33hp for river travel?

[bassplayer]

goose bumps ?

I vaguely remember those when I worked at the British Shipbuilders Ship Model Experimentation Tank many years ago.

 

We made the hulls out of wax and GRP and had our own workshop making scaled down props.

 

I owe you an apology too for my cider comments. I just got a bit miffed when you dismissed my original comment about torque being a factor.

[John V]

In that case you deserve an apology from me.....I think I was fair in taking you to task but inadequacy was undeserved

[bassplayer]

In that case you deserve an apology from me.....I think I was fair in taking you to task but inadequacy was undeserved

No problem John...that Old Rosie is bloomin' strong though! I should know better really, I knew someone who went mad on cider...it's dodgy stuff...

[Pluto]

What you really need for inland waters is Barcroft's semi-immersed propellor. Designed to make conversion of horse boats easy, in theory it was only a little less efficient than a conventional propellor, but in practise on canals …

 

[Dalslandia]

The argument about torque and HP, is almost as old as the hen and the egg. we can't have one without the other. This torq/hp thread come up on the home build airplane forum from time to time too, so it start to get amusing.

 

But we see as the example I made with half and double rpm/torque, that at the end it is the propeller that make thrust, and that from HP

In the more advanced propeller calculations the input is HP and RPM, but at the end propeller torque is balanced with engine torque.

 

Power is what we get when making more or less useful work, a propeller moves a mass of water (or air) to get thrust that propel us forward

Since John Ericson and others at the same time inventing a useful propeller, no one come up with anything better, it have just been refined, especially lately with CFD and computer assisted calculations, it still have to be programmed by man.

[bassplayer]

The argument about torque and HP, is almost as old as the hen and the egg. we can't have one without the other. This torq/hp thread come up on the home build airplane forum from time to time too, so it start to get amusing.

 

But we see as the example I made with half and double rpm/torque, that at the end it is the propeller that make thrust, and that from HP

In the more advanced propeller calculations the input is HP and RPM, but at the end propeller torque is balanced with engine torque.

 

Power is what we get when making more or less useful work, a propeller moves a mass of water (or air) to get thrust that propel us forward

Since John Ericson and others at the same time inventing a useful propeller, no one come up with anything better, it have just been refined, especially lately with CFD and computer assisted calculations, it still have to be programmed by man.

Any contra rotating props being used these days? It is quite funny how some designs just stick. A bit like the wheel really.

[Naughty Cal]

Any contra rotating props being used these days? It is quite funny how some designs just stick. A bit like the wheel really.

We have them on our boat although Vp call them counter rotating.

 

A 3 bladed and a 4 bladed prop.

 

Great for picking up lumps of wood!

[Dalslandia]

O yes, Volvo have them on there Duo-prop Z rig, and now also as tractor propellers on there ? IPS (name) drive, that is mounted at the bottom of the boat instead of on the transom.

 

http://www.volvopenta.com/volvopenta/se/sv-se/marine_leisure_engines/drives/dps_duoprop/pages/dps%20_duoprop.aspx

 

http://www.volvopenta.com/VOLVOPENTA/SE/SV-SE/MARINE_LEISURE_ENGINES/VOLVO_PENTA_IPS/FORWARD_FACING/Pages/forwardfacing.aspx

 

I know one of the designers of those Volvo PENTA drives. when I was designing dual-rotating propellers for the only Bugatti Airplane 100P, a replica Is being built in USA, and the PENTA engineer was building a RC model of the same airplane.

 

He said the "only" thing better with duo-prop is that the housing can be made smaller/slimmer, because the torque is divided on two gear set.

The duo props them self is more efficient, but some or most of that is lost in bearing and gear friction, and they also make more vibrations and noise, but no prop walk

Edited October 6, 2014 by Dalslandia

[bassplayer]

We have them on our boat although Vp call them counter rotating.

 

A 3 bladed and a 4 bladed prop.

 

Great for picking up lumps of wood!

So are yours on 2 shafts, side by side then?

[John V]

What you really need for inland waters is Barcroft's semi-immersed propellor. Designed to make conversion of horse boats easy, in theory it was only a little less efficient than a conventional propellor, but in practise on canals …

 

 

 

 

 

Brilliant Pluto!!! I mentioned something like this in a thread a bit ago, I don't think this is the same one that I knew about but it's good to know the memory isn't totally banjaxed

[Dalslandia]

 

 

 

 

Brilliant Pluto!!! I mentioned something like this in a thread a bit ago, I don't think this is the same one that I knew about but it's good to know the memory isn't totally banjaxed

Isn't the propeller fully submerged when full cargo load? Look at the propellers they look fully modern :-)

[Naughty Cal]

So are yours on 2 shafts, side by side then?

No. Two shafts one inside the other.

[John V]

So are yours on 2 shafts, side by side then?

 

There's an American Lake boat along from me has contrarotating props on a pair of outdrive legs ( the chap who skippered it across the channel for them reckoned it was the only thing about the boat that wasn't cxxp)

Edited October 6, 2014 by John V

[Naughty Cal]

 

There's an American Lake boat along from me has contrarotating props on a pair of outdrive legs ( the chap who skippered it across the channel for them reckoned it was the only thing about the boat that wasn't cxxp)

Oh I don't know. They usually have a big fridge

[Dalslandia]

 

There's an American Lake boat along from me has contrarotating props on a pair of outdrive legs ( the chap who skippered it across the channel for them reckoned it was the only thing about the boat that wasn't cxxp)

 

American design and built isn't crap, it is just fast and wrong :-)

[John V]

 

American design and built isn't crap, it is just fast and wrong :-)

[Bod]

I have a boat with a 35hp engine.

Earlier in this thread, the idea was given that at canal speeds only 3.5hp was used to propel the boat.

Can I declare 10% for Fuel Duty for propulsion?

 

Bod

[MtB]

Fair comment, apologies for the cider induced name calling (I'm paying for it now!)...post duly edited.

 

Fair play for manning up to the cider thing. Duly greenied.

 

And I'll edit the name out where I quoted your post as you've edited your original.

 

 

MtB

[bassplayer]

 

Fair play for manning up to the cider thing. Duly greenied.

 

And I'll edit the name out where I quoted your post as you've edited your original.

 

 

MtB

Thanks.When I used to be on facebook I had a rule not to post stuff after a few drinks.I should apply that rule here!

[bizzard]

The Fairy Gannet aeroplane had contra-rotating props on the same shaft for aircraft carrier use.

[bassplayer]

The Fairy Gannet aeroplane had contra-rotating props on the same shaft for aircraft carrier use.

It's on some helicopters too. I presume another good side effect is that you don't need a tail rotor to stabilise the yaw effect....

[Timleech]

The Fairy Gannet aeroplane had contra-rotating props on the same shaft for aircraft carrier use.

 

So did the Shackleton, some of them anyway.

 

I can see (admittedly as someone who has never flown anything) it could make powerful single-engined aircraft easier to handle.

 

Tim

[redfastlad]

when we had our 57ft nb boat built I specified the 45hp Shire Barrus mainly because we would be spending most of our time on the river Trent including the tidal, also we had the 3 alternator travel pack option as well. I have punched back up the Trent in flood on 3 ocassions and one year we managed to collect Trout and its butty (70ft working boats) breasted them up and got them to Sawley lock safely, now this engine is well on top of the job and on our last trip up the river I put on *dashboard* on my mobile phone and using the GPS watched the speed of the boat with the rpm counter it is quite interesting that over 1900 rpm the boat did not go signifiguently faster ie 2000rpm gained nothing and 2100rpm gained .5 of a mile per hour. so I settled for 1900rpm and 3.8-4.0 miles per hour. This would indicate that the hull shape and swim area are the most important parts not really the engine, so whilst I have reserves of power ( up to 3000rpm) it is only in flood conditions that I need to use them, by the way my prop which I thought was under sized at 17x12 is bang on according to the people over in Manchester who make the props, so 33hp would be good enough in my book for normal river work.

[c c]

Still don't know the horsepower of a DM2

[Dalslandia]

Can it be 27?

http://www.russellnewbery.com/engines.html