New to power

[propwash]

Hello everyone,

Another relative newbi here.

 

I've been a member of a couple of clubs in the past but although they say that they are friendly and welcome new comers, I've found they can be quite cliquey.

I'm no wallflower, neither am I too forward and pushy so maybe it’s me.

 

So I thought I would join your forum.

The reason being like a lot of other modellers is that I need help and advise occasionally.

 

I've always built and sailed RC yachts,but I would like to have a go at powered models.

 

So When asked by my lovely wife what I would like for Christmas I said the 1/8th scale model Perkasa by Precedent.

Sorry to be scouting all round the houses but feel the need to explain myself.

I don’t want to screw up an expensive bit of gear by getting it wrong.

So the question I would like to put to any of you fellow modeller’s is this.

The model is 49” long, would it be wise to go for twin props.

If twin props, would it be better to have them counter-rotate.

.

If so would a 50 amp controller be adequate for two 550 brushed motors that I was thinking of using? 

Or would a single prop be enough to put her up on the plane.

 

Thank’s

Dave 

 

[NMBROOK]

Hi Dave

Although I have more experience with scale RC builds,I would say the minimum of two props.If you want to get the boat on plane properly,a hull of this size would need an IC engine to do this with a single prop.Counter rotation is a must.When viewed from the stern the rhs prop needs to rotate anti-clockwise and the lhs prop clockwise.I would go for large motors say graupner 700bb turbo's as anything smaller may end up being a disappointment.Water cooling coils on the motors may be a good safeguard.The key to planing and handling in the turns is going to be a lot of experimentation of battery placement within the hull,so I wouldn't go mad with glue on any battery holders until you have got her on the water and had a play.Some experimentation with prop size and pitch may also be required.A good start point may be to find a log on the net of someone that has built one of these.It may give you a 'heads up'as to where better to start with the drivetrain.Don't rule out the new brushless motors either as they have a very high output for their size and weight,but I don't know enough about these to give you any further advice.I have seen one of these kits on the net running three IC engines and triple props!

Kind Regards Nigel

[propwash]

Hi Nigel,

Thanks for all your helpful suggestions.

I've read articles on the use of brushless motors  for marine  models and it seems that they are not so good at slow revs.

So based on what you advised with the twin  graupner 700bb turbo's do you think I would get away with a single 50 amp controller?

And what size props would your recommend?

Best regards and thanks again.

Dave

[NMBROOK]

Hi Dave

I checked the spec on the motor and the current drain at maximum efficiency is 15a.However the stall current is rated at 77a.The 77a draw would only happen if the prop fouled something in the water.This could be protected against by using a suitable inline fuse between controller and motor.You may find it is as cheap to get two smaller controllers as buying one big one.Two would enable you to balance the boat better by placing one at each side of the hull.Personally I would go for two 40amp controllers protected by 35a fuses.As regards props,I would have said start with 35mm and work from there.If you are in the UK,I would recommend calling Propshop and discuss the project them.With their experience they should be able to advise better than me.I would start with cheap nylon props first until you find the ideal dia/pitch that works best.Then by all means invest in some nice balanced props,other wise you may end up spending a fortune on propellers.Looking in Graupners catalogue they do a complete drive unit consisting of 700bb turbo motor,motor mount,coupling,shaft with grease nipple and prop.They also include a rudder but this is transom mount,so if you are going for scale appearance this would be no use.

Kind Regards Nigel

[cdogg]

Dave, I am a static boat guy but would like to make an RC boat in the future.  Hope you enjoy MSW and hopefully yourself and Nigel can help me out when I have RC boat questions.  Welcome!

[propwash]

Hi every body,

Thanks for the welcome, and to Nigel for giving me food for thought.

 

As to modelling as a whole I am finding it increasingly harder to find a decent Model shop near me.

A few weeks ago I needed some Balsa and other bits and pieces and had to travel about 40 miles to get what I required an 80 mile round trip.

I mentioned to the salesman about this problem, and said half joking "Hope you're not thinking of closing"  and he said that it might be about another 4/5 years and they would be gone.

I asked why this was and he said that the youngsters today are not interested in modelling, they have their I-phones and tablets and game consoles and that the generation of modellers that are left are dying out.

 

I came out of the shop quite depressed.

I didn't think that the modelling world was declining that badly, I know we all shop on line a lot more but there are times when you need to see the product, like when you're buying timber.

I don't want a snotty nosed youth in a warehouse  tapping away on face book picking soft Balsa when I want hard, and lite ply all twisted and bowed.

Have any of forum had this experience of Model shops closing like there's no tomorrow?

 

(Modulator)  I don't have the experience to put this post where it would be best seen. 

 

Regards to All

Dave

[NMBROOK]

It is a very sad day Dave,I must agree and fairly typical in the Uk.As you know modelzone folded,not that they really sold anything I wanted,but a shop fairly local to me shut(been going there for thirty five years!)This was especially upsetting because it was a real aladin's cave with staff that knew their stuff. I am faced mainly with buying stuff mail order,but if I know that the modelshop 20 miles away stocks what I want,I will make a point of buying it from them.I don't want that one to close otherwise I may need something immediately and have to wait two days for the postman.Mail order is great but to a point.If you buy your planking ready cut then it is nice to go to the shop and pick through the timber to get strips all of the same colour.As for your running gear your best option is unfortunately mail order and cornwall model boats is your best bet.The best traditional model shop I know of and have actually been a couple of times is westbourne model centre but unfortunately it is the wrong side of the New Forest for you.

Kind Regards Nigel

[cdnfurball]

Well Propwash,. I have been down the same road regarding setting up the drive.    Everyone told me " trial and error "   voltage, how many motors, brushed or brushless, diameter of props, 3 blade or 4, flex or hard driveshaft... Etc..  etc

So, buy a bunch of extra parts and what you don't use for this boat.....    You will have some inventory for your next project

[No Idea]

Hi Dave - If you want some really good advice regarding building and using a Perkasa this is the place to ask 

 

https://www.modelboatmayhem.co.uk/forum/index.php

 

There have been many built on here and they tend to specialise in RC too.  You will also find all of the model shops and websites that you need in the UK