Tips & Tricks

Jim Hiller sent me a few pictures and some construction notes describing how to build a fixture to hold dowel hard points allowing you to pre-drill them.  Below are the details on how to build this handy device.

Jim Hiller’s Hard Point Fixture.

The fixture is made from 1/2" x 5/8" maple motor mount material about 4 1/2" long to pre-drill dowel hard points. I use them for wing mount and strut attachment hard points as well as machine screw control horn mounts. After drilling and tapping each end for 10-24 x 3/4" socket heat cap screws I clamped a 1/16" spacer between them and drilled 3/16" through 1/2" diameter holes to clamp short pieces of dowel. I like to pre-drill them and this fixture clamps them and holds them vertical while drilling.

Hard Point Fixture in use.

Thanks Jim for sharing this idea! I encourage you to share your ideas and tips with the pattern community.  All you have to do is send me your great ideas and I will publish them in the K-factor for all to enjoy.

Below are a number of facts, most of this information I have learned from the NSRCA list or other pilots. I'm placing this here for reference. This material is in no particular order:

1.) Setup for a Webra 145 AAR running a Johnson 2 1/4 rise header and a ES D2C160L9 pipe.

Set it up for 24" from the baffle to the glow plug (IIRC the baffle is 13.5" back from the front of the pipe). That length gives a nice amount of boost without being peaky whether you run 15% nitro or Magnum #1. With an APC 17x12 you should see ~8200 rpm +/- 200 rpm depending on what nitro and whose fuel you choose. Be aware that if the motor is new the idle won't be too great until you get >15 or 20 flights on it. The top end numbers won't come into their own until about then either. The sleeve on the Webra's is really hard and it takes 20+ flights for it to really "settle in" and then it just gets better and better. (Jerry Budd)
 

2.) Here are Rex’s instructions on how to modify a True Turn spinner to pump cool air into your electric motor:   

“I taped up the prop slots with tape, and put a piece of tape over the bolt hole on the inside, then waxed the complete inside.  I used some stuff called Fix-It-All to make the mold.  It's a plaster repair that just mixes with water.  It sets up really fast.  I just filled the spinner and let it set till the next morning.  I just stuck a bolt in the hole and tapped it with a hammer, and the mold popped out.  The slots I made are about 30mm long.  I think a guy could make them up to around 40mm with no problem.

Mark the lines for the slots on the spinner.  Put the spinner back on the mold, the prop cutouts will line it up perfect every time.  Drill a small hole at each end of the slots.  Then I just used a thin Diamond wheel to cut the slots.  You have to do all this while it's on the mold, that way you get the mold marked exactly.  When I cut my slots, I ran the diamond wheel right down into the mold.  After that, just take the spinner off the mold and use a sanding drum to shape the louver depression in the mold. You'll have to make a soft punch for forming the louver.  I used a piece of balsa that was about 20mm X 10mm.  I rounded the end to about the shape that the louver was and then used a heavy hammer to pound the louver in.  You have to start in the middle of the louver, and work your way to the ends.  It's really pretty simple. The aluminum forms pretty easy, but you have to keep pressure on the spinner to keep it forced down on the mold, so there can't be any deforming.  I just set it down on a piece of carpet and stood on the spinner tip.

The thing I like most about this mod, is that you don't really notice it unless you are looking right into the louver.  I doubt that it uses up any power to speak of, because it's just chopping off the air in a high pressure area.”

Thanks Rex for the tip!

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Revised: 03/11/2007