#1 2021-11-24 14:08:48

Mo_Jefferies
Additional Member
Registered: 2011-03-14
Posts: 20

Help with prop sizing please!

We're in the process of replacing the Volvo 2010 on our V800 with a Beta 14. The original prop was a Vetus 2-bladed 12x10RH. We've been advised by the 'prop people' that a 12x8.5 2-blade or a12x8 3-blade would work with the Beta.

We noticed that a previous poster had opted for a 13" 2-blade but hadn't specified the pitch.

Our stern tube doesn't leave enough clearance for a feathering prop.

Can anyone help us to choose a suitable fixed prop please?

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#2 2021-11-24 18:15:57

Kevin_Misselbrook
Member
Registered: 2017-05-26
Posts: 34

Re: Help with prop sizing please!

Hi Mo,
It may be worth your while completing the form on the Betamarine site at https://betamarine.co.uk/seagoing-propellers/ 
They will then assess all the data you provide about your boat (which includes whether you want a 2 or 3 blade) and they will then make a recommendation. 
I have a 13 x 9 three bladed prop in my Frances 26 with a Beta 16 but looking at the general guidelines on the Betamarine site they reckon a 12 x 9 for a boat with the Beta 14. 
But ... if you complete the on-line form then they will be able to give you a more educated assessment based on the characteristics of your V800.

Last edited by Kevin_Misselbrook (2021-11-24 18:18:04)

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#3 2021-11-25 10:53:18

Mo_Jefferies
Additional Member
Registered: 2011-03-14
Posts: 20

Re: Help with prop sizing please!

Thanks Kevin,
We've already done what you suggested, and just wanted to check what other owners with the same engine found was best for them. We are trying to avoid multiple attempts at finding the right prop, a process that others may have been through.
We are also interested to find out any differences people may have noticed in sailing performance moving from 2 to 3 bladed.

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#4 2021-11-25 15:31:28

Murray_Fraser
Member
From: Weymouth
Registered: 2016-11-22
Posts: 23

Re: Help with prop sizing please!

Hello Mo.  I bought my V800 in May this year and it is fitted with a Beta 14 and a Darglow featherstream 3 bladed prop.  I do not have the Prop size to hand but will try and dig it out for you but I agree with Kevin about source of advice.  Interestingly the previous engine was a Volvo 2010B and the Darglow was retro fitted to this prior to the Beta.  There is ample room for the Darglow on my boat including the placement of the anode on the end so a chat to the company might help, I found them helpful.  I do not have the Prop size to hand but will try and dig it out for you but I agree with Kevin about source of advice.

I cannot comment on performance as this is my first V800 but I have not found power to be a problem.  Depending on sea conditions (and hull fouling) I achieve 5 to 5.5 knots at 1800 revs, well under the engines maximum torque output at 2600 revs.  According to everything I have read compared to a 2 blade prop the three blade prop improves 'bite' in the water both ahead and astern. 

DARGLOW.docxDARGLOW.docx


VICTORIA 800 Dulcibella

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#5 2021-11-25 17:04:05

Mo_Jefferies
Additional Member
Registered: 2011-03-14
Posts: 20

Re: Help with prop sizing please!

Hi Murray,
Unfortunately the Darglow won't fit unless we replace the stern tube or hack a bit off the rudder.
I would be interested to know the diameter and pitch though if you get chance to find it.
Thanks for the input though!

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#6 2021-11-25 17:06:53

Mo_Jefferies
Additional Member
Registered: 2011-03-14
Posts: 20

Re: Help with prop sizing please!

Hi Murray,
Unfortunately the Darglow won't fit unless we replace the stern tube or hack a bit off the rudder.
I would be interested to know the diameter and pitch if you get chance to find it.
Thanks for the input though!

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#7 2021-11-27 16:02:51

Jonathan_Hopper
Member
Registered: 2004-03-23
Posts: 122

Re: Help with prop sizing please!

Mo -

I have used 3 props with my Beta14 - all 3 bladed so cannot comment on differences with 2 blade.

I don't think there is a best, but certainly different characteristics.

Assuming you have the 2:1 gearbox, the 12 x 9 is recommended by Beta. Since that is what was on the original Yanmar it is what Francesca started with.   It was good, but in a short chop I wanted to try something with a bit more grip/area, so tried a 13 x 8.   This does not achieve quite so many rpm, but is ok.   It is certainly better in poor weather, but a a cost of not so good sailing, especially in light winds.   Lastly I have a 13 1/2" Featherstream.   I think this diameter is too high - 13 would have been better.   It is substantially better in reverse so handy at close quarters, and better sailing, but not so good in forward at 'cruising' speed, and certainly do not the speeds that Murray quotes - I too would be interested in knowing exactly what that set-up is.   All of these will give more grip than the 2 blade, but assuming the 2 blade can be parked behind the deadwood then your sailing performance will be good, and probably on a flat sea will be compare well to a similar 3 blade.

Which do I prefer?   It depends....!

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#8 2021-11-28 14:56:54

Mo_Jefferies
Additional Member
Registered: 2011-03-14
Posts: 20

Re: Help with prop sizing please!

Thanks Jonathan for sharing your experience.
The new engine does indeed have a 2:1 gearbox ratio.
The 12x10 2-bladed has served us well for 25 years. The lack of bite in a sea has been inconvenient and uncomfortable at times, but I guess you just have to cope with that. I think because we always prefer to sail if we can, and we are on a swinging mooring, the close quarters manoeuvring hasn't been so much of an issue.
We're very interested to find out what props other owners have used that work well for them, and I would be keen to find out what pitch of 13" 2-blade Dingeman fitted on his boat.
We hadn't realise before embarking on this project, just what a black art prop speccing seems to be! I think you may have mentioned on a previous thread that the logical way is to start with the prop and then work out the appropriate  engine and gearbox to suit!

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#9 2021-12-01 17:36:59

Murray_Fraser
Member
From: Weymouth
Registered: 2016-11-22
Posts: 23

Re: Help with prop sizing please!

Mo, Jonathan, I was down at the boat today and noted down my prop details.  It has raised an interesting question for me as I have discovered that the Darglow Featherstream was fitted to the previous engine, a Volvo MD2010.  This has a gearbox ratio of 2.4:1 whereas the Beta 14 is 2:1.  The prop is a 13x8 and the pitch cassette is Forward 19:1 and Reverse 17:1.  Frankly I am not absolutely clear how the cassette alters the prop performance and need to better understand this as you can purchase different cassettes from Darglow.  I am going to contact Darglow and ask them if the prop/cassette that was fitted for the Volvo is optimium for the Beta but I think I need to do some speed measurements first as described on theri website.  Hope this helps and doesn't confuse!


VICTORIA 800 Dulcibella

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#10 2021-12-02 19:15:25

Jonathan_Hopper
Member
Registered: 2004-03-23
Posts: 122

Re: Help with prop sizing please!

Murray - thanks for the interesting post.

From memory, Featherstream suggested starting with a 13 x 8 or a 13 1/2 x 7 1/2 to see how this loaded the engine, and look at max rpm.  We went for the latter on the assumption that it was easier to lop a bit more off than stick it back on.   Max rpm at the time seemed the main driver for the decision.    For the 13 x 8 fixed I got 3,200 max, as I do with the Featherstream.  The cassette will presumably alter the pitch, so it will be interesting to hear if a change is beneficial - what max rpm do you get with what you have (clean!)?   It may well be that the Volvo would have been able to rev to the max, but the Beta more restricted

For the record, with a clean hull and prop, and with a boat load of cruising clobber, I get 5.2kn at 2400 rpm, increasing by 0.1kn every 100 rpm up to a max of 5.9kn at 3200 - flat sea no wind.   If yours is substantially better than this then I might have to get it re-cut!   Francesca's blades are made from the larger profile blade in an attempt to keep the blade area up - the slightly smaller blade may well rev higher for the same diameter+pitch.

Apologies to Mo for branching out in this way!

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#11 Yesterday 19:06:42

Murray_Fraser
Member
From: Weymouth
Registered: 2016-11-22
Posts: 23

Re: Help with prop sizing please!

I'll let you know what Darglow say.  They need the job number etc. so I hope to get that this weekend.  Biggest issue is first to make sure my log is reading correctly and secondly to find a flat sea day to do the RPM versus Log speed plot!  Boat coming out at Xmas so not a lot of days left to do this.


VICTORIA 800 Dulcibella

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#12 Yesterday 23:18:45

Mo_Jefferies
Additional Member
Registered: 2011-03-14
Posts: 20

Re: Help with prop sizing please!

Jonathan and Murray,
This information is really useful. Hearing about what works for other people is fascinating and hopefully will help us in our search for the 'ideal' prop.

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