How much faster?

[Fascadale]

How much faster will the boat sail with a super smooth hull and a feathering prop? Given reasonable weather.

Rival 34, easily sails at 5 to 6.5 kts in suitable conditions, faster at times

Layer upon layer of cracked and pitted old AF laboriously removed.

As I scrape and scrape I’m trying to make the pain all seem worthwhile by working out (guessing) how many extra nautical miles I’ll sail in a 24 hour day

A quarter of a knot for the AF, half a knot for the feathering prop? 18 nms over 24 hours?

 

[Sandy]

I was copper coated and swapped my fixed prop for a folding one last August. My average speed on passage, is 2 knots faster than before, The maximum speed has gone from 6.6 to 8 knots (STW).

The boat is a Gib'Sea 96 10.1m meters or 33 feet in old money.

 

[RJJ]

How much faster will the boat sail with a super smooth hull and a feathering prop? Given reasonable weather.

Rival 34, easily sails at 5 to 6.5 kts in suitable conditions, faster at times

Layer upon layer of cracked and pitted old AF laboriously removed.

As I scrape and scrape I’m trying to make the pain all seem worthwhile by working out (guessing) how many extra nautical miles I’ll sail in a 24 hour day

A quarter of a knot for the AF, half a knot for the feathering prop? 18 nms over 24 hours?

There was a pbo test that indicated something like 0.5 knot. But it will vary; in lighter airs when you are "looking for power" drag reductions make the greatest difference. When you are powered up, reaching or running at hull speed, your rig probably is giving power in reserve so there will be minor gains only. Upwind, reduced drag translates to reduced leeway for a given speed.

 

[Norman_E]

You will really see a big improvement in light winds, because at low speeds a fixed prop is a big proportion of the boat's total resistance. I know the Rival is a heavy boat and very different to my Jeanneau 45.2, but changing from a 20 inch 3 blade fixed prop to a 21 inch Maxprop gained me about 3/4 of a knot in the sort of light winds that result in 3 to 4 knot speeds. At the top end of the scale I have now hit 10 knots on a beam reach in about 20 knots of wind, and had not done that before the changes to the feathering prop and coppercoat. Coppercoat feels smoother than even newly applied conventional AF, so that may well account for half a knot.

 

[Habebty]

When I fold my two blade folding prop by selecting reverse (after stopping the engine before some wag comments ? ) I see a 0.7 knot increase in speed through the water. Last weekend on my way to the scrubbing grid, Best speed I could make under engine was 4.8 knots. After a scrub and prop clean it was 7knots.
So my folding prop is good for a 10% speed increase under sail.

 

[matt1]

My 12m boat was appreciably quicker at the start of the season and has slowed down noticeably as the season has worn on. The hull is fairly clear still but there is a lot of growth on the folding prop and saildrive. I reckon .7kn-.9k for a folding prop and another .3 kn -.5k depending how clean / fouled the hull is

 

[Pye_End]

Feathering prop - difficult to give a number - the difference is particularly noticeable in lighter wind speeds, so it depends a bit on what your motoring habits.

 

[awol]

Why not fit foils while your at it?

 

[LadyInBed]

In my case, shedding half a ton of excess weight would help a bit!

 

[Channel Sailor]

Compared to fairly good hull surface (not racing smooth but OK for a cruiser) and fresh antifouling. I reckon at the end of this this season I have lost close to 5% of max speed on engine, mostly I would guess due to fouling on the prop. The hull antifouling looks to be working well. The difference between feathered and not Feathered on the propellor seems to be around 5% as well.

After leaving the yacht for a week or two there looks to be slight slime all over the hull bottom and the yacht does not feel quite so slippery in light air. But this seems to improve after some sailing in choppy water.

 

[newtothis]

In my case, shedding half a ton of excess weight would help a bit!

But who would sail it if you weren't on board?

 

[Concerto]

Fascadale I would say your estimate of about ¾ knot is about right.

On my Fulmar I have a Gori folding propeller and when I was sailing against another fin keeled Fulmar, I just walked away. We later compared what was different and the only difference was they had a fixed 2 bladed propeller. On another day I had a bilge keeled Fulmar with fixed propeller try to keep up and had to keep turning his engine on to keep up in about 10 knots of wind over the deck at about 40 degrees off the bow.

 

[38mess]

I was once told having a big fixed 3 bladed prop on a sailing boat is like towing a bucket behind you

 

[johnalison]

Another advantage of a folding prop is the improved feel as the flow over the rudder loses its turbulence. My feeling is that the different improvements won't add up to a magnificent total but the combination will add something around half a knot or a little more perhaps.

 

[JumbleDuck]

In my case, shedding half a ton of excess weight would help a bit!

Me too. I might try to lighten the boat as well.

 

[wully1]

I tried scraping off antifouling- for about 10 mins...Sod that. Bought a tub of stripper gel, slapped that on, left overnight then power washed it off..

 

[JumbleDuck]

I tried scraping off antifouling- for about 10 mins...Sod that. Bought a tub of stripper gel, slapped that on, left overnight then power washed it off..

I've stripped the paint off the bottom of a 16' boat. Sod that. The yard blast the remains off at haul out and if it starts building up I'll sell the boat when the antifouling is an inch thick.

 

[RupertW]

I would love to install a folding/feathering prop but it’s the annual maintenance that puts me off. We often don’t have access to a yard with haulout over winter, let alone one with the experience to maintain a complex prop, so it’s as non-starter. This winter we have a broken seacock and no real options for getting it fixed as the big marina we are in has no haul out facilities.

Are there any folding/feathering props that don’t need annual maintenance?

 

[JumbleDuck]

I would love to install a folding/feathering prop but it’s the annual maintenance that puts me off. We often don’t have access to a yard with haulout over winter, let alone one with the experience to maintain a complex prop, so it’s as non-starter. This winter we have a broken seacock and no real options for getting it fixed as the big marina we are in has no haul out facilities.

Are there any folding/feathering props that don’t need annual maintenance?

I'm in a similar position. I need to change prop and while I am tempted by either a flexofold or an autoprop, I rather like having something with no moving parts (well, one moving part) down there.

 

[Mudisox]

In my case, shedding half a ton of excess weight would help a bit!

That is what my wife says too.