Eric --

It was interesting to read about the fin brace #2 got. I too am going to brace the fin -- probably will run it from the bottom of the fuselage up into the fin in a fashion similar to the Temptation but probably farther aft to pick up more of the actual fin "volume." The other night I was puzzling over some other building issues and remembered I wanted to look at the whole problem of Impacts self destructing. Twisting the fin (even with my tail post taped in place) showed a concentration of movement in the linear "dimple" where the fin transitions out of the fuselage. I think I want to stabilize that…Isn't it interesting how size and shape (with the same construction material) can make such a difference in keeping all the parts going in the same direction on a consistent basis (Temptation fuse shape vs. Impact)?

Look forward to hearing about your results wih #2

Tom

I did manage one big test flight today. (The test day was cut short by number 2 son blowing a hose on his '86 Lincoln on his way back to Norfolk Naval base - Several cell calls and I was in Delaware on a search and recovery mission!!!!!)

The hardest part of the test was the initial setting of the mix carb. After that it was time to fly. I used the same settings as number 1 but had neutral elevator and had already allowed for the slight twist in all of the right wings. This twist must happen in the right wing mold. It corrects easily if you buld in a little bit of left roll into the incidences of each wing.

On take off it climbed on its own. I had the 10X on soft trim settings so it took about twenty beeps to get level. This resulted in about 1/16" down trim. I have this on both models. I modified the two-bolts-per-wing retention syetm this evening and will try taking out a bit of wing incidence. (Lower the LE).

Right from the moment it was flying level all felt very good. Spent most of the flight looking at up and own lines, rolls going away - to look for differential issues. Snaps and spins, 45 degree climbs and dives all good.. The KE on #2 goes to the belly, most likely due to the down trim on the elevator. Not much though and certanily not enough to mess up a small foray into the major rolls in P-05.

I will not dial any corrective mixes etc. until I try an incidence change. The way I am doing the incidences is to bore the bolt holes oversize and use 1/8" hard ply doughnuts, with exact 1/4" holes, on the inside. When the wings are right I touch the rear doughnuits with CA. I then fly about another 30 times and when really sure I CA all four.


All in all a great first flight.

Some static pictures.

Eric.

A couple of closer shots.

Interesting you mention a fin former. I installed exactly the same when I carried out the repairs to my Impact. I ran the former ( Rib ) from the fin base former to the rear rudder post, which follows the angle of the fin leading edge. I notched the former in to both the fin base former and the rudder post, holding out great so far!

Regards,

Andy.

I now have one fin with a rib and one without. You can't "squeeze" the fin sides together on one and you can get a liittle concave-result on the other. It springs back immediately and is stiff.

I have full length fuselage braces in both, resulting in very stiff assemblies. I also put the rudder-tray very high in the fuse, in-line with the end of the brace. There is a vertical former that prevents the canopy opening from twisting at the back. Two bolts per wing stiffen the center. I also thickened up the stab tube and siliconed the stab halves to the fuse sides to take out the stab rocking that was there on both of them.

With all of the above, there isn't much left that can be done. It is either going to hold up on not!

Regards,

Eric.

Attached is a pic/sketch of where the fin rib is fitted

Eric had discussed his rudder oscillation thought I would post some vids of my rudder oscillation the last 3 planes Ive had have done this, the previous two I built a structure to bind the cables:

Well...trying to find a better spot for them....but they will be here under Rudder Dance 1 and 2 when available:

http://www.geocities.com/b.young8070...t/hobbies.html

I havent built a lightened rudder yet, my Impact rudder was 70grams out of the box. Previous planes were a convential foam core rudder. I tightened the cables on this one and the oscillation reduced but could still be set into continuos motion. Then I moved the subtrim off center and retrim with the tab and the oscillation would not continue.

I just love the technology that allows us to see this stuff - thanks for the effort it took to put it up.

What you did allows me to say that my oscillation was not a blurr type buzz like yours. My SIO (I am now calling it Servo Induced Oscillation), was much greater than you illustrated.

The rudder on mine moved violently at leat two inches in both directions and the plane was jumping in the stand and was moving the whole thing across the bench. It did it with 5 different digital servos including an 8611.

Having reiterated on the SIO, I wanted to add that I do not dissagree the thinking around the other failures. It could could simply be structural! Fuselage folding is not new on many of the FG versions of the past. Fin-seam spliting is also not that uncommon.

The beauty of this forum is that we can warn others and advise on preventative "medicine". If one idea saves one plane we did a good thing.

Regards,

Eric.

P.S. Flew the "Yeller-Peril" version 8 times today. It liked the reduced wing incidence and is now flying with 1% up mix from the right rudder and 2% up mix from the left rudder to get killer knife-edges. down lines very good. Added 2% right rudder mix at full throttle for the up-line.

Don't see the need to do much else except learn to do the 3 roll circle :-)

Eric.

Took the"Brothers" out yesterday and flew them six times alternately to try and achieve the goal of having two planes that fly exactly the same. I had to be careful with the selction of model in the radio each time. I have them named IMPACT red and IMPACT yellow to go with their rudders, which helps.

I think that it is fair to say that they are close! I wanted to see if molded planes could come out "cookie-cutter" style and fly the same. The next time I go out I will fly three lights on one and then 3 on the other and see how it shapes up. It is definitely a lot of work and I have a much deeper respect for FAI worlds-contestants since I tried doing this for myself.

Here some views of them together on a sunny South Jersey day in MAy...

Regards,

Eric.

A couple more of them "breathing !"

My IMPACT is reading for clear coat whicjh I hope to do tomorrow and hopefully test fly in the next week or two. Here are some pictures before it gets the shiny coat.

Here are some other pictures showing throttle servo installation, canopy former, support crutch

Peter,

That´s without the slightest doubt the most beautiful Impact I have seen.

/Erik

I agree - great job!!

Rgds,
Mark

Hi joyfull pattern flyers
This impact is really very beautiful.
I like this design.
A+

After walking away for three weeks, I started measuring again with a GP laser incidence meter. They claim .25 degree accuracy but you can read less than .1 degree. However, measurements are not real consistent. The solution is to make many and find the mean. After what seemed like a thousand measurements I finally concluded that both wings were twisted as if they were made in the same fixture. This results in the right wing being washed out (wants to roll right) and the left wing is washed in (wants to roll right). So Eric's solution that rotated both wings, left trailing edge up and right trailing edge down is the right solution. Now the million dollar question is where do you set the .25 degrees positive incidence?
I finally picked a spot and glued in the "donuts" for the four anti rotation/wing retaining bolts. I can always redo them after flight tests if required.
Jim O

Hey PeterP --

What material(s) is your crutch made from? I really like your paint/trimming scheme.

Thanks,
Tom

Hi Tom,


The crutch is made from depron and balsa. I used 1/4 square balsa along each edge of the crutch running down the entire length of the fuse. There is also balsa supports across the depron crutch to minimise buckling. The front of the crutch (section were rudder servo is mounted is 1/16 ply with carbon which really stiffens this area of the fuse.


I also have a small balsa crutch between the tailplane tube and the rudder post. I have employed Eric's tail fin support and support behind the canopy which has really locked everthing in. Rudder weighs 60grams and I have relocated rudder horn to the middle of the rudder to minimise flex. I have also reinforced the tail fin seam. I used the rudder hinge method they suggested but the exposed parts of the hinge itself has been supported with wooden dowel (approx 3/8 inch with hole in middle - robart hinge slides into)


Thanks for the compliment with the paint scheme. I have used a similar scheme on the Alliance I built previously. Looks quite striking on the ground. Cant wait to get the clear coat on it as they come to life when it has a gloss over it.


I dont think I can do anymore to stop these failures. I hope to have addressed the issues with at least one of the mods I have made. I know some people are saying you shouldnt need to doo all of this but I look at positives - The model is by far the stiffest model I have ever built. This can only be good for flight performance and noise.



Here is photo of my Alliance with siilmar paint scheme.

OK Peter,
Time to put some radio in and fly this thing. I am flying mine in all winds. Doing some 3-D. Doing reverse avalaches wit 1.5 snaps, 1/2 square loops with down snaps etc. It will either stay together or not. There is no half-way point for me any more with the planes.

I suspect that the fin former, the fuse crutch and the TE of the wing fus. former cannot be busted in the air? Time and stress will tell! Sure they should have been in the instructions etc. - but that's hindsight. I watched Jason Shulman fly the crap out of his and it is still available for this years US Nat's or the Worlds.

BTW, I checked and all of my composite type fuselages have a former just behind the wing/TE/rear-of-canopy. Funny that!

Regards,

Eric.

Seriously, I am personally looking forward to your flight reports :-)

G'day Blue! (England plays rugby, Austrailia does it for real)

Hi Eric,


Believe me I want to get this thing finished but for some reason work and family seems to get in the way. I had hoped to get it flying for our state titles but I simply ran out of time. Looks like I will be flying the Alliance there.

I am also waiting for some goodies to arrive from Central Hobbies which I need to get it going. My target is still 4.5kg maybe slightly less with Lipo's and carbon pipe.

I hope to get it going in the next couple of weeks.


From the sound of it you seem happy with the way they fly?



Regards,

Peter

From the sound of it you seem happy with the way they fly?

Any plane that makes the inverted 8-point easier is a one that I like.

E.

Hi peter (yout post n° 592)
I think your pattern Alliance is very very beautifull.
I 'm going to copy it for a new plane Oxalys. I think it don't disagree you because I live in a country very far from you in France (Europe).
I have a question. You modified the nose, how did you do that ?
thank for your answer
claude

Hi Claude,

I am happy for you to use this colour scheme on your model. I had made carboard templates of most parts so it is easy when I paint my next model.

The Alliance has some cheek cowls which I moulded and glued onto the side of the fuse. They are functional and provide additional cooling to the engine. Here is another photo.

Good luck with the Oxalys. I hear they fly well.


Peter

I have an Impact with OS140RX. Being used to flying four-stroke YS140's , I find throttle management much more demanding with the 2-stroke( otherwise an excellent engine). I simply like flying four strokes.....

I have a YS140 DZ that I am thinking of swapping in for the OS. My concern is about vibrations. The Impact is extremely stiff and probably doesn't dampen strong vibrations very well. The vibration level with the OS and Hyde mount is acceptable.

Does anyone have experience with vibration levels and DZ's / Hyde mount in the Impact ?

Hello everyone,

Well I’ve notice this, the past Saturday while prep. My plane for a nice Sunday flight.
Well, the plane laid in my hangar for about 4 week’s and when I went to check on everything the past
Sunday I’ve notice this. But Mine was much, much less. The movement could been @ 5mm to 15mm, but the
strange thing is, after a while it just disappeared.

Now I’m wondering what could this be?
I’m using the JR 8411 SA, on my Focus II.

Reading Brian Young post, I’m wondering if this is due that the Pull cables might be a little lose?
I’ve check them, but in my opinion they are still stiff ( tight ), but there is room for some tightening.
Using steel cable.

Just wondering out off curiosity.
Any ideas?

Regards,
Danny Koolman
www.arubarcclub.com

This is very common, here are some common causes and solutions:

On a new (or fairly new) 8411 servo:

1. Try tightening the cables. Often this is all that's needed to fix the problem. You should be aware that changes in temperature sometimes cause the oscillation due to shrinking/stretching of the fuse and cables in different temperatures. I've experienced this.
2. If #1 doesn't work then it's possible the dead band is too narrow. The "proper" way to fix this is to send the servo back to Horizon and have them increase the dead band. However, another option that will sometimes get around the problem is to use the sub trim to move the servo off of center and then replace the servo arm so that it is centered. For some reason changing the center will sometimes fix the problem. This is a good solution if you don't want to wait for a round trip to Horizon.

On an older servo (I'm assuming it's not always had the problem) you can also try tightening the cables a bit, it's possible they've stretched. If this does not fix the problem it's probably time to send the servo in for an overhaul. The off-center trick will also sometimes work on servos with worn pots, but I prefer to send them off and get them overhauled.

Remember that JR has a three year warranty and they will repair even worn servos free of charge if they are in warranty.

Keith B