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ruddym's blog
Posted by ruddym | Apr 30, 2011 @ 04:21 PM | 4,200 Views
1) remove the plastic covering from the ESC
2) stick on a bit of masking tape cut just smaller than the factory heat sink -- leave a flap sticking up so you can peel it off easily
Note: this assumes a flat plate heat sink and would not work with a finned heat sink
3) pour a sufficient amount of Brush on Electrical Tape (or other liquid conformal coating) in a container you can throw out later
4) immerse the ESC in the liquid bath (Yes, immerse it. Contrary to the name, don't try to brush on this stuff.)
5) remove from the bath
6) peel off the masking tape
7) let dry

You are left with a sealed ESC that still has its heat sink surface exposed. Make sure you work outside and wear latex gloves. This stuff reeks and I'm sure it's not healthy to handle it. I "treat" several ESCs as a batch, because once the Brush on Electrical Tape is out of its can, it soon congeals and is no good for further use.

I recently "tested" one such treated ESC on my Smart Dart when the motor mount pulled away in flight and the plane plummeted into a pond of snow melt. Full immersion for a couple of minutes until I could wade out to retrieve it. After drying everything thoroughly in a container of dry rice... not a single problem with the electronics.
Posted by ruddym | Oct 07, 2010 @ 08:26 AM | 5,371 Views
I am really liking carbon fiber ribbon for strengthening foamies. It's a Dave Brown product that comes as a 1/2" ribbon about 1 meter long. I found it at my LHS.

To work with the stuff, nick an end and peel off a strip of the width you need.

I like to glue up a right-angle cross and stick it on the elevator/rudder hinge line on Nutballs. It holds the vertical stab upright without need for CF rod triangle reinforcements, etc. Then I carry the CF ribbon along the bottom spine. This gives (especially EPP) Nutballs front-to-back stiffness and reinforces the "chin" area behind the motor mount. Another thing you can do is chop off the back corner of the spine and allow the CF ribbon to bulge out there, forming a tail skid. See the attached picture for clarification.

I suggest using hot glue and a covering iron to attach the CF ribbon. Apply a line of hot glue along the edge, then flatten and spread it with a covering iron. Let cool. Lay the CF ribbon and iron it on; the heat of the iron re-melts the glue for a strong bond.

The only downside to CF ribbon is that you have to be careful of slivers. It's easy to get a sliver off the stuff and yes it hurts.

This product has helped make my planes stiffer and lighter. If I think up more uses for it, I'll post back here. If you have discovered other good uses, please comment.
Posted by ruddym | Sep 21, 2010 @ 09:49 PM | 6,190 Views
Thanks to good information from Dave North and others, I successfully completed my second motor rewind. It was one of the red 'n blue Turnigy 2211s and I used a winding documented by Mike Bergy, 18T #26 wire terminated wye.

What a way to wake up this little motor. Running it on 2S with a 7035 prop "feels" like similar thrust as the stock motor delivered with an 8043. I wish I had some measuring equipment. What I do know is my flight times are up noticeably, so efficiency has improved along with power output.

This project happened to coincide with me buying two Hyperion 3G 450mAh 2S batteries. Using a fast 3.3C charge rate on the batteries, combined with the longer flights enabled by this new winding, I can fly continuously with just the two batteries. Yahoo!
Posted by ruddym | Sep 14, 2010 @ 02:09 PM | 11,543 Views
RC aircraft I've made:

^Latest build on top^

19) "Stingray" Smart Dart (my own design) - A mash-up of my Bonanza V-tail dart and the Longhorn. Good, but not as good as the mighty Bonanza. Details here.
18) Fiddlehead 24" - A bigger version of the Fiddlehead. It's a trainer for Jonah and Chi. Set up with low throws, it's a nice, docile plane for learning on.
17) Fatty F4F Wildcat by redwhskers - for Chi. RW's whole "Fatty" series of warbirds looks great. I built the Wildcat with Smart Dart mods, as described here. It is one fantastic RET plane.
16) Fiddlehead 18" (my own design) - I started out intending to build joseico90's Underball but ended up blending his design with gpw's Bullseye and Otto Deiffenbach's prop slot noise reduction technique, for a completely new design. The result is excellent and Fiddlehead now has its own discussion thread.
15) "Beechcraft Bonanza" Smart Dart (my own design) - This V-tail is superb. A real wolf in sheep's clothing. Details, starting here.
14) Snowball - 25-1/2" diameter with KFm-1 step (mostly for reinforcing the fuselage and sponsons). It took a few flights to get the CG and control throws sorted. Still flies only so-so. (pictures) Decision: scrapped for parts.
13) Dart-51 by Gene Bond - with Zeke. Once properly balanced and trimmed, this plane is pure magic. It's my favourite scratch build so far, I think. Gracefully aerobatic, responsive, forgiving. Who can resist its cartoon warbird...Continue Reading
Posted by ruddym | Jul 09, 2010 @ 09:15 AM | 6,836 Views
UPDATE: Calculations were previously limited to down and right thrust. Now, down, up, right, and left thrust angles are possible.

Here's a simple and accurate way make a motor mount with thrust angles as spec'd in your airplane design.

Grab the following spreadsheet:

motor_mount_calc.zip

After entering your thrust angles, print the spreadsheet and cut out the pie chart you need (3-hole in the following example). I make the following sandwich and clamp it onto a hard flat surface until dry:

==TOP==
wax paper
square piece of 1/8" birch plywood
epoxy
printed paper pie chart, face down
epoxy
wax paper
==BOTTOM==

This gives a super strong motor mount and the clamping squeezes out most of the epoxy, so it's lightweight. The wax paper protects your workbench and tools; remove when dry.

Next, center punch the pie chart lamination, tack down onto a scrap of wood, and cut out with a hole saw of the size you need, preferably on a drill press. Sand rough edges. Now place the motor on the mount and line up its flange holes to the lines on the pie chart. Drill holes for the screws.

Now it'll look like this:

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The picture shows it already mounted on the plane. The "top" line (left of the shaded area on the pie chart) was used to visually align the mount.

Now you're ready to mount the motor. Add washers to get the required shim thickness, like so:

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Done! This motor is angled 5° down and 3° right.

Note: This is just my preferred motor mount building method, but you can use the spreadsheet with other mounts. Just enter your numbers, print and align the pie chart to the mount, mark the hole locations, remove the chart, drill, shim, etc.