Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
May 29, 2020, 12:53:24 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   Go Down
Print
Author Topic: Chipmunk  (Read 5023 times)
0 Members and 1 Guest are viewing this topic.
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« on: February 24, 2018, 04:51:59 PM »

Started a new project............ so far so good.  DHC-1 Chipmunk, 1:8 scale, 51 1/2" span for diesel power.

There is a 1/8 ply firewall. 1/32 ply doubler and the rest is 3/32 balsa. Also fitted is a box for knock-off wing tongues.

Steve



Attached files Thumbnail(s):
Chipmunk
Chipmunk
Chipmunk
Logged
billdennis747
Palladium Member
********

Kudos: 60
Offline Offline

United Kingdom United Kingdom

Posts: 4,031



Ignore
« Reply #1 on: February 24, 2018, 05:12:59 PM »

Steve, Ivan Taylor did a rubber one and converted it to diesel. I advise - heavy wheels!
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #2 on: February 25, 2018, 05:14:32 AM »

Thanks Bill,  shouldn't be a problem making something heavy!

Steve
Logged
Balsa Ace
Gold Member
*****

Kudos: 25
Offline Offline

Canada Canada

Posts: 466


FAC Member



Ignore
« Reply #3 on: February 25, 2018, 05:15:28 AM »

Very nice,I'll be following your build.

Scott
Logged

Hawker Sea Fury FB.11
HMCS Magnificent
VF-871   Royal Canadian Navy
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #4 on: February 25, 2018, 03:30:04 PM »

Thanks Scott. 

The Chipmunk wing-root area was quite challenging to model.
The next challenge, for me anyway, will be the engine cowl.  Hope to mould one from fibreglass.

Steve 
Attached files Thumbnail(s):
Re: Chipmunk
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #5 on: March 01, 2018, 01:35:31 PM »

It's cold in the workshop!

Trying to make a plug for the engine cowl.

Steve
Attached files Thumbnail(s):
Re: Chipmunk
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #6 on: March 06, 2018, 09:17:20 AM »

This build has descended into farce, my usual comedy of errors.  

After spraying a test piece of foam OK the paint decided to attack the foam in the plug,  put that right and then damaged the plug further by placing it too close to the fire to dry.  Also the plug moved inside the casting box?

Nevertheless I might have a usable mould.............when it dries out!

Steve

Attached files Thumbnail(s):
Re: Chipmunk
Re: Chipmunk
Re: Chipmunk
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #7 on: March 11, 2018, 05:31:24 AM »

The Chipmunk has a sort of gull-wing shape at the wing root.

The wing root trailing edge has been beefed up, it will take a lot of stress, hope it's strong enough.

Steve

Attached files Thumbnail(s):
Re: Chipmunk
Re: Chipmunk
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #8 on: March 20, 2018, 06:21:35 AM »

Cold in the workshop so progress has been slow.

Made a dedicated wing building board.  Photo shows the checking of both tip incidences and they are both equal!

Should be able to make accurate wings.

Steve
Attached files Thumbnail(s):
Re: Chipmunk
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #9 on: March 21, 2018, 10:49:13 AM »

The angles at the wing root on the bespoke building board have somehow contrived to give about 1/2 a degree of washout at the tips.  Now this is great and I see it as a good omen.

I've had to redraw (well Profili has redrawn) all the wing ribs with a little less washout.

Research gives the wing root section as the NACA2415 and the tip section USA-35B.  The Profili program seamlessly blends the intermediate ribs and also adds building tabs to give the desired washout.  I paid the 15Euros, I think?, to register for the fully supported program, well worth it!

Steve
Attached files Thumbnail(s):
Re: Chipmunk
Re: Chipmunk
Logged
Hepcat
OOS, January 2019
Platinum Member
******

Kudos: 279
Offline Offline

United Kingdom United Kingdom

Posts: 1,777



Ignore
« Reply #10 on: March 21, 2018, 08:42:05 PM »

That looks an ambitious build 3View, I wish you luck with it. I really enjoyed the nose view in #4.  I was just wondering why you are going for a tongue and box wing fixing when most modellers seem to have given up on them many years ago.  Do you see some benefit in them over, say, a simple rod and tube arrangement?
John
 
Logged

John Barker UK - Will be missed by all that knew him.
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #11 on: March 22, 2018, 05:24:14 AM »

John,

I think that my way is a neat lightweight solution that has served well on a couple of models now.  However, it makes wing construction a bit of a jigsaw puzzle.

The wing tongues are of 3mm hard balsa, 3mm carbon rod and are glassed as well.  I've staggered everything to avoid stress points and it neatly holds the u/c torsion tube.

Steve

Attached files Thumbnail(s):
Re: Chipmunk
Re: Chipmunk
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #12 on: March 26, 2018, 07:41:56 AM »

PAW 1.5 on its' engine mount.
Attached files Thumbnail(s):
Re: Chipmunk
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #13 on: March 31, 2018, 06:43:02 AM »

Here's the 'power-egg'.

Bolted to the workmate, initial tests look promising.  The well used PAW 149 starts very easily inverted.  Turns a graupner 10x3 @ 8000rpm.

Also reduced the venturi air intake area for more suck!  Even with all this plumbing the motor does not falter with its' nose in the air.

Steve 
Attached files Thumbnail(s):
Re: Chipmunk
Logged
billdennis747
Palladium Member
********

Kudos: 60
Offline Offline

United Kingdom United Kingdom

Posts: 4,031



Ignore
« Reply #14 on: March 31, 2018, 07:53:53 AM »

Hello Steve. Agree about the old PAW 149. I have one from the 60s which I had in an RE8. It started, handled and ran like a Mills and sucked through some very convoluted plumbing. And you can ´feel´what it´s doing when starting, unlike the modern ones. I think I ran it on an 11 x 4
Logged
applehoney
Titanium Member
*******

Kudos: 279
Offline Offline

Canada Canada

Posts: 3,179




Ignore
« Reply #15 on: March 31, 2018, 02:55:30 PM »

Is an older PAW 1.5 - straight intake, Nostalgia Gas legal - 1956 or earlier; have one like it but compression is low.  If you need more power .. can trade you a 1.5BB for it!
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #16 on: April 01, 2018, 04:09:48 AM »

There's an interesting article by Maris Dislers in the July 2015 Aeromodeller that champions the PAW 149 as a Mills replacement. Personally, I just needed a motor with a strong crankshaft as my pile of broken Mills' grew (all repaired now!).

applehoney....... I doubt if my early PAW is in a better condition than yours. I called it well used, well worn might be closer to the truth.

Steve
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #17 on: April 06, 2018, 07:33:39 AM »

Just don't look at the brush bristles in the layup!  However, I'm quite pleased, perfectly good enough for a one-off.

The mould was given umpteen coats of wax ons/ wax offs followed by pva release agent.  Still had to break open the mould to release the part!

The layup is 2 layers of 110g/M^2 glass cloth twill weave.  Twill weave drapes better than plain weave.   I said 2 layers, but 3 layers in places where there are overlaps.  Used West epoxy as it is readily available here from the boat chandlers.

The cowl weighs 45g roughly 20g of cloth and 25g of resin, not too bad for a hand layup.  Maybe slightly over-engineered?

When working with composites you have to prepare ahead and have your glass cloth cut and ready to use. I always 'double-glove' and have loads of toilet tissue at hand for wiping spills etc.  If you have to cut more glass or mix more epoxy you can strip off the outer gloves revealing the clean pair underneath.

The West epoxy is mixed 5:1 resin/hardener. I mix by weight which is the easiest way to measure small batches accurately.

Steve
Attached files Thumbnail(s):
Re: Chipmunk
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #18 on: April 08, 2018, 05:38:16 AM »

Made a start on the wings.  There is a hole in the building board where the u/c leg pokes through.

Steve
Attached files Thumbnail(s):
Re: Chipmunk
Re: Chipmunk
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #19 on: April 22, 2018, 02:42:33 PM »

The bespoke building board failed to do its' job and both wings ended up with wash-in!  Several steaming sessions later the wings are now to my liking, however at one point I thought the project might have to be abandoned.

I'm going to use a wing-levelling system with 5g. aileron servos.  The servos use a rotary drive so that the mechanism remains hidden.

Steve



Attached files Thumbnail(s):
Re: Chipmunk
Logged
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #20 on: April 26, 2018, 04:22:11 PM »

Steady progress.

Note the stain on the port wing LE sheeting.  My blood! DNA proof for the builder of the model rule?

Steve
Attached files Thumbnail(s):
Re: Chipmunk
Logged
glidermaster
Gold Member
*****

Kudos: 19
Offline Offline

Canada Canada

Posts: 866




Ignore
« Reply #21 on: April 26, 2018, 04:59:25 PM »

It's coming together well, Steve.
You've got some blood, what about sweat and tears?

John
Logged

Gliders are a part of me.
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #22 on: April 27, 2018, 05:40:33 AM »

John,

Tears, yes....  Sweat no, not at my rate of building.

Steve
Logged
Balsa Ace
Gold Member
*****

Kudos: 25
Offline Offline

Canada Canada

Posts: 466


FAC Member



Ignore
« Reply #23 on: April 28, 2018, 08:38:37 AM »

Very nice progress,Steve.

Scott
Logged

Hawker Sea Fury FB.11
HMCS Magnificent
VF-871   Royal Canadian Navy
3view
Silver Member
****

Kudos: 15
Offline Offline

United Kingdom United Kingdom

Posts: 211

Topic starter


Ignore
« Reply #24 on: April 29, 2018, 02:19:14 PM »

Thanks Scott,

The Chippie has grown a tail and I can soon think about covering. Covering will be tissue on sheeted areas and silk over tissue over open framework.

Steve

Attached files Thumbnail(s):
Re: Chipmunk
Re: Chipmunk
Re: Chipmunk
Logged
Pages: [1] 2 3   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!