Model Boat Mayhem

The Shipyard ( Dry Dock ): Builds & Questions => Pleasure boats, Sports, Race, Power and Leisure Boats: => Topic started by: GarthT on June 28, 2020, 09:57:04 am

Title: Diana, 14" semi-scale Huntress
Post by: GarthT on June 28, 2020, 09:57:04 am
This boat was featured in Model Boats, Winter 2010.  The idea of a small but fast boat appeals, so I'm considering this for my next model.  The recommended motor is a Graupner Multispeed 380 unit.  As far as I can see this motor is no longer available and, in any case, I thought a small brushless/Lipo combination would save weight.


Has anyone any experience/suggestions for a motor, coupling, prop combination for this size of boat?


Of course I could perfectly well build one of the Fairey kits available, and I may well end up doing that, but I'd like to consider this option first.


Thanks, Garth
Title: Re: Diana, 14" semi-scale Huntress
Post by: Tug Fanatic on June 28, 2020, 10:47:58 am
Try this for starters. As always these are just my thoughts.

A Graupner Multispeed 380 was actually a 2:1 reduction gearbox on the back of a 7.2v Graupner 400 motor. The Graupner 400 on 7.2v = 16400rpm which with the 2:1 reduction is 8400rpm or more usefully 1200kv on 2S or 800kv on 3S.

Any brushless motor with a suitable kv and weighing around 40-50 grammes (or perhaps less) would be a good place to start and coupled with a suitable Li-Po pack should be very sprightly.

Build light.
Title: Re: Diana, 14" semi-scale Huntress
Post by: ChrisF on June 28, 2020, 09:45:12 pm
If you do decide to build something else and would rather build from plans than a kit then Sarik do the plans for a 1:12 Huntress which is a nice size and more accurate with regards to the full size boat.

Chris
Title: Re: Diana, 14" semi-scale Huntress
Post by: Tug Fanatic on June 29, 2020, 08:02:18 am
I should have added that the prop on the Multispeed was a 2 Blade plastic "X" style 32.5mm Diameter and 52mm Pitch
Title: Re: Diana, 14" semi-scale Huntress
Post by: roycv on June 29, 2020, 09:06:27 am
Hello You reminded me, I made a 16 inch Fairey, I thought Hunter, but it is the one with the rear accomodation as well.  I think it was based on the free plan Twinkler or a derivative.  But I designed the s/s from photographs.  That was in the early 1980's. 

She has a 5 inch beam and runs on an MFA 380 with 1 : 2 reduction gears the prop is Prop shop 3 blade 30mm.  Running on 6 volts (5 cells, a discarded camera battery).  She is made from 0.8mm ply.
The first few minutes are insane on the water and then she calms down and planes with only 3 or 4 inches of hull in the water. 

Probably 30 watts i.e. 6 volts at 5 amps.  There was also a small Rx battery and a standard 2 ch. Rx. and rudder servo.

I have just weighed her at 499 grms less batteries rx and rudder servo.
I need to do a repair to the wrapparround windshield as I had the boat all ready for an outing after a small refurbishment, closed the shed door and a stout length of 1/2 inch dowel crashed down from storage across the perspex and broke off one side of the perspex.

 Having just got her out of the cupboard again I might work out a repair!  But I shall reduce the voltage to 4.8 and may use a smaller prop.
Good luck with your model 30 watts is beyond what this hull can deal with and I shall go down to 20 watts.  Do make sure you incorporate spray rails.

regards
Roy


Title: Re: Diana, 14" semi-scale Huntress
Post by: roycv on June 29, 2020, 09:31:09 am
Hope this comes out, just photo'd this morning while the sun was out.Roy
Title: Re: Diana, 14" semi-scale Huntress
Post by: roycv on June 29, 2020, 09:32:25 am
You can see the broken perspex on the port side.
Roy
Title: Re: Diana, 14" semi-scale Huntress
Post by: GarthT on July 01, 2020, 05:02:35 pm
Thanks for the input.  Roy, your boat is lovely.  I've decided after all to build from a kit.
Title: Re: Diana, 14" semi-scale Huntress
Post by: roycv on July 01, 2020, 05:25:37 pm
Hi thanks for the kind words, the 23 inch kit I have seen on line looks very nice, no experience of it.  My one is a Fairey Huntsman 31 with aft superstructure.  There is a build log of a very similar boat on the forum at the moment.

If you are going sailing with RC then a 23 inch boat is better than going too small, as anything smaller will be a bit affected by weather conditions.

regards
Roy
Title: Re: Diana, 14" semi-scale Huntress
Post by: DaveM on July 01, 2020, 08:06:42 pm
My prototype 23" Huntress at Wicksteed in 2016. Starts at 7.22-ish  https://www.youtube.com/watch?reload=9&v=JzHGhfT45wo&feature=youtu.be (https://www.youtube.com/watch?reload=9&v=JzHGhfT45wo&feature=youtu.be)

DaveM