Lack of speed with current set up

[Andrew Cadden 1Participant @andrewcadden1]

I am building Yorkshireman from Model Slipway I am using 919D series 8/1 ratio motors with Lipo 7.4V 2 cell battery. The twin propellers are 4 bladed approx 45mm in diameter with approx 30 deg pitch. I have approx3.5 KG lead ballast.

The boat seems to lack any speed compared to same boat others have built I am seeking advice as to what I need to change to increase the speed of the boat.

I dont want it to travel like a speed boat but a bit faster than it travels now. bow thruster works fine as does my rudder set.

I look forward to any number of suggestions, thanks in advance.

Andrew

[Andrew Cadden 1Participant @andrewcadden1]

Yorkshireman

[Chris EParticipant @chrise]

I thought that the recommended heating was 2.5:1 on 6v of 6:1 on 12v.

I didn't know that MFA made an 8:1 919D

Edited By Chris E on 09/07/2022 06:35:41

[Tim CooperParticipant @timcooper90034]

Andrew

I have a Model Slipway Aziz. It has 2.5 ratio motors running on 9.6 volts. It doesn't seem to go too fast to me.

Tim

[Colin BishopModerator @colinbishop34627]

If the motors are geared down 8:1 tjhen they will be far too slow. As said above, a typical gearing might be between 2:1 to 2.5:1

Colin

[Tim CooperParticipant @timcooper90034]

Andrew /Colin

I have checked my instruction book (I seem to keep them all). Recommended motors are 2.5:1 MFG .

My model doesn't go too fast but Dave M always said that proportional control was there for a reason.

Tim

[Colin BishopModerator @colinbishop34627]

The perceived wisdom is always to try and keep some extra power in hand as it is often needed when conditions are against you.

If it is available you don't have to use it but if it isn't you could be stuffed!

Colin

[Chris EParticipant @chrise]

Posted by Colin Bishop on 09/07/2022 19:59:25:

The perceived wisdom is always to try and keep some extra power in hand as it is often needed when conditions are against you.

If it is available you don't have to use it but if it isn't you could be stuffed!

Colin

………. and you are building a tugboat which always has power it doesn't need solo.

[Andrew Cadden 1Participant @andrewcadden1]

Thank you all for your thoughts I will see if I can change props first with a larger pitch if that doesnt work then its new motors.

Cheers

Andrew

[Richard SimpsonParticipant @richardsimpson88330]

I have seen tugs fitted with props designed for steam use, obviously designed with quite a high pitch to give lots of torque at lower revs. It would be worth knowing what the current is with them though to ensure you are still within the motor's capabilities.

It is all a bit of a balance though between scale speed and a bit of excess to get you out of trouble. I once played with a RTR Graupner Corvette and fitted a 12V lead acid battery for propulsion. It looked absolutely ridiculous on the water at a scale 90 knots! I changed it for a 6V lead acid battery and it is still over scale speed at full throttle but a lot easier to manoeuvre and I don't use full.

[Ray Wood 3Participant @raywood3]

Hi Andrew,

I wouldn't bother changing the props for a different pitch that won't make much difference if you havn't got sufficient RPM on the shafts

Speed is all relative, If it goes too fast flat out use the throttle control after all tugs are designed to pull & push things around, not free range round a lake, build a barge/ship to tow.

Regards Ray

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