CEF Profile Scale Speed 2015!

modelbuilder49 wrote:

roddie wrote:Hi Jim, Have you thought of using a little less fuel? How many cc's is getting you 23 laps? The leaning-out (speeding-up) of the engine will come sooner in the flight; preferably (I would think..) toward the last few laps. Personally.. I'd rather turn 16 or 17 laps at 50+ mph.. than 23!

Greetings Roddie!  For the purpose of the example, I was using a Black Widow with its stock tank and just filling it up .  As silly as this may sound, I honestly never thought about that, short tanking, that is   !!  It's a great idea!  Thanks, I'll give a shot !!

Jim

If you don't already have one Jim; a cc-graduated syringe for fueling is very helpful. I believe that some contestants were easily getting their laps in on 5cc's. (Babe Bee tank) with laps to spare.. The APC 4" props add instant performance.. I bought (x3) 4.75" x 4's from Tower Hobbies. I didn't get tach #'s.. but there was a marked gain in rpm's over a Cox black 5 x 4 using Sig's 1/2A 25% nitro blend. If you haven't tried that prop yet, you could see a lot more speed at less laps on a full tank. Your Black Widow would like that prop!

ARUP wrote:Roddie- we were using 35' lines (handle to ~center of model) and standard 2 bladed black Cox props. The lines are green fishing line. Can't remember exactly but mine are braided DuPont 'Iron Line(?)' 10lb test or some such. They are pretty draggy. You really see them bow due to air pressure. I'll have to find a way to get videos for the races!
Thanks for compliment, Getback (Eric)!

Yea.. I've heard about line-drag with synthetic braid. Apparently it gets worse if they become oil soaked. I bought 30# SpiderWire EZBraid for the 1st CEF contest. I never got the plane airborne to see how the 42' set felt. Since then I bought 15# test.. which I plan on making a 35' set with.



The 30# is .3mm dia. (.0118") and the 15# is .2mm dia. (.0079"). The 30# test was definitely overkill..

getback wrote:do the props from towers fit on the cox 049 engines or do they need an adaptor ?   http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHMK2&P=7 Thanks , Eric

They need a bushing to fit the Cox .049's 5-40 prop-screw Eric. I believe that Ken Cook knows where to find them.

I made the adapter over a friends house. I passed my adapter onto Mike Parkin who made them a lot faster and in more quantity then I could produce them. Mike was responsible for the aluminum TD carb bodies that he was making and selling on Ebay. Mike went under the name I believe which was Ridenfligh. I haven't seen anything from Mike listed on Ebay in months. I really need to get in touch with him. Not all APC props have the same relief in the back of the prop. However, I designed the adapter to work with the plastic bushing that comes with the props. They're a direct fit without the plastic bushing for several and from memory: 5x3 6x2 5.5x2 . The plastic bushing is required when you get into the 4.4x2 4.25 x 3.75 4.2 x 4 and so on. If you use a short piece of tubing and place it on the thread of the screw, you can screw the prop screw into the prop and spin the entire assembly onto the engine. I did it for years and still do it. It works fine. The only reason I designed the bushing was to not only and 100% center the prop but for the ease of swapping a prop in 1/2A combat. Every second your plane is airborne is 1 point. It's critical not to be futzing with your equipment and having a fast pitman. That's where my son comes into play.