RE: Impact
 

Malcolm,

I lifted the tray and put rudder and elevator servos on it -- so it was between the wings. I make sure there is a brace between the back of wings on all aerobatic models in case I ever accidentally touch a wing tip (translates load through to other wing rather than breaking fuz).

While I am no expert, I sense the failures are rudder flutter related and more of an airspeed/mounting issue than a vibration issue.

David

RE: Impact
 

Malcolm, you will likely get several responses on your question and these could differ significantly from one another. I suggest that one should err on the side of caution and safety with this model. The fuselage compression buckles some have experienced is as much a function of weak fuse sides as it is vibration induced resonance. As such, your Hacker set-up will experience less of the latter.

But since weakness of the fuse sides is the other variable of that equation, it's a good idea to reduce the free, unsupported fuselage span in the longitudinal direction, by adding at least two more fuse formers to go along with the one in the tail. Then the formers can be tied together with a pair of 6-8mm square balsa longerons glued to the fuse sides, at the formers' mid section.

I have written about this approach before as alternate to the crutch bridge, since this will open the center area of the fuse. This is similar to how airliner fuselages are designed. FWIW

MattK

RE: Impact
 

Is putting the elevator servo in the fuse a better way than two servos in the tail? I'm wondering after painting this Impact (white /red model) if the tail will get too heavy even with the batteries pushed all the way forward. Looking at the photo it appears you join two rods together. Are there details on this tip of installation anywhere with photos?

I was hesitant at first to build this model but after reading all these posts and some of the eleaborate methods used to align and modify I am so worried now that I'm going to screw it up[:o] Maybe I have already screwed it up now that the wing and stab tubes are glued in place.

Thanks,

Kelvin

RE: Impact
 

I just finished mine up. I have the servos in the stab and it balances between the wing mount bolts and the wing tube without the battery. My rudder servo is at the aft most point on the canopy. So a battery position between the wing tube and firewall will be required. Im using a 5 cell nimh battery.

10lbs 9oz w/ YS ES pipe, and Vinyl graphics

One guy told me he painted and added only 2-3 ounces paint.

RE: Impact
 

Did you build and install the tail former and the reinforcement bracings for the fuse?

RE: Impact
 

Yes, I added the rear former and fuse crutch from aft of canopy to the rear former.

My servo tray is positioned as per Mr.Gibbs photo above.

RE: Impact
 

Is the datum line level when the cowl flange is level so I can accurately set the incidence of the stabs?

Thanks

Kelvin

RE: Impact
 

You can read the engineer's findings for why this happens and the factory recommended fix on the announcements page at www.composite-arf.co.uk

Rgds,
Mark

RE: Impact
 

How come that info is not on http://www.composite-arf.com/ar/Main . Is the UK site the main site?

Kelvin

RE: Impact
 

How did you strip off the front of the rudder? Do you have any pics at all? I've been toying with building a totally new rudder but if it is easy to cut off the front and replace it with balsa then I'm all for that instead...

RE: Impact
 

The front of the rudder is easy to take off, its hollow back to the support for the hinges. A sharp exacto, hot knife, or friction wheel on the dremel will get you started. A sanding block and a new leading edge will finish.

RE: Impact
 

Hi Derek,

In the rudder there is a former about 1cm behind the leading edge. I originally set up the rudder hinges per the plan, but wasn't happy with the way the lower hinge is cantalevered. If you just dremel out a hole in the leading edge then you can take it down to the former, then sand flush. Build it up with 1/2" balsa then treat as usual.

A couple of side effects to note though - this changes the hinge line to the back of the fin, where stock it is countersunk somewhat. With the new tail post flush, the LE of the rudder has to be tapered to get the correct fit for the rudder overhang.

Sorry, tried to take a pic but they look terrible (not a photographer!).

RE: Impact
 

As an FYI, I can confirm that the Karl Mueller FOCUS-2 header for the OS 1.60 FX side exhaust fits the Impact quite nicely.

RE: Impact
 

Kelvin,

My site is not the main site - as an individual I can develop and post items a little quicker than Comp-ARF themselves as their site is managed for them by an external company. It will be on the main site very soon.

Kind Rgds,
Mark

RE: Impact
 

Say I was putting my Stab on last night and noticed that I sanded a little of my Carbon tube down where it, where it exits the right stab, does not look like it hurt the stab tube at all but should I be concerned? As I mentioned before it looks fine, and I am sure it will hold up, but It is always better to be safe than sorry. Your inputs would be apprecaited.

RE: Impact
 

I didn't realize this was your personal site. I thought is was Composite-ARF site.

I'm really disappointed in Composite-ARFs customer service and communciations. They have major issues with this model and they don't even have the info on their website. It took C-ARF over a month to ship me out some CF parts to replace wrong parts that came with the kit. Look how long it took for them to come out with instructions and they aren't the best.
Now I read in the addendum downloaded from the UK site that these parts; the tail formers and the styrene floor are parts of an "Update" pack? All these parts are available from C-ARF?

What thickness Depron is needed to make the fuselage floor?

Thanks,

Kelvin

RE: Impact
 

Kelvin,

I am simply a rep for Comp-ARF in the UK and created the site as a way of communicating info, hints and tips to builders/owners of these kits.

Comp-ARF rely on their reps to help their cutomers and they should always be your first port of call. I would suggest that you contact the Comp-ARF rep through whom the kit was purchased. They will then be able to request the update kit for those that want the factory to supply the materials. For those who want to make the items themselves, the dimensions can be found on the above mentioned announcements page.

I'll let you know the depron thickness asap.

Rgds,
Mark

RE: Impact
 

It's 5mm.

Rgds,
Mark

RE: Impact
 

Thanks, I saw the graphic for the depron floor and the dimensions were shown but not the thickness.

Kelvin

RE: Impact
 

Ok, Finally made my ladder in the fuse tonight anfd it was a pain, but I got it done. Took me about a half hour to do it, and I could not beleive, how stiff it made the fuse! I used a 1/4 balsa pieces to run on the sides and then used left over to make the ladder.

RE: Impact
 

Very nice. How were you able to apply the glue all the way to the back?

Kelvin

RE: Impact
 

I am going your route Brian, the stern post hinge points are too easy to crush with the mechanical advantage of the exposed part of the hinge. I figured out the same angle issue as you did and also that I can sand down the TE of the fin so that the rudder counter balance will move forward realign with the fin.

Feel much better with that set up.


Regards.

P.S. That hot knife (Foam cutter) is great for this skin and foam material. Just be careful where you put the old blade when you swap in a new blade, while everything is still hot -- don't ask :-(

RE: Impact
 

Can anyone post photos of the rudder mod as just described. I'm not confident to start cutting into an $800+ model.

Thanks

Kelvin

RE: Impact
 

took the first flight today, and was very impressed with the plane. Made a slight whisteling noise; must be due to the airframe. I am flying a 1.60 DZ and I don't think I went above 1/2 throttle. This is a very impressive engine. The shake and rattle of the 1.40 is lost on the 1.60. The engine is really smooth. My CG is located a 1/4 inch behind the wing bolts. This postion I think for me will work out very well. Down lines were very strait no mix. my setup is wings at .25+ stab at 0 degrees. Will put some more flights on it in the cming days and let you know what else I find out.

RE: Impact
 

Whistling is common sounds like Banshees...right?

Robert did you use the spring load canopy device and the hooks that came w/ the Kit? I was curious as I was test running my engine today and noticed some shake of the canopy. Also the YS 1.60, I didnt have a 1.40 dz but this 1.60 seems pretty smooth so far. What spinner did you wind up with?