the german shorthair needs garlic and a nice red wine

1. How old is the german shorthair?

2. I used carbon fiber pushrods, one for each elevator.

3. I added 3oz of lead to the nose with my saito 1.80 to hit the recommended balance point (tru-turn spinner). I have since moved my battery back because the balance seemd a bit "over stable". I think mine would have been just fine without the weight in the first place.

Rcpilet,

I also used carbon fiber pushrods (about 14" long) and have noticed no tendency to flex with the straight backmounting (servo to elevator half). On my MVVS engined plane I actually had to add about 2oz to the tail and move the servo/rx battery as far back as I could put it to balance. On the Saito engined plane I had to add 1.5oz to the nose to get balance. this plane has the battery all the way forward. But it is lucky for me I guess that both of my planes came out around 12.4 pounds and required very little weight to adjust the balance.
On my second plane I made the following change to mounting the wing that made things a lot easier and stornger. On my first stock built plane the front wing mounting holes the dowels go into strectch out after several flights and had to be reinforced. Additionally the plans method to isntall is a complete pain. Here is what I did. Install a 1/8" piece of aircraft grade ply (make sure grain horizontal) behind the backing plate the wing dowels go into. Put a dab of chalk or something to mark correct location on the end of the wing dowels and slide wing forward until they mark the proper location on the oiece of ply you installed. Now remove wing, drill the holes and you are all set.

The dog is 4 years old, she may or may not see 5. (I hear once they develop a taste for balsa there is not much else you can do)

Splais, thank you for the wing mounting tip. I thought the method outlined in the manual looked 1. kind of weak 2. a real pain in the arse.

The other hokey lookin' thing about this ARF is the elevator pushrod. I am using one hitec 645, and I will be making a carbon fiber (arrow shaft) Y pushrod, and I may or may not brace it in the tail, depending on how solid the linkage "feels".

For Sale: German Shorthair. Docile, great with kids, no trouble at all.... really.....

If you are using a pull-pull for the rudder and mount the servo in the center of the rails, you might want to consider using the bellcrank assembly from Central Hobbies. THis will eliminate any slop and the differential from locating the elevator servo off center wsith a "Y" pushrod type arrangement.


Bellcrank Link

It's not cheap, but it is very well made and works great!

Jim!

Yes,
I have the MK bellcrank on a pattern plane, and it is a very slick, smooth, and reliable setup. I am, however, very concerned about tail weight on this plane. I am planning on mounting the elevator servo below and aft of the rudder servo, or barring that, I will use 2 hitec 605's, and just use dual elevator servos. I will explore that possibility more as I get to that point in the building.

I guess in the long run, you'll weigh the stuff out and determine what is the best to put in the plane to save weight in the tail. You're right, this plane comes out very tail heavy which was why I had no problem putting the MVVS 1.6 in it. Didn't need any additional weight anywhere.

Good luck with your installation!

...set up with dual servos.

RCpilet;

If you're interested, I'll post a pic of my set-up, which uses one servo per function, with an offset rudder servo and central elevator servo.

I too use a bellcrank to get around the necessity of having both the elevator and rudder servos centrally mounted.

Agreed, the supplied elevator pushrod is zilch. Ditto for the supplied push-pull hardware too, IMO. I used the Dubro kit for rudder cables, and a Dave Brown f/g arrow shaft for the elevator rod.

The elevator pushrod is, however, exactly the right size for adding an extension to the hardwood elevator frames where they want you to mount the Sullivan horns. IMO, that area is WAY too small. I cut a chunk off of the supplied elevator pushrod, which is the same thickness as the elevator wood, cut open the UltraCoate, and epoxied it in place.

Steve

I am going to put a bellcrank on the elevators for a PA GeeBee I'm going to assemble as soon as it arrives. I would love to see some pics and explanation of how to install a bellcrank setup for the elevators.

Definetely post pics of anything that would help out, guys.

I'm in the process of negotiating a trade with a guy for an engine. He's got an MVVS 2.15. Hopefully things will work out for both of us.

I think this will be a perfect gasser for this plane. I'm still a bit uneasy about the gasser weight, but the price of glow fuel for a big 2-stroke is makeing me cringe. Mixing my own glowfuel is out-homeowners association rules won't allow storage of chemicals like methanol and nitro in my garage. I'm sure it's probably safer than gasoline, but you all know how rediculous these "Old Bitty Commities" can be.

I talked to a guy today that flies a lot of big 35% and 40% planes. He said the MVVS 2.15 would be a great choice for the plane- should I decide on gass. I trust his opinion.

Thanks for the help guys.

RCPILET, the only thing I would be worried about is the weight of the 2.15 and fitting in the cowl. My 1.60 balances perfect as is with the battery/receiver stuff way back. You may be able to offset the weight of the 2.15 by putting the elevator servos in the rear. Hmmm, the 2.15 should be a great performer

I think the MVVS 2.15 will take this plane to the moon and back, and do it on only a few ounces of gas; rather than 10 gallons of glow fuel.

I'm still undecided on the gasser. If things work out with my trade negotiations, I'll probably get the MVVS. It would be great if I could put a few servos in the tail to offset the weight of the gasser. I just love short linkages. It makes for a nice, positively controled surface with very little or no slop in linkages. There are two different places that I could use to mount the servos in the tail. One is WAAAAAAY in the back, right by the rear surfaces, and the other is about 1/4 of the way up the fuselage towards the nose. If I need the tail weight to compensate for a large gasser, there are a few options for me.

I'm settled on servos for the plane. Hitec 625MG for elevators and ailerons, and a Hitec 805BB Giant for the rudder. Standard JR 517 for throttle, and maybe, just maybe, a Hitec HS-81 for a servo actuated choke. I always run a 6Volt pack, so the Hitec servos will deliver around 94oz.in of torque. That should be plenty of torque. The 805BB is something over 300oz.in. at 6Volt. Can you say "Figure 8 knife edges"??

HOT DIGGITY!! I'm excited!

Here ya go.

The Nelson rudder bellcrank is mounted on a home-made platform. The elevator pushrod runs right over the top; you have all sorts of room to do it like you want.

If you go with a single split elevator pushrod, it is extremely important that it be centered, or else yoi will get differential throw on the elevators and the plane will be nearly impossible to trim properly. I still can't believe Horizon tells you to offset the servo and pushrod...

Keep in mind that it is EXTREMELY important, when doing a closed-loop (push-pull, pull-pull, whatever) system, that the distance between attachment points at the servo is exactly the same as between the two rudder horn attachment points. IOW, the linkage should describe a parallelogram. Failure to do this will result in assymetrical response, cable slack, the common cold, dandruff, etc.

Have fun. This is a great model.

Steve

BTW, while the really big engines (Saito 180, etc.) that are needed for hovering, etc., are indeed glow fuel hogs, my initial concern that this Saito 150 was going to drastically increase my fuel costs has been unfounded.

Overpower the plane if you must, but a good 120 will fly it just fine. This 150 is more engine than I need, and the only time it sees full throttle is on an extended up-line.

Steve

What a great idea Steve! Almost makes me want to take out what I have! Wish I had thought of that! It would have saved me some work on the bottom sode of the plane with the bellcrank that I put in the rear.

I'm going to keep the pic for later use, thanks!

I bout a used one the guy had the elevator set up with a Y and one 605 Hitec servo is this OK or should I split them & what servos should I use for the Rudder and elevator I have a digital 1/4 servo from Hitec would that work on the elevator and I have a 5945 and 5925 I could use one of them for the rudder

Thanks Tim

Steve, actually, as long as the line drawn between the two attachment points intersect the hinge point exactly on both servo end and control surface end, it's okay if the driven end moment arm does not equal the driving end. The geometry will be such that the servo arm will push on one side of the control horn exactly the same distance as it will pull on the other side. The caveat is that the servo must be sufficient distance away from the control horns so that the nonlinear effect of the two different arc radii is minimized.

Sorry for being geeky about this, I've done this with both solid pushrods and cables and haven't caught a cold because of it yet.

BTW, there was an article on the geometry of pull-pull linkages recently in one of the RC mags. Forgot which one it was.

Steve thats a great setup. Very clean and functional.

I know the big glow engine or the gasser will be overpowering the snot outta this plane. I want to be able to fly 3D with authority. At this altitude (6000'), it's going to take a lot of horsepower and plenty of dinosaurs down the carb. to make the plane perform well.

Many people don't realize just how much power loss we suffer at this altitude. It's at least 20%. You ALWAYS put the biggest engine on a plane that the manuf. suggests. And thats just for trainers and sport planes. If you want true 3D capability (hovering and waterfalls, for instance); you need to put an engine on your plane thats about 2 or 3 times bigger than recommended.

This gets really tricky. Such large engines require taller landing gear, bigger tanks, strategic balancing tecniques, and of course, bigger servos. This all equates to higher wing loading. You'd be amazed at our landing speeds. We bring the big birds in with power on and moving fast. I don't cut my power completely, untill I'm over the end of the runway and/or less than 3 feet off the runway and sinking. These planes sink fast up here, even with a little power on.

I flew my Sig Cap 231EX 1/4 scale today. You all know that sound a big ST3000 makes when you finally cut back to an idle--ning ning ning ning ning ning ning ding ding ding ding--well; I don't usually hear that sound untill shes about 2 feet off the runway and sinking fast. The Cap only weighs about 10.5 or 10.75 pounds. It wouldn't hover with a ST2500 or an MDS 148. It does hover with the ST3000. It really does take that much engine up here.

I guess I'm saying that I don't think the MVVS 2.15 will be all that big for this altitude. It's sure gonna bring my landing speeds up even higher though. BUT, when I decide it's time to hover--------she'll do it.

I concur with steve's comment. it also applies to my 1.60 Gasser. I am only at full throttle on long up lines or when trying to hover. The plane will hover with the 1.60. Just not close to the ground because you have zero margin for error. But the 1.60 gas flies this thing fine. There is another gas engine you might look at that is light and powerful between the 1.60 mvvs and 2.15 mvvs. Thats the RCS 1.80, although I am not familiar with it.

PS: RC I should have read your whole post. the altitute thing must make flying up there interesting and it sounds like it kind of throws all the normal dynamics out the window.

Steve I have a couple of questions. After seeing both your and my setups I think I want to try a combination of the two for my GeeBee (my rudder with your elevator). I am not sure why you needed to use the rudder setup you did. The second servo and linkage seems unnecessary unless you just like building neat looking things (thats a compliment, not a dig). Does the elevator rod running back to the bellcrank in the rear have to be near the center of the system or could it be offset to one side? also I hate to admit that I am having a hard time understanding what it is you guys are talking about with all the angle stuff on attachment and hinge points. of your push-pull setups.

Here's some information that I dug up on a few engines that we have been talking about. I am not formulating an opinion, just saving you some surfing.

RCS 1.8 (rear carb)
$345.00
Wt: 3.25 lbs
HP: 4.0

RCS F 1.8
$345.00
Wt: 3.15 lbs
HP: 4.0

ZDZ 40
$410
Wt: 3.15 lbs
HP: 4.8

BME 2.7
$499
Wt: 2.7 lbs
HP: > 4

Brison 2.4
$471
Wt: 2.75
HP: ??

MVVS 1.6
$295
Wt 2.1 lbs
HP: 3.8

MVVS 1.8
$325
Wt: 3.25 lbs
HP: 4.25

I am putting a MVVS 1.6 in mine. You guys are right that this will not hover the plane at anything less than full throttle. I do have the 3rd generation version with the new coated piston and new ignition so, we'll se how she flys. I only want to practice IMAC maneuvers anyway, so anything more than that is a plus.

Neat site of a guy that put a MVVS 1.6 in a H9 Cap

Splais,

You're talking two different things; a split elevator pushrod, where you have two independently-hinged elevator halves, each driven by one side of a split pushrod, is an entirely different animal from a push-pull or pull-pull rudder (or elevator) set-up.

Not sure what you mean by "extra servo". I have one servo driving the rudder bellcrank and one servo driving the elevator pushrod. The rudder servo is offset because when using a split elevator pushrod it MUST be centered in the fuselage; otherwise, as it moves it will move one elevator half more than the other. You can see the problem that would cause.

It is possible to remove the differential in an offset pushrod by bending one side, but that would take quite a bit of trial-and-error, and we know that the less bends in a wire pushrod, the better.

Anyway, the use of a bellcrank allows the rudder servo to be offset so the elevator servo can be centered, while keeping the bellcrank for the rudder centered as well. Ya just have to think in three dimensions...<BG>

Volfy, I don't doubt you for a minute. But I'm drawing on my experiences with helicopter linkages and solid pushrod/ball link set-ups. With those, you had BETTER have a perfect parallelogram, or binding will result. I guess the short distances involved do not allow the radii differential to erase itself. Interesting...

Steve

Rcpilet,

I too should have looked more closely before making a snide comment about overpowering your model. Altitude density is very real, and a problem for you guys at higher elevations.

I guess I'm just a bit perplexed why someone will spend much time and money crafting a big, expensive model like these, and then grossly overpower it and throw it around like a dog's chew toy. I have been watching the same thing in the heli community for years now. The phenomenon has just recently infected airplane drivers.

Guess I'm out of touch... Anyway, enjoy your model. Mine is my first "big" plane, and I have learned much while doing it.

Steve

Steve, long story short. I did a lousy job of describing my questions. but you answered them anyway. I thought the elevator pushrod in your picture above was to a bellcrank, not a Y.