I have a teedee 049 and an 051, on a smaller plane (22" wingspan, 110 sq in). I have in my collection several propellers that I acquired about 10 years ago, and they have not been used. 6x4, 6x3, 5.5x4, 5x4, 5.3. Any recommendations as to which one would work best?
In the past I used 6x3. Then one day I switched to a 5 1/4 x 3, and it flat screamed. Not sure how good it was on the engine. But I've never flown a teedee before - what difference, performance wise, is there between a 5 1/4 x 4, a 5.5x4 and a 6x4? I had someone once tell me to use a 6x4 for combat, but I've never flown combat. I am much better at building then I am at flying :-P
Almost everything about Cox engines, including manuals,
From memory a 5x3 gave the best overall power..6x4's will lower the RPM and give more thrust on a larger plane, and may suit the 051 better.
Try em all!
TeeDees need RPMs to develop their power. Any 6" prop will likely be too much on a TeeDee. For control line combat they use rip-snorting pressurized .36 screamers and use 7.5" or so props. I'd say the 5-3 or 5.25-3 or 4" pitch would be where to start.
Also, the brand of the prop makes a big difference as well. The Cox grey (stiffer) or black (more flexible) props have a very wide blade and will load the engine more than a similarly sized prop with a narrower blade.
On a fast, sleek plane the smaller prop will allow the engine to spin faster and propel the plane faster. Using a big slow prop on a sleek plane will feel like driving around in the wrong gear.
On the other hand, high RPM is wasted on a large draggy plane. A bigger prop will bring out the advantages of slower planes, which are acceleration and climbing. Like the sleek plane with a big prop, a big plane with a little prop will feel like a car driving around in the wrong gear.
To prove this to yourself and get a feel for it, try each of your different props on your engine and see what happens. Next time you build a plane, build a bigger, draggier one such as a small trainer or biplane, and try all of the different props again and see what happens.
You can fly a fairly large trainer nicely with an 049 if you use the correct prop. In fact, I designed a nifty little 1/2A trainer in 1994 that ALMOST got published in RC Modeler. They canceled the article because they saw the coming trend of cheap ARFs and the waning interest in small glow engines. Oh well... Anyway, my trainer has a 42 inch wingspan with a target weight of 20 ounces or less, and it will fly with authority using a low powered Texaco 049 and a 7x4.5 prop. Just a few years ago I also designed my own small version of the Ugly Stick with a
26 inch wingspan. The one I built for myself used to go pretty fast with the same Texaco engine and a 6 inch prop. One of the local guys here in Kansas City had me build 10 of them to use for pylon racing and other fun stuff in their club. They used to fly them with Cox Killer Bee engines and 5X4 props. Their planes would go so fast it would make your head spin.
Interesting - a 6" is ok for say bees or medallions, but use a shorter prop on a teedee? I do distinctly recall the 5 1/4x3 gave a very noticeable increase in speed with a black widow, and wondered why a 6x3 was recommended.
So do you still have the plans? If so, why not publish them through one of the on-line plan sites? There are still lots of 1/2A engines lying around unused!
That's a good idea. I was digging through some stuff about 2 weeks ago and came across my article, building photos, and captions. I assumed that times have changed and there would be little interest in building one's own balsa trainer for 049 power. But you never know.
It's a nice little airplane built out of sheet wood with a few sticks and a single piece of plywood for the firewall. I trained 3 new pilots with it, and when they thought they had mastered it I showed them that it could do a lot of stunts that they didn't even know about yet.
The 6x4 is too much load for either engine. BTW the .051 develops exactly the same power as the .049 so treat them as the same engine.
A 6-3 is okay for these engines, but it is the largest prop you should run on them. It is a good choice for larger and/or draggier aircraft. For scooting around on a small clean airplane the 5-3 is good, and yes the engine will turn it fast, perhaps over 20k. Just remember that these small engines love to run up there, it is where they are happiest. As a matter of fact, just this past Friday night I was at a garage party that involved grilled porterhouses, olive oil fried french fries (oh yeah!) and beverages of course, and we talked about airplanes all night - model and full scale. Anyhow, as a treat for these guys who had never even heard of one, I brought a TeeDee .010 and fired it up in the garage (early in the night, pre-beverages..). I was running it on 40% nitro fuel (yes, 22% oil and >50% castor you small engine people) and you should have seen the look on their faces as I tuned it up and got it running just shy of peak, at somewhere around 27-28,000 rpm. They were totally amazed at how crazy this little thing sounded at that speed, and I had to explain to them that 28,000 prm on that small an engine is everyday business, no more stress than a larger engine running at say 15,000. Anyhow I digress, the point I wanted to make is except for small and exceptionally aerodynamically clean airframes, I have usually seen the best overall performance on the 3" pitch props versus
4", regardless of whether we're talking 5, 5,5, or 6" diameter. I think it is the nature of these small engines that they make their best HP up high, and don't like a lot of load due to their low torque. There are technical holes in that generalized theory I know, but they just seem happier and the aircraft seem to perform better. In fact, some of the APC 2" pitch props are the bees knees in certain applications.. the larger diameters have a fair bit of disk area in conjunction with the low pitch/high rpm, resulting in a lot of thrust at low airspeeds, i.e. high "static" thrust. But hey, experiment with the 4" pitch props and see for yourself which works the best, you might find the 5-4 gives higher airspeeds. I just do not recommend running 6-4 props on Cox .049's, I think they are too much load and the engines don't seem to like them, at least none of mine ever did. Well, sure you could run one on a Texaco .049 but why?MJD
olive oil fried french fries? Num!
I once put a popsicle stick on my peewee .02 just to see what it would do. OMG it screamed! And then it overheated - doh. I was maybe 15 at the time, and just wanted to see what would happen.
Yeah. Most definitely pre-beverages. Otherwise fingertips can get cut off, or worse lol :(
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