Doug Cronkhite

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OK guys,

Time to get started on my new Composite ARF 2 x 2 Extra building:

Since I'm big into the electrics stuff these days, this airplane is going to use the Comp-ARF supplied Hacker conversion kit for nice, quiet, clean, impressive power.

So far.. the weight situation is as follows:

Fuse w/chin cowl - 30.4 ounces
Canopy (opaque, no clear available) - 4.2 ounces
Stab/elevator - 4.5 ounces each (they were identical down to the gram)
Rudder - 4.6 ounces
Wing panels - 18.5 oz right panel, 19.2 oz left panel
landing gear legs - 5.6 ounces total for both
Wheel pants - 2.4 ounces total
Included hardware - 16.2 ounces (not all hardware will be used as much is for glow/gas installation
Hacker conversion kit - 11.9 ounces.

Total bare airframe weight - 122 ounces. I'm guessing a full 8 ounces of stuff is for the glow/gas version but I won't take that off my weight list just yet.

Motor - 18.5 ounces
Battery - 42.7 ounces
Controller - 3.2 ounces
Prop - 4 ounces
Spinner - 2.6 ounces
Servos - 11 ounces total (5 x 2.2)
Receiver - .9 ounces

So now we're at 204.9 ounces (12.8 pounds) not counting any misc additional weight from assembly, glue, pushrods, etc..

I'll post some basic airframe pictures here a bit later today.

Doug Cronkhite

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OK.. here come some pictures..

1st is the chin cowl. Plenty of room here to work in and the fit is perfect.

2nd is the wing tube. Nice carbon supports inside.

3rd is the gear plate. Very sturdy. If you break this out you're doing something very wrong.

4th is the gear plate from the above.

Doug Cronkhite

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The fuselage and chin cowl have been opened and sanded for motor installation. The firewall has also been installed using BVM Aeropoxy. Since this former sets the thrust line I've opted to install this one alone to ensure the proper angles are set. Once this has cured (tomorrow), I'll go ahead and put the rest of the formers in place at one time as they're less critical. One nice touch is this former is slightly non-symmetrical so the thrust offset places the spinner in the center of the cowl opening.

I'm sure things will progress rapidly once these critical alignment steps are complete. There just isn't much to do on this airplane really!

cleyland

keep posting pics!

JohnVH

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Nice, keep them coming

Doug Cronkhite

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Well I'm back to building.

The remaining fuselage formers are in place for the Hacker install. Again, I used BVM Aeropoxy to ensure a solid bond. The motor mount is also in place here. The idea is taken directly from Jason Shulman's F3A airplanes in that the motor is mounted to a plate, which is then mounted to F1 via rubber grommets to help isolate the noise from the gearbox. A rear plate captures the rear of the motor to help stabilize it.

Doug Cronkhite

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The canopy mounting comes next. The rear is attached with a spring loaded pin arrangment similar to the BVM unit in function. The front end is held by a hook and groove assembly. I deviated slightly from the instructions here to ensure I didn't attach the canopy permanently :-P

Doug Cronkhite

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And the end result is.. a perfect fitting canopy!

Stab and elevator servo mounting comes next. Stay tuned!

rmh

Doug - that model sure looks like my EXCESS design from years back - Mike Cross flew one in early on IMAC competition.
I designed it to be 6'x6'- never dreaming the rules would instantly shift in FAI to 2mmx2mm.
we did some of these at wellunder 10 lbs -with 1.20's
Here is Dave Villwock's- from 1999

JohnVH

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Wow, first time I have seen a pic of Dave with a mustache, almost didnt recognize him. That pic looks like the RAMS field in Auburn, where I flew with him.

Doug Cronkhite

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Yep.. the Excess was the 1st thing I thought of when I saw this airplane. The Comp-ARF airplane is quite a bit wider than the Excess though.. Max width at the back of the chin cowl is just under 11 inches.

Anyway.. back to work. Tonight I got started on the stabs. Only thing that needed adjusting was a slight change in the anti-rotation pin alignment in the stab. Incidence and fuselage fit was perfect otherwise. Because the stab gets a bit thin at this size (compared to their bigger airplanes) the elevator servos need to go into the fuselage. Using measurements in the instructions, I cut holes in the fuse sides for JR 8411's. A pre-cut lite-ply piece provides backing and support for the servos screws. These were glued in using BVM aeropoxy after scuffing the inside glass surface.

Doug Cronkhite

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While the elevator servo supports are curing, I started working on the rudder. Comp-ARF provides composite control horn that fits into a pre-cut slot in the rudder. The holes in the arm are such that the pivot point is exactly on the hinge line giving you perfect geometry when complete. The masking tape is put in place to protect the paint finish from any excess epoxy. The horn was glued in with BVM Aeropoxy filling the slot and then set aside to dry after removing the tape. Tomorrow I'll get the rudder/fin closed up and start on the wings.

pizza

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hey Doug, is there a direct drive outrunner available that would haul it around? I like that soft motor setup very much - in conjunction with outrunner you would not hear anything! that hacker gear box will sound like a rock crusher - you will need hearing protection

Doug Cronkhite

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Yes.. the electric conversion kit also contains parts for use with the Plettenberg outrunner. I don't know the actual motor number though. I'm also not familiar with the power level it produces in relation to the Hacker (which is ballistic!)

As for the noise of this setup, it's not bad and will actually meet the F3A noise limit over both pavement and grass, and once in the air you can't hear it at all.

rmh

Bro Rojecki will be here Saturday (we will go bashing some new foamies,inc a Knuffler) and I will see if there is something in my box of horribly outmoded designs which will work as a larger electric.
I am guessing that a lightly built Runaround might be a good candidate.
I am looking at a AUW of 6 lbs.
The motors available seem to be proliferating steadily -so SOMETHING should fit the job.
That 2x2 is really pretty .

Doug Cronkhite

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Tell Rojo I said hello and hope he can maybe make it to one of the west coast electric events coming up shortly.

didiwatt

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Hey Doug, for us who are electric ignorant but leaning in this direction, could you please give us a general ideal of the cost of each componant required for your conversion.

I was also amazed that the hacker could produce that much noise on the ground. How about just a short pros & cons for geared units versus outrunners.

I have a 2x2 coming and am intriqued with your thread.

Thanks
Paul Eagon

RichD

talk about mini !

Doug Cronkhite

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Sure Paul.. Be sure to sit down first though..

Motor - $429
Controller - $419
Battery - $650 roughly.. and you'll need at least 2 for any kind of normal flying.

As for geared vs outrunner.. it's kind of getting to be a pick your preference sort of thing. I haven't seen an outrunner yet that will perform with the geared Hackers but I'm sure it's only a matter of time. The hacker setup is easier to mount in a small nosed airframe. The outrunners are fairly large in diameter and there's a lot of rotating mass to deal with. Geared systems are very quiet in the air but DO have a bit more noise on the ground. The outrunners are just plain dead quiet for the most part. Often they're lighter too.

I'll be back to work on the Extra this weekend. Just have some real life things in the queue at the moment.

didiwatt

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Doug:
Ouch!!!!!!!!!!!!!! You are right, glad I was sitting down. Think I will stick to the DA-50 w/mini-pipe. Will keep on your thread though.
Paul Eagon

rmh

Don't despair - the new motors -especially outrunners are improving steadily -
I have a new Hacker 20/22L Outrunner that has power formerly associated with the geared setups -
Not better but so close as to ditch the geared setup --
I am looking now at getting a outrunner for an AUW6 lb model (as mentioned earlier)
If any spies have insight about one - lemme know .
I have a ZDZNG on a tuned pipe made in CZ that turns an easy 7700 on 22x8 Mejzlic. 23x8 at 7200 and very quiet.
A friend is doing ultra light pipe from composite -material --
However - I see the handwriting on the wall for models a little smaller -----
Especially the fact that I can use smaller public park for 3D flying with NO complaints .
Just lots of interest.

Doug Cronkhite

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Yep.. a couple friends and I went to our local city park and flew small 3D stuff with nothing but stares and compliments. The best thing for me is I have an electric only field that's 10 minutes from my house, but my closest gas-friendly site is almost an hour away.

Doug Cronkhite

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I got back to work on the Extra this morning. I basically got the rudder installed but it's not finished yet.

First up was to install the rudder servo tray under the canopy. This is a pre-cut balsa/fiberglass laminate. There are 2 ribs that lock into the slots to make it VERY stiff. Then you add the lite-ply servo screw backing like in the fuselage and then the whole piece gets installed into the fuse. I basically tacked it all together using thin CA and then went back over it all with a thin fillet of Aeropoxy. Then I tacked it into the fuselage with slow CA being VERY careful not to distort the fuse at all. This plate needs to be at least 70mm off of the fuselage floor so the rudder cables don't hit the elevator servos.

Doug Cronkhite

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With the tray in place and curing, I went to work on the rudder post and hinging. This was a bit harder to accomplish due to the tight tolerances of the rudder to fin. This time I used a gel CA to ensure it didn't run all over the place. Basically you attach the blade hinges to the rudder post, and then put the rudder onto the assembly. This allows you to position the rudder correctly in the fuselage without guesswork. Once it's all in place and taped for proper alignment, you dribble some CA Kicker down the fuse to set the gel CA. Once set, remove the rudder and go over the entire joint with Aeropoxy.

Doug Cronkhite

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Once it all cures, you wind up with the final assembly looking like this..

I get over 45 degrees of smooth friction free rudder travel. Now it's time to get to work on the stab mounting and elevator control horns.