Trimming Small Planes

My first thoughts are to increase the wingtip weight, and increase engine offset to as much as 5 degrees (maybe more?).

More extreme - shorten the lines, or put a .15 on it and add tail weight.

Any thoughts/suggestions?

Thanks in advance,
Ed N.

I would guess that you have too much leadout sweep, although that's not the whole problem. More tipweight will certainly increase the tension, but with the rudder this may well cause it to hinge severely.

There could be so many things, I hesitate to suggest anything much. Make sure the wings are level, and adjust the leadouts and rudder for near-0 yaw. Make sure the CG is no further aft than 15% of the MGC, and preferably more like 10. I've never seen the model, but if this is anything like most kits, the marked CG is way too far aft, like 30%. This is guaranteed to make it very squirrely in all three axes.

I keep a u-reely around to seek line length on little planes.... while most agree that they pretty much suck as flying handles, they work well in these cases.

See Ya

I have been flying a Jr. Lightning Streak for a couple of years. Mine is powered by a PAW .09 with anywhere from a 7x4 to 7x6 prop, so we're probably talking about the same power. Mine flies much better on 45' lines than 52'. The lap times are quicker, but the line tension is much better. Try slowly decreasing the line length.

Also, be sure you aren't using heavier lines than necessary (0.012" dia), per the previous posting.

This is a nice flying airplane when you get everything trimmed out.

Your description of flight performance sounds like a woefully underpowered CL model. You can adjust leadouts, and do a bunch of tricks, but underpowered models have no line tension. Get the power up, THEN do some fine tuning. CL Models need some HP to fly well.

First, the model is the same size as the Flite Streak Junior, which shows a .15 to .25 size engine. Odd that the Jr. Lightning Streak shows a .09 to .19 engine, huh? Scott's flies well with a .15, but I'd stick on at least that much a** to keep it taut. Follow Scott's lead, as he has no problems.

I am not familiar with these size planes, but a .10 engine and the prop sizes you mentioned would make me predict the performance you described. Need more a**.

A good power check is a hand launch. Have the helper release the plane without "throwing" it. Tell the helper to release the plane as if he were just laying it on a card table in front of him. The slightest struggle for control from such a hand launch is a sign of being underpowered. The plane should, with no wobbles, immediately assume normal flight and line tension.

In regards to the other replies:

1) The leadouts are not adjustable & I would have to do some major work to the wingtips to change them.

2) The center of gravity was forward of where the plans showed.
In fact, it might be too far forward, & I might need to add weight at the tail.

3) I was using .015" dia. lines. I have a set of .012 lines, I am going to use those next time.

4) I had posted awhile back on another board regarding line length with the .10 engine, everyone pretty much seemed to think 52' lines were OK (this was before I actually flew it).

5) A member of the club I'm in also said he flew it with a PAW .09, I believe he said he used 42' or 45' lines.

I guess the conclusion is either use shorter lines or a bigger engine. Thanks to everyone who replied.

I have an OS .10 Schneurle port engine that I will attach to an Akromaster because I think they match up well. But with .012's, and the Akromaster is larger than any of the various "Junior" named profiles. There was an early OS Max .10 with a baffle piston that was closely related to the "Pet" .099's - not really a powerhouse.

Perhaps you have one of those instead of a more modern powerplant. Try adding some wing weight if the line tension remains poor with the correct line diameter. I've flown a couple of different planes on the 52' by .012 lines with Cox Medallion and TeeDee .09's, but those were at least average or better than average for that engine size. (One was the same Ring Jr. that I still have here with a 15X on it now.)

If your engine is actually a Schneurle-ported OS, go to a small prop with low pitch to get the rpm's up in the power band, and feed it more nitro than bigger engines require for sport flying. I generally use 15% Nitro mixes for .09's and .15's, although I still like a "healthy" percentage of lube - 25% or so.

My OS .10 runs nicely on a gray 7-3.5 prop, but would do fine on a 6-4 I think.

The K.

The original post says .10FP, so it should be plenty of power if it is running correctly, the prop is correct, and the fuel has 10%-15% nitro. If it is straight as you say, then the problem is the lines being too big and too long. It's too bad there is no such thing as .010" braided lines, but .012"s about 45' should be ok. Definitely go with more nitro, shorter .012"s and more tip weight. Starting with too much is way better than a total rebuild. If you're using the Master AirScrew props, you might find a huge difference with an APC, the Cox Grey 7x3.5, or Graupner 7-3 or 7-4. A 7.5x3 might be best, if anybody makes one. APC makes some weird sizes, check their website for the full list. Would .008" braids be safe enough, I wonder? Any 1/2A fliers use them? If they'd take 15 lb pull test, it should be ok. Steve

Ny experience with smaller airplanes says that they need to truck along to fly well. If you can get down to 4.1 or 4.2 sc laps on 52' lines you should notice a real improvement in how the airplane flys. If you can't do that, then try cutting about 3 feet off your lines. A light, slow airplane flying a big circle is not supposed to give you much line tension.

1. .015 lines are definitely overkill for a OS 10 FP.

2. This engine has plenty of power for your plane, which essentially is a Streak, Jr. Larry, don't confuse engine size recommendations made in the 50s or 60s with loop scavenged engines with today's Schnuerle offerings.

3. Cut the length down about 5 feet.

4. A few more grams of tip wt.

5. Where is the wind when you launch? Have it pretty much blowing down the tail, or slightly from the inboard side, like about the 7 o'clock position.

6. Don't try to 4-2-4 the FP. Launch at a slightly rich 2.

7. Zero engine and rudder usually work OK, but I'd one washer offset the OS just to be sure.

Let us know how it comes out. Currell

Where are they relative to the CG? The proper range would be about 1.5-2.5 degrees once you go to the proper line size. It's my guess that they are too far aft, which would pretty much force you to leave in the rudder offset. You can't have the leadouts and rudder/engine offset fighting each other.

Yaw angle is a very bad thing - if you can see it easily from the center, it's way too much. This actually tends to kill the line tension, particularly in the maneuvers.

>
>2) The center of gravity was
>forward of where the plans
>showed.
>In fact, it might be too
>far forward, & I might
>need to add weight at
>the tail.

Where is it in terms of MGC? 15% is the absolute max aft limit.

>3) I was using .015" dia.
>lines. I have a set
>of .012 lines, I am
>going to use those next
>time.

This will make a big difference in the drag and flight speed, but will tend to exacerbate the line sweep issue (presuming it's already too far aft).

>4) I had posted awhile back
>on another board regarding line
>length with the .10 engine,
>everyone pretty much seemed to
>think 52' lines were OK
>(this was before I actually
>flew it).

I would leave the shorter lines to absolute last resort. The model needs plenty of airspeed, and shorter lines mean either supersonic lap times, or low airspeed. A 10FP should have absolutely no problem with .012x52 lines. I have flown Medallion .049 planes on those lines with good success.

If it won't work in this case, then there is either some sort of trim issue, or you are flying too slowly. Shoot for 3.5-4.0 second laps. If this doesn't get you enough tension, there's something wrong in the trim area, and a larger engine will not really help it.

Take an 8-3 prop and turn it into a 7.5-3. I think that might be close to an ideal stunt prop for an FP 10.

As many have stated, CG is a huge factor in line tension. It should be very much acquainted with the leading edge, if not actually making love to it. Err on the side of William Buckley's favorite political persuasion. Later, as you are assured that the plane is takeoffable, and you actually desire a tighter turning rate, subtract some of that nose avoidupois.

One of my fave planes is a Streak Jr with a baffle Fox 15, and your plane is close to this. It is so tossable, literally bounces off grass fields if you don't dork it too badly, and there's no reason why your Jr. L S can't be the same.

>Where is it in terms of MGC?
>15% is the absolute max aft limit.

I'm not familiar with what the term MGC stands for.

Making a guess, is that the length of the chord where
the wing meets the fuselage? Or on a tapered wing, the
mean chord?

It is still probably easier to check the CG at the center and then, measuring from the trailing edge (if you have a straight trailing edge) mark the location half way out on the wing. Then calculate the percentage back from the leading edge.

I think it should, also, be noted that Brett is referring to this plane and not every plane. Planes with larger tails and flaps will allow for a different, usually more rearward, location for the maximum Aft center of gravity.

One other question then - the Jr. Lightning Streak has a straight
wing with a flat, tapered stationary flap. Is the flap included in measuring the wing chord?

I'm sorry, I shouldn't have abbreviated. Include the flap in the wing chord measurement.

15% is only the aft limit for elevator-only planes. This seems to be pretty generally true, even the Doctor is like that. They will usually fly and be at least stable further back, but they don't fly well.

Flapped airplanes are a different ballgame altogether.