Since the plane didn't have any specific thrust line markings I went with the pre-molded markings to set the stab. ASSUMING this is zero then I have the stab at zero and initially set the main wing at +0.25. I also started with the CG 1/4" behind the wing tube.

First thing I found was the plane rolled to the left and pulled to the canopy in vertical dives (both fairly significantly). I then lowered the leading edge of the right wing pannel until the ailerons were centered with level flight. At this point the plane was still pulling to the canopy in vertical dives so I moved the CG back another 3/8" to 1/2". Even at this I still had a slight pull to the canopy which I mixed out with 3% down elevator on low throttle.

At this setting the stall turns were very difficult so I moved the CG back forward to around 1/2" to 5/8" behind the wing tube. This fixed the stall turn problem, however when inverted it still felt nose heavy and wanted to drop its nose quickly, even on the 45 degree upline. I then reduced the incidence of both wings about 5/8ths turn of the Gator adjusters. With this it seemed to be getting much better but at the time the wind 15 to 20 mph and it was hard to tell. BTW, I also reduced the down expo to make the down more sensitive to help reduce the feel of down elevator when inverted.

Another thing I noted was it required much more rudder throw on the four point than I was used to. I lowered the expo to about 33% and it still felt soft. So I increased the initial total throw from 2 1/2" to around 3+". This too helped get the rudder to where I'm used to it.

Once I get to fly on a calmer day I should know more.

KeithB

To those who have put a OS 160 engine on their Impacts, did you mount your elevator servos in the tail of the plane? and if you did, did you mount the servos in the elevator stabs or on the side of the fuse?

Hi All, Below is a note I passed to the NSRCA discussion list regarding flying this weekend.

I flew the Impact 4 flights this weekend. I did this while flying my Aggressor, and breaking in a new OS 140 RX. It was one of the funnest, BEST pattern day's I've ever had. I flew the E-Impact and immediately liked the power and speed control (and ease). The Impact itself, didn't jump off the board as a perfectly trimmed plane, so I knew I had a little work to do. After the first flight, the concept was DEFINITELY proven, and I quickly deduced that I need more batteries (first flight was Saturday evening). After this first flight (with John B. from Surinam watching), we determined the need to paint the bottom of the wings and canopy. We ran to Lowes and bought some florescent red/orange to paint the stab and wing tips, and we also painted the canopy metallic silver. Also determined that the plane was tail heavy quite a bit. Anyone familiar with the Impact thread on RCU knows exactly what I'm talking about in regards to the Impact.

Sunday morning with CG moved forward, the plane flew better and the small amount of color we put on the plane definitely made a huge difference. After this second flight, also determined that the CG was still too far aft, and that the battery needed to be moved forward (at this point, knife edge needed no mixing), and the plane was carrying a small amount of aileron trim.

Then, I flew the Aggressor for the first flight with the OS 140 RX and 17x10 APC. With th 17x10, the OS was nearly "super-sonic" compared to the Impact, however immediately, the Aggressor's trimmed status and "locked-on" look/feel was evident (as anyone who has seen the plane fly in D3 would attest to. Due to charging time of the E-Impact, I swapped props to the Mez 18x10, adjusted the throttle curve, and started moving the speed envelope of the Aggressor down to match the Impact in a couple more flights. My first thought was that if I had the E-setup in the Aggressor, it would be an unstoppable machine! (Aggressor weight without fuel is 10 lbs 13 oz).

Time for another flight on the Impact. I flew through PO5 this time, and started getting used to the E-power curve, some rates, etc. The forward CG move started to pay off, and the plane was drawing better lines (but still not like my glow plane, which is understandable as this was only the third flight on the model). After this flight, again, decided the CG needed to go MORE forward. Also, we determined that the right wing tip needed about 14 grams of weight to laterally balance the model (a step I did not do in the garage, we added the tip weight at the field).

Back to the Aggressor: I flew two more flight back to back on the Aggressor, each time improving the throttle curve to make it easier to match the envelop of the Impact. The OS ran perfect, and I'm sad that after 5 years of screwing with other engines, to have not just spent the little bit of extra money and ran the OS all along. Through each flight (90 degrees, 90% humidity), the OS ran superb. Inflight throttling was great, you could tell the motor was not getting hot, and it was making ridiculous vertical power. (by the way, this was on an OS A5 plug, C.P. 25% pro-pattern, and ES pipe). The OS runs VERY smooth with a crazy low idle. I'm VERY happy with how it ran - not a single dead stick through its first 5 flights - nothing but awesome performance. The locked in (trimmed) status of the Aggressor, now flying in the slower speed enveloped, had convinced John that this was still the "ticket" as compared to where the Impact was after 3 flights.

Back to the E-Impact!!!!!!!!!! For this flight, the 6000 Pro-Lite T.P. battery was moved as far forward as possible (just behind motor). This flight showed some incredible potential. In this CG config., the Impact was driving lines similar to the Aggressor (up, down, 45's, etc), and rolling VERY well. Also, the wing tip weight on the right wing made EVERY SINGLE MANEUVER look better. The wings were much more locked on, the plane rolled better, exited snaps better, spinned better. This was a great trimming lesson to me, as the day was getting cross-windy (worse) through out the day as the ruminants of the tropical storm passed through, however in the worsening conditions, this was the BEST of the flights.. After this flight, John immediately was convinced that this was indeed going to be a solid backup or first plane for the nats. I'm still going to move the receiver battery forward now though, and probably make a lighter rudder (which wouldn't hurt things anyway). (hacker controller has 3 degrees timing).

Charging: I alternated by charging from the car battery, then letting the car idle for the next charge (guess what - no big deal to do this if necessary). However my limitation is that I only have one Astro 109 as the second one has not arrived yet. Thus, instead of 45 minute turnaround times, I was 1.5 hrs between flights.

Impact: I followed some RCU advice and started with a CG on the center of the wing tube, without wings on. This is in serious error. However, the plane will dive mildly when in inverted flight, and it gives the impression through simple tests that the CG is correct. With this CG, the plane flys off the tail. In radius, the tails squats and the plane will fly tail low. After I was done with it, the plane was following the nose, driving excellent lines, similar to the Aggressor (still thanking Tony F. for the trimming help on my Lazulite,which has now gone into all my planes!).

Glow / Electric: In a quick comparison, a trimmed plane is what you need. Electric power itself will help with presentation and probably hide some airplane tendencies (if bad), due to the smaller speed envelope. Although, the power and the plane are working together, they are still a bit separate. I guess I'm trying to say that a poorly trimmed plane is going to hurt you no matter what motor you have in it. I'm guessing purely guessing now though, that if two identical planes, both completely trimmed, were equipped with glow and electric, that the E-setup would take the cake as it would allow more of a "show-casing" of the maneuver set. More to follow.........

Thanks, welcome questions, comments, public or private

IMPACT: I'm carrying a slight aileron trim, and will need to "pin" the front of the wings once I decide if the trim is worth adjusting out or not.

Thanks,
Jim W.

Hi Jim,

Playing with CG is a really interesting issue, and i am doing it right now with my Impact.

Have you measured the CG with wings on since youre latest tests ?

My old Larimar are my truly comp bird this seaon for the P-05 program,and i fly the Impact between the comp events to get better known to it. maybe it will be used later in the season ...

I guess i have belonged to the "tail-heavy-group" so far,moving the CG to the most aft position... not neutral, but very little push inverted.. I like my Larimar that way, but the Impact is quite different. It really dont like it at all when we start the fight, guess i have to reset myself and start all over ...

I really like youre flying tests issues Jim, hope you continue..

Kjell Olav

Hey Jim --

Interesting discussion on trimming. Where is your CG in relation to the wing LE at the root? With the recent posts about different fuselage lengths and wing tube positions this might be the clearest way to describe it -- how far back from the LE at the root?

Thanks!

Hi tggilky,

I've just checked mine and can report, l/e of wing @ root to l/e of wing spar tube = 150mm, l/e of wing @ root to my c/g = 195mm.

Hope this helps,

Anyone else got any measurements to share?

Andy.

My CG is at 178 mm from the LE of wing. LE of wing to LE of tube is 150mm.

Im also using 2 degree down thrust, anyone else using down thrust?

The Plane is flying straight up, needs some down pressure on downlines, needs slight down pressure inverted. Knife has no tuck or pull. Very heavy rudder does roll and tuck the nose.

AndyP, Brian, was the cg measured upright or inverted? Seems like a large difference between {17mm} the two planes.

I measured upright.

Previously my CG was same as Andys, moved the battery to the fire wall from the wing tube. This made very little difference in the inverted feel of the plane and settled it down in wind some, I would try further forward If I could easily do it. Stall turns got easier.

Amen to that Jim,
Suggest a 17x12 or a 15x13 3B. I use 15% nitro with great results.

My CG is at 191 mm from the LE of wing. LE of wing to LE of tube is 150 mm.

YOWZA! That's nearly 5/8" further back than Brian Y.

Brian, was your measurement with the wings on or off? Mine was measured with the wings on.

Keith

Hi Brian,

Mine was measured upright with the wings on. No nasties during k/e but very slight pull to canopy in down line.

Regards,

Andy.

Wings on, 178mm from LE.

Wings off the fuse balances on the center of the tube.

Moving the CG about 13 mm forward barely changed the elevator trim.

The flying sites Im at right now have a lot of turbulance so the plane keeps getting bounced around, wanted a more stable platform, this helped.

Hi Guys,

My Impact needed 14 grams on the tip of one wing panel to laterally balance, and it made a HUGE difference in flight. My CG is just ahead, of the forward edge of the wing tube now (wings off). After more reflection on Sunday's flights, I decided to move the receiver battery forward to the engine bay area. I will fly this in the am and report the CG finding.
Thanks,
Jim W.

OK, guys, I'm starting to come around to Brian's way of thinking. I moved my CG forward about 4 or 5 more millimeters today so now it's about 1/4" behind the wing tube. The elevator trim didn't change at all, but it definitely flew more stable and did much better stall turns. Landing still seems a bit squirrelly so I think it could use even more nose weight, but I hate to put more weight up there. Guess I should try moving the CG further forward to see how it affects things.

It still requires quite a bit of rudder and elevator on slow rolls to keep the nose from dropping, something I'm not used to. I guess I'll just have to get used to it if I want to keep and compete with this plane.

KeithB

Jim, how did you determine lateral balance wasn't quite balanced? Slight roll in inverted flight?

Hi Adam,

I noticed a few things. Rolls were a bit bobbly, almost like it needed differential. Snaps seemed not so axial. The biggest item was roll during inverted flight. While positive loop tracking seemed fine, inverted loop tracking was WAY OFF. During this morning's flight, inside and outside loop tracking was much better.

Also - thanks for sendin the 5300's. My wife said that the DHL truck came to the house this am.

Thanks,
Jim

Hi All,

After lots of vertical lines, and inside loops, I have set the rudder trim and the result is not good. The lower tip of the rudder counterbalance is 3/16" offcenter to the vertical fin, in a Left rudder direction. I've gone through this rudder trim trial for several flights, not believeing my eyes that this was necessary, but it is. When pushing from inverted flight to an upline, a lot of right rudder is needed to hold the line through the radius. I do believe I can see some Right rudder direction molded into the vertical fin.

Has anyone else done loop tracking, and needed a bunch of left rudder? Possibly an effect of the E-22x12???
Thanks,
Jim W.

Jim,
My Mark 1 eyeball says that the top of the vertical fin is offset. If you then line up the counter balance on the rudder to the top of the fin you will indeed have right rudder. I split the top of the fin and then attempted to straighten it out when I installed the rudder post. Hopefully it will not be a problem.
Did you offset the wings to compensate for the slight twist in them? I went crazy trying to set the incidence with differences if I measured inboard or at the tips. A good reason to plan on adjustment after flying.

Regards, Jim O

With both of mine the rudder and elevator servos are at the back of the canopy area. The Li-ion is on the landing gear. Goes up and down hands off with a bit of throttle mix.

Jim,
The fin needed to be held straight and squeezed with a "former" when fitting the stab tubes and the stern post. Sorry if this is late info.

Eric.

Hi Guys,

Tomorrow I'm going to fly again with some R-thrust removed from the motor. This should aid the left rudder trim, and some of the need for so much R-rudder during outside maneuvers.

That said, the plane does fly well. Knife edge is close without any mixing, pleasing to fly, etc. I just want to fix the amount of L rudder trim in the plane.

Thanks,
Jim W.

Hey Impact(ers) --

Any new developments with flying or airframe behavior? Mine's still not done -- finally getting to fly some using the Temptation (lead us not into...)

Curious,
Tom

Another Impact bites the dust. I took Thurs. and Fri. off to practice for our State Pattern contest. The second flight on Thurs. I got a flame out. Well trying to avoid straining the plane through a barbed wire fence, I ran out of air speed about 4 feet off the ground. The plane went in at a 45 degree angle and as soon as the spinner touched the earth the tail wrapped around the fuse and broke off about 3in in front of the stab. The only other damage to the plane was a cracked chin cowl. The spinner and prop were not even nicked. This was one of the first Impacts to hit US soil, It came with no directions and no tail formers. On a side note, I dusted off the Focus, mounted my motor and electronics and got 3 trim flights in. Then flew to a first place in Advanced. I do have to say, for me the Focus flies much better then the Impact. I'm sad for the lost $$$ but somehow glad to be flying the Focus again.

Hey FG --

Just out of curiousity, did your Impact have the crutch in it? Sorry you lost the Impact on a flameout of all things!

Tom

Tom,
No it didn't, it was one of the first ones in the states and I put it together according to what little directions there was at the time. The way its going I will probably scrap the fuselage and sell off the parts. I am way happier flying the focus.