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Old Dec 01, 2013, 02:54 PM
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Update

RC gear installed and tested trims set everything fits great and CG is right on the money 35% forward from the transom. There is enough offset to the left side in balance to counter act prop torque.
So for ease of access I dry fitted the gear and set up the push rods prior to making the top deck / hatch. This allows you to see the required hatch dimension for ease of access to place back the gear without much fuss. Aluminum strap type servo holders for easy swap out if needed.

Will use as shown a 5 cell 260 mah Nimh pack (was going to use lipo but had this on hand already set up for a RX) Note 1 extra cell for longer duration as the mah amp draw from the servos will be less additionally it adds little extra range and faster servo response.

I float tested to check sit and gear balance -the first coat of paint has done a great job of sealing with no leaks.

Down to stripping out the gear and fabricating the top deck and radio hatch then final paint let cure for a few days and it should hold up to 40%nitro
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Old Dec 01, 2013, 04:10 PM
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Nice. What flywheel is that?

No, my prop screw is waay to small for the dumas flywheel. Maybe I could wrap the screw with silver tape or something to shim it centered?

.098 flex cable which I have a coupler for somewhere..

Good luck
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Old Dec 01, 2013, 07:15 PM
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Could shim with copper tube, tape may not maintain over time. Perhaps you have the next size up flywheel by dumas. which was made for up to 19 size engines as I recall. What is the bolt size of your engine if not 3mm? .098 equal to 2.5mm so with brass tube you get 3mm or 1/8.
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Old Dec 02, 2013, 12:50 AM
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Update I have finished the top deck, going with a tape down flush hatch.
Now 58.3g / 2.08 oz painted empty hull and hatch.

Next:
Need to make / install a front center skeg and do the water pickup along with a second coat on the top deck.
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Old Dec 04, 2013, 03:25 AM
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Gear going back in perhaps a test run this weekend
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Old Dec 04, 2013, 04:34 AM
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USA, ID, Coeur D'Alene
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sweet build, can't wait to see it run
if i tried anything but indoor boats here, they would come out as an icicle
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Old Dec 04, 2013, 02:09 PM
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Yea lol it is getting colder here. There is a cold front heading our way friday may make the weekend messy. If I can would like to test this and vid the effort.
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Old Dec 06, 2013, 06:35 PM
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Ok did a vid of the engine idle and a few braps of full throttle the TD .020 is very responsive idles good and instant full throttle with a throttle sleeve. the servo has plenty of throw and if you release the trigger its trimmed to idle if you push away on the trigger it will shut the engine off instantly choking it out. Took about 3 tries to set the needle to a good idle and fast ramp up to full throttle. After that it has remained consistent I have it running rich till it gets in the water. I would imagine walking speed at idle we will see. A cold front has hit my area so weather pending I will try to get some running vid next.
Did an audio Tach test 25.5 rpm at full throttle and around 15.8 rpm in idle.
video 2013 12 06 17 56 06 (0 min 48 sec)
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Old Dec 06, 2013, 07:10 PM
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Added in the center skeg and water pickup. All thats left is solder up a switch and shrink wrap the battery. Sounded like 27k rpm no load. I have a doppler program I may run it to see or use my tach. I have a radar gun will try to get a reading with that too at some point. CG is between the water pickup and the skeg. Total weight less fuel 194.2g /6.94oz power to weight ratio: 1w per 3.9g
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Old Dec 09, 2013, 01:59 PM
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That TD 0.20 sounded like an ticked off Hornet.
I have a Dumas HalfPint and a couple of Short Stuffs that I would like to put 0.49 s in with a hybread electric drive but not too sure how to go about it with the brushlles motors.
Regards,
Gerald.
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Old Dec 09, 2013, 02:48 PM
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What do you mean by Hybrid-electric? The Dumas "Half Pint"&"Short Stuff" in wood don't have much hull space and are rather heavy(barely adequate with a .049, even Cox TD). Adding the complexity of a Glow/electric drive would only make that worse!
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Old Dec 09, 2013, 03:18 PM
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Hi Gerald
Post some pics if you can I would like to see your boats. I put together a shortstuff back in the day and ran a .051 later put a QB .074
I have been looking forward to trying a TD 020 as the rpm is insane and well suited for surface drive.

A few pages in this thread I show pics of how I did a hybrid with an outrunner one is for starting a GMark 061 and a way to bring it back in when the engine dies and another was for a retrofit for a Cox TD the outrunner is to look like a flywheel but really is the power source. Out runners can be wound for very high torque eliminating the need for a gear box.
Here are the links:
http://www.rcgroups.com/forums/showp...&postcount=109
http://www.rcgroups.com/forums/showp...0&postcount=85
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Old Dec 09, 2013, 07:28 PM
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A TD .051 set up as surface drive with a modern detounged 24 to 27mm prop with lightweight RC gear using 1S lipo battery for the rx could make the Short Stuff perform. Back in the day the old rx gear was too heavy and anything less then a TD didnt do much for performance. I would suggest the grunt of a QB .074 or be done with it and install a TD .09 / the dumas 1/2A flywheel bored out to suit the .09. The mass of the flywheel was originally made to work with less power submerged drive.
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Old Dec 11, 2013, 10:41 AM
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Quote:
Originally Posted by Amp Abuser View Post
Hi Gerald
Post some pics if you can I would like to see your boats. I put together a shortstuff back in the day and ran a .051 later put a QB .074
I have been looking forward to trying a TD 020 as the rpm is insane and well suited for surface drive.

A few pages in this thread I show pics of how I did a hybrid with an outrunner one is for starting a GMark 061 and a way to bring it back in when the engine dies and another was for a retrofit for a Cox TD the outrunner is to look like a flywheel but really is the power source. Out runners can be wound for very high torque eliminating the need for a gear box.
Here are the links:
http://www.rcgroups.com/forums/showp...&postcount=109
http://www.rcgroups.com/forums/showp...0&postcount=85
There isn't much too see yet the Boats are still in there original Boxes, I have had them out to read the instructions and check the parts.
Regards,
Gerald.
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Old Dec 14, 2013, 08:38 PM
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My next project will be a out rigger hydro I am going to use this modified TD .051 has intake throttled controled rear induction to be run on 40% nitro castor blend. As a boat motor no load rpm should be over 26k on the flywheel.

List of performance enhancements:

- Rear intake gulps in more fresh air in lieu of it being mounted up front
- Pressure tap for finer max needle settings when the boat is bouncing
- Bored out the stock muffler for min loss
- Water cooled the engine for no sag
- Phenolic thrust washer to increases rpm under load
- Vibration mounting to reduce rpm loss
- No air prop by nature allows more top end I should exceed 24k rpm at load
- Sanded down the high compression glow head seats lower for higher compression
- 40% Nitro with castor
- Better reed material
- Bored out intake tube a hair
- Improved tolerance by resetting brand new piston ball socket improves snap
- Polished ports
- Replaced the needle valve for Harry Higley high performance fine threaded needle
- May remove 2mm of the piston skirt
- May widen exhaust ports 1mm each end per port for 4mm total

If anyone can think of some other tricks please pipe in
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