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Jul 24, 2017, 09:37 PM
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Build Log

Trail Boat


Greetings, I am new to this forum as of today and wanted to share my most recent build. The hull is a 13 inch balsa wattscraft river hull. I wanted to try something no one had done before and build a "trail boat" sort of like a nqd jet boat or a thrasher however I am using a surface drive. Here is the build progress so far. Enjoy
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Jul 26, 2017, 01:36 AM
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Update


Got a bit more painting done today. Next step is a clear coat and then some tests in the bath!
Jul 26, 2017, 06:26 AM
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Looks fantastic, congratulations !
Joao
Jul 26, 2017, 08:21 AM
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Thanks Joao!
Jul 27, 2017, 10:02 AM
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Hi KB,

Nice build, but I have a few observations:
- a boat this size with a solid shaft should use a longer propshaft, so the motor slides under the front deck to reduce the propshaft angle.
Built as it is, the proshaft angle is too steep, if you can elongate the hole where it exits the transom, so the propshaft angle is reduced, it may run better.

Right now the thrust of the prop will lift the transom and push the bow down.

- depending on the prop choice, you may get away without watercooling, but I wouldn't count on it.
Brushtab cooling is the least you'll need, adding a cooling coil too would be better.

Regards, Jan.
Jul 27, 2017, 05:39 PM
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Thanks so much for the suggestions Jan. I figured I would need water cooling. I will absolutely look into adding a longer propshaft. Thanks again!
Jul 28, 2017, 11:32 PM
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Update


Machined my own dual rudder system today so It's closer to completion! Still waiting on a RC4WD LED Lightbar to arrive and a few more details to the deck before I put her in some proper water larger than the bath!
Jul 29, 2017, 05:03 AM
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Hi KB,

Here's a link to one of my posts regarding brushtab cooling:
https://www.rcgroups.com/forums/show...93&postcount=4

If you google for brushtab cooling you'll get more pictures, often mine...: https://www.google.nl/search?q=Brush...LcktwkzvG_oXM:

Regards, Jan.
Jul 29, 2017, 05:19 AM
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Thanks again Jan. Just wondering would I have to remove the armature to cut the cooling tabs in the can?

Regards KB
Jul 29, 2017, 04:44 PM
Boaters are nice people.
Hi KB,

Brushtab cooling on a Mabuchi/Johnson does not involve any cutting, or taking out the armature.

Basically you solder a piece of brass tubing to each brushtab, making sure you keep the brass free from the can, avoiding a short.
Please study the pictures in the link I provided.

The brass tubes are connected on one side to create a loop, the other two ends are the inlet and outlet of the watercooling.

Running in sweet water won't short out the brushtabs through the tubes connecting them. Salt water has a higher conductivety for current, but making seperate inlets and outlets for each brushtab (not connecting the two with a short piece of silicon tubing) creates a long enough path to avoid a short.

Regards, Jan.
Jul 29, 2017, 08:47 PM
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Thanks again Jan that looks like a great idea I will look into it!
Jul 30, 2017, 04:48 AM
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Update


I am currently installing a longer prop shaft to reduce the angle of the shaft and propeller like Jan has suggested. I also found a perfect fitting outershaft stuffing for it!
Jul 31, 2017, 06:50 AM
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Hi KB,

Pictures please!?

It's no good to have a perfect fitting stuffing tube, as the name says, there should be a bearing at each end, leaving room between the tube and the shaft to 'stuff' some grease into it, lubricating the bearings and keep the water out.

A 'stuffing tube' that hugs the shaft over its entire length has a huge amount of drag, specially if grease is used.

Regards, Jan.
Jul 31, 2017, 10:05 PM
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Hey Jan although Your advice is great and I have followed your suggestions on the prop/shaft angle this build is simply a fun basher type boat, not a racing boat. Hence why I am not very worried about drag and making everything precise. No offence im sure you know a lot more about this stuff than I do, however I am just looking to have fun and not spend much money. Pics to come soon!
Aug 01, 2017, 04:38 AM
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Update


Here's my latest photos I have just tried her out in the bath and everything went very well! Although one thing I noticed is the boat did tend to find it hard to get up on plane but I imagine this is due to the fact that i'm using it in the bath. So tomorrow if the weather allows me I plan to take it to my nearest swale ( a small man made lake in my country) and try her out!


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