Build log 1/4 Scale Tiger Moth from kit

Started by flyingboxcar, June 17, 2011, 12:19:49 PM

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flyingboxcar

No takers for that precious offer? Come on guys it is free 
If you are really into scale you should be here. www.rcscalebuilder.com

K K Iyer


bmblb

#227
...flyingboxcar.....missed out on the offer bit....

...nevertheless, I have reason to believe you are possessed !!!  ;D

superb stuff ! :thumbsup:
"The Flight Of The Bumblebee"

K K Iyer

Captain,
You do have admirers who are too polite to clog up your build thread...
Regards

flyingboxcar

bmblb, yes that's the right word. I am sure possessed by anything that has a DH prefix to it. And the 82 being on top of the list.

Now since there have been no serious takers for the offer, the said offer is withdrawn. If any one still wants to own a piece of that cardboard cut in oval shape, I will sell each for 5 paise, if I have any left over after they are fixed on the model.

For all those who are wondering what these are for, the answer lies in the picture attached
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flyingboxcar

These are drain eyelets on a fabric covered airframe (especially the flying surfaces) giving a route for condensed moisture to escape.
These are attached on the under-surface and were made of fiber. On the model these are cut from thin card stock and will be glued in scale location and a hole with a hot wire poked through to create the opening that would also allow the model structure to breathe as in full scale, not mandatory but would be scale       
If you are really into scale you should be here. www.rcscalebuilder.com

flyingboxcar

#231
Tried some simulated rib stitching on the under surface of the tail plane and what a massive disappointment.
I chose to simulate the rib stitches via the PVA glue route, marked the location of each rib stitch at 1/2" (full size spacing on tail is 2") and using a toothpick tried to lay a tiny line of glue on the rib. Once this was done the whole was left to dry.
Making sure the glue was dry, today ironed on few strips of pinked rib tapes to see how it would come out.
And what a disappointment  :banghead:
Those stitches are far too obvious and look more like big domed rivets that subtle stitching. :'(
Will have to rip off the tapes, and take off all the glue drops (rag dipped in hot water with some patience should do the trick)
The first picture is of the dried out glue drops on the rib on one side.
The other two pictures are of the pinked tapes ironed over the glue lines        
If you are really into scale you should be here. www.rcscalebuilder.com

sanjayrai55

Captain: what exactly is "Tape Pinking?"

flyingboxcar

#233
Pinked tapes are the straight tapes you see with serrated edges. The zig zag or serrated edges are called as pinks.
While covering an aircraft with fabric (or even while cutting any fabric) the fabric is cut with scissors that give zig zag edges. This prevents the edges from fraying.
On aircraft, you will find that the on the flying surfaces after the covering has been applied, a strip of reinforcing tape is applied over the ribs, then the ribs are stitched (or riveted/screwed etc) and then a layer of of finishing tapes applied to cover the stitches. These finishing tapes will be have pinked edges and commonly referred as Pinked tapes. The other kind of tape is just ripped off the fabric and is called Egyptian tape. If you guessed that the name comes from Egyptian mummies you are right {:)}

Then there are  perimeter tapes that are applied on perimeter of all surfaces as reinforcement. These are double the width of flying surface tapes. For example the rib tapes on Tiger Moth are 2" and Perimeter tapes are 4" in full size, giving 1/2" and 1" sizes for 1/4 scale

Hope that helped  :)     
If you are really into scale you should be here. www.rcscalebuilder.com

flyingboxcar

Was contemplating to rip off the ironed on tapes and redo those massive stitches. But being the scrooge I am, decided to leave them on to remind me of my follies. But wiped off the rest of the glue lines with a rag soaked in hot water and redid the simulated stiches.

Bit of experiment on the size of wet glue line and I am much more satisfied. Did the complete under surface of the tail plane and ironed on the tapes. On the upper surface yet to lay the glue lines.

Similarly finished the simulated stitches on one side of the rudder and the entire fin . While the rudder and tail are yet to be completely finished, stitching, rib tapes and perimeter tapes on the fin are done. Next would be to glue on the inspection rings and patches and that would complete all the embellishments as far the fin is concerned and ready to receive a coat of silver paint.
Here are some pictures of the fin complete with stitches, pinked rib and perimeter tapes
   
If you are really into scale you should be here. www.rcscalebuilder.com

flyingboxcar

The next embellishment on the fin was to put on the inspection rings and patches. I had got some quantity laser cut in thin styrene and also in thin card. The styrene one seemed to be bit thicker and fearing that it may not handle the iron temprature well, decided to use the card ones.

The two inspection rings were glued on the covering in approximate scale location (Picture 1), allowed to dry and then a patch of solartex was ironed over the ring. But the effect was hideous. The ring was quite thick and stood out like a sore thumb. Picture 2 should tell the tale. The bare offending ring can be seen on top still uncovered

Not happy, the only course of action was adopted, rip off the two rings and decided to go DIY route on the rings. I needed thinner material to cut the rings from and, a just landed A4 brown envelope seemed suitable. Out with the Olfa circle cutter and got some nice thin rings (Pictures 3 and 4).

     
If you are really into scale you should be here. www.rcscalebuilder.com

flyingboxcar

The new cut rings were glued, allowed to dry and then the patches ironed on. The effect was much better and hence the other ring and patch was completed as well.
Picture 1 shows the new rings glued on, the card ring is placed besides the new ring for comparison.

On to rudder and the rib tapes were glued on the simulated stitches, and perimeter tapes applied all around except for the trailing edge. Picture 2 and 3 shows the almost complete fin and rudder. Do note that the inspection rings and patches are applied on only one side  ;D    
If you are really into scale you should be here. www.rcscalebuilder.com

flyingboxcar

Next task, complete the simulated stitching, tapes, rings etc for the stabilizer. And open up the covering from the elevators. Yes the elevators need to be shod of covering, and reworked as they have warped horribly after they were covered. Plan is to modify the structure to resist warping and recover   
If you are really into scale you should be here. www.rcscalebuilder.com

flyingboxcar

Here are few pictures of the simulated stitches being applied.
Lay a length of tape along the rib, marked with the appropriate distance marking (in this case 1/2" corresponding to 2" of full scale) and with that ever so useful toothpick lay a tiny line of glue along the markings, pull off the tape, go to next rib and so on and so forth. Then let it dry out overnight. Presto! the stitches are done.
The last picture is of the tail group (less the elevators) that have been completed with stitches, rib and perimeter tapes. The perimeter tapes on the rudder trailing edge actually spoiled the nice curved edges I had been able to achieve with the covering.    
If you are really into scale you should be here. www.rcscalebuilder.com

peterf

Coming along nicely, I keep looking in from time to time. A pity to hear about the warping of the elevators, always a trouble with these light open structures. Hope you manage to sort it OK. My build has stalled as I have had a few other things to do along with assembling a new ARTF 3.0m electric glider. Only trouble is it is the wrong time of the year to be looking for thermals in the UK as we have just had our first snow of the winter this past few days.

flyingboxcar

Hi Peter, always good to hear from you and Trevor and exchange notes on the build. What glider is that you are on to? I have a 3.5 Masala in box that I am itching to get at, but resisting the temptation so as not to further delay work on the Tiger Moth.
Work on my Tiger is currently stopped due to various reasons, will get back to it ASAP.
If you are really into scale you should be here. www.rcscalebuilder.com

peterf

Gracia from Topmodel cz. Ready to maiden when the wind reduces.

flyingboxcar

Good choice. I was contemplating it post demise of my Masala 1 ;)
If you are really into scale you should be here. www.rcscalebuilder.com

flyingboxcar

#243
The plan depicts conventional aileron actuation through a thin wing servo that is side mounted and the arm sticking out. Decide to deviate from the plans and was toying up with ideas to replicate a scale aileron operation.
The idea I had was to operate a circular disc (like the full size) from the same side mounted thin wing servo.
Got two suitable size discs designed and 3D printed in metal and the bushing in nylon.
Here are few pictures
1. The full size aileron actuation mechanism box
2. The 3D printed discs with crank and bushing
3. With the bushing and disc separate  
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flyingboxcar

Here are the pictures of the the disc installed with the servo on to the wing. All connections are ball link to minimize any slop
1. The general layout as seen from bottom of the wing
2. Servo arm to disc crank connection
3. Disc to aileron horn connection
4. Another view of servo arm to crank connection
If you are really into scale you should be here. www.rcscalebuilder.com

flyingboxcar

This arrangement results in throws that are roughly 7/8 inch each side. While that is fine (mmore than required) with the down travel the up travel has to be minimum 1 inch and I want more so that I do not have to use 140% throws on Tx program.
In the pictures you can see a steel rule clamped to to the TE of the wing with the 1 inch mark coinciding with the TE. The aileron trailing edge has an arrow mark to easily identify the movement.
1. Aileron on neutral
2. Down travel
3. Up travel 
If you are really into scale you should be here. www.rcscalebuilder.com

flyingboxcar

So not being happy with that, I will try another idea that has been borrowed from this build loghttp://www.rcmf.co.uk/4um/plan-scratch-builds/dennis-bryant-15th-scale-tiger-moth/160/
I intend to use the same servo to drive two gear wheels, where the larger 50 teeth wheel would be connected to the servo and this large wheel will drive a smaller 20 tooth wheel, that would be fixed on to the disc.
From what I gather the larger, when able to move 1 tooth would move the smaller one 2.5 teeth. Which means if I am able to rotate the large wheel by 3 teeth I get 7.5 teeth movement on smaller one and that equates to 135 degrees of travel on the disc. Based on how far from the centre of the disc the aileron push rod is connected, I should be able to extract enough throws from this mechanism.
The pictures show the plan and the gear mechanism arrangement as well
In case one sees a fundamental error in the calculation you are welcome to point it out.
So now to wait for the gears              
If you are really into scale you should be here. www.rcscalebuilder.com

Tanmay.mathur

Beautiful, superb,wow and nice like words seem tiny in front of you efforts and level of perfection.
Mr. Perfectionist seem the right word for you.
And paramount of perfection is for your build.
Still figuring out how and why  person could go to such height ?
Ps. Ignore if sound to silly , dont you think that much detailing will cost in flight characteristics and duration?
Hatsoff
Regards,
Tanmay mathur

K K Iyer

Captain sir,
Looks like a full scale build with miniature pics to make it look like a model...
:hatsoff:
Regards

peterf

Wow, 3D printed metal, it is amazing how the technology is developing, perhaps a smaller radius for the actuation arm on the disc would have given more disc rotation gor a given servo travel. I am only planning on silver soldering a steel disc onto a steel shaft for mine - truly low tech.