The Whirled At One.

[bizzard]

A variable pitch propeller might be the ideal. Fine pitch for starting off, which would help to prevent engine stalling if the alternators using up too much of the engine power, which might mean that a lot of boats could reduce the engines idle speed back to normal again and so be able to go nice and slow when needed, like they used to be able to do, moving to a courser pitch for cruising along. Reverse the pitch for going astern, no reverse gearbox required. Some boats and ships and steam powered have this. Many propeller driven aircraft too. In fact we have a Dutch barge here with variable pitch prop, but its locked now and using a reverse gearbox.

Edited September 27, 2016 by bizzard

[j04n]

 

In my opinion they are wrong, having had what they seem to be implying are not proper boats, where the props were over size and close to the plate. Replace with a prop that had the same basic thrust capability and whose tips were approx 2 inches away from the plate, 18 inch prop, speed through the water increase and apparent power to achieve that decreased, prop walk decreased and general handling of the boat improved. So it does seem to make a difference even on the non-proper boats!

They did not imply anything! ....... those are my words which I have heard many times from plastic boaters ........ no harm in a little ribbing between the different camps! ....... see what I did there?! ;D lol

[Dalslandia]

Unfortunately not. Although the the distance from the centre of the shaft to the Uxster plate must be circa 20 inches as the only clearance when the 20 inch prop was fitted was the step, the thickness of the bottom of the boat to the anti cavitation plate. I did take a photo though just to give some idea.

you mean 10" radii

 

would be 16" with 2" left

 

17" with 10%

 

18" with one inch left

 

the free shaft length can be/should be shorter then 1,5 X shaft D so max 2" 1/4 free length, I see you have lot of distance left to rudder.

[j04n]

A variable pitch propeller might be the ideal. Fine pitch for starting off, which would help to prevent engine stalling if the alternators using up too much of the engine power, which might mean that a lot of boats could reduce the engines idle speed back to normal again and so be able to go nice and slow when needed, like they used to be able to do, moving to a courser pitch for cruising along. Reverse the pitch for going astern, no reverse gearbox required. Some boats and ships and steam powered have this. Many propeller driven aircraft too. In fact we have a Dutch barge here with variable pitch prop, but its locked now and using a reverse gearbox.

Cant imaging it fairing too well in this!

you mean 10" radii

 

would be 16" with 2" left

 

17" with 10%

 

18" with one inch left

 

the free shaft length can be/should be shorter then 1,5 X shaft D so max 2" 1/4 free length, I see you have lot of distance left to rudder.

woops! of course ........ sorry its still early!

 

Yes, made it easy to get the prop puller on........ only pity it wouldnt come off! ....... is that bad? and more clearance to skeg.

Edited September 27, 2016 by j04n

[Dalslandia]

Cant imaging it fairing too well in this!

woops! of course ........ sorry its still early!

 

You might need a weed-less prop or a rotating knife

 

https://www.bing.com/images/search?q=weedless+propeller&qpvt=weedless+propeller&qpvt=weedless+propeller&qpvt=weedless+propeller&FORM=IGRE​

Edited September 27, 2016 by Dalslandia

[Geo]

They did not imply anything! ....... those are my words which I have heard many times from plastic boaters ........ no harm in a little ribbing between the different camps! ....... see what I did there?! ;D lol

 

Well as the owner of two plastic boats I know better

[cuthound]

I thought that these days Viking stuck to river cruises as advertised on ITV3 in the afternoons

I believe that they are still "Afloat" at Gailey on the Staffs & Worcester

[bizzard]

 

You might need a weed-less prop or a rotating knife

 

https://www.bing.com/images/search?q=weedless+propeller&qpvt=weedless+propeller&qpvt=weedless+propeller&qpvt=weedless+propeller&FORM=IGRE​

No, a Repeller instead of a Propeller.

[alan_fincher]

Yep, It must be the Viking thing ,travel far,Drink the Ale of neighbouring countries, make sturdy reliable vehicles. and Longships

 

CT:)

 

ETA to add preferred method of Viking excursion Craft

 

 

they build narrowboats, don't they?

 

did they really cross the North Sea in a sewer tube?

 

 

Here is photographic evidence that they may have done!

 

 

[MtB]

Photographic proof there from Alan that narrow boaters are truly crackers!!

[Dalslandia]

More blades is less prone to get tangled, 5 blade might be a good one, 18Xxx but at a cost

[MtB]

Swerving back onto topic for a second, are we allowed to discuss the (ahem) various brands of propeller on the CWF Facebook page? Or will that lead to trouble for Dan too?

[j04n]

 

In my opinion they are wrong, having had what they seem to be implying are not proper boats, where the props were over size and close to the plate. Replace with a prop that had the same basic thrust capability and whose tips were approx 2 inches away from the plate, 18 inch prop, speed through the water increase and apparent power to achieve that decreased, prop walk decreased and general handling of the boat improved. So it does seem to make a difference even on the non-proper boats!

That is the exact same logic I was sold on but it certainly hasnt worked for me....... Being a very simple person I like to keep things simple ........ otherwise my head starts to hurt. I have now come up with my own theory. After all we are talking about floating skips! So I guess we can dispense with any rule book and theories on hydrodynamics - nice word - I just learnt it recently. I need to be spinning a propellor the size of a dustbin lid. If I cant I need to spin the next largest possible with a huge pitch but not exceeding a ratio of 1:1 otherwise it will handle like a pig (derived from my experience with my 20 x 23), as fast as I can! ta daaaaa!! Anybody else want a prop designing?!

Swerving back onto topic for a second, are we allowed to discuss the (ahem) various brands of propeller on the CWF Facebook page? Or will that lead to trouble for Dan too?

What, the one that sounds like a washing powder?

[Dalslandia]

That is the exact same logic I was sold on but it certainly hasnt worked for me....... Being a very simple person I like to keep things simple ........ otherwise my head starts to hurt. I have now come up with my own theory. After all we are talking about floating skips! So I guess we can dispense with any rule book and theories on hydrodynamics - nice word - I just learnt it recently. I need to be spinning a propellor the size of a dustbin lid. If I cant I need to spin the next largest possible with a huge pitch but not exceeding a ratio of 1:1 otherwise it will handle like a pig (derived from my experience with my 20 x 23), as fast as I can! ta daaaaa!! Anybody else want a prop designing?!

 

seems you grasped the basic stuff, we you me, want, need a propeller that load the engine fully at max speed in open water. Bigger slower propeller is always more efficient, efficient isn't the same as effect, but a big slow prop with lot of pitch will have a lot of prop walk.

 

an smaller prop will increase the need for more pitch because the water passing the prop disk will go faster in a smaller tube. more blade area will decrease pitch.

so also more rpm.

 

if the engine is under propped, the diesel engine that often is rpm limited, will not make full power at rated rpm.

if over propped, rated rpm will not be meet, and max power will be down slightly, but prop efficiency up, the cruise at lower rpm will be more efficient at a slightly lower rpm

[j04n]

seems you grasped the basic stuff, we you me, want, need a propeller that load the engine fully at max speed in open water. Bigger slower propeller is always more efficient, efficient isn't the same as effect, but a big slow prop with lot of pitch will have a lot of prop walk.

 

an smaller prop will increase the need for more pitch because the water passing the prop disk will go faster in a smaller tube. more blade area will decrease pitch.

so also more rpm.

 

if the engine is under propped, the diesel engine that often is rpm limited, will not make full power at rated rpm.

if over propped, rated rpm will not be meet, and max power will be down slightly, but prop efficiency up, the cruise at lower rpm will be more efficient at a slightly lower rpm

I couldnt have done it without you Dalslandia! ;D ......... my 160amp alternator should keep my engine working even if the prop doesnt! ......... Im looking forward to getting this 2:1 box fitted this weekend. It has always bugged me since realizing. Having spent a small fortune on sound proofing only to have to run my engine faster because of the 3:1 box. I'm hoping its going to be a win win!

[MtB]

That is the exact same logic I was sold on but it certainly hasnt worked for me....... Being a very simple person I like to keep things simple ........ otherwise my head starts to hurt. I have now come up with my own theory. After all we are talking about floating skips! So I guess we can dispense with any rule book and theories on hydrodynamics - nice word - I just learnt it recently. I need to be spinning a propellor the size of a dustbin lid. If I cant I need to spin the next largest possible with a huge pitch but not exceeding a ratio of 1:1 otherwise it will handle like a pig (derived from my experience with my 20 x 23), as fast as I can! ta daaaaa!! Anybody else want a prop designing?!

What, the one that sounds like a washing powder?

 

 

That makes the prop 'over square', the pitch being longer than the diameter. Over square blades are Bad News (on narrow boats at least) as as effect not mentioned so far in any of your threads takes place. 'Turbine effect'. On a long pitched blade it gets a 'grip' on the 'tube' of water roughly in line with the prop and spins the water around rather than cutting through it and creating thrust.

 

The longer the pitch the stronger this effect and the rule of thumb point at which this effect becomes unacceptably strong is a 'square' blade i.e. when the pitch is the same as the diameter.

[Dalslandia]

You might need a 3th prop, but that is a or the charm, with the money back from the current, you can buy a 5 blade.

 

 

That makes the prop 'over square', the pitch being longer than the diameter. Over square blades are Bad News (on narrow boats at least) as as effect not mentioned so far in any of your threads takes place. 'Turbine effect'. On a long pitched blade it gets a 'grip' on the 'tube' of water roughly in line with the prop and spins the water around rather than cutting through it and creating thrust.

 

The longer the pitch the stronger this effect and the rule of thumb point at which this effect becomes unacceptably strong is a 'square' blade i.e. when the pitch is the same as the diameter.

 

Yes should stay away from square propellers, or over square

 

https://store8952293.ecwid.com/#!/4-Blade-73-DAR-GLO473/c/18478923/offset=0&sort=normal​

Edited September 27, 2016 by Dalslandia

[j04n]

 

 

That makes the prop 'over square', the pitch being longer than the diameter. Over square blades are Bad News (on narrow boats at least) as as effect not mentioned so far in any of your threads takes place. 'Turbine effect'. On a long pitched blade it gets a 'grip' on the 'tube' of water roughly in line with the prop and spins the water around rather than cutting through it and creating thrust.

 

The longer the pitch the stronger this effect and the rule of thumb point at which this effect becomes unacceptably strong is a 'square' blade i.e. when the pitch is the same as the diameter.

I didnt know about that but I know it was a b***er to moor! It was impossible to drift into a mooring. As soon as you hit reverse the back end ........ sorry, stern, tramped back out.

 

ps. just to clarify the 20 x 23 was my original prop already on the boat when I bought it.

Edited September 27, 2016 by j04n

[Geo]

That is the exact same logic I was sold on but it certainly hasnt worked for me....... Being a very simple person I like to keep things simple ........ otherwise my head starts to hurt. I have now come up with my own theory. After all we are talking about floating skips! So I guess we can dispense with any rule book and theories on hydrodynamics - nice word - I just learnt it recently. I need to be spinning a propellor the size of a dustbin lid. If I cant I need to spin the next largest possible with a huge pitch but not exceeding a ratio of 1:1 otherwise it will handle like a pig (derived from my experience with my 20 x 23), as fast as I can! ta daaaaa!! Anybody else want a prop designing?!

 

 

I do not know what logic you were sold on, mine was based on knowledge and experience. Nor do I know what went wrong, from the little I know of your boat etc with a 3:1 gearbox and a diesel engine it is very unlikely that you could turn that prop fast enough to achieve the thrusts required and have control of the boat. Glad you are changing the gbox to a 2:1. It will be interesting to see the results when it is done.

[j04n]

 

I do not know what logic you were sold on, mine was based on knowledge and experience. Nor do I know what went wrong, from the little I know of your boat etc with a 3:1 gearbox and a diesel engine it is very unlikely that you could turn that prop fast enough to achieve the thrusts required and have control of the boat. Glad you are changing the gbox to a 2:1. It will be interesting to see the results when it is done.

oh I know you do! ;D .......... it certainly seems to be the case ........ its only a pity the prop experts didnt know ....... I will be happy to share. I am expecting still a little under propped but the best it will have been. fingers crossed.

Edited September 27, 2016 by j04n

[gazza]

I didnt know about that but I know it was a b***er to moor! It was impossible to drift into a mooring. As soon as you hit reverse the back end ........ sorry, stern, tramped back out.

 

ps. just to clarify the 20 x 23 was my original prop already on the boat when I bought it.

Prop walk.

 

You can use it to your benefit - trying to eliminate it with a magic prop isn't the answer.

It's cheaper to learn to allow for it and use it to your advantage.

 

Our LH prop on a transom stern throws to starboard in reverse, choose which way (upstream/downstream) or which side of the river or canal you moor (space to turn or mooring either side permitting) and you can neatly drop onto your chosen spot like a boss - I normally try and make sure I moor starboard side on - even if it's in the opposite direction to what I am traveling.

 

If i need to stop port side on I will turn in towards the mooring then apply a fair bit of starboard lock, this swings the bow out and the stern in, a burst of astern halts the stern swinging to port and brings us alongside perfectly - well 9/10 times

 

Wind and current should also be factored.

 

I'm often without crew so you soon learn to make life easy for yourself!

[Geo]

oh I know you do! ;D .......... it certainly seems to be the case ........ its only a pity the prop experts didnt know ....... I will be happy to share. I am expecting still a little under propped but the best it will have been. fingers crossed.

 

As an engineer I learnt many years ago not to listen to sales hype and to do my own research. I have owned boats for something approaching 50 plus years and I don't remember how many props I have put on boats but through research and some expensive research, buying and being wrong, I have learnt a little. One thing is leave room for the prop to shall we say breath, the 15% gap. If you don't things are not as they should be. The other is the need for the power and rpm to be able to turn the prop at the correct speed to develop its thrust, right engine and gearbox. I never ask for a quote from just one place and if there is a major difference in the size and pitch I ask why. I know that in my experience the prop you have bought has some distinct advantages but it will still be of the same order of size etc as a prop from elsewhere to achieve the required on a given boat. I will be interested to know how it performs on the new gearbox. BTW go gentle when you first go astern with it on the 2:1 gbox it has more thrust astern than most other props.

[j04n]

Prop walk.

 

You can use it to your benefit - trying to eliminate it with a magic prop isn't the answer.

It's cheaper to learn to allow for it and use it to your advantage.

 

Our LH prop on a transom stern throws to starboard in reverse, choose which way (upstream/downstream) or which side of the river or canal you moor (space to turn or mooring either side permitting) and you can neatly drop onto your chosen spot like a boss - I normally try and make sure I moor starboard side on - even if it's in the opposite direction to what I am traveling.

 

If i need to stop port side on I will turn in towards the mooring then apply a fair bit of starboard lock, this swings the bow out and the stern in, a burst of astern halts the stern swinging to port and brings us alongside perfectly - well 9/10 times

 

Wind and current should also be factored.

 

I'm often without crew so you soon learn to make life easy for yourself!

No, I wasnt. The main reason was to get more thrust for the tidal rivers. Any reduction in prop walk would just be a bonus.

[gazza]

No, I wasnt. The main reason was to get more thrust for the tidal rivers. Any reduction in prop walk would just be a bonus.

Sorry, I didn't mean you, I meant the claims made by he who shall not be named

[j04n]

Sorry, I didn't mean you, I meant the claims made by he who shall not be named

lol! no need to apologise. I didnt take offence honestly! ........ I enjoyed your explanation on taking advantage of said 'prop walk' and it made me chuckle reminding me of an occasion this summer when I was cruising up to Ripon on the river Ouse. I thought I had got the hang of mooring and even surprised myself getting into some tight spots in York but on this occasion at a lock I could not get my stern into the bank for love nor money. Even the gongoozlers were getting embarrassed and walking away. The next lock mooring was on the opposite bank so I expected it to be a breeze but still could not get my stern into the bank!

Edited September 27, 2016 by j04n