(pictures)big problem with MAKING UP MY MIND
 

Hi all! [>:]
Im currently building a Yak 18, 72" wingspan. Saito 100 is planned for power source. Now to the problem:
Because of the stab construction, I need to go with dual elevator servos. The thing is that i only got two kinds of servos to choose from. HS 81MG or HS225MG.

The elevator controlsurfaces are pretty big. (3D size) I got two HS81MG. I got two HS225MG. What should i do?


1. the two HS81MG:s as elevator servos, and one HS225 as (single) rudder servo.

2. buy one more HS81MG: two for the elevator servos, one for the rudder.

3. the two HS225 as elevator servos, one single HS81MG as rudder servo

4. Buy one more HS225 and go for three of them. Two for the elevator, one for the rudder.

PLz help me out!

RE: advanced problems with making up my mind..
 

i'll ask the obvious question...why don't you buy some servos that are made for that plane like some HS 645mg's ?

RE: advanced problems with making up my mind..
 

whats wrong with HS81MG or HS225MG?

RE: advanced problems with making up my mind..
 

i think the servos you want to use aren't strong enough for the size plane you have

the HS81 at 6v only gives you 40 .oz of torque and the 225's give you only 60 .oz at 6V

do you have a link to the plane you are building? there should be something in the manual or a website that will tell you what the servo recommendations are

RE: advanced problems with making up my mind..
 

http://image.rcuniverse.com/forum/up...65/Yw67819.jpg
Its not my model on the picture but i looks exactly the same.

One elevator half messures 11x3,5 inches.

BM.

RE: advanced problems with making up my mind..
 

Eeh? The 225:s are much stronger then a normal standard servo, and they got metal gears...! They just cant be "too weak". Or?

RE: (pictures)big problem with making up my mind..
 

what battery are you going to use with it..how many volts?...and yes if you are considering flying that plane 3D style it is considered too weak...but if you are not convinced then i would say use the 225 on the rudder and the 81's on the elevator

RE: (pictures)big problem with making up my mind..
 

4.8V. Its not a 3D plane, but its nice to fly knife edge and so on.
Its very hard to agree that 225s are too weak, they can almost pull the control horn off...

Someone else who agree with tukkus?

RE: (pictures)big problem with making up my mind..
 

The HS 81 is for smaller birds. I would only use one on throttle on that plane. The 225 might work with one on each elevator but I would go with a beefer servo on the rudder. Personally I would go with standard size high torque servos. Lots of options depending on what you want to spend.

The hs645 would be a good option for the rudder and you could get away with the more economical hs 475 on the elevators. Both are decent but not top notch servos. I would definetly spen more money on the rudder servo. i think you could even put standard servos on the elevator. Run them at 6volt and you should be in good shape.

However, if you the money nothing is better than top notch servos. I have a set of coreless servos on my 90 sized plane and they are great.... although a little more pricey

RE: (pictures)big problem with making up my mind..
 

what does the kit manual say as far as torque needed?

If you are going to use 4.8 volt those micro sevos will not be enough on that elevator.

RE: (pictures)big problem with making up my mind..
 

?

The 225s are much stronger then a normal standard servo, and they got metal instead of resin gears!

RE: (pictures)big problem with making up my mind..
 

Use plain ol standard servos. Back when the plane was first kitted servos were bigger and weaker. You'll be just fine with normal servos.


Woops:)

RE: (pictures)big problem with making up my mind..
 

Blue moon you asked for advice and you got advice, better safe than sorry ;)

RE: (pictures)big problem with making up my mind..
 

Ok, is one HS81MG to each side enough for the elevator? OR should i go with the 225MG´s ?

But three 225s in the tail section of the plane is quite heavy. Hmm..

RE: (pictures)big problem with making up my mind..
 

Yeah but i want facts...


Anyone else got opinions?

RE: (pictures)big problem with making up my mind..
 

Woops:)

Ok, is one HS81MG to each side enough for the elevator? OR should i go with the 225MG´s ?

But three 225s in the tail section of the plane is quite heavy. Hmm..
[/quote]

Its not too heavy in that tail. The plane has a 6 foot wingspan!!!

I have a 40 sized plane with 3 standard servos in the tail and it is fine.

You are right the mighty minis do have more torque than a standard servo. So they would be fine one the elevator halves, although standard servos would be A.O.K

I think for a clean knife edge you will need a little more torque. (better to have a little extra than not enough)

And technically you might be able to get away with the mini servos, but the weight savings is not that significant in that size plane and you only get 36oz of torque (less than a standard servo)

[/quote]
Yeah but i want facts...
[/quote]

You need to check the manual for the plane for facts!

RE: (pictures)big problem with MAKING UP MY MIND
 

Gringo Volador, That was a better explaination! Thanks! What do you mean with that a knife edge is less nice if i got less torque?



So what do you gays recomend for the ailerons? Its a dual setup as well.

PLEASE feel free anyone to give me your opinion about the original question.

RE: (pictures)big problem with MAKING UP MY MIND
 

It would be better to have more power than not enough on the rudder for a knife edge.

For ailerons, again I would go with standard servos. The might minis would be ok too. The mini servos would be too small.


Thats really a little unnecessary dont you think

RE: (pictures)big problem with MAKING UP MY MIND
 

I'd do standards on the ailerons and the minis on the elevators and do pull-pull for the rudder. This will help keep the tail weight down, give you plenty of elevator authroity.

Here are the specs on the 225 minis

Length: 32.4mm (1.3") Weight: 27g (0.95 oz.)
Width: 16.8mm (0.7") Torque: 3.9kg/cm (56.4 oz/in)
Height: 30.8mm (1.2") Speed : 0.14 sec/60 deg.

So now you have 2 servos as light as a standard putting out a little more torque than most standard servos

I would then use something like a hitech 635 or 645 on the rudder in a puull-pull configuration is you are conerned about tail weight as the HS81 is no where near what you will need for the rudder or for anywhere else on the plane. The rudder is the most powerful surface you have on ANY plane.

Also Blue Moon, it appears that you want fact, myself a few others have given them to you, BUT we need info/facts from you to give you better opinions in regards to your servo choices

That info would really really help

RE: (pictures)big problem with MAKING UP MY MIND
 

SORRY! i meant "guys"... [:o]

Thanks for the advise.

RE: (pictures)big problem with MAKING UP MY MIND
 

lmao , read like a scene out of a comedy show.

I think blue moon wants to know how to physically set up the split elevator , verses what to use.

Correct me if I am wrong, the bigger the surface of the tail or elevator , doesn't mean it has to have higher torque servos. The slightest movement of either will make the plane change the angle of attack drastically.

RE: (pictures)big problem with MAKING UP MY MIND
 

I would NEVER use a HS81MG on any control surface of a plane that big. Don't just be looking at torque ratings. The size of the gears makes a difference. Just because they are metal, does not mean they won't strip. The 225's are a little smaller than a standard, right?

RE: (pictures)big problem with MAKING UP MY MIND
 

OK, I thought that sounded kind of strange!:)

RE: (pictures)big problem with MAKING UP MY MIND
 

the funny thing is, he is in the 3D forum trying to convince us that a servo with 48 .oz of torque should be enough for the size plane he has

Blue Moon, maybe the questions and answers forum will be of more help to you or the pattern flying forum

RE: (pictures)big problem with making up my mind..
 

No i want to discuss it here because i want to know what kind of servos that are 3D able on this bird. And by the way its always fun to make people smile :) Now back on track.

Im sorry to say, i aint got no manual. The kit was produced over 20 years ago.


Ok, i now understand that my HS81 are totally useless. Now, the question is if three HS225MG are too heavy for mounting in the tail. Do i need to use long rods? The engine is pretty big so perhaps the CG will be OK even with 100gr (4oz) of servos in the tail??