VQ Ki-61 w/ 15cc RCGF - RC Groups
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Oct 08, 2017, 10:04 PM
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HillbillyJones's Avatar
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VQ Ki-61 w/ 15cc RCGF


I bought one of the last .60 size VQ Tonys from JB Hobbies (with electric retracts) just before they closed. They had a price I just couldn't pass up ($205 shipped). I had some servos and Rx I salvaged from a wreck, and an RCGF 15cc gasser I picked up cheap from HK I wanted to try. I don't like nitro, and electric becomes too costly above 1400mm (balsa). Plus, I like the longer flights gas provides over electric (not to mention the hours of battery charging the night before flying).

I have multiple Phoenix models, and like them a lot - especially the cost effectiveness. This is my first VQ, and I am impressed with the sheeted/built-up wing and tail surfaces, as well as the clear instructions. The only issue I had was the metal clevises were a little too loose on the pushrods. I had to basically crimp them on.

The interesting part of the build was modifying the motor box for the RCGF. The engine has a rear carb and is, therefore, very long. I had to cut 7/8 of an inch from the middle of the motor box and epoxy the firewall, and reinforce it with "plates" of light ply over the seam and fiberglass wrapped around the entirety of the box.

The hardest part of this mod was getting the throttle and choke linkage worked out. The gas tank is interlocked with the hole in the firewall, so it's almost too close to the carb to plumb the fuel lines. The tank prevents a straight shot at the throttle, so I used a flexible pushrod to get around it, but I couldn't get it close enough to the throttle to use a clevis. I had to bend a threaded rod into a zig zag to reach. It's definitely not optimum, but it works.

I balanced the plane a tad nose heavy at 100mm, inverted, empty tank, gear deployed. The manual calls for 100-105mm. It took 3.5 ounces of lead in the nose. I set the throws per the manual....they ended up being too conservative.

This is my first RCGF, and only my second gasser. My other is a DLE 30 that gave me hell at first - ended up being a faulty fuel filter sucking air - but runs perfectly now. The RCGF seemed to run fine on the stand, but I only ran one tank through it. On the plane, it wants to shut off past half throttle. After much tinkering with the needles, I got it running well across the full range. I took it to the field the next morning, and AGAIN it tried to shut off past half throttle! Spent more time tinkering and she was doing well again. My DLE was set and forget.

I did a few taxi runs up and down the runway. She tracked straight as an arrow. We have 750 feet of asphalt, so I started from the middle and gave her the gas. The engine was not smooth, but it was doing well enough. I had full up elevator and the wheels were playing patty cake with the runway. She wouldn't lift off. I cut the throttle but she hit the grass and flipped over, bending the LG back and breaking the down tube on the muffler. My motor box mod held up, though.

I will weld the muffler back together, and I already straightened the gear. This is a good looking plane, and it's not a P-51 or P-47 like most every other warbird at my field. I really hope this temperamental engine works out, eventually.
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Oct 09, 2017, 09:58 AM
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bonemadderek's Avatar
I'd have balanced her inverted, feul tank empty with gear retracted, which would then make her a touch nose heavy when the gear is deployed. Looking forward to hearing your experience wih the HK RCGF 15cc as I've been thinking of getting a couple for a twin that I have nib.
Oct 09, 2017, 10:33 AM
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I would suggest you cut the muffler exhaust pipe short then find some Teflon tube and clamps to put it back on. If you hit it again, it won't break the metal tubing. Been there done that, lots of times.
Edwin
Oct 09, 2017, 05:53 PM
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HillbillyJones's Avatar
Quote:
Originally Posted by edwin1
I would suggest you cut the muffler exhaust pipe short then find some Teflon tube and clamps to put it back on. If you hit it again, it won't break the metal tubing. Been there done that, lots of times.
Edwin
Good idea. I've welded the tube, and it won't break there again, but I'm concerned the impact could damage the firewall next time.
Oct 09, 2017, 05:56 PM
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HillbillyJones's Avatar
Quote:
Originally Posted by bonemadderek
I'd have balanced her inverted, feul tank empty with gear retracted, which would then make her a touch nose heavy when the gear is deployed. Looking forward to hearing your experience wih the HK RCGF 15cc as I've been thinking of getting a couple for a twin that I have nib.
There seems to be a lot of back and forth on gear up or down. I've always set it gear down because I want to know the exact CG for take off and landing. I can see the benefit for either way.
Oct 09, 2017, 11:39 PM
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I'm a gear up guy. That's the way it flys.
Edwin
Oct 14, 2017, 07:08 PM
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HillbillyJones's Avatar
Quote:
Originally Posted by edwin1
I'm a gear up guy. That's the way it flys.
Edwin
Just to double check, I did it with gear up, too. The spec is 100 - 105mm. She balances gear down at 100mm, and at 103mm gear up. I like them less nose heavy in flight, they generally feel lighter, more maneuverable to me.
Oct 14, 2017, 08:28 PM
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bonemadderek's Avatar
Wow, that rcgf head sticks out a lot more than I thought it would.
Oct 16, 2017, 07:17 PM
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HillbillyJones's Avatar

Maiden Report


So, it took four trips to the field to get this thing airborne. The first two trips, I've already described. The third resulted in the engine shutting off as I was on the take-off run, then the tail wheel control horn broke when I attempted to turn around while it was still rolling. That tiny piece of cheap plastic is never going to support the weight of this plane. So, I went home and made another one from a Dubro horn I drilled out and sanded to fit. It's still going to be a weak link, I can tell. I will fab one from solid aluminum this week.

On the fourth trip to the field, the engine did it's cut off at half throttle crap again. After several minutes of tuning, I got it to work somewhat, however, it was very rich on top end.

The flight: the take off run was smooth, no left turn tendencies, but I immediately felt she was tail heavy upon lift off. She took a few clicks of left aileron and a bit of messing around with the elevator trim that ended up being 6 clicks down at the end. The engine was sputtering incessantly, rich, and full throttle was a lot slower than I had hoped. I know the 14x7 three-blade prop doesn't help speed, but this was painfully slow. I flew 5 minutes at mostly 3/4 to full throttle. Loops were nice, and I did one axial roll that startled me - it stopped rolling for a long split second when inverted, then completed the roll. It looked like I did it on purpose, but I certainly didn't. Landing approach was gentle at full flaps with a slight headwind, at just over idle. It touched down nicely and ALMOST nosed over. I caught it with up elevator just in time to save that $17 prop. That little teeter-totter action slightly bent one LG strut back a bit. BTW I increased the elevator throw from 10 to 18mm, and it worked really well.

In summary, tail heavy, too rich on top end (and SLOW), weird aileron glitch, weak LG struts. I really hope further tuning will get this plane to move like a fighter. I tried a 13x8 2-blade on the second flight, but it made zero improvement in speed (I didn't tune it between flights for testing purposes). So far, I'm not thrilled with the RCGF.
Nov 01, 2017, 11:01 AM
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I also have one of these ARFs.
Plan to use a 20cc RCGF. 7480 rpms on test stand with a 16x8" prop.
I have the VQ P-40, and it is too heavy to fly well. (The Ki-61 is 1.5 lbs lighter).
The P-40 flies nicely when it is up to speed, but lands like a brick with 45 degree flaps.

I also like the direction that VQ is going. The 1-piece wings are stronger than the 2-piece plug-in wings of Phoenix models. And VQ is trying to make their .60 size fighters 6.5 lbs, instead of the heavier 8-8.5 lbs of the TopFlight designs.

VQ is producing .60 size fighters that correlate with the bigger ESM 30-50cc gas models. This .60 size is a good steppingstone size out of trainers, and on the way to bigger gas models.
Nov 02, 2017, 10:09 PM
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HillbillyJones's Avatar
Quote:
Originally Posted by wuest3141
I also have one of these ARFs.
Plan to use a 20cc RCGF. 7480 rpms on test stand with a 16x8" prop.
I have the VQ P-40, and it is too heavy to fly well. (The Ki-61 is 1.5 lbs lighter).
The P-40 flies nicely when it is up to speed, but lands like a brick with 45 degree flaps.

I also like the direction that VQ is going. The 1-piece wings are stronger than the 2-piece plug-in wings of Phoenix models. And VQ is trying to make their .60 size fighters 6.5 lbs, instead of the heavier 8-8.5 lbs of the TopFlight designs.

VQ is producing .60 size fighters that correlate with the bigger ESM 30-50cc gas models. This .60 size is a good steppingstone size out of trainers, and on the way to bigger gas models.
I have three Phoenix models and they all have one-piece wings. Anyway, I haven't had good enough weather to get her figured out, yet. I actually saw a plane flip backwards from a wind gust on touchdown last week. Hopefully, this weekend.


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