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[DickyD]

Divvent fret wor Dicky - jus reed slowa man! 

Sorry, cant read that slow I have a life to be getting on with.

[John W E]

Hi there

One of the reasons that both the props are left-handed is the space available inboard.  The gearboxes on the end of the motor face towards the stern.   To incorporate a reversed gearing into one of the gear boxes - you would have to slightly increase the length of the gearbox and therefore shortening the propshaft.   Or, do what they do on the military vessels and use a reverse 'V' drive - where the engines are literally mounted over the top of the prop shafts drive through a 'V' drive gear box which incorporates a reversing gear for one of the engines.   Now, one of the other reasons through tests carried out, it has been proven that both props turning the same way produces a slightly faster boat.

The other thing is of course, cost.   Reverse drive gear boxes are pretty expensive in the 'real I am world' some of them may cost as much as the main motor themselves.

aye
john

[Flying Sparks]

The extensions on the bottom of the ‘P’ brackets are rope cutters.  These are there to try and prevent the propellers from being fouled and also to give some protection against the tips of the blades on grounding.

Hi Bluebird

Aha. Thanks for your reply, obvious really, except for people like me.

Phil.

[Perkasaman2]

A semi bare shaft + bushed 'p' bracket setup will certainly have the scale look but an ultra/zultra high rev engine (brushless or 700 BB) installation may wear out the unlubricated 'p' bracket/shaft very quickly. The much (50%?) slower  12 pole 900 (MMB/BB's) on big prop(s) may be an alternative and avoid/reduce this wear n' tear and give sparkling performance and increase  serviceability. The model single bush bracket is cooled by waterflow but friction/vibration may be a real issue with an ultra  hi rev scale setup.

[DickyD]

 

[Bradley]

The model single bush bracket is cooled by waterflow but friction/vibration may be a real issue with an ultra  hi rev scale setup. 

Many thanks.  This is something I have thought about and am considering.

Derek.   

[John W E]

Hi ya there Derek

I wouldn't concern yourself too much about vibrations on an open shaft.  The distance between your tube and the 'P' bracket will be no more than 75mm on a 4mm shaft.  Even running on a standard prop tube without any open shaft, you still have the same length of shaft.   With an open shaft though, you have the added bonus of there being a 3rd support bearing.   I am including 2 photographs....of an M.T.B.... it has 3 shafts, runs 3 MTronek motors, and these motors run between 16,000 rpm and 20,000 rpm.  This boat will whitewash many a /Perkassa/aye/ / / /

aye john e/blue/bird

[Perkasaman2]

 Perks were almost 20 knots faster....     (Happy New Year to ALL!  )

[John W E]

  ///// ///////////////

[Bradley]

Many thanks, John.  I have already got one prop and shaft from Sitek, to help with setting up and intend getting the rest from him (including 'P' brackets) as he makes them as required and, I think, his prices and workmanship are pretty good.
Just as an aside, I believe that the bearings in full size 'P' brackets were rubber with channels cut in them to allow water to flow through to lubricate.

Derek.   

[DickyD]

Perks were almost 20 knots faster....     (Happy New Year to ALL!  )

Faster than what ? 

[Perkasaman2]

Ok Dicky Marra, here's one clue..........................  488  ( my favourite type of that period) Further clues in 2010 if sober enough. 

[Flying Sparks]

Derek

Any news on your Huntsman?

I've had some progress on mine now, could be running in a couple of weeks. Will have to wait for warmer weather until I do the finishing and detailing, too cold at present for spraying paint outside. Do you mind if I post some updates on your Huntsman thread, don't want to hijack it.

Phil.

[Bradley]

Hi Phil,

My Huntsman has progressed very slightly but due to the cold  and trying to work on my Cygnus 33 I have not got very far but will post a couple of pics soon.

I will be more than pleased to see some of your pics and updates on here and I am sure other Mayhemmers will also - it all helps to keep the thread going.

Derek.

[Flying Sparks]

My Huntsman will be ready for a run this weekend, just need to fasten down the superstructure I don't want it flying off! The prop tube has been replaced and fitted at a sensible angle.A bracket has been made up to mount the motor, and the motor fitted. Will post some piccys soon. The paintwork will have to wait for the warmer weather so it still looks a bit rough.

Does anybody know where a Huntsman should balance? I've left space so that the battery can be moved around and changed for different sizes. When I work out which pack I will use I can make up a box to hold it in place.

Phil.

[Bradley]

Well done, Phil.  I think that the balance point should be about midships as the boat should run almost level (or very slightly bows up) when planing but the final level can only be gained by experimenting 'on the water'.

Derek.

[HS93 (RIP)]

there are so many variables have long battery leads and if using more than one be able to move them about, forget static see how it runs and play with weight moving don't add extra weight it just looses you speed and a Huntsman has to be fast, don't feel dispondant if it is not as fast as you hoped it may just need a prop change.

Peter

[Flying Sparks]

Thanks for your input guys. When I was given the model it had a couple of pounds of lead in the stern and the first thing I did was rip this out. I would rather use more batteries than lead, at least then any extra wight is earning its keep. With the battery pack in the centre of the hull it balance just about aft of the centre so I guess this should be a good starting point. Also I have several props to try and I will plug in my data logger to see how much current the motor is drawing.

Phil.

[HS93 (RIP)]

we used data logging and gps testing pauls two boats red181 , plus where fortunat to have a few Props to try these are some of them.

Peter

[Perkasaman2]

The 'Rainhill Trials' .......... was there a 'Rocket' amongst them in the case? They look fairly large -- I'm researching for a pair of 50/52.5 mm dia. handed props and a lot of them look pretty close to those sizes. 

[HS93 (RIP)]

no that was down the road, yes there a a few around that size some smaller some larger the thinking is low a low KV and big steam prop or similar we found a clever worked well with both geared 700s and Brushelss.

peter

[Flying Sparks]

Peter

WOW, thats quite a collection of props there!!!  I will have to do with a few plastic one for now. I haven't got a GPS (yet) for my logger but I have got amps, volts and temperature, enough to make sure I don't wreck anything.

Phil

[red181]

I know every set up is different, but the 52.5mm "x2 prop seems to win all the time, with amp draw speed and acceleration on my boat. 55mm things get too hot, and its no faster, 50mm and under a noticable drop in speed, testing is the only real test!
Good luck, keep us posted

[HS93 (RIP)]

the best way is to start small and work up, you can see if the temp start rising, if you go big straight away you can have a barbecue before you start..     

peter 

[red181]

well............................................there is a tale to HS93's post, might aswell share it for a laugh. Few months ago I was testing my floating gym palace, the Huntsman, decided, as it was very cold, and rain threatening, to just go straight for the biggest prop that would fit, for approx 5 seconds the boat was so fast I was petrified, then I finally achieved that ellusive very black smoke that all smoke units cannot deliver, very impressive. Ubec literally blew up, the capacitor left the boat at a fast speed, one of the lipos died, and the esc fried (very impressively)Thats what you get for not being careful

I remember the day well, sept 29th, my birthday! HS93 p***ed himself laughing! and will not let me forget it. Lot to be said for testing in private on your own.....................................