Shikra- Build and Fly log from RCforall

Started by rcpilotacro, May 06, 2011, 06:15:53 AM

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rcforall

Indian brands of CA glue are Anabond , Feviquick etc .
Search the threads for common names for products I remember it being there  somewhere in the material thread

Sai
www.zuppa.io : vehicle telematics, ADAS, IoT , Drones

vishwasvm

Thanx Augustine and Sai,

I will use FEVIQUICK. It is available with me. I am a bit worried about refurbishing of motor mount due my inadequate skills. But I will give a try.

Vishwas

rcforall

#77
When you fix a motor mount on a pusher you need to understand that it has to be angled in such a way that the thrust line intersects the vertical CG Line  about 1-1.5 cm below the CG  , this will create a resultant upward force acting in front of the CG thus lifting the nose up on take off  . This can be done using a scale in the case of the Shikra and getting a fair idea of the thrust line in relation to the CG .

The easy way to do this is to hold the fuse without the wing lightly suspended by two fingers at the CG line in a such a way that it is free to oscillate.
After fitting and powering up the motor , when you throttle up note the tendency of the nose and adjust the angle of the motor by giving packing at either the top or the bottom of the motor mount till the nose has a very slight pitch up or level  tendency this will ensure a smooth take off . I don't know how to better explain this in words .

Please note the angle should not be too high either otherwise the nose up tendency will be too high resulting in a stall.

Sai
www.zuppa.io : vehicle telematics, ADAS, IoT , Drones

vishwasvm

#78
Checked everything. Batt, ESC, Motor, servos, Tx, Rx. Everything working fine. Aileron servos connected. Initially I was a bit confused about the programming of ESC, but later came to know that there is no need to program it.

I am not getting fibre tape in our local market. Does anyone know a shop in chembur/Vashi?? Of course, I can purchase it from one of the online dealers.

Pushrod is thicker for servo arm/control horn holes. Can not connect with Z bends. So I am using nylon clevises at both ends. But there is some 'play' as locking is not perfect and some sideways movement is possible. will this pose any problem. I will upload photos by evening.

Regards

Vishwas


vishwasvm

Hi all,

I have started to put together the parts.  As I posted earlier, the push rod is thicker and hence can not be used with z bends for servo arm and control horn. Hence, I tried to put clevises at both ends. But the movement was not very smooth.

I put an order to rcforall for push rod connectors and fit them as shown in the picture. Please tell me if I have done correctly. The problem I am facing is, the screw tends to become loose with movement and may fall off. What is the solution to this??


My other query is about the CF rod length for boom. It will be clear from the pictures that the CF rod is not reaching to the end of boom. Where I should put the CF rod?? At the end of tail or towards wings?? Other question is about the strength of part of boom not covered by CF rod.

I am a complete newbie and do not know much. This is my first plane and I seek a lot of guidance from everyone on this forum.

Regards
Vishwas

rcpilotacro

Quote from: vishwasvm on March 18, 2012, 02:12:53 PM
..But the movement was not very smooth.
That is because your link connector should rotate about its axis (don't over tighten it it will bend the push rod and load your servo and the horn), the washer that's why goes below and you need to drop a little thread lock so that the connector nut doesn't fall off in flight.

Quote from: vishwasvm on March 18, 2012, 02:12:53 PM
..the screw tends to become loose with movement and may fall off. What is the solution to this??

..Thread lock

Quote from: vishwasvm on March 18, 2012, 02:12:53 PM
My other query is about the CF rod length for boom. It will be clear from the pictures that the CF rod is not reaching to the end of boom. Where I should put the CF rod?? At the end of tail or towards wings?? Other question is about the strength of part of boom not covered by CF rod.

Neither, Could be in the centre, actually it is not required at all (Neither Easy star nor Sky surfer has any boom CF), [is it wing joiner cf tube ?)

any issues do post, don't be in a hurry take your time, do consult for cg issues
Gusty's Hangar and Introduction.

A Good pilot will practice until he gets it right,
A Great pilot will practice until he can't get it wrong.

vishwasvm

Thanks Augustine,

Quote..Thread lock

Can I put  little epoxy to lock the thread?? :headscratch:

Quote[is it wing joiner cf tube ?)

It is not wing joinder CF tube. That is much longer and that I have put in correct place. From the slot in the boom, I could figure out that it is meant for boom.

I have mounted by motor. Pic here.

http://www.rcindia.org/electric-power/help-with-motor-and-its-mount/msg94115/#25

Please comment and give suggestions.

Regards

Vishwas

vishwasvm

Dear all,

How about putting landing gear to Shikra?? Which one and how to fix?? I am afraid I may damage the bottom foam while landing. Has anyone tried before the landing gear on Shikra??

Regards
Vishwas

vishwasvm

QuoteToo Nose down, undesirable pitch changes with throttle is envisaged, be gentle with the throttle especially when going around

Dear rcpilotcacro,

What do you mean by too nose down?? Shall I reduce the motor angle??

Vishwas

rcpilotacro

You need to, go with the stock angle, it is perfect also you need to strengthen base of the motor pod
Gusty's Hangar and Introduction.

A Good pilot will practice until he gets it right,
A Great pilot will practice until he can't get it wrong.

vishwasvm

#85
I will do that. Thanks for your response.

Vishwas

EDIT: I am putting a link of post with photos for everyone to comment and help

http://www.rcindia.org/wanted/motor-mount-for-shikra-glider/msg97614/#msg97614


Moderator Note: Unnecessary quote removed.

hangingtough

hi,

I want to plan shakira for my son to fly, so can i plan 3 channel or i have to go with 4 channel only

just want to reduce weight now

rcpilotacro

Shikra
For son is not a good idea, it is a very agile glider. easy star or sky surfer will be better.
Gusty's Hangar and Introduction.

A Good pilot will practice until he gets it right,
A Great pilot will practice until he can't get it wrong.

hangingtough

Quote from: rcpilotacro on August 29, 2012, 10:17:53 AM
Shikra
For son is not a good idea, it is a very agile glider. easy star or sky surfer will be better.

sorry, i already bought it .

My son was able to fly a GWS beaver and also practices on SIM.

I beleive a 3 ch will be easy for him to handle.

hangingtough

dear all,

i did buy the shikra and put the fuse together,

Now i have some problems and need advise
1. Motor seems to point upwards
    - is the angle to the wing center line or the bottom line
2. How to join the wing
    - Glue  or not
    - Not able to understand how to configure the wing servo wiring. it is obstructing

need hhelp

rcforall

Hi ,
1) Motor pointing upwards : there is a scientific reason for this motor position in the case of all pushers like the shikra ie the motor thrust line passing slightly below the CG will produce a resultant upward moment in front of the CG there by lifting the nose when the motor is on.
This is especially useful at the time of take off.
2) You can use anabond or feviquick to glue
3) I will post  photos for the aeilron servo mounting in a day or two as time permits

Sai
www.zuppa.io : vehicle telematics, ADAS, IoT , Drones

hangingtough

thanks

But do you think i should glue the wings or just keep them together with magnets
i prefer removable wings for transportation and storage

there is hardly any space for wiring of aileron to be connected with Y connector
, what is the best method of placement

sundaram

Just cut a hole in the foam lower plate inside the slot for wing fitment for 'Y' cable.

rcforall

Stick the wing with magnets that is OK.
I have the Y connector come out of the receiver into the wing cavity on the fuse and the two aileron servos connect to this.

Sai
www.zuppa.io : vehicle telematics, ADAS, IoT , Drones

hangingtough

hi,

i test flew my shikra today,

There was no dip on take off as expected from all these flyers.

But what i faced issue is that the plane has a high tendency to dip to the right and go in circles.
I still did not glue the wings or apply any wing retainer method of magnet/rubber band.
Also i did not setup the ailerons and wanted to try a 3ch operation on this plane
Rudder is perfectly straight

what could be the possible reason of plane dipping to the right
1. Wing : not 100% secured
2. Normally required to trim any plane with ailerons

So i need advise why the plane is turning right and the possible cure

rastsaurabh

where do you fly in delhi???

Turning right ... check
1. Ailerons are fixed ( since you have 3Ch operation) straight and no movement possible ( stick tape to ensure)
2. Motor shaft to point to rudder
3. Rudder to be straight
4.Balance and see if the right wing is heavier...



hangingtough

i fly near mayapuri flyer , there is a big park and takes park flyers very easily,

I am trying Shikra near the rajouri garden malls as space is very big.


hangingtough

hi,

again i want to share the beauty of flying shikra

My take on this bird
1. It is very stable flyer in the sky
2. I am using only 3channel, still flyable except that the rudder turn seems less professional
3. Make CG ahead of the carbon spar and it will fly stably

Pictures and video to follow  :thumbsup:

Some bugs needs expert advise  :banghead:
1. It is difficult to take off (Even with up trim & 60~70% trottle
This bird requires you to give good throttle and give a hard toss in the air, takes about 15~20 meters to get air worthy
Dont fly this in the evening as the air becomes thin and the plan will dip into the ground faster than you think
Is there a better way
2. Tried the Dip method to find if this is nose heavy or not

Result : Astonishing behaviour in the air, Dip the nose and close throttle
           Dips the nose & it comes back level, again dips the nose and come back level (Oscilates and slowly losses altitude
why this happen
3. You cannot crash it
This plane is a trainer plane and no matter how much you want it to crash, it will not. I have safely landed after loosing radio link 2 to 3 times
4. Why it does not fly straight
If it goes right , it keeps on going right , if you can the direction then it will keep on going left.
Why it does not fly straight (Is this related to CG)

sundaram

1.  A very good Javelin Throw 30-40 degrees up (Real hard one) with 50-60% throttle is the only way. No up trim required. Let it follow attitude from 30-40 degrees up to level and then some 10-20 degrees down by this time it would have attained some speed now gradually pull elevator as well as open throttle gradually. Premature Opening of throttle before attaining speed results in it getting dashed to ground due to upward thrust angle. Pulling of elevator early also prevents in attaining speed faster (Uptrim).

2.   I am suspecting due to your uptrim not getting fully evened out. Or may be due to too light AUW if so make it further CG forward.

4.   Unlike an easystar the self leveling capability of shikra is slow. You should fly with aileron it is a pleasure to fly with it.

My all time best airframe too. On a 1300 mah I have glided for nearly 35-40mins.

rcforall

Quote from: hangingtough on October 13, 2012, 11:41:58 AM
hi,

Some bugs needs expert advise  :banghead:
1. It is difficult to take off (Even with up trim & 60~70% trottle
This bird requires you to give good throttle and give a hard toss in the air, takes about 15~20 meters to get air worthy
Dont fly this in the evening as the air becomes thin and the plan will dip into the ground faster than you think
Is there a better way

4. Why it does not fly straight
If it goes right , it keeps on going right , if you can the direction then it will keep on going left.
Why it does not fly straight (Is this related to CG)


Well my experience with it  has been in  our high wind conditions .
1) 75++ % throttle into a strong head wind gets her up fairly quickly by Shikra Standards but the take off is slow on low wind conditions.
2) The right turn I suspect might have something to do with the thrust line as you have ruled out other obvious reasons like ailerons etc , check if the  turn is opposite to the motor direction , if yes then it could indicate a slight torque roll , which could be rectified with a slight offset to the motor by a couple of degrees .
I have not experienced this but could be a possibility . The other possibility could be a slight angular   difference  at the polyhedral. Both these are valid possibilities if the roll indicated by you is in the same direction irrespective of the wind direction.

Sai
www.zuppa.io : vehicle telematics, ADAS, IoT , Drones