Thread Tools
Old Feb 25, 2012, 11:31 PM
KiwiDavid is offline
Find More Posts by KiwiDavid
Registered User

Highly accurate useless information (my 1930 Dumas Chris Craft.)

Hi All,
Being a nice day I decided to take my (nearly finished) 1930 Dumas Chris Craft to the pond to check it's performance.
I have a GPS widget I designed some time ago to log max speed, avg speed, elapsed time and distance traveled. Battery used was a 2000mA.H, 11.1V LiPo.
Max speed 13.4kph (looked fast but a tad short of hoped for speed)
Duration 38 mins (usual somewhat heavy foot but also some cruising)
Distance covered 4.04 Km

I was impressed with the run time compared to my other boats with a 12-15 min run time, even if they are somewhat quicker at around 18-19kph.

The motor I'm using has the following spec-
No load rpm 11800 at 12v, 0.8A
Stall torque at 26A
Max power 79W
At max efficiency - 43W, 9800rpm, torque 0.42kgcm, 4.7A
Prop (currently) Octura Y543P Diam 1.34". Pitch 2.05"

While the boat planes nicely I do wonder if the speed is just a bit lame. I have a spare Graupner Speed 500 which will drop in and I know this combo will drive me to around 18kph but only for around 12 minutes.

Should I leave well enough alone and enjoy the scale look and long duration or cater for the (elderly) boy racer in me?

Sign up now
to remove ads between posts
Old Feb 26, 2012, 12:30 AM
CaptCB is offline
Find More Posts by CaptCB
Registered User
CaptCB's Avatar
I will take run time, over speed, any day. I want to enjoy myself, otherwise, I would get into some sort of racing, and spend CUBIC DOLLARS. CB
Old Feb 26, 2012, 01:56 AM
jeepers1940 is offline
Find More Posts by jeepers1940
Registered User
What he said.
Old Feb 26, 2012, 04:05 AM
KiwiDavid is offline
Find More Posts by KiwiDavid
Registered User
Thanks for the replies. I think you're probably correct and run time is important for a scale boat.
I may drop the prop down a step in pitch just to see if revving a tad higher may help. Based on my other boats measured speed and the motor data I have on them this boat should have been nearer 20kph so obviously I have a lot more learning to do to get things right.

Old Feb 26, 2012, 09:09 AM
der kapitan is offline
Find More Posts by der kapitan
"day ain't over yet-"
der kapitan's Avatar
David, be happy with the setup you've come up with---.
Old Feb 26, 2012, 09:13 AM
Kcal is offline
Find More Posts by Kcal
Registered User
You could also switch back and forth as your mood dictates?
Old Feb 26, 2012, 11:52 PM
KiwiDavid is offline
Find More Posts by KiwiDavid
Registered User
You're right. I should be happy with what I have and I can always switch the motor for added wow factor.
I guess I wanted to get an idea as to what was a reasonable speed for a 1/8 scale runabout. I've watched a lot of videos with inflated claims of speed - "30mph" boats being passed by ducks.
If I hadn't measured the speed I'd be happy - the look and the duration are fine and it's just the number that looks slow.

Old Feb 27, 2012, 04:22 AM
woodybob is offline
Find More Posts by woodybob
woodybob's Avatar
The 1930 Dumas runabout is a heavy one. Here’s a video kmot did of my 1930 C~C. Kmot introduced me to the group here. My runabout went through several props before I got a Raboesch Brass Prop. Not as fast as the old Octura props, but the runtime makes up for any lost speed.
Old Feb 27, 2012, 06:02 AM
Sharky1dk is offline
Find More Posts by Sharky1dk
Sharky1dk's Avatar
????? no pictures????
Old Feb 27, 2012, 06:20 PM
frankg is offline
Find More Posts by frankg
Registered User
Speed in the Dumas 1930 - 24ft runabout can be obtained but with big power and battery capacity. The propeller used in this model was one of the old Dumas cast bronze props, 1 3/4” diameter, 2” pitch.
Old Feb 28, 2012, 02:59 AM
KiwiDavid is offline
Find More Posts by KiwiDavid
Registered User
Those are impressive models and no doubt the standard by which all others will be judged. A tough act to follow!

I have uploaded a very short clip of my boat in the video forum section which I didn't know existed until tonight. I had never scrolled down there but did click on the video of woodybob's boat on the sidebar the other day - very nice.

I have the bronze Dumas prop and also a BeCu prop OCY534 which I'm too scared to process after dire warnings from a friend.
I'll drop the pitch down and see if the increase in revs can give it a slight improvement. If nothing else it should further improve the battery life as I move further away from the maximum power and back nearer maximum efficiency.
I can model these things in Spice (full electrical and mechanical modelling) but things like hull drag and air resistance are unknowns. I need a full wave tank and wind tunnel with lots of data acquisition.......or I could just go to the pond.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion 1930 Chris Craft/Dumas 1230 KiwiDavid Scale Boats 11 Oct 18, 2011 05:57 AM
Discussion Dumas 1930 Chris Craft KiwiDavid Scale Boats 4 Aug 03, 2011 07:11 AM
Discussion Dumas Chris Craft 1230 kit contents. (1930 24' ) KiwiDavid Scale Boats 18 Jun 21, 2011 07:59 PM
Discussion Help needed with Dumas 1930 Chris Craft bub9797 Scale Boats 19 Apr 15, 2010 05:34 PM
For Sale Dumas Chris Craft 1930 Runabout W/Extras Mo.Hawk Boats (FS/W) 0 Dec 28, 2005 04:14 PM