CEF speed contest Design Discussions

BTW Rusty, I like your plane. That engine needs some attention though.   

Well, phooey! I don't want to make any enemies by helping Ron compete, just thought I'd give him a hand.

Didn't think of the B.O.M. rule on this competition, but it makes sense; in all the flying events: here, R/C, and regular contests. I am vehemently against ARFs in any contest, but it still comes down to the flying. That's where the visible talent shows, to people who don't know about models, and stuff. I think: If you're gonna fly, you ought to build. That brings up the old time-issue, though. Then, the dollar situation. There's just no pleasing me! At least I can say the things I fly, are planes that I've built. The broken pieces of some guy's little electric ARF, that I made into the ride for my Cox Engine Flight Contest plane, are the exception to this. The parts were going into the trash, had he not directed them to me. But then, I'll bet I have more time cobbling-up a fuselage, and globbing those parts together, than he had in getting that ARF airborne, initially. It's a trade-off, and there is no purple on that one, either. What's happening to me?!

And you know, Ron has a hot engine, so he's a threat on the speed, already!

It would be cheaper to send a flat box of parts, than to ship an assembled model, too. Ha ha. Well, what's the verdict? You know we want to play fair.

Cribbs74 wrote:BTW Rusty, I like your plane. That engine needs some attention though.   

That isn't the engine I'm going to use, just some frozen up junk. But the configuration is the same and I just stuck it in to see if the engine and firewall fit the cutout before I block it in. What's the problem you see with it? Just 'cause it's a plier scarred old hunkajunk?
Rusty-the average engine guy

GUS THE I.A. wrote:...It would be cheaper to send a flat box of parts, than to ship an assembled model, too. Ha ha. Well, what's the verdict? You know we want to play fair.

I think Jim already approved it as long as Ron sends you the specs and receives the airframe in kit form. I have not the power of approval, only the power of personal opinion.
Rusty

Well, I cut templates tonight. Should have wood cut tomorrow. I am building it myself so there will be no questions.

I am doing something a little different than most designs. I took inventory and wouldn't you know it, I am out of 1/2A leadouts.  

Worst case is I can scavenge a set out of another plane. Not much time to place an order and I don't feel like paying big shipping for a $3 part.

Ron

Cribbs74 wrote:Well, I cut templates tonight. Should have wood cut tomorrow. I am building it myself so there will be no questions.

I am doing something a little different than most designs. I took inventory and wouldn't you know it, I am out of 1/2A leadouts.  

Worst case is I can scavenge a set out of another plane. Not much time to place an order and I don't feel like paying big shipping for a $3 part.

Ron

Why not just use some flying line Ron? Do you have an old spool of braided line with kinks that you wouldn't use to fly with? Cut a couple 12" pieces.. install line connectors/crimps.. and you'd be good to go..   

yep, some .015 or .018 would be good...that's what I was thinking about but don't have any bad lines to cut up and send you. I'm gonna use a button style bellcrank...if I get the plane done.

Funny,

Rusty hit me up and offered to send me some line. I couldn't remember the size and looked it up. As I was writing a reply I realized I had a .018 line reel with only a single line on it. So I am good!

Mark Boesen wrote:yep, some .015 or .018 would be good...that's what I was thinking about but don't have any bad lines to cut up and send you. I'm gonna use a button style bellcrank...if I get the plane done.

Button style? Care to explain? Never heard of that.

I've got issues with my engine configuration. I'm afraid I can't get sufficient suction for my tank(s) using the high-flow (Bernie's red) horseshoe back-plate. A bench-run and re-test of my tanks yesterday began with; the cylinder loosening up..    then the needle felt very loose; despite my installing a fuel-tubing sleeve/seal. The engine was hard-starting.. and once running; would not hold peak rpm long enough to get a tach reading.. and wouldn't run long enough to determine a tank's run-time.  

I had assembled a 2nd stock prod. engine for comparison; single bypass cylinder/standard horse-shoe back-plate... and when I'd become completely frustrated..   I bolted that engine on the stand.. and it started easily.. and ran smoothly with each of the four tanks I had built... right to the last drop of fuel before leaning-out and quitting... although it had "nowhere near" the power or rpm's of the Tee Dee cylinder/high-flow back-plate engine.

I doubt if it was the needle causing trouble.. but just in case; I cut a new sleeve/seal and installed a compression-spring in between the washer and a wheel collar, to tighten it up some.




So... I may have to try a bladder set-up, if I could get the parts in time... ($$ is an issue right now too) I "may" have what I need here, but not sure. I have some small size Sig latex surgical fuel tubing that is 1/16" i.d. and has a 1/32" wall-thickness. Does anyone know if that might work? I have a syringe/fitting.. but I don't have a fill/check-valve. The only other option is for me to use a smaller venturi... because I don't have one of those tiny check-valves needed for a reed-engine crankcase pressure tap.

Here's the latex tubing that I have.

I just started playing with pressure tanks, I have some new hi-start bungie tubing for small gliders I never used, send me your address and i'll send you some. Its slightly larger the r/c fuel line and thinner wall.

Mark Boesen wrote:I just started playing with pressure tanks, I have some new hi-start bungie tubing for small gliders I never used, send me your address and i'll send you some. Its slightly larger the r/c fuel line and thinner wall.

PM sent

The fill/check valve is convenient but not necessary. Pop the connection at the engine, or with the horseshoe put an extra connection in with some metal tubing to pop, fill, clamp, reconnect and away you go!

Phil

pkrankow wrote:The fill/check valve is convenient but not necessary.  Pop the connection at the engine, or with the horseshoe put an extra connection in with some metal tubing to pop, fill, clamp, reconnect and away you go!

Phil

Thanks Phil, I'll have to go that route if I use a bladder.

Last night I decided to pull the back-plate off my engine to measure it's venturi, as compared to the other stock plastic back-plates I have. I had read that the red high-flow back-plate that I got from Cox International was larger from the description... so I wanted to see how much. It measures .198" in diameter at the reed-seat. My stock prod. engine style back-plates measure .173" in diameter at the reed-seat. That's a WHOPPING .025" difference!! This seems to taper down slightly toward the spray-bar. The air intake on the back is oval-shaped and smoothed for less restriction.



The uni-vent tanks I built; all have 1/8" Copper tubes. Jim mentioned running the largest fuel line that I could.. which I haven't tried yet. It's worth a shot.. because although the nipple on the spray-bar has a small i.d.; using a larger i.d. fuel line would require less suction over the distance from the tank... theoretically.

I had some large size line on hand.. so to secure it on the small spray-bar nipple (and also my tank's feed-tube) I used sleeves of 1/4" Brass tubing as "ferrules".. and twisted the ends of the fuel line into them; compressing the fuel-line to a smaller i.d. The fittings are nice and tight.

JPvelo wrote:When I set maximum nitro at 30% I didn't consider the lack of commercially available 30% 1/2a fuel. How does everyone feel about bumping nitro to 35% so the readily available sig fuel can be used? Feedback please.

Jim

I was just pondering this question myself. I was gonna buy some car fuel and add a bunch of castor to it but would rather just buy the Sig stuff. 25 or 35... eithers fine with me as long as its available.

Mike

Edit.... I just had a thought. If you buy one of each and mix them> instant 30%. Problem solved right?

Cryhavoc wrote:

JPvelo wrote:When I set maximum nitro at 30% I didn't consider the lack of commercially available 30% 1/2a fuel. How does everyone feel about bumping nitro to 35% so the readily available sig fuel can be used? Feedback please.

Jim

I was just pondering this question myself. I was gonna buy some car fuel and add a bunch of castor to it but would rather just buy the Sig stuff. 25 or 35... eithers fine with me as long as its available.

Mike

Edit.... I just had a thought. If you buy one of each and mix them> instant 30%. Problem solved right?

Did we ever come to an agreement on this? I already have on hand 35%, 15% and 10% Sig. If we decide on 35% it will be simple for me, but I can mix two if necessary.
Rusty

RknRusty wrote:

Cryhavoc wrote:

JPvelo wrote:When I set maximum nitro at 30% I didn't consider the lack of commercially available 30% 1/2a fuel. How does everyone feel about bumping nitro to 35% so the readily available sig fuel can be used? Feedback please.

Jim

I was just pondering this question myself. I was gonna buy some car fuel and add a bunch of castor to it but would rather just buy the Sig stuff. 25 or 35... eithers fine with me as long as its available.

Mike

Edit.... I just had a thought. If you buy one of each and mix them> instant 30%. Problem solved right?

Did we ever come to an agreement on this? I already have on hand 35%, 15% and 10% Sig. If we decide on 35% it will be simple for me, but I can mix two if necessary.
Rusty

I didn't get much of a response one way or the other when I put it out there so it stayed at 30.

Jim

Okay, I called my son, who conveniently is a chemist. Mixing already made 3 part solutions gets tricky, but he brute forced it with a couple of excel charts and came up with these combinations for what I have on the shelf:
35% nitro/ 20% oil/ 45% methanol
15% nitro/ 20% oil/ 65% methanol
10% nitro/ 20% oil/ 70% methanol

Two ways to get to 30% nitro, 20% oil, 50% methanol
1. mix 4 parts 35% with 1 part 10%
2. mix 3 parts 35% with 1 part 15%

If you have different mixtures to combine, I'll call him back and ask.

Hope this helps.
Rusty

Ok guys, don't count me out yet..... Can anyone guess what it is?



Hint: It's a Bendix trophy race winner. The pilot was J.H.D.

Laird Solution?

JPvelo wrote:Laird Solution?

Close... You forgot the "Super"

I love this plane, don't know why. I just like the way it looks. It was flown in the first Bendix Trophy race in 1931 by James Doolittle. Very interesting guy who lived from 1896-1993. His military career is impressive as well. The "Super Solution" now resides in the Smithsonian.

I hope it flies as well as the original. Mine won't have 535hp though.

JPvelo wrote:

Cryhavoc wrote:Wow.... The wing is alot thicker than I thought. So it goes, spar> 1/8 base> wire> 1/8 cover?

How thick is the spar? Which brings up another question. Is a spar really needed? I used to fling my little Sig Skyray around pretty good and the wing is just a thin sheet of wood.

Mike

The bottom isn't as pretty as the top! The wing is 3/16 balsa with a basswood leading edge sanded to an airfoil. The spar is 1/8 carbon rod, its purpose is to prevent the landing gear from punching through the wing on landing. These  things fly like a rocket and land like a rock.

Jim

Okay Jim, It all makes more sense now. I'm also working back through this thread and found some of your build pics. I moved my thread string to this thread as it seems a more appropriate one to discuss build issues.

That being said. The cowl on your Corsair. Is that the one from the Sig Beechcraft. If so, what is the diameter. I'd like order one if it'll work for my build.

Thanks,
Mike

Cryhavoc wrote:

That being said. The cowl on your Corsair. Is that the one from the Sig Beechcraft. If so, what is the diameter. I'd like order one if it'll work for my build.

Thanks,
Mike

Mike, there's hope for you yet. Jim's cowl is the top off of a Lysol air freshener spray bottle.  

Rusty