Are folding props less efficient than a standard prop. eg for speed, fuel efficiency etc
short answer yes but gains under sail well make up for it if you go feathering similar performance under motor ahead improved performance astern with still good under sail
gains under sail about 5 % and 5 degrees of height as you are sailing faster you also get more lift
Well, yes and yes, but...
Perhaps, first l must point out that l am writing about cruising boats, my reflections got nothing to do with racing craft or cats of any sort.
If one is sailing on a sea-cow where sails are almost just for decor the difference could be less indeed, compared to a yare boat where sailing performance is more important than speed and performance under engine power.
I remember sailing on a friends boat, a sea-cow, with full keel and keel-hung rudder, which was impossible to drive into a pen against the prop walk with a folding prop. After changing the prop, the three blade solid prop was able to do the job, just, but still, not against current or wind. It had to be driven into the pen from the opposite side using the boat's characteristics to one's advantage. The boat's sailing performance was not much to write home about but stronger the wind blew the old tub came more and more to life. Please, do not miss my point, l am not bagging boats with hulls like a dutch herringbuss, just trying to make the differences obvious.
On my Adams 28 which is a yare boat with fin keel and transom hung rudder with skeg, the twin folding prop does the job amicably all the time, every time.
As the prop walk is minimal and the skeg and rudder combination helps the twin Gori prop perform very well.
The difference between folded and open prop was approx. .2-.3 knots on calm waters in 12 knots wind. The clean hull also helped the performance.
On the other hand, the R27 which we sail the shoal draught keel and solid three blade prop works just fine in marinas considering a slight prop walk. The vessels age and sailing performance does not warrant a prop change. It would do marginally better with a three blade folding Gori or such, but the costs would not be acceptable.
It is sailing l am writing about and so, l am not considering fuel consumption at all. As l usually sail off and on to my mooring and l start the engine just as a back-up fuel consumption is negigable and not in the picture. It would be around 1,2L/hour for the 7.8Kw twin cylinder Vetus.
The verdict is open, the jury is still considering, however, if only the best would do, in my opinion, the least desirable is the solid two or three blade option while the three blade folding option is the most versatile available for a cruiser.
This was a great article until they hid it behind a subscribe-wall ...
www.yachtingmonthly.com/gear/folding-and-feathering-propeller-test-29807
As I recall, a folding or feathering prop will give you about half a knot for a 30ft boat. Some props are better than others. There is more to go wrong with feathering or folding props, but modern designs are improving reliability.
I fitted a 2-blade geared Brunton folding propeller on the advice of the fitter. It does the job nicely, which is mainly to get the boat in and out of the marina. The boat came with an old style flapping-folding prop that had got out of balance and was shaking the transom to pieces.
My S&S34 had a 15" by 10" Gori two bladed folding. I would swear by it for all round performance.
however that prop replaced a 15" by 9". It is critical to get the right prop for your engine and boat. Porters in Parramatta were invaluable in getting it right for Morning Bird.
Recently installed a slipstream 3 blade feathering prop and did a quick speed test this morning after dropping in the water with a clean bum. Wanted to make sure the pitch were correctly setup. Results were (flat water):
2000rpm = boat speed 7knts
Flat out 2600rpm boat speed 8knts
Does'nt appear to have lost any performance from the fixed blade.
The sailing performance appears to have added 0.5 to 1 knot boat speed, but still working this out.
Ilenart
Bit of a vague question. Are folding props less efficient, when motoring,maybe. Fuel efficiency is questionable depending on the prop, boat and setup.
Getting the right diameter and pitch for the boat and engine is the most important thing.
A clean bottom will make a huge difference. No point having a folding prop if you have a dirty bottom.
Gori props with the overdrive can be amazing when on the right boat or not so special on the wrong boat. We looked at getting one years ago and they said dont waste your money. The overdrive function won't work on a heavy full keel. We are never going to do 8-9 knots under motor. On a modern light boat the difference is huge.
Folding props are less efficient when motoring. Especially when they have some shell on the blades. Takes very little to effect the performance. But once you have had a folder it would be hard to go back to a fixed blade propeller. It all depends whether you have a motor sailer or a yacht.
I have heard people say the Gori is more fuel efficient than a fixed blade. On a modern fast hull it works.
We have a Bruntons 2 blade folding and a Bruntons 3 blade feathering.
The difference when sailing is noticeable in light airs but not so much in windier conditions.
As Ramona says folding props need to be kept clean as well.
There were a couple of light air races where no matter what I did I would be getting pantsed.
I'd trim, ease, stare up the mast, loosen the luff, let go leach lines, lower the boom, swap to light sheets, go below and look for heavy things...swap drivers...and yeah..nah, nothing seemed to make a difference.
Till the end of the race when I realised I hadn't folded the prop shut properly before the start.
So in light airs, a fixed vs folding makes a big difference IMO.
Reading another thread he is talking about an efoil. Thats why it seemed a bit vague.
Looking at a quick vid yes that small 2 blade folding prop will be a lot less efficient than the 3 blade fixed prop. There will be a huge difference as he dosnt put the prop guard back on. If you put the prop guard on with that 2 blade folding prop you probably wouldn't even get foiling.
