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[John W E]

good doy thore my friend Martin doon under

Just been looking right through the build to check up on the props that you used on this model; although the actual diameter of the propeller at 50 mm looks about right for scale; the actual surface area of the blade or the props you used looks small?

So, to compensate, you could go up to about a 60 - 65 mm diameter; prop - Dont want to go to big cos you dont want to begin to put excessive load on the motors, cos then consequences will be shorter running times etc., etc.

See you on SKYPE my mate  to discuss further.

aye
john
bluebird

[Shipmate60]

Martin,
What rpm do those motors run at?
With a 3:1 reduction g/box those props shouldn't let them break into a sweat.
But as John says there isnt a great blade area or pitch so you would need plenty of rpm to drive her.
It might be cavitating but would take quite a few revs to do that with those props.

Bob

[pugwash]

 Hi Martin,  Something in back of my mind seems to think Vosper Thorneycroft got round the cavitation
problem by using high revving but small propellers - I don't know if it would work in a scaled down state
but I dont see why not.

Geoff

[Shipmate60]

The props on the full size ship were quite small but had a large blade area and almost 45 degree pitch.

Bob

[FullLeatherJacket]

The Darke Horse catalogue gives the following figures for the output shaft speed:-

3:1 gearbox: 9330RPM @ 24v; 10880RPM @ 28v
4:1 gearbox: 6700RPM @ 24v; 8150RPM @ 28v.

John Darke recommends using 55mm brass 3 or 4 blade props with the 4:1 version. Hope this helps.
Personally I wouldn't pay too much attention to making the props look scale-size; performance is what matters most (and the things are under the water anyway).
FLJ

[Martin13]

Taking into consideration the cost of props (not cheap for three).

What size props do you recommend  - I was thinking Type "A" 60mm or 65mm three blade props-  Hope to travel down south tomorrow and purchase some new props.

By the way, these motors are fitted with the 3:1 gearbox

I'm not fussy with how many blades or what size just as long as this boat goes a bit quicker - Ive seen tugs move faster in the water

Mdu

[FullLeatherJacket]

PM sent.

[Martin13]

PM sent.

PM received, PM sent

Mdu

[John W E]

hi ya there Martin Doon Under

After looking at the specs of Dark Horse motors, I myself, don't rate em very well.  Plenty of tork obviously through the gear box but no revs there, especially on 24 volts.  To get your boat up on the plane; you should be looking at somewhere between 15000 and 20000 rpm - hindsight should have used Graupner/Mtroniks.  You will have to go to 60 mm props minimum.

Anyway, its up to your goodself my mate.

Another cuppa tea 

[pugwash]

Martin I don't know whether these will be any help to you.

Geoff

[Perkasaman2]

Another BB clip Martin (with an impressive triple sound track).                            

http://www.britishpathe.com/record.php?id=36057

[gbolddak]

Hi Martin,
I'm really very interested in seeing how you get on with this one!!  In particular how much power you end up having to provide.  Based on my 30" one that consumes around 45 watts to get on the plane and using the scale cubed rule, I guess you'll need around 400 watts total power from your three motors.  I'm not convinced about this rule of thumb so hopefully your experience can help.

Fascinating ........ and very well done.  I'm learning as you go along, so please keep up the posting  :)

Thanks
Iain

hi I would sujest 3 900 would be more than enogh power and with a low comsumtion 2 12v 9amphr would kive you long running time

[ooyah/2]

Hi Martin,
I have been watching your build of Brave Borderer and must compliment you on your building skill and attention to detail.
Many years ago ( about 30 ) I built a B.B. from model maker plans to a scale of 3/8" to 1 ft but as the plan had no details other than hull lines I found a great deal of info on PRESEDENT PERKASA's booklet on their model.
It originally had an I.C. engine in it but as the Glasgow Parks Dept band I.C's it lay in the loft for many years.
I have always been a steam enthusiast but recently have taken up as a diversion fast electric, so she was resurrected from the loft , cleaned up and a brushless motor installed.
As I am not a very good boat builder ( rather cut metal and machine engines ) I have been reluctant to post, but as it's very much stand off ( 50ft) don't look too close.
A club member recently videod it so here is the link to You-tube (  http://www.youtube.com/watch?v=c2FxmJ20mkk )  and some pics of the boat.
I see that you havn't posted your progress recently so how about an up date.
George.

[treeboa]

what a cracking thread, many years ago a lad i knew built a big `perky` after seeing my 1/24 scale, times and attitudes were a bit different to now and his had a pair of modded and watercooled chainsaw engines in it, i have a fond memory of laying on it adjusting his throttle linkages while it was underway  , once i had done that and got off it was given a handfull of ooomph, it shrieked off up the lake sounding like a kamikazi milkfloat, left my 65 powered 50 inch perkasa in its wake, main thing was at speed it refused to have a decent turn rate and had to be throttled right back to turn it around

[pugwash]

Martin - any updates on BB and KGV was really enjoying the builds.

Geoff

[CLASHED]

as above 

[Martin13]

Thanks for all the kind comments and prodding by many to get back to BB. Leg is sort-of heeling after break but impossible to launch models without help from others.
Have also been tied up with commitments to get "Task Force 72 Fleet Base Victoria" up and running and can say we have Albert Park Lake as our permanent sailing venue. For all the European and UK based members, you may know of the Lake as its in the middle of the Australian F1 GP track.

BB - as you are aware, I painted BB in its original paint scheme of "Light Admiralty Grey" and as time went on I grew to dislike the colour - it just didn't look right. I mixed up some AP507C (HMS Vanguard) and Light Weatherworks Grey (Arkeigh Burke DDG) and came up with a shade of grey which looked great for a model of this size, then re-painted BB. I took the model down to the Lake and my fellow sailing  members thought BB looked the part.

The main battery box assembly  has been moved and now installed between motors and transom with the 4 ballast batteries removed altogether - I have also installed 60mm props.

Now the bad news -  the motors installed are only pulling around 4200 rpm - clearly not enough to get this beast on the plane. Later on (much later on ) when finances are improved, Ill see about getting some 12V Graupner or similar motors.

Currently I have 4 other models on the building board plus a couple of gliders all wanting my attention but intend to spend most time on BB and USS Lassen DDG..

I'll post some pics in the near future and thanks again for all the kind comments and by all means, post any relevent info etc here on this thread..

Martin doon under

[pugwash]

Martin nice to see BB is back on the slipway again

Geoff

[Peter Fitness]

Good to hear from you again, Martin. I hope the leg continues to improve and you are soon back modelling.

Peter.

[chandler]

i really like your build and technique u are a true inspiration, i hope i get enough knowledge to some day build my own like that 

[martin13]

HELLO

Must post some pics - no excuse for not doing so - think its gonna rain for 40 nights and 40 days down ere'

Martin du

[DickyD]

Hi Martin

An update would not go amiss.

Not a good idea to talk about rain in UK at the moment.   

[Peter Fitness]

Must post some pics - no excuse for not doing so - think its gonna rain for 40 nights and 40 days down ere'

Definitely, Martin - the pics that is As for the rain - it seems that it has already rained for 40 days and 40 nights here. Ever since we moved back to the farm I've been ankle deep in mud. Thank goodness for Wellington boots

Peter.

[RAAArtyGunner]

No Sunshine up here either 

[BrianB6]

Nor down this way either. 
We are supposed to go to the sunshine coast sometime but whats the point?