CEF speed contest Design Discussions (2014)

Man Man just rotate the needle to the other side and put it at a 20 degree angle or so if needed tie wrap your fuel hose but you should not have to . Eric

getback wrote:Man Man just rotate the needle to the other side and put it at a 20 degree angle or so  if needed tie wrap your fuel hose but you should not have to . Eric

... well.. I did say that Tee Dee's were a new animal for me.. Thanks Eric!

Your welcome and if you get that in the air and break something I have probably got you covered other than a pis./cyl. set   GET TO SANDING !! I ran a .051 well tried and would only run for a couple sec. the one I show TD.049 tached at 20,860 on 35% and I am good with that on the table // and started pretty easy so its time to clean and mount ,, was going to fly the Baby ring and the BB didn't want to run right , kind a like my son couldn't pull his self away from the computer so I didn't go through the fun of getting everthing out just for maybe one run It will bee difft. next week when that high temp comes through . the race will get it on !!  getback

getback wrote:Your welcome and if you get that in the air and break something I have probably got you covered other than a pis./cyl. set   GET TO SANDING !! I ran a .051 well tried and would only run for a couple sec. the one I show TD.049 tached at 20,860 on 35% and I am good with that on the table // and started pretty easy so its time to clean and mount ,, was going to fly the Baby ring and the BB didn't want to run right , kind a like my son couldn't pull his self away from the computer so I didn't go through the fun of getting everthing out just for maybe one run It will bee difft. next week when that high temp comes through . the race will get it on !!  getback

Is your .051 down on compression compared to the .049? Did you try a different head/gasket combos? Is the back-plate tight? ( I'm suddenly an expert.. ) Glad you've got a runner in the .049  

GET TO SANDING..   .... even if I through this model together.. it wouldn't be ready in time. I might get the tail-feathers cut and hinging cut-in tonight.. We'll see what happens..



P.S. The knife-sharpener I use to taper the leading/trailing edge surfaces.

Looks awesome!

Cutting in the Sig Easy-Hinges. This method has worked very well for me. I mark the blade for the desired depth, hold it flat against the 1/2-thickness gage.. and rock the blade back and forth slightly while pushing it into the edge of the wood.



It took less than 5 minutes to make the six slots.



The knife-sharpener tool for tapering the edges takes some practice.. and believe me; it's much easier with bigger parts to work with.. It's fun to use though. The carbide blades take the edge down pretty fast if you're not careful. The round ceramic (finishing) rods smooth it out nicely after, by just rubbing the tool back and forth.



I will disassemble and finish-fill/sand the parts. This close-up shows how rough the surfaces are.



Someday I will try a stitched hinge-line.. but not today. This is a tiny stab.. 5" span x 1" root-chord x .5" tip-chord.. hmm.. 3.75 sq. in. Elev. is 5" x .5" for a total stab./elev. area of 6.25 sq. in... less the tip radii. I hope it does the job.

I'm hoping that a 1/16" music-wire pushrod and a lot of paint.. will help to balance this thing. There's still the tip-tanks to build though. I have no idea where the C of G should be.

That is a cool bird you are building! It has a l-o-n-g nose.... so balancing might be problematic. Have you put the engine on the nose to make a 'test balance'? If it were mine I'd place c.g. at 25% of MAC then mount the bell crank ~1/4" to 1/2" back from that. Make the fore Lead Out rake back so that it goes through its guide the same distance back that the c.g. is from LE at root. Let the rear Lead Out just go straight or, as is the correct term, 'normal' to the fuselage. The tail volume is so low that a nose heavy c.g. will be almost as bad as a tail heavy one! First flight would need to be over that mystical and rare 'tall grassy area' that is mentioned so much for testing FF models! This is how I would approach it but is by no means gospel!

ARUP wrote:That is a cool bird you are building! It has a l-o-n-g nose.... so balancing might be problematic. Have you put the engine on the nose to make a 'test balance'? If it were mine I'd place c.g. at 25% of MAC then mount the bell crank ~1/4" to 1/2" back from that. Make the fore Lead Out rake back so that it goes through its guide the same distance back that the c.g. is from LE at root. Let the rear Lead Out just go straight or, as is the correct term, 'normal' to the fuselage. The tail volume is so low that a nose heavy c.g. will be almost as bad as a tail heavy one! First flight would need to be over that mystical and rare 'tall grassy area' that is mentioned so much for testing FF models! This is how I would approach it but is by no means gospel!

Thank You! Yes.. this is going to be a handful. I don't know why I went with this design.. it wasn't very smart of me. Who knows.. maybe I'll get lucky. Thanks for the recommendations. I know they're not gospel.. but maybe if I have some gospel music playing for the first flight, it might help!

Balance ON the LE of the wing will be safe. Since the LE is swept then pick something that is a little further back but well forward of 25%. After it flies take weight out of the nose till it flies like you think it should. (or add to the tail)

Tail heavy will crash. Guaranteed.

CG forward of the wing when the fuel is gone will be a problem since it won't glide. Under power it won't matter as much if the CG is in front of the wing a little.

This is for a successful first flight with the intent of fuel and fly again, maybe a new prop. Better trim will naturally fly better.

Phil

pkrankow wrote:Balance ON the LE of the wing will be safe.  Since the LE is swept then pick something that is a little further back but well forward of 25%.  After it flies take weight out of the nose till it flies like you think it should.  (or add to the tail)

Tail heavy will crash.  Guaranteed.

CG forward of the wing when the fuel is gone will be a problem since it won't glide.  Under power it won't matter as much if the CG is in front of the wing a little.

This is for a successful first flight with the intent of fuel and fly again, maybe a new prop.  Better trim will naturally fly better.

Phil

Thanks Phil. I really appreciate these comments from you guys. I mentioned to Ken that I'll be using a balloon tank. I'm using a long narrow balloon inside this capsule.



The placement will be higher-up than this.. and have fore/aft adjustment. I plan to use a large-size silicone feed-line with a compression-sleeve at the needle end so it will fit tightly on the nipple. As well as being streamlined.. it will spread the weight of the fuel more evenly over the CG. In theory.. the larger ID line will be less resistant to fuel flow; given the length that the line will need to be.

Looking GOOD !! I had some trouble running the balloon tank but haven't given up , I am waiting for my third arm to grow lol just going with a wedge tank for lack of time (my fault) . If you can even get the CG at the tip of the wing I think you'll bee ok as of now mine is not even on the wing but I am going to work on that ,, plan on mounting the tank and hopefully some decals today that will tell me more where I am at for the CG (((( Q how much fuel should I expect to use for 15 laps and the starting of coarse the TD seems to use fuel a lot faster than the reedie for sure ??? Thanks ,Eric

Roddie, I've watched the progress on your plane. The nose is indeed rather long compared to the tail. I imagined this plane with a central engine right in way of the wing. You streched your engine mounts far enough back. And it would solve the CG adjustment !! On my model, with the central and rear music wire skids plus nut and screw on the tail, the CG is just on the leading edge (but without fuel).

I love the way you did your hinges, very neath.

getback wrote:Looking GOOD !! I had some trouble running the balloon tank but haven't given up , I am waiting for my third arm to grow lol just going with a wedge tank for lack of time (my fault) . If you can even get the CG at the tip of the wing I think you'll bee ok as of now mine is not even on the wing but I am going to work on that ,, plan on mounting the tank and hopefully some decals today that will tell me more where I am at for the CG (((( Q how much fuel should I expect to use for 15 laps and the starting of coarse the TD seems to use fuel a lot faster than the reedie for sure ??? Thanks ,Eric

Hey Bud, your "third arm" comment makes me wonder if you're referring to a bladder? I'm not using a bladder. This is a non-pressure "suction-feed" set-up. I have to do the math.. but I think that my balloon/capsule will hold at least 10cc's of go-juice. If that's not enough fuel; I'll cut a finger off of a latex surgical glove for more capacity. The balloon-style tank uses a length of silicone fuel-line inside of it (the pick-up) that has a series of notches cut through it's wall, so that fuel will still flow.. even if the balloon collapses over one or more of the pick-up inlets.



Andras (Balogh) uses them on all his 1/2A RC "rocket-ships" I've seen his vids.. and that's proof enough for me that they should feed a roundy-round engine.


Hey Lieven, yea.. you're 100% correct. A mid-engine mount would help. Richard Kennedy did one with a Golden Bee in his P39.. and I still marvel over that model! I'm praying that I have enough root-chord in the wing to sustain ragged-edge "rock on a string".. but controllable flight. I'm running a full-span elevator.. but the horizontal tail-feathers are scale-proportionate.. and tiny. The more I build.. the more I realize how bad this is looking. Add to that; my first experience running a Tee Dee.. and there's a recipe for disaster. The tall grass field that Arup recommended, isn't feasible if I use the take-off dolly.. which I purposely designed to help launch these little models. It places the model in a positive angle of attack so that it will generate "some" lift to get it in the air. I'm pretty sure; if I can get the dolly rolling.. that the model will lift out of it. The incline angle is 20 degrees. At that point I'll find out a lot.

Something I haven't discussed is offset; either thrust or airframe. Maybe it would help this model? It's a wicked drag penalty though.. I'm thinking that the lead-out position might make or break this model.. as long as the CG is close to where it should be. It won't help though.. if I don't gain line-tension right away. I suppose I should be prepared to lead (whip) the model as soon as it becomes airborne.

Thanks all.. for the encouragement.

I notice that you haven't tackled the wing-tip tanks yet. Can I suggest that you consider adding some significant ballast to the rear half of the outer tip tank. This would serve two purposes- adding extra weight rearwards to improve your C of G and acting as a tip weight, all contained within a streamlined pod with the same aerodynamics at the inner pod. Just thinking out loud here. If it wasn't a Tee Dee I'd also suggest using a LH prop to eliminate the need for offset, unless you get a LH crank for the engine.

Rod.

I'm going to try the silicone tube in balloon tank! That's a good idea for tip weight. Put right thrust in it. You can always decrease it after some flight time.

Question : are you suppose to use a balloon that is big enough that it want cause pressure ? the one I used was small and had pressure on it when full. That could have been some of my problem as I didn't see much difference that the pressure silicone style . getback ?

getback wrote:Question : are you suppose to use a balloon that is big enough that it want cause pressure ? the one I used was small and had pressure on it when full. That could have been some of my problem as I didn't see much difference that the pressure silicone style . getback ?

Hey Eric, "Yes".. the balloon needs to be big enough to hold the fuel without stretching. If it stretches.. you can run the engine.. but the balloon will need to relax before you can get a steady needle adjustment. Take into consideration; the area of the pick-up line inside.. along with whatever you use for a stopper.. and that will be the capacity. Try one again.. and it helps if you have a Tee-fitting. Install it in between the balloon and the carb for a fueler. Close the needle and fuel-up with a syringe by drawing-back on it; to suck ALL the air out of the balloon.. then pump-in the fuel. Open the needle until fuel flows to the carb too.. then cap-off the Tee when full. Alternately; pull the line off the carb and fuel it that way. Just make sure you suck all the air out of the balloon first. Any length of solid line will transfer some air.. so might as well keep the length to a minimum.  A Tee is best.. because you can position it just up-stream from the stopper.. which minimizes the amount of air that gets in.. and also primes the line to the carb.. which serves as a vent when filling.  

Rod, I've got these airfoil templates that I made some years ago, with the intent of hot-wire cutting a foam wing.



They're about the correct size to trace tip-tanks from. The T33's tip-tanks have a horizontal fin/stab. at the rear.. which I can replicate by using this aluminum stock as you suggested.. to add some functional weight to the outboard wing.

Either run a "pressure bladder" system, or a "non-pressure bladder" system. Having pressure then loosing it messes with everything.

Yes, if you need that extra 1/4 oz for time you can overfill a non-pressure and pinch the line to keep it running till the pressure stops... Better to just put a new, slightly larger balloon on, or adjust the position of the existing balloon to allow more volume.

Phil

Thanks Roddie and Phil I did pick up some larger balloons a the Wal-Mart the other dad since I was there I kinda thought that was going to bee the answer after thinking about the whole thing As usually life has gotten in the way last few days and haven't got squat done to the airplane I have started after a inside search rereading this thread https://www.coxengineforum.com/t6185-simple-ballon-tank?highlight=balloon+tank These guys know there stuff and it is good to have them around Eric

Hi all, The 1/4" balsa wing-tip-tank pieces are rough-cut and slotted to accept the 1/8 sheet wing-tip. I've cut four parts.. and slotted two.





I was going to double these up; capping the inner slotted part, with an outer non-slotted one.. but these are hard/heavy grade balsa. It would sand to a nice bullet-shape.. but could end-up being too heavy at finish.




My wife says it looks like a duck.. If it fly's like one.. I'll be happy!

It's currently 54F and rainy here in North Smithfield. Good day for making coffee and balsa dust!

Thats looking good Roddie. How are you going to finish it?

akjgardner wrote:Thats looking good Roddie. How are you going to finish it?

I've considered a "Blue Angels" finish.. but I'm not settled on anything yet. I did browse the paint aisle at Wal-Mart for that Krylon brushed-nickel that Eric used on his Mustang. That's slick..

Something like this would be pretty simple though..