Frayed lines, stiff wings, and little engines
By Gene Pape
Have you ever jumped in head first and wished you hadn't? Yeah, me too. Since I had such great success with the Seal Lamin on the open frames, I cut out cores and parts to make 5 new Millennium Underdogs. I got them all ready to cover, then finished one to make sure all was well before covering the rest. Then it rained. Since no one would go out to test with me, I finished the other 4 models. What could go wrong? If you've ever built a model that's not rigid enough against twisting, you know. When the model was launched, because of a slight warp, it rolled a bit outboard wing down. When it did that, the leadouts pulled down on the inboard tip causing the model to roll more. By now, it was pulling really hard. I decided to just fly it level until it ran out of fuel and I could deal with the warp. Just before it ran out of fuel, both lines snapped and the plane flew away. Happiness is an H&R shutoff. There was little damage to the plane, but taking it home t fix properly seemed like the thing to do at the time.
The latest Millennium Underdog. All photos by Gene Pape.
My next flight was on another new model which was covered instead with my usual FasCal. This flight went without a hitch until I landed. I immediately noticed one of the lines was frayed at the leadout guides, all but a few strand were broken. What the!? It seemed like a good time to call it a day and think about things for a bit. I took the planes home and installed brass bushings in all of my steel leadout guides which, by the way, I have been using since 2008 when I started flying again. I also stopped to realize that the lines that had failed had been in use for four years. While visiting with Norm McFadden, he pointed out that as the lines moved through the leadout guides, they were continually flexing causing the lines to fatigue and ultimately fail. Since I have had other lines fail in a similar fashion during matches in the last few years, I am now going to pay attention to how many flights are put on each set of lines and do some rather extreme pull testing at regular intervals to determine what the life expectancy of a set of lines is. I am also going to move the bellcrank pivot to very near the cg on future models to minimize the flexing at the leadout guide. I now have several sets of new lines.
My first fix of the Seal Lamin covered models was to simply put a diagonal strip of 2" wide clear packing tape diagonally from the spar at the root to the trailing edge at the tip on the inboard wing. This didn't help much, if at all. I then added to that a zig zag pattern of 2" wide clear packing tape starting on the top of the wing at the trailing edge tip going diagonal to about 4" in from the tip at the leading edge, and continuing around the wing until I got to the root. I then repeated this pattern on the bottom of the wing. This resulted in the stiffest foam wing I've ever had. It was then easy to trim the remaining models. Note that the added tape is virtually invisible.
John Thompson brought to everyone's attention that the Evolution .36 control line engine is still available from Horizon Hobby:
This is a great engine which I have used for speed limit for years. They run right out of the box, and they're much easier to start than F2D .15s. What I discovered when going to the website is that most of the parts are available including the venturi inserts and tongue mufflers, which just happen to bolt onto the ASP .25 RC engine, which is also a very good choice for speed limit combat. The ASP .25 with the Evolution venturi and tongue muffler weigh almost exactly the same as a Nelson .36. You do, however, have to fabricate custom mounts as both of these engines are about 1/8" narrower than the Nelson. This picture shows an ASP .25 with the Evolution .36 parts. With the muffler on this engine, I can now fly my combat models at the county park we are allowed to fly at when the airport site is not available.
The ASP .25 with an Evolution .36 tongue muffler and venturi.
I finally got around to trying the carbon fiber 1/2A combat props from Eliminator Props.
They were consistently better than the fiberglass props they are copied from. If you want the very best and don't mind the work to finish them, these are the props for you.
While I have been flying fast combat as my main focus since 1962, I've always thought more could be done with Cox reed valve .049s. I set out to build a model using a bladder tank and one of the engines that comes with no tank about 2 years ago when Ken Burdick got me sidetracked with the Wido Satan project. Ken finally got a Black Widow to work consistently after doing serious modifications to the tank using uniflow style venting. Being too lazy to do this, I still can't get one of the integral tank engines to run through maneuvers. I'm not convinced I'm not fighting some as yet undiscovered gremlin, but you would think I would have found it after trying since 2009 to get one to work. After doing the Wido Satan, I was also convinced that virtually all 1/2A models aver built were way too small.
Last week, I finally bolted one of the tankless engines I got from coxengines.ca onto a Yuvenko high-performance 1/2a model. The Cox .049 bolted up to a Cyclon/Fora engine mount after elongating the two lower mounting holes slightly. I then made extensions for the mount using 3/8" wide strips of 16 gage aluminum sheet 4" long to get the model to balance properly. I figured the 35' long lines used for the low-performance 1/2A combat event should work fine for this model. I firmly believe I now have the best Cox reed valve .049-powered control line sport model on the planet! John Thompson did the entire stunt pattern with it on his first flight. Mike Denlis flew it and had a huge grin on his face after the flight. My current plan includes using these models for practice combat and general sport flying. Give it a try with your favorite high performance 1/2A. You'll have a ball!
A Yuvenko high-performance 1/2-A Combat plane powered by a reed valve Cox engine.
This page was upated May 19, 2016