ajcoholic

My Feedback: (10)

Some of you may remember about three years ago I had built a KJ66 and had it running. I started building a simple ply and balsa sport jet for it two winters ago, but over the past year and a half my time for modeling jets was not happening. So, I finally got the thing finished and ready to fly this week. Tonight I maidened it, and it flew pretty darn good!

I named it the "Lesjet" - it is a very inexpensive ply box fuse, balsa tail (glassed and painted) with foam core wings I had cut and then sheeted with wood veneer and monokoted. The retracts are bought (Valley mold) but the struts and wheel & brakes I machined myself, with Trim tires.

The wingspan is 62", length is 80" and the weight is 21 lbs dry. My KJ66 is putting out between 16 and 17 lbs thrust at 120K rpm.

My flying partner Dan Nadeau got most of the flight on tape. In a nutshell, it took off smoothly and without any issue in about 400 feet off our grass strip. Once in the air, I immediately realised i Had way too much aileron and elevator (especially elev) throw. I went to my low rates which gave me just the right aileron but still too much elevator. I trimmed it out (needed some down elev, thats it) and it will fly across the sky smooth and stright without inputs. Turns are smooth and without loss or gain in altitude. I tried a roll (crisp and fast and axial) but not any looping maneuvers as I was not going to push my luck with the overly sensitive elevator.

After 5 minutes I set it up and on my glide path decided to kill the turbine (which was operating wonderfully!) and see how it would glide. Well, it glides really well! I set it down long and ran off the runway into the long grass. Just bent my struts a little. The nose gear I bent back and the mains I will replace with solid legs. My home made aluminum shock absorbing legs bent at the retract blocks and I dont think they are necessary anyhow. The plane didnt bouce at all on take off or landing.

I only used a litre of fuel in 5 minutes! I was flying mainly at 1/2 throttle on my KJ66 - I can carry 3 litres so a 10 minute flight will be possible.

I only went to full power on take off. I did work the retracts a few times, but didnt want to try a high speed pass wheels up with the elevator set so touchy.

Dan will process the video and pics and send them to me, then I will post them. But I am off to NEw York for a holiday right after work tomorrow, so I wont get to put them up untill I return.

I am pumped to FINALLY get both this plane, but mainly my home built KJ66 actually flying... its a rush I wont forget for some time. I love the fancy ARF composite jets, but let me tell you flying your own stuff you hand made is a feeling you cant buy with any amount of $$...

AJC

Boomerang1

Wow, is your name Andrew or Hard Way Harry? I scratch built my first jet but I left the engine building business to the experts. I do fly with a friend who built his own KJ66 though, great engine. Strangely I picked a similar configuration for my jet which is also balsa/ply/foam & weighs about the same..

I struggled with oleos & grass strips for a while before changing to simple wire legs. Bending 1/4 in piano wire into coils was a challenge (step 1, make a bender) but it solved all my problems.

Yep, absolutely!! Congratulations! - John.

lear31A

My Feedback: (123)

Pretty cool stuff to say the least. I always enjoy your engine articles. Maybe this can be you new testbed for testing turbine engines, eh'? Take Care

ajcoholic

My Feedback: (10)

I was flying a Super Reaper (with a Moore's turbine) and an AV8R (with Wren MKII kit engine) for a number of seasons but in 2005 I had to sell them.

I built the KJ 66 just for "fun"... and to see if I could. WHen it ran quite well, I decided it was going to fly.

Here are some pics from this evening... video will hopefully come later.

AJC

JET FX

Gday Andrew, Good to see your back to burning the kero... I was wondering where you had gone? Nice looking jet you have designed there too, sorta looks bit like an F-22 and a DV8R's off spring. Just gotta add some maple leaf roundels now to those wings I reckon

Cheers- Marty
from down under

Bob.R

My Feedback: (2)

Very nice work! Scratch built air frame and turbine - quite an accomplishment.

i3dm

My Feedback: (51)

WOW , that is truly amazing craftsmanship !

ajcoholic

My Feedback: (10)

Thanks, but the jet is very simple (yet rugged) - I am sure anyone can build something similar all I used is my book on aircraft design to make sure that everything was going to work (at least in theory). The turbine, well, thats a little more work but there have been a lot of them made by many home builders so I am just one of them around the world.

The struts werent as bad as I thought. One wasnt bent at all and the other I unbent it and its fine.

I readjusted the throws on the elev/ail links and flight test #2 will take place as soon as I return from my vacation. Hopefully get the video on here then as well.

AJC

PS Hey Marty! How's it going? I will get some decals on it now that I know it flies - hope all is well with you!

WrenTurbines

Good to see you back, Andrew - and good to see the KJ committing aviation at last! I must be getting old ... I can remember when you started building that engine but it seems a very long time ago.

Sara Parish
Wren Turbines

1Eye

My Feedback: (2)

I'm glad you've (literally) engineered a successful return to RC jets, Andrew! Nice to have you back.

ajcoholic

My Feedback: (10)

Sara, I never did "go away".. just got quiet for a bit. I was concentrating on IMAC flying for a few summers, and since our seasons are short, you cant do everything - but I try!I am going to be buying a WRen SS from Peter/Altecare this winter and get another AV8R flying (on reduced power) and then start building the Ziroli Panther I have been talking about for too long as well. Yes, the KJ has been ready to fly for a while now but better late than never!

MrMike thanks for the welcome back. I did forget for a while how sweet those kero fumes and the sound of a turbine can be...

AJC

rcdriver22

My Feedback: (1)

Andrew

Found this old thread and really liked the home made jet you built and put together. The location of the turbine on the rear tail is great for access. What type of balancing was needed up front ie with church roof. How was the CoG on the initial flights? It's a real achievement to have built both the turbine and model from scratch.

Paul

drdoom

My Feedback: (9)

Congratulations on a Job well done. Your summers may be short, but your building season is long, and you will have more time for the Ziroli Panther.
I will be looking for the build thread on the Panther.

Ed

Nice build Andrew. Did you have any problems with the rudders getting burnt ?

> Jim

ajcoholic

My Feedback: (10)

Wow, back from the dead!

First I have to say, the jet is no longer On flight # 4 or 5, I had a flame out while doing a high speed pass fairly low to the ground. I tried to get the jet turned around and headed back for the runway but I was too low and flew right into some tree tops. The jet was completely wrecked (fuse broken in a number of places and one wing smashed. I felt it was too far to rebuild.

I am happy to say, the engfine was fine and I ffound out the problem (I am certain) of the cause of the flame out (and that of a few others using the same controller).

My GB Hobbies controller uses an in line fuse. The fuse holder was making intermitant contact. I later discovered this by bench running the engine, and shaking the wiring on the test stand. Every time I touched the fuse holder the ecu would turn off and back on quickly. Upon closer inspection, thecontacts inside the holder were corroded and the fuse itself slightly oxidised. It cost me a jet, but at least I figured it out.

I wont have time this winter to rebuild - just too many other projects and commitments. But I am hoping some day to take what I learned from this one and build another.

As for the design, in the few flights I had I discovered this:

#1 the engine in the tail design is sound, the fins didnt get too hot and it works fine.
#2 I needed to lighten the entire construction, and make the nose longer to have the batteries further up front, to avoid adding lead to balance. I had initially about a pound or so of lead in the nose. My first two flights were slightly tail heavy, it was stable but pitchy. I later rebalanced and the last few flights were very groovy.
#3 overall the delta style wings with the traditional style tail, even being so close coupled, worked fine. The elevators were very strong and the roll rate was awesome.

One other thing, I had a previous dead stick and glided right back to the runway, so I knew also the plane was a decent glider. However, after inspection I figured the cause of the engine out muct have been an air bubble. RUnning on the ground after was fine (but I guess in flight, with some bouncing around or abrupt maneuver, the fuse would break contact for a split second and reset my ecu which of course flamed out.

WHen I checked the parameters afterward the engine rpm, temp and so on were all within god running conditions so I couldnt figure it out. It was not untill a fellow Canadian jet flyer suggested it may be the style of fuse holder I was using, that I checked it out and he was correct.

Live and learn! I will make something else some day...

AJC

Woketman

My Feedback: (6)

Andrew: on #2, don't forget that if you wanna retain the same degree of yaw stability when you extend the nose, remember to increase the vertical stab area in-line with the nose area increase times the distance from the aero-center. Of course, if you already had a cornocopia of yaw stability, you would be just dandy!

I, as I am certain everyone else here, am very glad that you have returned from the dead. Now, if only we can get ET & Woj back.........

b.bixel

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Whoa, please say again in english. I'm about to extend the nose of a plane about 2 inches and I want to make sure I understand the concept.

Regards,
Bart

Woketman

My Feedback: (6)

Bart, think of an aircraft as a dart. On a dart, you have heaps of yaw stability because the aerodynamic center (kind of the CG of all of the aero side forces) is way behind the CG. That keeps it stable in yaw (and pitch, but we are talking yaw here) so that the needle nosed end always points forward. In a plane, we want the same basic thing. We certainly DO NOT want the aircraft's tail to suddenly swap around and point forward. We may not want as much positive yaw stability as a dart, but we do not want to be close to neutral stability (that would be where it does not care where the nose points and will spin either way if a force tries to make it). Now, when you lengthen the nose of the plane, it is like adding a little bit of dart fins to the nose. Think of the dart: if you added the same big fins on the front as you already had on the back, it would no longer fly nose forward. So when you extend the nose on the plane, you are robbing it of some yaw stability because you are adding more side area in front of the CG, thereby moving the aerodynamic center further forward. If you already had gobs of yaw stability then you can likely sacrifice some and still be just fine. But if you were getting low on yaw stability before, and you add significant side area up front, you could get too close to neutral stability. Actually, this all applies to pitch stability too. Bob Parks is the rEAL expert on all of this though. He has said several times that an easy way to test this is by making small hand chuck gliders with the same proportions and GC locale.

Woketman

My Feedback: (6)

PS. so one easy way (well, maybe not easy on an already built airframe) to make certain you are OK is to add tail vertical stab area to compensate for the added nose area. The "volume" needs to stay the same. So if you add 10 square inches of side area to the nose (in front of the aero-center) and the new area's centroid is 10 inches in front of the aero-center, then you need to add the same amount of "volume" to the tail (100 in^3). Say the centroid of the added tail area is 5 inches aft of the aero-center than you need to add 100 in^3/5 in = 20 sq in. Therefore the new added tail volume is 5 in times 20 in sq = 100 in^3, same as was added to the nose!!!

SECRET AGENT

My Feedback: (18)

Hey Woketman, I realize I have had quite a bit of rum, but your speaking martian man, HA!! Please don't re-explain on account of me, I am just a bullet sponge and wouldn't understand anyway.

Woketman

My Feedback: (6)

Hope the rum has now worn off, I know the Miller Light has for me. If you have square pants, you'd be a far more famous and wealthy sponge. I shall give you a call.

polishedbrother

what you think about this F-16??
[youtube][/youtube]
http://www.youtube.com/watch?v=lGJTCfMW7QI

PaulD

My Feedback: (39)

Wow interesting thread. Nothin' like diggin up an old one!

PaulD

SinCityJets

It was a neat video the first 5 times you posted it.......

blighty

WOW! home built turbine and plane.

i have just finished a mw54 from wren plans. working on the retracts, oleos and brakes at the mo. didn't want to push my luck with designing my own plane to put it in. so i got a pjp jets eurofighter.

good luck with your next project.