ARF Flite Streak

Finally got the engine for my streak ready. I have a PAW .19 plain bearing diesel on it. Took it out last weekend, had to twist out a warp but it flew great. With the 6 Oz engine and stock tank the balance was about 3/4" in front of the spar. At this balance point the plane is stable but responsive in the squares and triangles. I have the landing gear on the plane, can't do a decent take off yet but landings are nice and smooth.

This is my first diesel with about 40 minutes running, don't think it is fully broken in and that it will improve with more running.

My current set up is
prop TF 10x6 super m
weight 21 1/2 Oz
lines .015" 60 ft. eyelet to eyelet
lap times 5.0 - 5.1 sec

Wouldn't call it a serious stunt ship, but for anyone trying to learn the pattern (or novice) it's a great way to have a nice plane with very little effort. As a bonus it's just fun to play around with.

Thought I'd borrow your post to say a few words about my Arf Streak. I put on a Fox 15 BB schneurle. Total up weight with stock tank was 22oz (using my new electronic scales--thanks Crist R. for that link!). I have recently changed tanks to a uniflow clunk (2 oz Sullivan).

I am flying on 60foot center-to-center 0.015 lines, and the plane is doing laps anywhere between 4.2 to 4.8 seconds. I am trying to find prop "Nirvana". Currently I have been trying various 8-4's, as recommended by Fox.

I'm not completely happy at this stage because I am way to sensitive to airspeed. When the plane speeds up, the engine leans out (and viceversa), which I take to mean that the extra fuel head pressure (due to change in "centrifugal" force) is causing the engine to lean out at higher speeds. I think this may imply that I am not getting a good enough venturi effect at the prop rpm's that I am flying (~12-13k estimated in the air). Of course, unless I simply jam a stick into one side of the venturi, the Fox Venturi isn't the easiest to change the opening size. So I am thinking either about a 7-4 prop, or maybe an 8-3 (don't have) just to get the rpm's up so I will get more airflow through the venturi, giving a larger pressure drop and maybe, just maybe making the engine less sensitive to these speed variations. I might also just try muffler pressure. I would like lap times in the 4.7 s range for my comfort.

I have a slight warp in the wing (due to the thin flaps) which I will take out tonite. I basically went stock (except I used sewn hinges instead of the stock cya ones). I need to bush the hole that the gear fits into, since it has already egged out in a slightly too hard landing (engine quit just before my pits, and I tried to put it down too early). I also changed the pushrod hole to the innermost hole in the bellcrank--boy was it sensitive when in the recommended middle hole!. Balance point is just forward of the spar, using the stock Fox muffler. No extra weight needed.

I think I will be pretty happy (eventually) with the Fox 15-Arf Streak Combo. I think I have plenty of power for the plane. I will eventually get around to ordering some 60 foot 0.012 lines, which should make things even better. And when it looks like it is dialed in, I plan to remove that stock glow head and replace it with my homemade diesel head and plan to even have some more fun!

After this last summer's "hard work" learning the full pattern, I deserve some fooling around time!

Alan:

I replaced the landing gear, the replacement is 1/8 and goes all the way through the fuselage. I bushed with copper sleeve this is the same problem the kit had so immediately made this change.

Have you tried cutting the 8x4 props down slightly to 7&3/4, 1/2, 1/4? I'm still trying to find the right prop too, tomorrow planning on trying a revup 10-6, top flite 10-5 power point, top flight 9-6 super M, and revup 9-6. As propped in my first post my engine is going off aroung 9400-9500 rpm, and seems to be slightly overloaded. If none of these work guess I'll be trying various sizes in APC and/or cutting props myself.

Do try muffler pressure, I've always had good luck with it. When you put your diesel head on aren't you going to have to reduce the venturi openning a lot?

After not flying for 5 years getting to where I can do a 400+ point intermediate pattern this summer seems like a good accomplishment and flying the FS just for fun seems an appropriate reward.

Yes I have come to that conclusion (cutting down the prop) after flying the plane today with muffler pressure. I am having some problem getting the plane speed to where I want it---a place where the engine is happy, the plane is happy and I am !

Right now the engine either seems too rich (with lap speeds >5 s, or supersonic with lap speeds <4.5 s. It is almost like the muffler is behaving like a tuned pipe. It is also possible that the engine isn't completely broken in yet either, but it seems to be able to hold a peak setting.

Just for info, I'm using Sig 25% castor, 20% Nitro fuel with a Fox short plug. The plug seems to be pretty cold (rpm's drop when igniter is pulled off), but I'm not sure where to get a hotter short reach plug. Even tho' the Fox instructions say to use a short reach plug, a long reach plug still doesn't extend past the head button into the combustion chamber, so maybe I might try that.

Incidentally.. has anyone tried building the Flite Streak with moveable flaps? How did it fly?

>Incidentally.. has anyone tried building the Flite Streak
>with moveable flaps? How did it fly?

I built one back in the early 70's as an experiment for what was then AMA Slow Combat. The airplane was pretty light (no finish or landing gear) with a Fox Mk III Combat Special. The flaps were 3/16 thick and had a 2" chord at the root. The outer 3" of flap on each side remained fixed. Flap movement was 2/3rd of elevator. The airplane was fast and turned very well, but not a great deal better than a stock Streak so I didn't pursue it. Anything that added complexity to a combat airplane really had to buy its way on.

Steve

>
>Just for info, I'm using Sig 25% castor, 20% Nitro fuel with
>a Fox short plug. The plug seems to be pretty cold (rpm's
>drop when igniter is pulled off), but I'm not sure where to
>get a hotter short reach plug. Even tho' the Fox
>instructions say to use a short reach plug, a long reach
>plug still doesn't extend past the head button into the
>combustion chamber, so maybe I might try that.

Fox short plugs are fairly hot plugs. My question is with the nitro content. Why 20%? These engines should run fine on 5%, and it may be the high nitro content that is making the engine touchy.

Oop's that was a typo (hands moving faster or slower than speed of thought). The nitro content is 10%. It is interesting that Fox recommends using their Missle Mist fuel--my impression was that MM has a lot of nitro.

By the way, I also filled in the slot in the front end (from venturi to front ball bearing housing) with JB Weld--otherwise it was almost impossible to choke the engine. The slot seems to be there to pull oil back from the bearing, instead of letting it leak out the front. I figure just let it leak!

>Oop's that was a typo (hands moving faster or slower than
>speed of thought). The nitro content is 10%. It is
>interesting that Fox recommends using their Missle Mist
>fuel--my impression was that MM has a lot of nitro.
>
>By the way, I also filled in the slot in the front end (from
>venturi to front ball bearing housing) with JB
>Weld--otherwise it was almost impossible to choke the
>engine. The slot seems to be there to pull oil back from the
>bearing, instead of letting it leak out the front. I figure
>just let it leak!

That slot is a "boo-boo", but it is to provide oil to the bearing, not suck it back. But, as you say, it does make it nearly impossible to choke the engine. It wants to draw air through the slot. If you put a little JB weld just at the very end of the slot, maybe an eighth of an inch wide, or so, it will still adequately oil the bearing while allowing you to choke the engine. I am not sure how well the bearing will last with the entire slot filled.

I was under the impression that these engines were rather high compression, so that higher nitro content could affect things negatively. You could try the "add a gasket" routine, also, but these engines are made to be screamers, and, unless modified, should just be let run with low pitch props.

Len,
I actually base that observation on the article by Scott Bair on 2 strokes. In it he shows how to cut down the oil being blown out the front (due to too much clearance between the crankshaft and the front end housing). He cuts a ring at the front of the engine, then a groove connecting the ring to the venturi. The ring must collect the oil which is being blown forward by crankcase pressure. The groove runs along the top if the front end housing, so when the intake port opens to the venturi (and this groove), the predominant effect there should be a "sucking" effect on the ring (and venturi), thus pulling back the slop which otherwise would be eventually blown out the front. In the case of the Fox 15, the groove goes all the way to the bearing housing.

I think that's why I am having such a hard time getting fuel up to the venturi---it was easier to suck the air from the bearing than fuel from my tank!

>I think that's why I am having such a hard time getting fuel
>up to the venturi---it was easier to suck the air from the
>bearing than fuel from my tank!

That part is definitely true. Same with the 40 BB. I was thinking Fox had stated the reason was to lubricate, however. In either case, it is a bad idea, and just a slight filling of the groove at the very far end is sufficient to solve the problem. If it is to oil, it will still oil that far (and leak the rest of the way.) If it is to suck the oil back, well, it will do that quite well that far as well.