I picked up some foam boards from Ed Skorepa (a.k.a. EScomposites of carbon-fiber pipes fame), and decided to use it as material for a brace for the Impact fusealge. I ran a couple of 1/8 sq longerons to the stab former to hold in place during gluing. I then keyed the board into the rudder and mix-carb servos' tray.

Between the rudder change and this "ladder" I can only hope we have it licked!

Eric.

Very nice work Eric -- I too hope the problems are licked.

BTW -- are those mounts your elevator servo is on readily available? I keep cutting up aluminium angle to make brackets -- but those you are using look neat, and I haven't seen them anywhere.

David

Looks good, Eric! Did you replace the tailpost as well or did you leave it as stock? Did the foam ladder stiffen up the fuselage at all? I'm planning to do one out of balsa instead... I've mounted the stabs but haven't put the former in YET - will do that shortly. I did notice that the fuse does flex quite a bit when I grab the stabs and wiggle them around... so I'm hoping that the crutch will stiffen it up quite a lot.

They are sold by [link]http://www.planesplus.com[/link] tel (630) 904-5075. (They are in Illinois BTW)

I have used the side-mounting brackets for many years. They used be RC City products and were subsequently purchased (and produced), by Planesplus after RC City went bust. PlanesPlus had them at the WRAM show also had quite a few pattern goodies including Chip's b.b. horns and clevices.

This final assembly is taking a bit longer than I thought it would but the good news is that the second one will be much faster because I am taking templates or making copies for the tricky bits.

I also picked up some really good wing bags for the Impact wings from [email protected] They are nicely padded and take the 1" wing tube in the wing-tube-pouch. My other bags either did not have a pouch or the tube was too tight a fit. Adrian is a keen pattern flyer and very helpful if you need anything. I particularly liked the slot for a business type card so that you could identify the panels for each plane exernally.

Regards,

Eric.

I can't speak to the composite brace that Eric Henderson is using Derek, but I can to the balsa brace that Brian Billings has installed. It added about 1 1/2 ozs all up to the tail and made the tail very firm. Hardly any wiggle side to side and very good in torsion. His pictures are a little further up in this post. Note that the sides of the ladder have considerable width, covering greater side area. Good luck with yours

MattK

I would add that a former is needed just behind the canopy opening. I think the MTK had already posted this info.

My current thinking is that;

a) The rudder hinging needs to right on. If the hinge-pins show any form of side-flexing it could flutter. I have already swtiched to a "flat"
stern post, as shown above.

b) The "ladder" is needed to avoid compression and expansion of the rear fuselage sides. (At least behind the rear wing anti-rotation-pin-cross-tube up to the stab)

c) The extra former is needed to prevent fuselage twisting at the rear of the canopy.

If I pause for a moment of refelction, I would really ike to thank all of the conributors who have rasied all of these issues and the suggested fixes. This is the magic of RCU, (especially when you can post pictures). For those who have goine before we all benefit.

Thanks again matey's

Matt,

Thanks... I've assembled a crutch using 3/8" x 1/4" balsa and the 3/8 is going to be against the fuse. I will also put another former in right behind the canopy... easy to do. The big difference is that I'm planning to use wing adjusters instead of the anti-rotation pins and based on the comments by the manufacturer that the solid carbon tube adds that stiffness across the rear of the fuse (by the canopy) I definitely think the former is needed.

-Derek

Eric

Does Adrian have a website that you know of where we can see his wingbags? Or can you take a picture for me?

Thanks!

Guys,

Fancy another look to the Impact? Here ya go....

http://www.composite-arf.com/ar/Product?513000

Rgds,
Mark

Thats much better.

I was unable to reply to this question earlier because I had not glued it all in place at the time. Even when the materials were dry-fitted you could feel the change in the stiffness.

I am please to report that the result gives an amazing difference. The stiffness is very acceptable and even enjoyable :-).

Eric.
[/quote]

Looks good, Eric! Did you replace the tailpost as well or did you leave it as stock? Did the foam ladder stiffen up the fuselage at all? I'm planning to do one out of balsa instead... I've mounted the stabs but haven't put the former in YET - will do that shortly. I did notice that the fuse does flex quite a bit when I grab the stabs and wiggle them around... so I'm hoping that the crutch will stiffen it up quite a lot.
[/quote]

[link=http://www.chingbergh.com/products.html]http://www.chingbergh.com/products.html[/link] Try this link.

Chad,
I took some pic's, but it's not an very exciting subject. Plus mine are still a little bit crumpled from shipping in a small box. I liked the velcro ends, the protection of the padding and the size of the wing tube pouch.

Regards,

Eric.

Perfect Eric, that is exactly what I was looking for

Thanks!

Is anyone using the Composite Arf engine soft mount? This is my first pattern ship in 20 years so I am a little behind the curve on how it is supposed to go together, and C-Arf's instructions are a little lacking from what I am used to. If anyone has a picture it would be helpfull.

Thanks in advance.

yes some are using the soft beam type that CARF has popularized. My friend Gary is using it in his Rev Pro. Power is a YS140L which shakes alot. His beams are the original fiberglass type and the engine bolts needed epoxy to stay tight. The new aluminum beams take care of that problem.

Many have opted to use either a Hyde of a Hyde clone. Either way, it's fine, with either 2 stroke or 4 stroke for power.

MattK

I am not familiar enough with these mounts to determine how it goes together. There are 4 urethane pieces two of them obviously slip over the aluminum beams, and the other two look like they could slip into the back of the first pair, if this is the case the supplied bolts are too short. There are a couple of rubber peices stud on one end and tapped on the other I would guess that I add a screw through the nose ring and into those then screw the stud into the aluminum beams? then there are four rings cut out of G-10 I am assuming these are supposed to be doublers for where the bolts pass through the firewall and nose ring?

BTW I will be using an OS 1.40

Sorry for the seemingly dense questions but I have been flying jets for the last 10 years and we don't really worry about vibration. If a turbine is vibrating it pretty much takes care of itself!

Brian, yestreday was extremely windy at the local field and models needed all the power the engines could muster. The 17x13 full blade prop makes a good windy weather prop for the W160. Still running it on the rich side (only 2 gallons so far) and slightly detuned, but, it had enough grunt to pull the plane fine. A larger prop would be reserved for calmer conditions.

MattK

Having a propblem with a plane and not knowing what is causing it is like that itchy nose when you are in the barber's chair, sooner or later you just have to scratch it!!

Last night I was doing the final installation of the rudder pull-pull wires and I had a servo go nuts on me. It is an 8411. I have seen this before with heavy control surfaces on 3-D ships. The side to side bouncing of the rudder was extremely violent. A replacement servo cured the problem but left me with food for thought.

The action was so strong that I could easily see the plane breaking if I had not stopped it. The servo did not like the 6V regulator and behaved better with a 5.2V regulator fitted. I use ball-bearing clevices on both ends of the wires so the friction is low with the wires tight. A light touch of the finger on the pull-pull wires stopped the bouncing back and forth.

Several of you have built lighter rudders that may well be curing the rudder-death-dance.

Any of you with broken fuselages been using this servo on the rudder?

Regards,

Eric.

Eric,
Has anyone tried replacing the cables in the pull pull with carbon fiber rods as used in the elevator set-up? Seems like we don't want any thing that works like a spring in our control system. We need to get the natural frequency of the mechanical system up higher than that of the servo. I'm using two solid pushrods on the rudder of my 2.6M Extra (to two servos) and there is no sign of oscillation and there is zero slop. Just a thought. I bought 8411s for my Impact but haven't decided how I'm going to install it.
Jim O

Jim O,
I have had brand new 8411's behave similarly to what Eric Henderson described above. Very rapid and extreme oscillation at neutral, on other surfaces besides rudder, on pattern and larger planes alike. I sent them back and was told that the dead band at neutral needed to be broadened. Yet some (most?) 8411's do not display that oscillation so maybe there is something to that. As an old Radio man, you probably know better than anyone. I would really like to know what the answer is.

MattK

I have used solid pull-pull on IMAC panes and have had it happen when one servo only was attached. When two servos were attached they seemed to dampen out each other.

I had all of my 8411's "softened" a long time ago. If you put a rubber band on across, (and pinching), the pull-pull wires it stops doing it. It seems to depend a lot upon the mass of the control surface and, in my case, it is most prevalent when ball bearing connectors are used. Any friction in the system, such as a regular pin clevice and horn, seems stop it happening with a known "bad" servo.

I am not talking about a "buzz" or small bad-pot flutter here. I am talking about a pretty destructive self-perpetuating oscillation. The rudder was moving very quickly and in excess of two inches in both directions.

Why I asked about the JR servo is that the instructions actually, and I have remarked, unsually so, call for the 8411 and a very strong servo arm. Furthermore the issue is still, "why are these fusealges experiencing damage?". I would hate to have done all of my "preventative-construction" only to find that the servo "weakness" was the real culprit.

Regards,

Eric.

BTW - I tried two different 8411's and two car steering "Z whatever" equivalents and they all did it to some degree or another. All were new or serviced recently. I then put in an 8611. Bingo! no more issues, no matter how much I bounced the sticks!

I too have had the 8411 rudder dance and the cure for me has been to fit the complete plastic gear set that has the JR part no. "JRC 8231GS for 811, 8201, 8301, 8300"

Initially I tried just fitting the intermediate plastic gears, leaving the metal output gear. Effectively this gives you an 8411SA This worked OK for a few flights and then the wiggle was back. Changing the output gear for the plastic one cured the wiggle completely. I am pretty sure that in this spec. what we have is designated 8401 here in UK. Basically, the 8411 servo is underdamped and the slight backlash in the metal gears is enough to excite it.

On another topic can anyone tell me what clevises fit the holes in the fibre horns of the Impact? I am used to the ball race MK system with no slop but as Composite say not to use a single sided attachment t their horns I have been trying to find a suitable clevis. All the ones I have tried have a little slop in the Impact horns, the best being an unbranded 3mm metal clevis.

Malcolm Harris

Malcolm,
I saw that they were very specific about not using ball and socket type of connectors. They didn't actually mention the ball-race connectors. The ball-race connectors fit very closely to the side of the horn.

Currently I am trying a servo-arm clevice on both ends. I am using a ny-loc 2-mm nut to hold the pivot point pretty ridgid. I put a ball and socket clevice on a horn as a test and the horn could be seen to flex when put under load. I could not get the same result with the ball-race clevice.

There is a way to be absolutely sure and that is to put two horns side-by-side with the ball-race bolted between them.


Regards,

Eric.

P.S. I'll try the tip about using the nylon ouput shaft to the servo arm. I had been a bit lazy and was only changing the middle gears.

The Dubro plastic clevis w/ the little clip retainer is a good fit. Watch using this clevis on 3421sa servos though it will hit the servo case.

I am using the MK bell crank on my bird, with ball links connected to the MK "BC" and the dubro locking clips to the clevis. So far with about 6 flights no fluttering issues. I did move the CG back further than recommended. I had to much up in the trim. Right now I think it flies better with a slightly rearward CG. Will continue to experiment