J'Tec 35% Extra Build

[dbcaster]

Well Al we truely do learn something new everyday Somehow my 2.7m Extra got frightened and lost all of it's covering last night. I will post pics of it's new skin when I get it finished.

[Barn-E-Stormer]

I have built a couple Jtec's for people. Keep in mind the manual is not much. It really needs a section on what servo linkage hardware to use. If you try to use long arms on the elevator, like we do with most models, the linkage comes out at bad angles. See Photo.

Just be careful if you ask the factory folks any questions. You'll get a big smack down for not buying their hardware and for not building a Carden before you buy from them. They'r a little on the defensive side.

Use a 1 inch arm on the elevators and turn it straight up.

The bright point to it all??? I have to say the Jtec is the best flying plane I have had my hands on.


This would be the point where everyone jumps on me like a pack of rabid wolves.

[columbo]

You mean, the best flying muffler you have had your hands on? Sorry AL, but you did say that Jtec is the muffler side .

Barnstormer, thanks for the information on the elevator linkage. That will be helpful when I start this. Do you get enough throw (3D rates ~ 45 degrees) with the 1 inch arm turned upright? When you say best flying, do you mean IMAC, 3D stability or both?

Greg

[dbcaster]

I am not sure why anybody would need to be careful when asking Al or Kevin a question. They are both some of the best people I have dealt with in the hobby. You are correct on the elevator arms not working with anything in the stock location over 1". It is my understanding that the plane was designed around IMAC so the 1" arm is plenty for that. Since I like to fly 3D I set mine up with a 1 1/4" arm. There is a much easier way to do this then to have that crazy linkage angle that you have in the pic. You can trim the servo hole in the fuse down enough to fit a 1 1/4" arm. There is plenty of material there to do so very easily. I have been flying mine this way with over 100 flights and it has worked very well.

[Barn-E-Stormer]

None of the owners have changed their linkage to the 1 inch arm so I can't say. I don't like the idea because you have to use a very short horn on the control surface. Personally I don't use short horns on giant scale sufaces because I like to have more leverage to work on the surface. This gives better control and cuts down on flutter. I have another Jtec coming up so I may try to move the servo opening down enough to allow a longer arm and better geometry.

As for flying I just 3D. The Jtec is great at everything. Hovering, torque rolling, harrier, and it does a killer rolling harrier. Easy to keep the nose up with little forward motion, very controllable. If I had to give it ding on anything it would be knife edge, but it is not bad. SD Yaks are the king of knife edge.

But what do I know, I never built a Carden.

[dbcaster]

I have never built a Carden either but I am not sure why that is relevant. Moving the servo down is easy and effective and there is not worry of flutter.

[JEFFRO503]

	Quote: Originally Posted by dbcaster
	I have never built a Carden either but I am not sure why that is relevant. Moving the servo down is easy and effective and there is not worry of flutter.

When you say "move the servo down"....do you mean , actually taking the servo slot in the fuse , and widening the hole a 1/4" so as to drop the servo down towards the ground a 1/4".....then re-glueing a small piece of ply on top to fill the hole? I think i understand what your saying....just clarifying.

Also....35% owners.....Columbo posted some pics ( i think on the first page....thanks Columbo!) of the front motor box area. Question....in the pics , the canister tunnel looks to be on the small side , can a person fit two canisters inside this tunnel? My motor choice for this bird will be a BME 116 , and i really want to run a canister setup on this motor whenever possible. Columbo....or anyone else , could you possibly tell me the width and heigth of the canister tunnel when you get time?

Thanks guys!

[dbcaster]

Yes that is exactly what I did. However, I think I only needed to cut about 1/8" out to clear a 1 1/4" arm. I didn't bother filling in the opening above because I started with an 85 so I used it as a fuse vent. I am not sure about the size of the cans that you want to use but I had a 1090 stuffed in mine.

[JEFFRO503]

	Quote: Originally Posted by dbcaster
	Yes that is exactly what I did. However, I think I only needed to cut about 1/8" out to clear a 1 1/4" arm. I didn't bother filling in the opening above because I started with an 85 so I used it as a fuse vent. I am not sure about the size of the cans that you want to use but I had a 1090 stuffed in mine.

Ok....that's what i thought you meant. I would think to get full deflection (45 degrees +) , you would have to run a 1-1/4" servo arm. On the canister.....if that tunnel is big enough for a 1090 ( big single can) then it is definetly tall enough for the smaller cans i would have to use on the BME. Just wondering if it would be wide enough....it looks like it would be. Looking at Columbo's pictures , i wouldn't of thought a 1090 would of fit....so that tunnel must be a little larger than what it looks like in the pics.

[dbcaster]

I need to re-state that. I had a 1090 in mine but the main barrel was beyond the tunnel. I can measure mine tonight and tell you how tall it is.

[jtec/radiowave]

	Quote: Originally Posted by JEFFRO503
	When you say "move the servo down"....do you mean , actually taking the servo slot in the fuse , and widening the hole a 1/4" so as to drop the servo down towards the ground a 1/4".....then re-glueing a small piece of ply on top to fill the hole? I think i understand what your saying....just clarifying. Also....35% owners.....Columbo posted some pics ( i think on the first page....thanks Columbo!) of the front motor box area. Question....in the pics , the canister tunnel looks to be on the small side , can a person fit two canisters inside this tunnel? My motor choice for this bird will be a BME 116 , and i really want to run a canister setup on this motor whenever possible. Columbo....or anyone else , could you possibly tell me the width and heigth of the canister tunnel when you get time? Thanks guys!

We personally use an 1" servo arm on the elevators and for 3d I use about 30-35 degrees of throw, I have never felt I needed any more then that. Actually I am pretty sure the electric one that Andrew has even has 1" arms on it still. I tend to set up our airplanes as neutral as possible because yes I fly more IMAC. As I alway understood it the more leverage on the servo arm the more loss of torque from the servo, so if you ran a 1" arm on the servo you would actually have more torque going to the surface then a 2" arm to the surface (I could be wrong though). If you want to use a 1 1/4" arm then I would do what Jon suggested and drop the servo hole down a bit.

As for the canisters if you are using a DA or DL 100 I would suggest the MTW TD75 (longer version) or the KS 86 and a 70mm drop MTW header. They should fit right in the tunnel. If you go with a DA85 you will want to use a MTW 110 (long version) and I don't remember what drop header but I have one at home so I can check. When using the 85 you will probably have to remove a little bit of the lip on the front side of the tunnel. The plane was designed before the 85 was out so we did not expect to put that big of a can in it but it can be easily opened up with a dremel.

Kevin

[columbo]

A shorter arm on the servo with a longer control horn moment (on the control surface) will give the servo more leverage. A long arm on the servo with a shorter control horn moment will give it less leverage causing it to work harder. With the modern high torque digital metal gear servos we
use today, this is less of an issue.

I will just move the servo down a little and go with 1-1/4 inch arms to get at least 40 degrees of throw. Seems simple enough to do.

Greg

[dbcaster]

Kevin,
That is a good point. The plane does not need a huge amount of throw even for 3D. For IMAC I am using only low rates which I believe I have around 12 degrees at max throw. For those that feel it needs 50 degrees for 3D, moving the servo down is very easy. I measured the opening for the tunnel and at F1 it is 2 7/8", at F3 it is 2 1/2. There is room in the former to remove material if needed without compromising the strength.

[Barn-E-Stormer]

I can tell you these planes do not need alot of throw. They fly so well huge throws are a waste. Right now huge throws are a fad, and generally not needed. They just make you fly sloppy. The reality is most people are not experienced enough to go full circle on the throws thinking. Huge throws are like huge boobs. Everybody wants to see them but they don't know what to do with em.

[columbo]

	Quote: Originally Posted by Barn-E-Stormer
	I can tell you these planes do not need alot of throw. They fly so well huge throws are a waste. Right now huge throws are a fad, and generally not needed. They just make you fly sloppy. The reality is most people are not experienced enough to go full circle on the throws thinking. Huge throws are like huge boobs. Everybody wants to see them but they don't know what to do with em.

In that case I will just start out with the one inch arms, fly it and see how she does. If I need more, then I will make the simple modification to the elevator servo bays. Some planes have a range of throw between low and high rates where they get squirly in 3D. I think this effect is less noticable in very stable good 3D planes...especially the larger ones. I just want to make sure that highest rates using a one inch arm are above that zone. I will take you guys word that 30-35 degrees is enough with this plane. I know what you mean by sloppy 3D. I don't like to see guys flopping all over the sky with no precision in their 3D maneuvers. Kyle has set the bar pretty high for precision 3D.

Greg