Darin's 25" Radtek Mystic N2 Build

[Darin Jordan]

I like this idea here Darin. You don't think it will compress too much air?

It might, but I really didn't have much choice. There just isn't room to mount the single power system in there. I tried to make the drop as minimally airflow disruptive as possible.

Guess we'll find out in a couple of weeks.

[properchopper]

D,

When I ended up years ago with Brian's "modded sponson" H&M Shovel I needed to drop the motor down a tad. Here's the "quick n' dirtyredneck technique" that worked for me :

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C Ya' Soon

[Darin Jordan]

D,

When I ended up years ago with Brian's "modded sponson" H&M Shovel I needed to drop the motor down a tad. Here's the "quick n' dirtyredneck technique" that worked for me :

Hahaha... Works though, right Tony!

Here are a couple more shots, including one of the motor next to a P-Ltd motor to give you an idea of just how tight the fit in this hull is for a single motor. A pair of 28mms, one in each sponson, would definitely be easier to fit. Wish N2-Cat allowed dual motors!

[srislash]

Wow, that is a tight squeeze Darin. I see the need for the drop down.

[Darin Jordan]

Now have the "stuffing tube" setup installed. Setting up for a 1/16" Wire drive. I used an inner and outer K&S Brass tubing setup, so I could replace the inner piece if necessary. I believe the inner piece is 3/32" x 0.014" (wall thickness), which slides into a 1/8" x 0.014" outer piece.

"Stuffing Tube" just supports the wire where it passes through the hull. Wire will be exposed the remainder of the way to the strut. I will "seal" the inner end of the brass tubing with a small piece of fuel tubing and grease. It's a SAW boat. It's not intended to side idle in the water for any long periods of time, and will have the drive-line serviced before each run.

The hole through the hull was one drill size larger than the tubing, and the full drive-line was installed prior to Epoxying the brass into place. Wire follows a nice natural smooth bend, for the most part. It's not "forced" into place. The black tape on the outside of the hull is to keep the epoxy on the inside while it sets up. The well on the inside provides a nice "pooling" area for the epoxy. Should be nice and stable under load.

That said, if I could go back and do this one more time, I would lay the motor down just a tad more to further relieve the bending.

The inner piece of brass will get a spot of silicone or CA or maybe some light sleeve retainer, all of which will provide a seal and will secure the piece in place, but that can be made to release with a little dissolver or heat.

I'm considering running a .047" (3/64") wire instead of the 1/16". Takes less energy to make the bend, and I do think, considering the power system and the size of the props I'll be attempting to use, it would be more than adequate for this purpose. I'm going to build both types of drives-shaft so I can try both.

[Darin Jordan]

Oh, one more thing...

The strut, motor, etc., were all set in place, and the strut set to about where I would expect it to need to run, PRIOR to gluing everything in place. I don't expect to have to move the strut much from where it is. If I have to move it, it will be better if it needs to go down rather than up, which would increase the bend. It really helps to make for a smooth drive-line if you take the steps to get EVERYTHING in place prior to installing the stuffing tube.

[Darin Jordan]

Made a little more progress this weekend.

Have the hardware all mounted, motor in place, and ESC is now connected and programmed.

Spent a good chunk of my time this weekend, which wasn't as much time as I'd hoped it to be, lathing up some couplers and bullets for the driveline.

I did a full "systems check" last night, and it's all ready to button things up. Not going to paint it for now. Going to actually do some testing and running BEFORE painting it for a change.

Waiting for my batteries to get here. Once they are here, I'll get some pics of everything installed and ready to run.

I'm a LITTLE bit concerned about the wire-drive bend, which is a little more than I wanted exiting the hull, but I think it'll be OK. I'll have to keep an eye on it. Luckily, if it breaks, which will be right about where it exists the hull, if experience has taught me anything, I won't lose a prop because of the bullet arrangement at the front of the strut. The stub-shaft is captured in the strut, so it'll just mean a failed run. If it's a problem, the fix will involve putting the motor in at a more relaxed angle, which is going to be some major rework, so hopefully not...

[kfxguy]

Oh, one more thing...

The strut, motor, etc., were all set in place, and the strut set to about where I would expect it to need to run, PRIOR to gluing everything in place. I don't expect to have to move the strut much from where it is. If I have to move it, it will be better if it needs to go down rather than up, which would increase the bend. It really helps to make for a smooth drive-line if you take the steps to get EVERYTHING in place prior to installing the stuffing tube.

That's how I did mine. My flex is super smooth compared to any other boat I have in my possession. I took a lot of time trying to get the least amount of bend and resistance as possible.

[Darin Jordan]

That's how I did mine. My flex is super smooth compared to any other bist I have in my possession. I even have a SAW boat someone else built and mine is smoother and easier to turn. I took a lot of time trying to get the least amount of bend and resistance as possible.

The bend on mine is a "natural bend", but it could be flatter if I repositioned the motor at a flatter angle.

I think it'll be OK. I'm considering trying a .047" wire at some point. This isn't a "high-torque", 15-series (36+mm) setup, so for pushing the ultimate limits, a .047" may work. I'll just make sure to have lots of replacements and will consider it a part that gets replaced frequently. :)

[Darin Jordan]

Well, despite having the miss the SAW event this weekend, I worked last night prepping anyhow and managed to get my Mystic together and ready for some test runs.

Got a shipment from Horizon Hobby and Thunder Power R/C containing my new batteries for this boat. Using paralleled 2S 2700mAh 70C G8 Pro Force cells, so I can mount one on each side.

I generally HATE paralleling cells, but it's the only way, in this hull, to get the balance I need.

Decided to use this boat to begin my switching over to 5.5mm contacts on the battery leads. I had been using 6mm, but I think that the extra grip length on the 5.5's actually make them a better connector, so I'm switching over.

Made up some paralleling adapters in the conventional fashion, but after trying to fit everything in the boat, I decided to make some dedicated paralleling adapters that would allow for better fit of the battery wires. Space is tight.

I made them by using the contacts with the holes in the barrels. I drilled them out to 5/32" (the male contacts were already that size) and used a piece of brass tubing to line them up and hold them in place. I then soldered them together and installed shrink wrap. Turned out pretty nice, and they allow for a better fit of the wiring inside this already cramped hull.

I had already prepped the ESC and trimmed the wires down. Were I to do it again (and I will do another ESC shortly, just waiting for the material for the cooling plates) I will leave the battery wires about 1" longer to allow a little easier fitment of the wiring.

[Darin Jordan]

The finished adapters look like this...

[Darin Jordan]

The sponson tubs are just barely wide enough to lay the battery packs down in, but they fit. The ESC and left battery pack are pretty much fixed in place. Any balancing will have to be done with the right-side battery.

As it sits in the picture, the hull balances at right about 30%, or 6.9" from the trailing edges of the sponsons. Plenty of room to move things around.

It's tight in there, but everything fits. Guess the next step would be the charge some cells, hook up a prop, and go see how she runs.

Since I'm not going to make this weekend's SAW event, I guess that'll give me time to get her painted, if she tests well.

Finished weight to this point is right about 3lbs 4.4oz. That's about 1/2lb or so heavier than I think it needs to be, but we'll see how it runs. I'm certain this hull could be laid up, still very strong, but at least 5 or 6oz lighter. That said, I think it's going to hold up VERY nicely!

[Rocstar]

Very cool, look forward to seeing what she can do.

[kfxguy]

Can't wait to see some video!

[srislash]

Looks good Darin. Geez, tipping the scales at just over 3lbs, Cute little gaffer. LOL Excellent job. Hope the maiden runs well.