New Featherstream Prop

[xeitosaphil]

I am contemplating a Feather stream 3 bladed prop as my 2 bladed one doesn’t seem to have enough grunt when it comes to chop and wind on the nose, and also suffers from vibration, which I attribute some to only having two blades.
With a Yanmar 2gm20 which has a continuous rating of 16hp @ 3400rpm, and a 1 hour rating of 18hp @ 3600rpm. What does the forum think about RPM to reach hull speed regarding Pitch?
Is it better to get a pitch that will run at 3400 rpm to reach hull speed and have the full range of horsepower through the range?
Or would it be better to say have hull speed achievable @ 3200 and at reduced hp.

Just as a matter of interest what do people with this engine run their engine rpm at, when cruising?

Boat is 5.4 tons in cruising mode so not really a lightweight.

Thanks for any comments

Philip

 

[sailorman]

My max prop is set to give rated rpm at Hull speed
.
It is a 2 blade 450mm dia with now vibration

 

[Kwik Decision]

Recommend you email Darglow, and ask them.

mail@darglow.co.uk

Chris is very helpful, and knows his props......

Incidentally, we've had our Featherstream for 18 mths now, and have been very happy with it.

 

[Halo]

+1 from me ( new format needs more than 3 characters). M

 

[seumask]

You may want to look at the Flexofold as well from Darglow, considerably more value for money IMHO. We went 2 blade fixed to Flexofold 2 blade and were very pleasantly surprised at the extra grunt we got. The larger blade area and small increase in pitch gave a huge improvement and comfortable cruising at a knot faster at 2000 rpm.
The team at Darglow have often been recommended on this forum and I am pleased with the advise they gave.
It may be that you have a "racing 2 Blade" which have been mentioned on here before as lacking in grunt but lower in drag due to skinny profile.

 

[bedouin]

Coincidentally I was talking to Darglow about fitting a Featherstream just a couple of hours ago so I am interested in hearing from anyone with any experience.

But why on earth are these propellers so expensive - just been quoted about half the cost of a new engine just for a propeller. Seriously considering getting a fixed prop instead

 

[savageseadog]

We very rarely go above 3000 RPM, it uses a lot of fuel and we probably only gain about 0.25Knt going to max RPM. Cruising RPM is between 2,000-3,000 RPM.

There's nothing wrong with two blade props and Flexofold are the best folders

 

[Malish]

I installed a 3 blade featherstream onto a Bukh DV24 last year, sent the old 2 blade prop to them as per their suggestion to ensure taper correct. Not long after they called to check the pitch I wanted as the prop I had sent them was not set correct for the DV24 gearbox - it had come from a DV20 (probably the previous engine) which had a different gearing (I had suspected as much as I could never achieve anything like full revs). Darglow's recommendation was to set the pitch appropriate for the DV24 gearbox and that was a good call - the engine sounds less strained and we certainly whizz along. BTW it was a great investment, certainly way less then half the cost of a DV24.

 

[bedouin]

I installed a 3 blade featherstream onto a Bukh DV24 last year, sent the old 2 blade prop to them as per their suggestion to ensure taper correct. Not long after they called to check the pitch I wanted as the prop I had sent them was not set correct for the DV24 gearbox - it had come from a DV20 (probably the previous engine) which had a different gearing (I had suspected as much as I could never achieve anything like full revs). Darglow's recommendation was to set the pitch appropriate for the DV24 gearbox and that was a good call - the engine sounds less strained and we certainly whizz along. BTW it was a great investment, certainly way less then half the cost of a DV24.

As it happens I am going with the DV24 with a gearbox from the DV20 (gives 2.5 rather than 3 reduction that works much better) and the quote I have had for the prop is more than half the cost of the engine (it is 2nd hand but low hours)

 

[Doineann]

Very happy with our feather stream after 4 years now. Darglow very easy to deal with and very expert

 

[Tranona]

I am contemplating a Feather stream 3 bladed prop as my 2 bladed one doesn’t seem to have enough grunt when it comes to chop and wind on the nose, and also suffers from vibration, which I attribute some to only having two blades.
With a Yanmar 2gm20 which has a continuous rating of 16hp @ 3400rpm, and a 1 hour rating of 18hp @ 3600rpm. What does the forum think about RPM to reach hull speed regarding Pitch?
Is it better to get a pitch that will run at 3400 rpm to reach hull speed and have the full range of horsepower through the range?
Or would it be better to say have hull speed achievable @ 3200 and at reduced hp.

Just as a matter of interest what do people with this engine run their engine rpm at, when cruising?

Boat is 5.4 tons in cruising mode so not really a lightweight.

Thanks for any comments

Philip

You have very marginal power for that weight of boat if you are expecting good motoring performance, so I expect Chris will size it to achieve maximum revs. Doubt you will achieve hull speed at 3200 - not enough power and you will not be loading the engine properly. Cruising revs depends in part on the speed you want to cruise at, but should be at least 70% of full power. Not unusual to cruise at around 3000 with a 2GM in a heavy boat. Correct me if my memory is wrong, but seem to remember that you do not have enough room to fit a folding prop, so the Featherstream will be a good choice and will definitely be an improvement on your 2 blade - as well of course giving benefit under sail.

 

[Tranona]

But why on earth are these propellers so expensive - just been quoted about half the cost of a new engine just for a propeller. Seriously considering getting a fixed prop instead

Unreasonable to compare the price of a new prop with an old second hand engine. A new Bukh would be £10k or so, not £2.5k which puts things in perspective.

They cost a lot of money because they are expensive to tool up for, particularly the investment castings for the blades and the volumes are tiny. Suggest you get a quote for one of the competitors for comparison. Whether you invest in one is a personal decision depending on how much you value the benefits over a fixed prop.

 

[bedouin]

Unreasonable to compare the price of a new prop with an old second hand engine. A new Bukh would be £10k or so, not £2.5k which puts things in perspective.

They cost a lot of money because they are expensive to tool up for, particularly the investment castings for the blades and the volumes are tiny. Suggest you get a quote for one of the competitors for comparison. Whether you invest in one is a personal decision depending on how much you value the benefits over a fixed prop.

I know Bukhs are expensive, but the starting price for marinised engines of similar power is under £3K. Also the featherstream is actually one of the cheaper propellers - I was quoted £2K for a like-for-like replacement of my existing 3 bladed folding prop.

 

[sadlerbob]

As it happens I am going with the DV24 with a gearbox from the DV20 (gives 2.5 rather than 3 reduction that works much better) and the quote I have had for the prop is more than half the cost of the engine (it is 2nd hand but low hours)

marine enterprises?

 

[bedouin]

marine enterprises?

That's them - seems like a good (but not outstanding) deal. Of course you are taking it on trust that engine is as described.

I think the Bukh is probably the best marine engine out there, and certainly the best replacement for my tired MD2B.

I have held off replacing the MD2B for a couple of seasons because it means I have to replace the propeller, and at just under £2K that would be a lot of money, but I am now thinking the the hassle of the folding prop outweighs the benefits when sailing so will probably revert to a fixed prop at least for now.

 

[GrahamD]

Very happy with our feather stream after 4 years now. Darglow very easy to deal with and very expert

+1. Chris is very knowledgable, and the company are good to deal with

 

[Tranona]

I know Bukhs are expensive, but the starting price for marinised engines of similar power is under £3K. Also the featherstream is actually one of the cheaper propellers - I was quoted £2K for a like-for-like replacement of my existing 3 bladed folding prop.

Engines of that price are Chinese and made in the thousands. The point that I was making, all feathering props are expensive as they are low volume bespoke products - and the Featherstream is the least expensive.

 

[Pye_End]

my 2 bladed one doesn’t seem to have enough grunt when it comes to chop and wind on the nose,

I think this is the tricky bit when deciding on a new prop. A fixed 3 blade may well have a bigger surface area than a 3 blade Featherstream, but then a featherer or folder improves sailing performance. A fixed will also have a better motoring performance by design. Still, starting from a 2 blader you may well see an improvement in motoring. There may be a couple of options when looking at surface area and combinations from Darglow, including a 4 blade option. I went for a larger size 3 blade cut down to 13.5 inch diameter, with a lower pitch. This is not the optimal combination for flat sea and requires a few more rpm for the same speed, but has better grip when the conditions are against.


3200 revs v's 3600 revs - if you look at the power curve of the engine, you may well find that you are not missing out on very much extra hp.

 

[cliff]

I am contemplating a Feather stream 3 bladed prop

May I suggest you look at http://www.steeldevelopments.net/sailing-boat-propellers-2.html before jumping in and blowing a year's beer tokens (or more).

 

[xeitosaphil]

Thanks for all the replies to my post.

Folding props are not an option for me as my aperture available opening size is too small.

Having sent numerous emails to Darglow Propellers and spoken to Chris, I can only reiterate what people have said in the fact they are most helpful very patient and pleasure to deal with, with customer satisfaction their top priority.

Thanks for the input to all re Cruising RPM vs hull speed, and Chris has indicated that Hull speed @ Continuous HP rating would be a good place to start, with the option of tweaking the outputs and speeds to suit my needs at next haul out, by supplying me with a new machined Pitch Cassette. All they need me to do is supply them with a sea trial data sheet prior to lift out, and they will machine a new Pitch Cassette at no extra cost. That plus a low season discount has swung it for me, and I don't think I could do better under the circumstances.

I am aware there might be supposedly better props available ? but funds dictate one of the cheaper options ( which is still a major leap in expense for me) and I don't think in my opinion I could get much better service than that anywhere.

Cheers

Philip