17' with Lister HA3 3:1, prop size?

[Monkeybox]

SCROLL DOWN... I have added some pics now so you can see what I'm on about. TA.

 

Hi, thought I would try the people on here for advice with this problem.

 

I have a small 17' hull, fairly crudely built, fitted with a Lister HA3. it has a 3:1 reduction and is turning a prop which I roughly measured at 18 1/2 so is prob 18'' or 19''.

 

It was built to tow large 40 odd ton gravel barges and had a huge towing point on the back for this.

 

It is 6' wide and is pretty deep draughted at 2 1/2ish foot depending on balasting

 

When I say crudely built I mean there are no fine lines, no long swim, although it does taper very quickly and obliquely to the prop.

 

So to the problem...

 

I have since converted this hull to a pusher tug for use on the canal. The current set up provides me with loads of power but the trouble is rather than pushing huge barges I am mainly pushing light, shallow, broken down narrowboats.

Often I have to travel long distances to fetch them.

Whilst I am traveling light I have to rev the engine to nearly full (which is 1800rpm) to go at barely walking speed. This is noisey and drinking diesel!

It is like driving a landrover down the motorway in low ratio.

 

I am wondering if the best solution is to change to a 2:1 reduction and (I don't know) keep the prop.

 

Or,

 

Put on a larger prop (but this can only go so far as there is only a few inches more before you hit counter/skeg)

 

Or,

 

Can I increase the pitch so it will push me further per rev or will I end up with a lot of froth and noise.

 

I realise these options will impact on the torque (is that right in this context?) I have available but I have oodles of power and no speed. It is a water tractor at the moment.

 

It is hardly noticing a 60' narrowboat on the front as it is, and is easier to drive with the extra length.

I know a longer boat is easier to push through the water than a short one. Also I know HA2s will happily push a 72' motor at LOW revs.

I'm trying to make this a good all rounder. Ie, can go long distance, light, at low revs but still have some serious power when pushing a large obstacle when it gets there.

Currently the wash out the back is a huge mess of turbulence which I put down to the bluff swim.

 

All contributions gratefully recieved and I will try to stick up a photo of the underside if anyone is interested/when I get the pics off my wifes computer.

 

Thanks

Edited September 18, 2009 by Monkeybox

[GUMPY]

When I had a similar problem (very under propped) I swoped to a 2:1 found that I was then over propped so then went to a finer blade.

[Monkeybox]

Thanks, interesting that you found you were then over propped. Wasn't sure if I would get away with leaving the prop as is.

[Iain_S]

Thanks, interesting that you found you were then over propped. Wasn't sure if I would get away with leaving the prop as is.

 

But Idleness (I assume) hasn;t changed how it is designed to be used. Tugs are massively under propped/geared to enable them to do their job.

 

Iain

[Monkeybox]

Right, I mean there is always going to be a degree of over gearing cos its designed to be highly geared to be able to push stuff. Don't think there is much difference whether pushing or pulling. It's getting an acceptable balance between light and laden,pushing something and not pushing something.

Edited September 17, 2009 by Monkeybox

[Iain_S]

I fed some figures into "Propking", and a 2 to 1 box with 18" prop with 13" pitch gives 6kts at 1800rpm, assuming a total length of 90' and draught of 3'. I put in a displacement of 40000lb, which is probably on the high side.

 

If you can get a 2 to 1 gearbox, it would probably be the simplest first step.

 

Iain

Edited September 17, 2009 by Iain_S

[Timleech]

Hi, thought I would try the people on here for advice with this problem.

 

I have a small 17' hull, fairly crudely built, fitted with a Lister HA3. it has a 3:1 reduction and is turning a prop which I roughly measured at 18 1/2 so is prob 18'' or 19''.

 

It was built to tow large 40 odd ton gravel barges and had a huge towing point on the back for this.

 

It is 6' wide and is pretty deep draughted at 2 1/2ish foot depending on balasting

 

 

Thanks

 

When I had a share in a boat with an HA3, 3:1, it had AFAIR about a 28" or 30" prop, from new, so there's obviously a serious mismatch in your case. Even with 2:1 I'd expect it to swing a bigger prop than yours but at least you would be getting a bit nearer to a match.

 

Tim

[nb Innisfree]

Afraid you have to accept a compromise i.e. less revs for unladen cruising with less power for towing, unless you find a two speed box or a variable pitch prop. You can't do both with one prop and single speed box

[Timleech]

Afraid you have to accept a compromise i.e. less revs for unladen cruising with less power for towing, unless you find a two speed box or a variable pitch prop. You can't do both with one prop and single speed box

 

He apparently has a gross mismatch at present, and needs to get closer to a proper match before worrying too much about that sort of sophistication

 

(that's assuming it really is an HA3!)

 

Tim

[PhilR]

He apparently has a gross mismatch at present, and needs to get closer to a proper match before worrying too much about that sort of sophistication

 

(that's assuming it really is an HA3!)

 

Tim

 

The HA3 is a lovely engine, but to work best it needs a much bigger dia prop than your boat can swing - and it sounds like the boat has a swim not much better than a brick? Changing the prop to a courser pitch and much bigger blade area is probably the best option, but everything will be a compromise

[Arnot]

The HA3 is a lovely engine, but to work best it needs a much bigger dia prop than your boat can swing - and it sounds like the boat has a swim not much better than a brick? Changing the prop to a courser pitch and much bigger blade area is probably the best option, but everything will be a compromise

It might be an idea to look at a four bladed prop... Better DAR.

 

Regards

 

Arnot

[Monkeybox]

Yes, going for 2:1 seems a good first step to get closer to an acceptable match. Also 4 bladed prop is a good idea. the surface area of the current one does not seem very high. I am no expert on props and not sure what the pitch of the one on now is.

Trying to put a pic up so you can see what I'm talking about but it's asking me for the url of the pic. It's on my hard drive, can't I upload it? I've compressed it to 400K.

Also, yes a two speed box would be great. I'll burn up to a job, hook up, then drop her into low for some serious work. But alas I don't think I am going to get that sophisticated.

And yes it is an HA3..! with a Lister Blackstone Gearbox. Main reason I bought it as it was worth it for the engine alone. Running lovely and only had to replace a leaking fuel pipe (diesel ending up in the sump and idle would ride up and down).

Thanks for all the replies.

[paulcatchpole]

Hi, thought I would try the people on here for advice with this problem.

Whilst I am traveling light I have to rev the engine to nearly full (which is 1800rpm) to go at barely walking speed. This is noisey and drinking diesel!

It is like driving a landrover down the motorway in low ratio.

 

It is hardly noticing a 60' narrowboat on the front as it is, and is easier to drive with the extra length.

 

I'm not particularly knowledgeable in this area, but is there a chance you're suffering from lots of cavitation when running unladen - perhaps the stern is so light you're getting lots of air to the prop rather than water?

 

I wonder, as you say it goes okay when it's actually pushing something, but not without!

 

I agree with sorting the mismatched prop/power/reduction issue too though!

 

PC

[GUMPY]

But Idleness (I assume) hasn;t changed how it is designed to be used. Tugs are massively under propped/geared to enable them to do their job.

 

Wasnt Idleness this time but the barge

And it was designed with an egg whisk on the back as it was on the Rochdale.

Now has much more power into the water.

When I say over propped I meant that I could only get 1400rpm out of the engine I now get 1750 flat out

went from 23X21 to 23X16 with 80% aspect blades

 

Come to think of it the only boat that I have had where I haven't changed the prop is the sailing boat.......

Edited September 18, 2009 by idleness

[Monkeybox]

Right,

Have worked out pictures so this is it.

 

Err ..yeah brick is an accurate assumption!

 

Now I look at this again it seems to have a tiny surface area, Bit of an ''egg whisk'' as someone said earlier. As you can see not much scope for more diameter but a much higher DAR is surely in order? not sure to what degree that is likey to improve things. Perhaps a 2:1 AND a better suited (higher DAR and pitch) prop and I'd be away.

They probably just put on whatever was spare around the yard. As you can see it has something of a ''homemade'' feel to it and was probably knocked up pretty roughly for the job. It came from a yard in Hull that dealt with MUCH bigger craft on the Humber. It's just coincidental its 6' and with the bumper beams, 7' wide. Ideal for the canal.

 

Going to take it to a yard, get it out and get it sorted but am interested in as many opinions as possible

 

 

The round bit you can see opposite the shaft on the vertical bar from counter to skeg is from a previous installation and does not line up with the shaft, although it does a good job of catching the bicycle tyres between itself and the prop!

 

For a clearer pic click here

http://i814.photobucket.com/albums/zz63/le...lcompressed.jpg

Edited September 18, 2009 by Monkeybox

[Monkeybox]

And now I've got pics working, this is the interior in it's ''as found state''. Looking a bit better now.

 

Massive solid stern tube too about 18 inches of it. Hardley ever get a drip!

Edited September 18, 2009 by Monkeybox