boat. This prop performs well in both directions, albeit without the static thrust in reverse of a feathering prop.

Cheers,

Jim

Perhaps true for most. My Hundested is 3-blade 24 inch feathering with a hand crank adjustment at the binacle. Blades rotate 90 degrees from zero thrust to in line with the boat long center (stalls the engine) Blades are nicely curved for forward. Forward/Reverse is through the twin disk transmission 2:1 reduction. It gives great thrust at low speed and can be tuned according to wave & wind conditions against the rpm and temperature to optimize output. We get about 4 mpg at 7-8 knots. 55000 displacement, 115 HP. Hundested Propeller A/S: Home

[CarinaPDX]

That's really a controllable pitch propeller, as opposed to a self-feathering prop.

My Saab had a controllable pitch prop - I loved it. Last I looked they still made them, mostly for fishing boats. And yes, the blades were curved.

Greg

[Windseeker]

I'm really ready to pull the trigger on something. I'm looking hard at the Autostream. It has flat blades I like the all stainless and appears to be beefy. Best part about this prop is I haven't read any complaints! AB-Marine suggested the variprofile. This is the same people (SPW) that make the Variprop. It's touted as being some fancy airplane wing profile and really low drag. It comes from Germany. I've always been impressed with the way Germans design and build mechanical things. I just hate to be the first kid on the block with a new toy field testing a new product. For this kind of money, I want tried and true. Set it and forget it.

I've never heard of the Luke product. It sounds interesting. I don't race. Anything will be an improvement on drag over a fixed. I was concerned about giving up some of my forward thrust in a headwind by going with a flat blade feathering. The Luke could be a compromise. Any other feedback on the Luke Product?

[malbert73]

Originally Posted by Windseeker

I'm really ready to pull the trigger on something. I'm looking hard at the Autostream. It has flat blades I like the all stainless and appears to be beefy. Best part about this prop is I haven't read any complaints! AB-Marine suggested the variprofile. This is the same people (SPW) that make the Variprop. It's touted as being some fancy airplane wing profile and really low drag. It comes from Germany. I've always been impressed with the way Germans design and build mechanical things. I just hate to be the first kid on the block with a new toy field testing a new product. For this kind of money, I want tried and true. Set it and forget it.

I've never heard of the Luke product. It sounds interesting. I don't race. Anything will be an improvement on drag over a fixed. I was concerned about giving up some of my forward thrust in a headwind by going with a flat blade feathering. The Luke could be a compromise. Any other feedback on the Luke Product?

I was able to score a used/new variprop 4 blade prop this winter, and was able to enlarge my aperture for it. Will be launching in 1-2 weeks so we'll see. What I have heard is that going up to 4 blades makes up for loss of curved blades. As far as I know variprop is only one with that feature. A beautiful piece of engineering, which I would admittedly not spent the money for if not much cheaper than new.

[Sabbatical II]

I have the Autostream 22" prop fitted as an option instead of the standard fixed 18". (Engine was upgraded to 75 hp from the standard 54 hp). I am very happy with the thrust in reverse although it does have significant prop walk in that I can only really reverse to port out of my slip. Since this was fitted when I took delivery of the boat I can't compare it to the standard fixed prop. As I have no bowthruster, in a significant cross wind, I can't dawdle when entering the slip, so the effective reverse is needed to wash off excessive speed.

[delmarrey]

If anyone's interested I have a fairly new (200 hours) Slipstream SS geared folding prop for sale, for a 1" shaft. It's 17.5" OD X 12" RH pitch. I'll sell it for half the cost of a new one @ $1000. It's also been balanced and hard to tell that it's ever been used. I went to a larger shaft and it will not fit anymore, of course.

And yes, it's in the classifieds.