vertical grimmace

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The spar resides in a channel cut in the foam. I have what I call spar slot templates, that I cut after the airfoil is cut with the hot wire. The spars are 1/8" x 1/4". I do not get fancy with tapering them , of trying to lighten them. They are just too small for that. These are glued in flush or just under the surface with white elmers glue. THe reason is it dries transparent. I have used many glues over the years, and always go back to elmers. It is very important to not have the spars protrude above the surface, as it will act like a spoiler and kill your lift. Killing your ability to turn tightly without a stall. I sure hope your right about how they fly! The original is a blast. Maybe I will be able to get some video here sometime soon.

vertical grimmace

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I think the Russians are finding 1/2 A useful. I always liked them for practice. This is from 2015.


https://www.youtube.com/watch?t=52&v=zAVVP01AI-o

combatpigg

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I'd like to see film footage of this by a major network camera crew.
Mike Wilcox shoots the action with a pole mounted camera near the circle, on something like a 50 foot PVC pole with guy wires.

vertical grimmace

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Maybe from a quadcopter! lol Oh, forget I said that, would not want our fun to devolve into the "drone" discussion!

combatpigg

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My first impression of 42 foot lines with the Cyclon was how slow it seemed to be. To a spectator outside the circle it looks blindingly fast, but if you're used to the hectic pace of 35 foot lines, 42 footers will seem pretty tame. The quality of the matches is better with more time to avoid mid airs and to figure out how to reverse line entanglements.

vertical grimmace

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I still have not flown a combat model on 42' lines, but it would seem it had to be done. An old school 1/2 A on 35' lines was pretty close to a Fast combat models lap times. Slowing things down a bit, and having more room to maneuver will be nice. I have flown 42's for racing, and I have flown on 70's for large stunt models. That is another thing I need to do is cut some sets of lines!

iron eagel

We have a pretty active CL group at our field, everything from F2b, stunt, fine scale, fast and slow combat, it is a real hoot to watch.

combatpigg

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IE, you're blessed with a great club.
The club I belonged to 15 years ago did not allow C/L, unless you were a club official who thought no one else was watching.

The pair of foamies are Larry Driskill's 1/2A Litehawks and the orange model is a Mike Hoffelt "Monoboom". There is a 1/2A Monoboom plan at Barry Baxter's plan service. Not practical for combat but a spectacular looping machine.

vertical grimmace

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The Litehawk was a fantasic model. On a trip down to Amarillo back in 95', they were the inspiration for my original Attitudinal design. Larry did a great deal to push 1/2 A forward. I am lucky enough to still have one of his AMA .049 engines. Not sure what he did to it, but it runs better than any I have had.

MJD

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Aren't they something like 42" span? They were the first contemporary 1/2A combat designs I became aware of.

CP - I need some 1/2A combat engine/bladder advice (I'm doing fine thanks, I mean 1/2A pressure bladder).. might PM you in case I'm being a total bonehead about the symptoms.. Had great luck until this past weekend when the Profi Toucan just would not behave.

MJD

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Not to mention the prop stopping near TDC 2 out of 3 times and beating on the motor mount on landing. I need to trim the props to 3-3/4" diameter, then the cowl might hit first.

combatpigg

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He published an article in the mid 1980's about how to prep a TD .049. The main thing was getting the crank fit just right by lapping it to the case with sink cleanser powder mixed with oil. He also showed how to open up the venturi to 5/32". I don't recall if he was cutting a relief in the crank journal ahead of the intake window or not, but this was done on the KillerBees..
Since that time the single biggest performance enhancer has been shaving the inside surface of the piston skirt. All you need is a drill motor and a safe holding fixture for the piston. You also need a length of wire to hold the rod off to one side while you reach in with a scraping tool [the back edge of an Xacto blade] to shave the skirt. The piston has a lot of lead in it, so it machines very easily. I have made the skirts paper thin and they hold up just fine. This takes a load off the crank pin and rod, plus it allows you to prop the engine for 25,000+ with better life expectancy. I've never had to rebalance the engine that I can recall...so the engine must be "over balanced" to begin with. Placing a divot in the counterweight resolves balancing issues if it ever crops up.
Now that you have the Fora...you don't need to know any of this trivia or own bins full of Cox junk...!

vertical grimmace

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Combat, I remember you saying that 24,000 was about the redline for the Tee Dee. That was my experience. My mods were to drill out the venturi, I thought to 1/8" but I may be wrong. Add the KK needle valve and use a 5-3 Grish prop. Anything over 24,000 and they did not last.
At this point I think I have 2 Tee Dee's left, while they are a lot of fun and reliable, their time has past in competition. Larry's Litehawk seemed to be mainstream as he was the go to source for 1/2 A components, and the only one to offer a great kit.

combatpigg

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1/8" is a good plan, especially if you aren't going to be running 40% nitro.

MJD, It's worth a look to pull the head and backplate, lower the piston and check the liner with a lens. While the head is off you can raise the piston and manipulate things to check for slop free movement. Check the backplate seal, look for signs of leakage around the head. These engines are so well designed they don't usually leak. Remove the needle and use your syringe to push / pull air and fuel out the orifices. Pop in a new plug, test flip, check for how well it stays pumped at TDC.
If it's a Nelson plug, be sure your glow power is fully charged. These engines ought to be like Timex watches, able to take full speed crashes and relaunches, over and over. Last resort is to test the fuel in another engine. Where I live, fuel just doesn't go bad. I've read somewhere that it can have quite a lot of water before it's useless.

aspeed

http://www.toadsrc.com/engines.htm has some ideas on modding the Norvels and Ames The Little Red Cap has less pressure than most bladders. You can get them at Lee Valley. They get kind of like a golf ball, but are good for 1/2A . We used to use 1/8th or 1/16th" surgical tubing for the tight 1/2A speed planes. They went to about the size of a finger. After a few runs they all get a bit inconsistent. Mike, did the jet go?

MJD

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I think I might just be doing a crappy job of diagnosing overcompression.. it is designed around 10% fuel, but if the compression ratio is right for 10% then too high is still.... too high. Most likely because of running these high pitch props that drag it down on the ground, 27-28k. It was a humid day and maybe mid-high 70's? Last fall when I had some great trouble free flights it was October. I flew it this spring but forget conditions.

Lemme see, there's this guy on RCU that always advises people to shim the engine to death then work up from undercompressed.. now where have I seen that..

Once I do this and either (a) discover it is the problem, or (b) eliminate it is a cause, there's not much point tearing the engine apart or doing much else I think. Fuel is good, engine runs pretty steady on the ground FWIW, and starts easily.

I'll put it on the bench and sort it out.

MJD

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So close.. still fitting satellite receivers out in the tips, might be done tonight. Only got them last week when I realized my original Rx scheme was insufficient. Lots of carbon.

vertical grimmace

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I have found that the larger 3/8" surgical tube with the thin wall works best for bladders all around. I got sick of the small 1/8" stuff breaking and invariably leaking onto my wing and melting the foam. At least high nitro will. I use the larger bladder tube on both my .36 combat models and the 1/2A's. I have found over the years that no bladder/pressure system will work reliably in the cold. Some have claimed the higher pressure from these bladders will not work with 1/2 A, but I have had no trouble getting needles.

MJD

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Oh, if I only knew who makes a miniature inline low pressure regulator made of solvent resistant lightweight materials with 1/8" barbs each end and that will flow a few cc per minute and that weighs a few grams. That would solve a lot of the problems otherwise created by a continually-decomposing bladder high pressure system metered through a fixed orifice.. at least regulate it.

I meant to order a Cline regulator or two for putzing with small pulsejets and pressure systems. They are huge and unwieldy for small models though.

MJD

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Oops double post..

MJD

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Yup, I got a few feet of that and fittings from Texas Timers a while back. I gave some to SmokinRV4 for his F2D engines (let's see if he's lurking), and have a bit still in my bin of goodies.

With 20-30cc fills for 1/2A, I imagine an egg shape not a cylinder.. would the pressure be steady? I guess I should run a 1/2A on some and see for myself! Not sure it will fit in the Toucan.

Thing is I had good runs before, and I replace the bladders after 5-6 fills, always take a couple of feet of spare tube in the flight kit.

And.. I have been thinking about the cantankerous behaviour of CrossCheck's BW on a Cox 6-3 and 15% fuel that same afternoon. Prop it for another 4-5k and it sang like a bird.

I US cleaned the engine in FAI fuel then stripped it mostly down this evening. It is mint and no leaks. Squeaky at TDC. A touch of heat and it spins freely. I can hardly tell it's been run.

I found my bag o' shims, ready to decompress and fool with it on the bench. Apart from the risk of learning something useful, it's good fun anyhow. With reasonable care I am not sure if I will outlive the engine from the looks of the internals.. "honey I shrunk the .15"

vertical grimmace

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Of note, on the Fora .049, it requires regular sized (small) fuel tubing. As opposed to the tiny 1/2 A types. I was down to very little 1/2 A fuel line and ordered a bunch. It showed up about the same time as my engines, and much to my surprise I needed the standard size fuel line I use on the .36's. The needle assembly looks like it may be the same as in the .15 size engine.

It has always been said that the walls of the bladder should be supported. So, many designs incorporate that 1" estes rocket tube, fuel proofed. I think this may have been more to preserve the bladder from breaking more than anything, not to get equal decompression, and more consistent runs. A couple of substitutions, aquarium plastic riser tubes, and the little cases some cigars com in. I just cut my bladder compartments in the foam wing though and fuel proof with pure silicone caulk. The bladders like that soft rubbery stuff, and I rarely break a bladder now.

vertical grimmace

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Well here is one ready to fly. 8 0z. on the nose, with 320 sq. in. area. Balance looks good. Should be within a penny or 2 I hope. Gonna get maiden within a day or 2. Gotta cut some lines and get my other one finished. The last pic is the original Attitudinal designed in 1995 ( I have inked plans for it) Powered by an AME .049. Times have changed a bit for 1/2 A

combatpigg

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Absolutely gorgeous VG...!

It seems like the last I heard.....electric starters were allowed for 1/2A now...? Maybe I just dreamed that.......?

I don't recall ever trying to hand flip this class of engine. I'd rather milk rattle snakes for a hobby.

iron eagel

Mike,
Did you ever get any speed put of the Profi Toucan?