Re: "Flying Blind" a build-thread for CEF 2018 Speed

[NEW222]

Not sure how I missed this thread till now. So, I have to say, simple, yetvery nice and clean. I like your elevator. I have seen a couple like this on plans, but yours is truly the first real one I have seen. I will now be watching the build.

[roddie]

Not sure how I missed this thread till now. So, I have to say, simple, yetvery nice and clean. I like your elevator. I have seen a couple  like this on plans, but yours is truly the first real one I have seen. I will now be watching the build.

Thanks for checking-in Chancy! This "half-span" elevator design is new to me. I'd seen it applied on several speed-model plans back when I built my first CEF speed-model. I didn't opt for that back then. I suppose that I should know "why" it's half-span.. but I honestly don't. It's likely less sensitive than a full-span elevator.. which makes sense to me. I'm hoping that I chose the correct "side" to hinge. I'll be flying CCW.. but I'm also running a left-hand propeller on the reed-valve engine. I don't know if that plays-into the equation. The elevator is hinged on the "inboard" side. This is consistent with the few drawings that I've seen.

[roddie]

There were a couple of "Perfect" #17 (.25oz.) tanks in that Box-O-Tanks that Dan McEntee sent me.



In case you're wondering; .25oz. equates to 7.4cc's. Will that be enough to feed a given engine for 12 laps? Who knows..  The #17 is not an end-all choice. I also have a home-brewed 7.7cc uniflow. I have other choices as well. The Perfect-brand #18 (1/3oz. capacity) converts to 9.8cc's.. and the Perfect-brand #2 (3/8oz. capacity) converts to 11.1cc's. The latter two are short-tanks. I like the idea of a long-tank.. and the #17 is a long-tank. I feel that it will stabilize the fuel better than a short tank.

I have a package of wood wedges that I bought years ago..



I've cut one to size for placing between the tank and the fuse.. on the top/outboard side of the wing.



Shimming-out the rear of the tank (where the fuel pick-up is) helps to keep the tank feeding-fuel under centrifugal-force, until empty.

As for engines................ the one shown thus-far, is a stock-configured Cox "product-engine".



That won't be the "contest-engine"... but it "will" be used for flight-testing-purposes. I may use the ExModel engines "Black-Lynx" that I won from the CEF "Engine of the Month" contest!!! Being a "reed-valve" engine.. it will drive the left-handed propeller that is planned!



I haven't run it yet.. but it's likely going to be a "thirsty" engine. The 7cc wedge-tank may be borderline-sufficient.

I plan to run the "Rare Bear" and the T33 next June as well! The T33 is "Tee Dee" class.. but the Rare-Bear is set-up for a reed-valve engine. I sent its engine to Ron Cribbs for running in this year's CEF "tach race''. It ran well.. and should be a formidable force if mounted in the Rare Bear.




Thanks for reading! I'll share more developments as they happen!

[MauricioB]

Hey Roddie, that's going to be great .... wooden wedges ?, I never would have imagined that they were sold ... I got a very good solution!
Your work is very neat Roddie congratulations!

[Ken Cook]

On a larger control line model, when suspended by it's leadouts, the nose of the plane is yawed outboard of the circle. Shimming the rear of the tank out will improve the engine's ability to use all the fuel in the tank by shimming the rear of the tank outboard. This promotes a clean shut off at the end rather than a on and off symptom until shut off. This is critical when trying to achieve a smooth landing as one doesn't need the engine revving up and shutting off and then ramping up again. This is not as critical on a 1/2A. A wedge tank for instance due to it's width is more of a problem than a help in terms of fuel supply. This is why the tank Roddie shows is longer and skinnier. The further outboard the tank is off of the profile fuse the more problematic the fuel draw becomes. So essentially with Roddie shimming the tank off of the fuse, he's creating a negative impact on fuel draw due to moving the fuel tank off of the engine's centerling further outboard. I'm not saying what's pictured won't work, but theoretically speaking, it's not correct.

          The problems become quickly evident when using a tank like this on a 1/2A model that's designed for speed. It's easier to design a tank for stunt over a tank for speed. This sounds ridiculous due to the fact that a stunt plane operates in different attitudes but I have found it much more difficult to achieve decent speed flights from a tank.

        Typically what happens is this, on launch, the plane has a lot of energy on the ground and on release, the engine tends to hiccup. The other is the engine will just quit. This is due to a few reasons, one being insufficient fuel draw due to too large of a venturi or a setting too lean. Tank shape is another reason and this is where the wedge can not be as efficient as other shapes.  Richening up the needle can fix this but the whole point is to go as fast as possible and a wedge tank in my opinion would not be my choice because it's limitations can be quickly recognized. However, one can overcome some of these limitations by pulling the fuel pickup out of the rear of the corner of the tank. This will assist fuel draw on initial acceleration somewhat relieving the hiccup.


            The Sure Start venturi can be opened to 11/64" without fuel draw issues offering more power. Product backplates generally have no issue of fuel draw which is why the tank can be of different lengths and shapes. But, if you start playing with modified backplates, fuel draw will be compromised and you will begin to experience similar problems that occur when using a TD on a profile. The ideal shape is a coffin shaped tank, one that's long and thin. The entire side is tapered to the rear which pins the fuel there.

[roddie]

I'll give the fuel-tank some more thought. Today I glued the wing and stab into their respective fuse-slots, so that I could set-up the control-linkage. I also glued-in the elevator hinges. The elevator-horn gave me some trouble. It's a "Dubro" type that uses 2-56 screws which pass through the control-surface and thread-into a plate on the opposing side. Not a "streamlined" set-up.. but I have a stock of them. The holes in the control-surface have to be drilled slightly "oversize" in order to easily thread the screws through.. and into that plate. (I should know this by now.. ) Working with tiny parts will try your patience....

Once I had the horn secured; I locked the elevator-neutral.. then focused my attention on the pushrod. It has two "L-bends".. and I needed to "tweak-it" so as to operate smoothly with the bellcrank.



The little "Perfect-brand" #233 bellcrank has a bushed-pivot that accepts a 3-48 machine-screw.. (scarce as hen's teeth..) The bellcrank comes with a #3 wood-screw.. and flat-washers.. but I wanted something more secure. As luck would have it; I had some 3-48 machine-screws and lock-nuts.

Now I need to "shim" the bellcrank-mount for free-movement of the pushrod. I'll need to fabricate some flat-washers from plastic sheet. I'll post some photos of that.

[roddie]

I make my own flat-washers when I want them a particular size ID. In this case; I needed washers to fit a #3 screw. I chose a piece of .020" sheet plastic. I checked first; to see if it could be easily "punched-out" with a standard "paper-punch". Yes.. so I proceeded to drill a series of holes using a #39 (.099") drill.



Then.. using the eye of the punch to center the hole; I punch-out the washers.




They're a little crude.. but they're just spacers.. and will do the job.



I want to get the hardware-mounting out of the way.. so I can throw a coat of paint on this little bastard!

[Ken Cook]

Roddie, I keep a bunch of those Perfect bellcranks. I don't even know if they're still produced. A few years ago I was in Baltimore and while driving around I saw the Perfect billboard painted on a train trestle. Barely legible nowadays however enough to make out what it said. The Perfect company is still making some hardware. 3-48 screws are certainly becoming harder to find. Micro Fasteners stocks them, Duke Fox apparently had somewhat of a fixation for them as he used them on several engines.

[roddie]

           Roddie, I keep a bunch of those Perfect bellcranks. I don't even know if they're still produced. A few years ago I was in Baltimore and while driving around I saw the Perfect billboard painted on a train trestle. Barely legible nowadays however enough to make out what it said. The Perfect company is still making some hardware. 3-48 screws are certainly becoming harder to find. Micro Fasteners stocks them, Duke Fox apparently had somewhat of a fixation for them as he used them on several engines.

Ken, When I first got "bitten" by the model-airplane bug.. I collected anything control-line related that I could find at various area hobby shops. That was in the early 1990's.. and some shops still had some NOS C/L hardware. Back then.. I was not into "computers" and didn't use the internet to find any types of hobby items. A lot of what I have was handed-down from my relatives that flew C/L back in the 60's/70's. Old kit-boxes containing scrap-wood and plans; I didn't care.. I wanted them. Their partially-built kits.. of which I have a few... and boxes full of old modelling magazines.

I have a "bellcrank-box"... Not all complete assy's.. but I can usually find something that works without having to buy anything.

[roddie]

I spent a little time this afternoon re-shaping/cutting a canopy and fin from the leftover hardwood "blind" stock. I also wanted to re-install the landing-gear and check the engine-mount holes that were re-drilled through the spacer-plates from the backside. They all line-up good.

It looks a little bit "space-ship-like".. but that doesn't bother me.




I wanted that fin-shape.. and I wanted to make it from the blind-stock. I'm thinking; a slight belly-contour is needed.. and I have just enough stock leftover to make the part in one piece.



I may have to install larger diameter wheels.. because I increased the forward-angle of the struts. There's less propeller-clearance now. I could bend the struts "inward".. but I'd rather maintain their current 5.5" track for stability during roll-out.   (I love to dramatize..)



Weight thus far with controls installed.. and a sample hard-tank is 4.2oz./119gr. The balance-point is exactly on the wing's L/E with the tank sitting chord-wise on the wing. There will be paint-weight to consider.. along with the addition of the belly-contour "and" a tailskid/stooge-link. The fuel-tank location/payload is planned to straddle the final balance-point once the airplane is finished.

[getback]

Looking Good Man !! you going to stay with that 3 blade prop? At 4.2oz. it should take you around the circle pretty quick !

[Ken Cook]

Most of the 3 bladed props are a 3 pitch. A 3 pitch prop is not going to offer you speed in control line. When using a 3 bladed prop, it usually equates in or around a 2 blade prop of the next inch size larger. Essentially the Cox 5x3 3 blade places a similar load on the engine as a 6x3. If your looking to go fast, more torque is needed to drive a smaller prop of higher pitch. This is where nitro is essential.  Seeing Jim's rules, there's no wiggle room as he states no carbon, or exotic props which leaves very few choices. This is where the HQ props from Hobbyking could be beneficial as they offer 4.5-5 pitch props. In my opinion, I don't feel that's bending the rules as some of them are nylon and they're commercially available. They would be the props that are going to offer one speed. Opting for the most pitch would be my choice.

      I posted some pics earlier today and somehow they fell into cyberland. Weight is really  a non issue in speed. A lighter plane is not going to go faster and in fact it can create just the opposite. Obviously too heavy is too heavy.  Flying into a headwind can essentially cause the plane to stall when it slows down. In addition, you lose momentum quickly making the plane floaty. Trimming the plane so that it tracks properly and flies tangent and LEVEL with the circle is imperative to go faster. This means that your leadouts should exit the wing as far forward as possible. Adding additional tip weight if required. More pitch equates to more torque which equates to the plane wanting to roll in which is why doubling the tip weight is critical.

                       
This plane is yielding a wood pan made from mahogany and basswood. TD powered it weighs almost 8 oz's and is affected very little in terms of it's weight. Streamlining is everything in speed. Obviously a profile is going to offer less options in terms of aerodynamics. Keeping everything that's hanging out trimmed back and clean and faired in  is critical. Barely visible, but the line exits directly on the leading edge of the wing.

[roddie]

Thanks Eric and Ken! Regarding the propeller.. I planned on running a L/H prop early on.. but my choices of what I "have" are limited. The prop shown is a L/H Cox 5 x 3.5 so I figure that it's going to provide at least 3" of pitch when wound-up.. unlike a standard/black Cox 5 x 3.  

I shouldn't need much (if any..) outboard tip-weight. The outboard tip already drops noticeably with the engine-cylinder orientation.. and "without" a fuel tank installed. I haven't decided on how to do the lead-out guides yet..   but I plan to use two guides; matching the 1.625" bellcrank spacing.

I may use small safety-pins as I did on the Rare-Bear.



I'm not too concerned about the models' weight.. but I like to "check" the weight as I build. I initially mocked-up a balsa canopy and fin to get an idea of how they'd look.. but knew that I'd later be using the harder-wood from the "blind-slat" to help add weight to the tail.. as well as making the fin a little more durable. As I mentioned; I still need to design a tail-skid. I'm leaning toward an elongated .025" music-wire skid with a loop formed in its end for a stooge-pin.

The lead-out guides and tailskid will be the next order of business.

[roddie]

I decided to spray a coat of primer on this little "gem" this afternoon... outdoors






Seen with my "Tee-33-Dee".. which is also being prepped for the CEF 2018 Speed Contest's Tee Dee class.

[roddie]

indoors.. later-on..

[roddie]

Three for three; getting some painting done this holiday weekend! Happy Easter!

This Rust-Oleum gloss base-color that I recently found/chose.. is called "Merlot". It's quite "rich".. I like it a LOT.. but I need to find a suitable "trim-color". I almost bought a "Khaki/Beige" aerosol for the trim-color.. but I could "hand-mix" something close to that.. with the "jar-paint" that I have on-hand.




One more coat to the top-side.. and I'll bring the model "inside" for the night. The temps. have been staying between 58/62F. over the last 48 hrs.. with light/moderate breezes. There air is "super-clean".. which is really nice. The finishes have been free of any foreign-particles in the air.

[roddie]

"Merlot".............. marketing by Rust-Oleum.. They "bagged me"... but I have to admit.. I like the color.

[roddie]

controls installed..



this sucked. It took a very long time to install the controls on this tiny model.

I painted a light-blue "canopy-reflection" a few weeks ago..



This model airplane is designed to utilize a Cox .049 cu. in. reed-valve engine platform with a gravity fuel-feed.



The main gear's wheels need to be a larger diameter. The 90-degree "inverted-V" gear's struts are only 3.5" long.

Not a deal-breaker, but I want to run a "left-hand propeller". They're only currently available in 5" diameter.. and I need more ground-clearance...

[getback]

Hey Roddie i have some 4" 3 bladed Lf. Hd. props if you want to go that route ? Now that i have more time (brought my tools home yesterday ) i should bee able to get the stuff i been meaning to send you together and get other things done

[roddie]

Thanks Eric, Let's PM each other over the next few days to discuss more. I've got a band gig today that I'm preparing for.

[roddie]

The landing-gear (inverted-"V" style) has been fitted with larger diameter wooden wheels.





I installed the gear backward on purpose... just to see how it would look with the engine installed. These struts are bent at an approx. 22 degree angle where they exit the captive firewall-mount.




I like the way it looks.. and may "keep" this position for the maiden-flight. The model will need a liberal amount of tail-weight regardless of the landing-gear position.

The model is grossly nose-heavy.. but I knew that it would be.. when I was designing it. I just need to figure-out how to add significant/streamlined weight to the tail. I'll know more about where I stand with balance; once the fuel-tank is fitted.

When you design your own flying-model; you can't consult the "plan" for the CG location.. or any other "proven" performance attributes. You just have to "wing-it"..

[Cribbs74]

It’s sitting on the gear so it’s not grossly nose heavy. Nose heavy is ok on a speed plane. All it needs to do is rise and fly on a level plane.

It’s the landing that’s going to be ugly. All speed planes land hard.

[roddie]

It’s sitting on the gear so it’s not grossly nose heavy. Nose heavy is ok on a speed plane. All it needs to do is rise and fly on a level plane.

It’s the landing that’s going to be ugly. All speed planes land hard.

Hi Ron! I miss you bud! Yea.. I know that it works for a strictly "roundy-round" C/L model to be nose-heavy.. but if it's fighting gravity "aerodynamically".. it can't be flying as fast as it's capable of.. correct? When I designed/built my Grumman F8F-2 "Rare-Bear" for the 1st CEF Speed-Contest, I concentrated on its balance.. and didn't worry so much about its overall weight. However; I haven't flown that model to prove that theory..

[roddie]

I worked on this little model.. more than intended tonight. It felt good to do a little "engine-work".. but nothing really special. I initially had my CEF 2017 Tach-Race engine slated for this model. That engine ran well.. but was literally thrown together. I decided to swap-out its "Golden Bee" case for one that had been completely disassembled and cleaned. I assembled the 2nd generation plain-aluminum case with a stock Bee crank.. and round drive-plate. The engine's top-end is Tee Dee spec.

I plumbed a Perfect-brand #17 (1/4oz.) long-tiny wedge-tank with Dubro-brand #222-medium silicone fuel-line, using my "compression-sleeve" method to reduce the line's ID to fit snug on the tank's small feed-tube.





The backplate/carb is a high-flow Killer-Bee clone.. and the propeller is a "left-hand" 5"D. x 4"P. made by "Dal" props.

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