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Galaxy Models Chipmunk

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Andy Green09/01/2011 20:31:28
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1894 forum posts
49 photos
2 articles
With the decks cleared, the bench cleared and permission to come indoors when I get really cold, I'm ready to start the build of my Galaxy Models Chipmunk.

I hope to build this quite quickly to have her flying for when the weather changes, so that still gives me 10 - 12 weeks as I dont go out when it's too cold.

I'm going to spend tonight going over the plans and instructions and I'll start gluing tomorrow.
 
As I've done previously I'll add additional text, photos and thoughts on my website.
 
Andy
Danny Fenton09/01/2011 22:13:22
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7112 forum posts
2904 photos
Nice one Andy, I have amassed a fair bit of data on the Chippie if you need anything let me know. Have you chosen a subject to model yet? will it be silver or red white and grey
 
I look forward to seeing how this one goes together.
 
Cheers
Danny
Andy Green09/01/2011 22:29:49
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1894 forum posts
49 photos
2 articles
I'm thinking a yellow one. Prettier than silver, but easier than red / white. I guess it will depend on how much time I think I'll have.
 
This will be a sports model so there is no particular subject I intend to base it on.
 
Andy
Alan Williams10/01/2011 21:39:22
93 forum posts
Just got back from holiday.Thanks for the  e mail.I will be following with interest.Alan Williams
 
fly boy310/01/2011 22:46:08
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2530 forum posts
22 photos
Hi Andy, I have a 2nd hand "Chippahawk "from Skyways Models loosely based on the Chipmunk.  It is covered in siver and maroon Profilm.  Looks as good as it flys, and it flies outstandingly well.   Great web site, FB3 Cheers.

Edited By fly boy3 on 10/01/2011 22:46:57

Andy Green11/01/2011 23:02:17
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1894 forum posts
49 photos
2 articles
Work has started.
 
I intend to loosly follow the instructions and won't dwell on the standard build, but I will highlight any deviation from the instructions and try to explain why.

Doublers added as per instructions, there is a discrepancy between the plan and the pre cut wood in that the wing seat does not match the plan. As the plan can stretch I'll go with the wood for now and see where we are later. In any event I'll check the incidence at wing fitting time.

The instructions say to drill the firewall to take the engine mount, I'll do this later when I fit the engine & cowl.

The foam blanks have been faced and sanded to shape.
 
Nothing interesting to show but I have put some images on my website
 
Andy
Andy Green14/02/2011 11:59:44
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1894 forum posts
49 photos
2 articles
Sorry for not posting, but I've cracked on as can be seen on my site.
 
Servo Prep.
 
I always take time getting my servos ready. Its all too easy these days to stick any servo in a model and use the transmitter sub trim to centre the servoc. I like to take 5 minutes and get the servos as near to centre buy moving the servo horn on the spline.

undefined


The picture shows a servo tester generating 1.5mS pulse - You can use your transmitter to do this, but make sure there is no Sub Trim dialed in. The photo doesn't show what we are looking for but if the horn is moved on the spline the horn can be slightly offset. What I look for is the best position.

I cut the unused horn arms off, and neatly sanded the stubs, Its just lazy to keep the cut ends unfinished.

Andy
Andy Green14/02/2011 12:02:43
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1894 forum posts
49 photos
2 articles
Wing Joining.
 
I did not fit the wing tips as I needed to join the wings first. This is the best way to join wings to keep any errors out of the final assemly.

Draw a line through the centre of the wingtip here you can also see some small glue blobs. Make a parallel jig which is as deep as the required dihedral, plus the distance from the skin to the centre line. The plan calls for 2" dihedral under each tip, so my spacers are 2.5". Make 2 and temporarily glue them to the wing tips.
 
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With the wings on a perfectly flat surface hold down the tips; what this does is it makes sure the tips are parallel but more importantly they are exactly in the same plane. Any errors will now be at the centre join. There is nothing you can you about this, but the errors will have a lesser effect that if it was at the tips. I'd suggest that if there is more than 5mm error between the 2 panles you request another pair from the manufacturer. These panels are very good.


 
Sand the roots to the correct angle and glue as normal. Once dried the jigs can be snapped off and the tip cleaned up and the tips fitted.
 
Andy
Andy Green14/02/2011 12:04:42
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1894 forum posts
49 photos
2 articles
Flaps
 
I looked at this for some time and in my mind I couldn't see how the instructions would work, but going with the Galaxy method I went with it, and guess what, the method of installation and operation doesn't work. The geometry is all wrong, as the flap torque rods move down because of the angle of the wing, they want to move apart, but can't because of the ball joint. Even removing the ball joint doesn't fit the problem because youcant get enough downward movement on the flaps.

The flaps are faces with 6mm balsa, chamfering this and hinging at the top as reccommended doesn't give enough downward movement.

My Solution

Because the root blocks wer drilled during the first attempt they were replaced. Had I remembered I could have taken the extra 1/2" off of the flap, but I forgot, so they remain 1/2" to long.

I positioned the torque rods on the trailing edge centre line and hinged the flaps (With propper hinges) on the bottom.
Now because the centre lines are different the torque rods will want to move in the blocks, as the flap goes down the rods will move out. To facilitate this I (luckily) found some carbon tubing that I made a bearing with.
To make it easier to get everything aligned, I made the hole in the bearing block a little bit bigger than the O/D of the carbon rod bearing, using slightly more epoxy than I needed I fitted the bearing and assembled the flap, the bearing dired perfectly aligned and any gap was filled with epoxy.

Most (if not all) the flap movement will be down, but I chamfered the flap L/E to match the ailerons so thay looked the same, and this will allow me some degree of reflex if I find I need it.



 
The centre section was slotted and glued in place, and the entire T/E aligned just to make sure everything lines up.
 
More pics and descriptions here.
 
Andy 

Edited By Andy Green on 14/02/2011 12:06:18

Andy Green16/02/2011 19:46:25
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1894 forum posts
49 photos
2 articles
A couple more updates.
 
Centre section glassed, note that I,ve extended the glass out to cover the undercarriage blocks, and the hard points are much better fitted first.

 
A
Andy Green16/02/2011 19:51:51
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1894 forum posts
49 photos
2 articles
The first shows the servo covers glued in place. A lot easier than removable covers.
 

The second shows my choice of control horn. These are from Giant Cod and are screwed through the ply hard point and epoxied onto the aileron. It keeps the top surface clean.
 

Andy
Andy Green26/02/2011 21:32:12
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1894 forum posts
49 photos
2 articles
The instructions now are out of the window. To make things work 'My Way' from here on in I'll be going solo. Firstly the wing mounting blocks are not identified so I'm using the 2 off 1/4 ply destined for the cowl (did I say I've ordered a Carbon Copy one - more on that later) , and fitted them across the fuselage in a more traditional setup.

By eye I marked the position on the fuselage and took and angle measurement from the wing and epoxied it in place, I've also added a support to give just a little more area for the glue (I know it would have been more effective the other way, but I wanted to keep the mount close to the wing seat.


Before gluing the wing was checked for incidence and alignment, then it was clamped and the screw holes drilled through the wing and into the block, using the already fitted wing hard points as a guide to get the angle right.

Unfortunately the block was say 3mm too far back that I didn't feel comfortable using the captive nuts (they would be over the edge, that I drilled and tapped the holes 6mm to accept the wing bolts. Once tapped I ran some thin cyano into the thread, and re tapped, and repeated one more time. This is a method I've used before with great success.
Also fitted here are the ply wing fillet bottoms.

The Great Mate is really useful for holding the model while getting the wing (and Tail straight and at the right incidence.
 

Andy

Andy Green26/02/2011 21:34:10
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1894 forum posts
49 photos
2 articles
On first fitting of the tail to the fuselage it the incidence was way off, about 3mm in measurement not sure what that angle is but I'm sure someone with trig will tell me.


No problems though I just stuck some 3mm sheet over the fuselage and made good again. You can see the line above - this is the zero incidence line and used to set the tail plane incidence. If I hadn't of check it, I would have the tail mounted with the equivalent of 3mm down elevator.
Andy
Andy Green15/03/2011 08:07:05
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1894 forum posts
49 photos
2 articles
Completed a lot of 'little' jobs.
 
The Elevator & rudder controls are now in, I've decided not to have a rear hatch to get to the controls, but I think I'll bore some holes to give some access that I can cover. This will also take some weight out of the back.
 
 

Rudder & Elevator controls


The wing fillets are on, as is the cockpit floor, and some trimmimg and tidying up. The fin is on, in fact I'm about ready for a mamoth sanding session to get it ready for covering.
 
Andy
Andy Green07/07/2011 08:40:31
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1894 forum posts
49 photos
2 articles
Fuselage was shaped & sanded and covered with glass cloth applied with PolyC. What a nightmare it took 10 coats to fill the weave, a a whole large can of primer filler to get to a smooth paint ready finish. This was a trial run before I cover my DB big Spitfire, and it think I'll cover that with epoxy or tissue & dope.

I had trouble getting the fin fairing to fit properly, in the end I discarded the supplied ABS one and used balsa. A lot easier to fit, and it still looks scale.
 


Andy
Andy Green27/11/2011 20:05:52
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1894 forum posts
49 photos
2 articles
Time for an overdue update.
 
Fuselage sprayed and the tail filmed, not quite as per scale but close enough. The wings as far as I have them, run out of red profilm so waiting for a trip to Penn Models for some more.
 


Andy
Graeme Poke14/05/2012 08:02:27
55 forum posts

I am interested in building a Chipmunk. How did this one end up please?

Regards Graeme

Andy Green14/05/2012 08:30:14
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1894 forum posts
49 photos
2 articles

Hi Graeme

Still as you see it I'm afraid. I put it on the back burner when I started my Super 60 & Astro Hog build for the Greenacres event..

Have you seen my additional info on my web site.

Just doing the finishing touches on said models, so will be back on this one soon. All I need to do to complete is finish the wing covering, the contro surface covering, and radio / engine installation.

Doesn't sound much but will take a few weeks.

Andy

Graeme Poke16/05/2012 07:48:12
55 forum posts

Thanks Andy,

I have looked at your web site and will continue to follow until you complete it. So it should be flying in a month or so or am I being a bit optimistic?

I should mention that I live in Tasmania. However I guess the only thing that will stop me buying a kit is cost. We will see.

Graeme

Ben B16/05/2012 08:53:24
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1244 forum posts
4 photos

Looks excellent. I too am getting a bit bored putting multiple coats of PolyC on glass fibre so am experimenting putting some microballoons in with the polyC for the last couple of coats before using then sanding gently. Should reduce the number of coats needed and ditto the amount of primer.

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