Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
December 12, 2019, 05:22:09 PM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: 1 2 3 4 [5]   Go Down
Print
Author Topic: Beginners attempt at Scale Rubber Power, Guillows 17" Chipmunk  (Read 5028 times)
0 Members and 1 Guest are viewing this topic.
Konrad
Titanium Member
*******

Kudos: 38
Offline Offline

United States United States

Posts: 2,169


Measure twice cut once



Ignore
« Reply #100 on: August 19, 2018, 05:47:44 PM »


Here is what happens if you forget a pin, Lesson learned in 2010.

KF
Always keep an eye on the oven!
It (the pin) will spark before the wood burns. Damage would be less than what we get with the laser burned edges.
Logged

Cut it twice and it's still too short!
Mooney
Gold Member
*****

Kudos: 30
Offline Offline

United States United States

Posts: 697


Whenever possible, fly with the sun at your back



Ignore
« Reply #101 on: August 19, 2018, 10:08:27 PM »

Hi
I still braid if the model has a short peg to hook distance. This occurs often as I usually move the peg forward on most models.  I did so on my Typhoon of this series.  I also don't use a spool on the rear peg, I will use a larger dia. tube over the motor peg tube.  Sometimes this might be a length of a drinking straw, depending on size of model/motor. This allows the motor to move around similar to the spool (I would guess, never used a spool).   Also, not trying to contradict Konrad, just showing a different way I s'pose. Skinning cats and all that odd stuff.
Logged
Dan Snow
Gold Member
*****

Kudos: 29
Offline Offline

United States United States

Posts: 522


Topic starter


Ignore
« Reply #102 on: August 19, 2018, 10:21:14 PM »

Winder (the direction of prop pitch, for counter rotating props. Actually any prop).

I think most folks don't braid anymore as it puts an uneven load on the strands when fully wound. But if not going to full power (often a good idea with scale models) braiding can control the moving of motor weight during the glide.

I think it was mentioned to use a spool on the rear of the motor at the rear of the fuselage.  This helps a lot with the smooth transition of power from the motor to the prop. It also helps prevent the motor from bunching in the rear (changing flight trim).

From the winder? So I am standing in front of the model, and I wind half the loops as if I'm winding it for flight? Then I bring the loops together and let it unwind to wind the two loops together?
Logged

"Curse you Red Baron!!"  - Snoopy
Konrad
Titanium Member
*******

Kudos: 38
Offline Offline

United States United States

Posts: 2,169


Measure twice cut once



Ignore
« Reply #103 on: August 19, 2018, 10:49:56 PM »

Hi
I still braid if the model has a short peg to hook distance. This occurs often as I usually move the peg forward on most models.  I did so on my Typhoon of this series.  I also don't use a spool on the rear peg, I will use a larger dia. tube over the motor peg tube.  Sometimes this might be a length of a drinking straw, depending on size of model/motor. This allows the motor to move around similar to the spool (I would guess, never used a spool).   Also, not trying to contradict Konrad, just showing a different way I s'pose. Skinning cats and all that odd stuff.
That is what I'd call a spool. A tube that allow the rubber to move about the rear peg. Wether the tube has sides on it is just an added "feature".
« Last Edit: August 19, 2018, 11:00:48 PM by Konrad » Logged

Cut it twice and it's still too short!
kittyfritters
Gold Member
*****

Kudos: 19
Offline Offline

United States United States

Posts: 511


WWW

Ignore
« Reply #104 on: August 19, 2018, 10:53:43 PM »

Hi
...I also don't use a spool on the rear peg, I will use a larger dia. tube over the motor peg tube.  Sometimes this might be a length of a drinking straw, depending on size of model/motor. This allows the motor to move around similar to the spool (I would guess, never used a spool)...   

Like this?  (2006 photo)   Now I use a drapery tieback ring.  Works just as well and has a larger hole to get the peg through.

KF
Attached files Thumbnail(s):
Re: Beginners attempt at Scale Rubber Power, Guillows 17" Chipmunk
Re: Beginners attempt at Scale Rubber Power, Guillows 17" Chipmunk
Logged

Qua sublata omnia praecepta legis
Indoorflyer
Platinum Member
******

Kudos: 15
Offline Offline

United States United States

Posts: 1,112




Ignore
« Reply #105 on: August 19, 2018, 11:25:29 PM »

.......
« Last Edit: August 20, 2018, 12:16:45 AM by Indoorflyer » Logged

Make the same mistake on both sides; nobody will notice...
Crabby
Titanium Member
*******

Kudos: 134
Offline Offline

United States United States

Posts: 2,191


I never met a modeler I didn't like



Ignore
« Reply #106 on: August 20, 2018, 09:55:37 AM »

Dan FWIW, here is a Chipmunk from Aerographics that marks the CG just aft of the LG. The plan came from Aerofred.
Attached files Thumbnail(s):
Re: Beginners attempt at Scale Rubber Power, Guillows 17" Chipmunk
Logged

The Threadkiller!
Konrad
Titanium Member
*******

Kudos: 38
Offline Offline

United States United States

Posts: 2,169


Measure twice cut once



Ignore
« Reply #107 on: August 20, 2018, 10:08:53 AM »

Winder (the direction of prop pitch, for counter rotating props. Actually any prop).

I think most folks don't braid anymore as it puts an uneven load on the strands when fully wound. But if not going to full power (often a good idea with scale models) braiding can control the moving of motor weight during the glide.
...
Sorry, that was clumsily written.

But yes, wind half the motor in the direction you "normally" would for the prop.
In Ross's book he shows this in Fig.10-7. Then bring the ends together and let the strands intertwine as the motor "unwinds".
"Winder" possition came from one of your post.

While the total number of winds a motor can handle goes down with braided motors. The add length more than makes up this loss of potential energy.
Logged

Cut it twice and it's still too short!
Konrad
Titanium Member
*******

Kudos: 38
Offline Offline

United States United States

Posts: 2,169


Measure twice cut once



Ignore
« Reply #108 on: August 20, 2018, 01:01:48 PM »

The winder in Ross's drawing (Fig. 10-7) has the input shaft turning the same direction as the output shaft. There is an idler gear or inner toothed ring gear in that housing.
Logged

Cut it twice and it's still too short!
TheLurker
Gold Member
*****

Kudos: 24
Offline Offline

United Kingdom United Kingdom

Posts: 762




Ignore
« Reply #109 on: August 20, 2018, 02:27:39 PM »

Quote from: Konrad
Well the paper ones aren't any good. They are from stiff paper and don't lay against the tissue
If you hit this again try sanding the back of them.  If you're careful you can get quite a bit of flexibility into even quite heavyweight paper doing this.  The results will never be wonderful but they will pass muster for the two (or three) foot rule and if your eyes are as bad as mine they might even look perfect. Smiley

Lurk.
Logged
Konrad
Titanium Member
*******

Kudos: 38
Offline Offline

United States United States

Posts: 2,169


Measure twice cut once



Ignore
« Reply #110 on: August 20, 2018, 02:38:43 PM »

...  The results will never be wonderful but ...
Lurk.
I agree.
Another issue with bond paper decals (markings) is that they often disrupt the fine balance of the structure, making flight trimming difficult. With these light weight models the tissue often adds a lot of structural strength. Having covering with areas of differing stiffness often makes it difficult to control the needed warps (washout and surface deflections).
Logged

Cut it twice and it's still too short!
Ex Member
Guest

« Reply #111 on: August 20, 2018, 05:29:22 PM »

The VMC Kit decals are paper, it was option to go with water slide ones, but they don’t stick to doped tissue very well at all and the paper ones are easily stuck with a glue stick.  They are also provided on the website so you can print more if you like in the event you should foul one up...

The paper used is 40gsm, very thin and relatively light.  Bond paper is far far too heavy.  At home I have a large stock of the stuff, it was being thrown away at work when the last of the tractor printers from the main frame was being thrown out...

It is white enough to be white when stuck over a dark colour, but light enough to be practical.

Andrew

Logged
Dan Snow
Gold Member
*****

Kudos: 29
Offline Offline

United States United States

Posts: 522


Topic starter


Ignore
« Reply #112 on: August 20, 2018, 08:59:09 PM »

Well drat! Looks like it'll be a while longer until I can get the Chipmunk in the air.  Undecided  I ordered some rubber from FAI the other day, and was just  informed that they are on holiday, and that sometime after the 29th of August my order should ship.  Oh well, them's the breaks!
Logged

"Curse you Red Baron!!"  - Snoopy
Konrad
Titanium Member
*******

Kudos: 38
Offline Offline

United States United States

Posts: 2,169


Measure twice cut once



Ignore
« Reply #113 on: August 20, 2018, 09:03:41 PM »

If you play your cards right, you could have 2 900 series ready for test flight by the time the motors are delivered.
Logged

Cut it twice and it's still too short!
Dan Snow
Gold Member
*****

Kudos: 29
Offline Offline

United States United States

Posts: 522


Topic starter


Ignore
« Reply #114 on: September 11, 2018, 03:39:40 PM »

Finally got the new nose block finished, ( haven't painted it yet), made my first attempt at a braided motor with a tube in a tube for the rear peg, and got her balanced at the recommended CG per Guillows.

Was anxious to try it so out to the back yard I went. A couple of test glides were very encouraging, flat, no signs of stalling, with a gentle turn to the left. Okay lets try a little power.  Lets start real slow, so how about oh, let's try 80 turns. Wow!! Almost immediate sharp downward turn to the left!!

Okay, time to dig out Ross's book and reread Chapter 11, Flight Trimming!
Attached files Thumbnail(s):
Re: Beginners attempt at Scale Rubber Power, Guillows 17" Chipmunk
Logged

"Curse you Red Baron!!"  - Snoopy
OZPAF
Palladium Member
********

Kudos: 180
Offline Offline

Australia Australia

Posts: 5,217



Ignore
« Reply #115 on: September 11, 2018, 07:46:54 PM »

Assuming that your rubber motor is not too powerful -that sounds like you may have a warp in the wings. Possibly wash out in the left wing near the tip or wash in on the right wing?

I would suggest checking both wings carefully with long strips of balsa rubber banded to the bottom of the wing at root and tips of both wings.

John
Logged
Dan Snow
Gold Member
*****

Kudos: 29
Offline Offline

United States United States

Posts: 522


Topic starter


Ignore
« Reply #116 on: September 12, 2018, 08:56:12 AM »

Good catch John! I checked as you suggested and sure enough, the right wing had some wash in. It is pinned to my work board right now drying with the right tip trailing edge blocked up.
The motor is the recommended 36" of 3/32". I did try Don Ross's suggestion of braiding the motor, 100 turns on half the strands then being in the other strands and let it unwind. Seemed to work pretty well.
I'm thinking that the slower speed of the unpowered glide minimized the effect of the warp.
Logged

"Curse you Red Baron!!"  - Snoopy
OZPAF
Palladium Member
********

Kudos: 180
Offline Offline

Australia Australia

Posts: 5,217



Ignore
« Reply #117 on: September 13, 2018, 08:53:25 PM »

Quote
I'm thinking that the slower speed of the unpowered glide minimized the effect of the warp
That's correct and is the reason you need to take the power testing in small steps to catch any bad warps before the model is damaged.

Glad it helped.

John
Logged
Dan Snow
Gold Member
*****

Kudos: 29
Offline Offline

United States United States

Posts: 522


Topic starter


Ignore
« Reply #118 on: January 24, 2019, 07:29:10 AM »

Well, I finally got the Chipmunk out to the field to try an actual trim flight. Only tried one because somewhere between the test glides last year and yesterday I must have taken out the nose weight I had used to balance it.  I put about 40-50 winds into it and gently launched it into a 4-5 mph breeze.  It promptly performed about an 8' loop and then gently flopped into the grass.

At least it showed that I got the warp out of the left wing!!
Attached files Thumbnail(s):
Re: Beginners attempt at Scale Rubber Power, Guillows 17" Chipmunk
Logged

"Curse you Red Baron!!"  - Snoopy
DavidJP
Titanium Member
*******

Kudos: 46
Offline Offline

United Kingdom United Kingdom

Posts: 2,907




Ignore
« Reply #119 on: January 24, 2019, 08:01:48 AM »

Well that is a jolly sight better than mashing itself into the ground.  So you don’t carry some weight with you.  23 or 30 gms would be ample for several trimming flights.  But glad you had no damage. I was thinking about your chippie only the other day and how it was flying.
Logged
Dan Snow
Gold Member
*****

Kudos: 29
Offline Offline

United States United States

Posts: 522


Topic starter


Ignore
« Reply #120 on: January 24, 2019, 11:16:26 AM »

I did have some weight with me, but the breeze was picking up and I wanted to try my Bostonian Porter before it got any higher. I'll recheck the balance and take it out again soon. The weather should be good for the next few days. (Said with all fingers and toes crossed! )   Grin
Logged

"Curse you Red Baron!!"  - Snoopy
Pages: 1 2 3 4 [5]   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!