Anyone here have a diesel powered Fjord 27 or know of one? What propeller size is fitted and what sort of speed does the boat have? I am having a problem sorting out a correct size propeller.
Boat has a 200 HP AD41, I am told the biggest propeller that will fit is 16 inches.
Two beers please: my friend will pay
Propeller size
Moderator: Lars Lundbladh
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Lars Lundbladh
- Inlägg: 1500
- Blev medlem: 26 jul 2003, 23:46
- Ort: Sweden
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On the Volvo sterndrives the biggest diameter that will fit is 16 inch however there are many different pitches. If you give me the speed measured by GPS and the motor rpm at this speed. If possible also the gear ratio of your sterndrive, maybe 1,61:1 and current propeller would be helpful? Then I can calculate a suitable propeller.
/Lars
/Lars
On the Volvo sterndrives the biggest diameter that will fit is 16 inch however there are many different pitches. If you give me the speed measured by GPS and the motor rpm at this speed. If possible also the gear ratio of your sterndrive, maybe 1,61:1 and current propeller would be helpful? Then I can calculate a suitable propeller.
>
The boat is shaft drive. I am told that the biggest propeller is still 16 inches. The gear ratio is 1.93:1. The original propeller fitted was 16 x 16 which seemed too small. Apparently the boatyard have now fitted a 16 x 19, as the engine won't rev beyond 3500 or so I suspect that this is too coarse. I used an Excel spreadsheet named PropKing which suggested 16 x 19.
I may have the weight wrong. I have, with the boat, some of the original Fjord test data (which I'm happy to scan and post to the archives if anyone is interested) which states that the boat weighed 2300kg. I have taken out the BB170 and put in an AD41 which is about 200kg heavier. Full tanks and five crew plus tender has been guessed at no more than 1250kg so all the calculations are based on a weight of 3750 kg. If this is wrong it makes a big difference.
At about 3300-3500 engine speed the GPS was showing about 15.5 knots but there may have been some tide affecting this by +/- 1 knot. The trim tabs were not being used at the time and the boat seemed to be just about starting to plane.
Thanks very much for your help.
Two beers please: my friend will pay
>
The boat is shaft drive. I am told that the biggest propeller is still 16 inches. The gear ratio is 1.93:1. The original propeller fitted was 16 x 16 which seemed too small. Apparently the boatyard have now fitted a 16 x 19, as the engine won't rev beyond 3500 or so I suspect that this is too coarse. I used an Excel spreadsheet named PropKing which suggested 16 x 19.
I may have the weight wrong. I have, with the boat, some of the original Fjord test data (which I'm happy to scan and post to the archives if anyone is interested) which states that the boat weighed 2300kg. I have taken out the BB170 and put in an AD41 which is about 200kg heavier. Full tanks and five crew plus tender has been guessed at no more than 1250kg so all the calculations are based on a weight of 3750 kg. If this is wrong it makes a big difference.
At about 3300-3500 engine speed the GPS was showing about 15.5 knots but there may have been some tide affecting this by +/- 1 knot. The trim tabs were not being used at the time and the boat seemed to be just about starting to plane.
Thanks very much for your help.
Two beers please: my friend will pay
-
Lars Lundbladh
- Inlägg: 1500
- Blev medlem: 26 jul 2003, 23:46
- Ort: Sweden
- Kontakt:
This was slightly different configuration than i first thought (I should know better?! sterndrive....)
How many hp have you in the AD41?
I have a new test on the Selcruiser in Swedish from mars 2003 there the top speed is said to be 15-20 knots.
My calculations show the same but please give me more data about motor hp.
Buy the way do you have the aft cabin?
/Lars
Where is the beer?
How many hp have you in the AD41?
I have a new test on the Selcruiser in Swedish from mars 2003 there the top speed is said to be 15-20 knots.
My calculations show the same but please give me more data about motor hp.
Buy the way do you have the aft cabin?
/Lars
Where is the beer?
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Lars Lundbladh</i>
This was slightly different configuration than i first thought (I should know better?! sterndrive....)
How many hp have you in the AD41?
>
200 HP
>
I have a new test on the Selcruiser in Swedish from mars 2003 there the top speed is said to be 15-20 knots.
>
I'd be interested in seeing that, if you can translate it into English for me
>
My calculations show the same but please give me more data about motor hp.
>
AD41A, max output 200HP, max rpm 3900. Gearbox ratio 1.93:1
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Buy the way do you have the aft cabin?
>
Yes I do. I mean to fit better ventilation some day, it gets hot and stuffy inside the cabin. I'd post some pictures but can't see how on this forum.
>
/Lars
Where is the beer?
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
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If ever you are in these parts (Hampshire, UK), let me know beforehand. A good friend owns a brewery, he is also the Head Brewer and makes prize winning beer. I am quite sure beer can be arranged:-)
Thanks for the advice so far.
Two beers please: my friend will pay
This was slightly different configuration than i first thought (I should know better?! sterndrive....)
How many hp have you in the AD41?
>
200 HP
>
I have a new test on the Selcruiser in Swedish from mars 2003 there the top speed is said to be 15-20 knots.
>
I'd be interested in seeing that, if you can translate it into English for me
>
My calculations show the same but please give me more data about motor hp.
>
AD41A, max output 200HP, max rpm 3900. Gearbox ratio 1.93:1
>
Buy the way do you have the aft cabin?
>
Yes I do. I mean to fit better ventilation some day, it gets hot and stuffy inside the cabin. I'd post some pictures but can't see how on this forum.
>
/Lars
Where is the beer?
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
>
If ever you are in these parts (Hampshire, UK), let me know beforehand. A good friend owns a brewery, he is also the Head Brewer and makes prize winning beer. I am quite sure beer can be arranged:-)
Thanks for the advice so far.
Two beers please: my friend will pay
-
Lars Lundbladh
- Inlägg: 1500
- Blev medlem: 26 jul 2003, 23:46
- Ort: Sweden
- Kontakt:
This is not an easy calculation as semi displacement hulls ahave so big wet surface. However the calculations I made in different spreadsheets and calc programs show that you today have a propellerslip of 45% I believe this is very high even on a semi displacement hull. I would like to se a figure around 20-30% for this type of boat. Bigger prop. diameter would probably help this but it is not possible. Calc show a possible 18-19 diameter and 15-16 in pitch. Is the reduction of 1,93 a leftover from the BB170? That motor has a top rpm of 5000 . The propeller speed as a function of 1,93 and 3900 rpm gives 2000 rpm which normally should mean a bigger prop diameter. I am not an expert on this type of boats I know much more of planning hulls. But the conclusion is that the slip I svery high 45% to reduce this normaly a bigger diameter would help or higher propeller speed. You can changes the propeller pitch down one inch or maybe 2 but I doubt you will gain much speed.
/Lars
/Lars
The gearbox reduction of 1.93 is in the replacement gearbox that was obtained with the engine, the BB170 gearbox was 2.5 or something like that. I was aware that the gearbox ratio needed to be lower for diesel power but was not able to get a different ratio. The gearbox is on now and I don't want to have to get it out.
It sounds to me that taking an inch of pitch off the propeller may be a good idea, or perhaps getting a propeller with four blades.
I was vaguely guided by this website, suggesting that in excess of 20 knots should be possible with a 200HP engine and a cruising speed of about 18 or 19.
http://b.homepage.dk/grandcru.htm
Of course, as I don't read Danish(?) I may have been entirely wrong.
Thank you for your advice so far.
Two beers please: my friend will pay
It sounds to me that taking an inch of pitch off the propeller may be a good idea, or perhaps getting a propeller with four blades.
I was vaguely guided by this website, suggesting that in excess of 20 knots should be possible with a 200HP engine and a cruising speed of about 18 or 19.
http://b.homepage.dk/grandcru.htm
Of course, as I don't read Danish(?) I may have been entirely wrong.
Thank you for your advice so far.
Two beers please: my friend will pay
-
Lars Lundbladh
- Inlägg: 1500
- Blev medlem: 26 jul 2003, 23:46
- Ort: Sweden
- Kontakt:
Thanks for the link. I will add that one to our linkpage.
The 4 blade could be a option oar maybe bigger blade surface area.
I think that the installation on the Danish boat is with 2 motors. It is not possible to gain nearly 24 knots with 150hk and 27 fot.
I can write a letter an ask and invite the fellow to Fjordclub.
/Lars
The 4 blade could be a option oar maybe bigger blade surface area.
I think that the installation on the Danish boat is with 2 motors. It is not possible to gain nearly 24 knots with 150hk and 27 fot.
I can write a letter an ask and invite the fellow to Fjordclub.
/Lars
hej Flinn
i Have a diesel powered Fjord 27 and the gear is 1:1 and that gives a prop size at 16 inches with 130 hp, 15 knots, full loaded
the boat can fit props up to 25 inches.
Lars Lundblads calculations is correct 18 to 19 inches,
and if you use propking it will give you the right pitch when the speed is around 18-20 knots with 200 hp 3500 kg boat
/Vagn
i Have a diesel powered Fjord 27 and the gear is 1:1 and that gives a prop size at 16 inches with 130 hp, 15 knots, full loaded
the boat can fit props up to 25 inches.
Lars Lundblads calculations is correct 18 to 19 inches,
and if you use propking it will give you the right pitch when the speed is around 18-20 knots with 200 hp 3500 kg boat
/Vagn
Thanks for this. The boat is due out of the water for the winter season at the end of this month. I'll have a much better look at everything and see what I can sort out. Swinging a 25 inch prop sounds as though a longer shaft is being used as I don't recall that much clearance. Changing the gearbox ratio will be too expensive at the moment so I'm stuck with the Volvo 1.93:1. Unless someone knows a way of getting the gearbox off without taking the engine out!
I'll post more when I know more
Two beers please: my friend will pay
I'll post more when I know more
Two beers please: my friend will pay