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Old Jan 01, 2015, 10:22 PM
Crafter of flying plugs
Owen Hedger's Avatar
Armidale, NSW
Joined Feb 2007
1,278 Posts
Build Log
1/5th Scale PSS Cessna T-37A Tweet Scratch Build

After a two year break itís time to start building again. This time is it a 1/5th scale Cessna T-37A Tweet.
I have 9 months to get it done for the 2015 Manilla Slope fest.



Construction will be more or less the same as my last PSSer http://www.rcgroups.com/forums/showthread.php?t=1537220. Wood frame with glass straight over the foam. However, this time I will be using a laser cutter rather than a scroll saw which makes me so happy!

I have built the model in SolidWorks from this 3-View



I may have gone a little over board with the cockpit area but itís nice not to have to worry about how hard cutting the parts out will be. I have included some ballast boxes at the front of the cockpit area for good measure.



Iím quite happy with what I was able to do with the wing joiner box/spars. Even without any carbon they feel like they will do the job.



Parts to make a canopy plug have been cut separately from MDF. The plan is to have a vacuformed canopy. The plug will be made in 2 parts but will require further separation once shaped and glassed so I can fit it in my vacformer, which I made to make the Sky Knight Canopy thinking that would be as large as I would ever go 



So that is it for now. I will be gluing foam into the frame for a little while. Taking my time and enjoying the precision of laser cut parts.
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Old Jan 01, 2015, 10:30 PM
Registered User
Australia, NSW, Hornsby
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I'm looking forward to seeing this one go together.
Is the laser cutter yours or did you pay someone?

Al
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Old Jan 01, 2015, 10:40 PM
Crafter of flying plugs
Owen Hedger's Avatar
Armidale, NSW
Joined Feb 2007
1,278 Posts
Quote:
Originally Posted by _AL_ View Post
I'm looking forward to seeing this one go together.
Is the laser cutter yours or did you pay someone?

Al
It's mine I figured I have enough uses for one I would get it. It will be useful all the way through a build up to the paint job at the end. It's fantastic for cutting stencils!

Only downside it's its size. It didn't help that the table I imagined it fitting on was about 15% too small
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Old Jan 02, 2015, 12:11 AM
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Australia, NSW, Hornsby
Joined Jul 2005
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Always the way. A very nice toy to have though.

Al
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Old Jan 02, 2015, 04:40 AM
SINK HAPPENS !!!!
EeleyEagle's Avatar
Coffs Harbour NSW Australia
Joined May 2006
468 Posts
Very nice Owen, You the man ! I will follow with interest.
Andrew
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Old Jan 02, 2015, 02:53 PM
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Tick Point's Avatar
Joined Mar 2008
557 Posts
Great subject! I'm just finishing mine!

Dave
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Old Jan 08, 2015, 06:39 AM
I failed linkage geometry
salisbug's Avatar
Melbourne, Australia
Joined Jun 2002
4,296 Posts
Great choice Owen.

This model was on the OZSkunkworx list of models-to-do. The plan was for a 3m span, but unfortunately none of us have time to invest

Looking forward to following your build.

Seeing as you have a laser cutter and the files to drive it, would you consider producing part kits?

Glenn
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Old Jan 08, 2015, 07:48 AM
Crafter of flying plugs
Owen Hedger's Avatar
Armidale, NSW
Joined Feb 2007
1,278 Posts
Quote:
Originally Posted by Tick Point View Post
Great subject! I'm just finishing mine!

Dave
Got any build pictures? Looks to be a nice size.

Quote:
Originally Posted by salisbug View Post
Great choice Owen.

This model was on the OZSkunkworx list of models-to-do. The plan was for a 3m span, but unfortunately none of us have time to invest

Looking forward to following your build.

Seeing as you have a laser cutter and the files to drive it, would you consider producing part kits?

Glenn
Thanks Glenn.

My laser is a cheap Chinese laser. Cheap being relative, It's 1/10 the cost of on an Epilog. As such the laser PSU is giving grief. It died 1 1/2 panels from the end of cutting the main parts. Worked out it was the internal 12V supply for the control electronics. So while I'm negotiating a new PSU I'm just feeding the logic with an alternate12V source

I'm also only using Bunning 3mm Ply. Not sure what Browny would charge to cut the parts. I'm happy to supply the DXF's

All the fiddly foam has gone in. Still not sure just how I wan to do the rudder. I think I will go with the ply frame I cut and see what the result it.

Still want a time lapse of the shaping Matin?
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Old Jan 08, 2015, 08:02 AM
Aerotow and sloping Holland
MaartenX's Avatar
Joined Mar 2012
605 Posts
Impressive. You are about to generate a lot of foam dust
Really like this building technique.

Maarten
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Old Jan 08, 2015, 01:48 PM
I failed linkage geometry
salisbug's Avatar
Melbourne, Australia
Joined Jun 2002
4,296 Posts
Quality workmanship Owen!
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Old Jan 08, 2015, 07:32 PM
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Tick Point's Avatar
Joined Mar 2008
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sorry, no construction pix.

Edit; Here's a youtube video I referenced often; Cessna A-37 Dragonfly at March Field Air Museum
and here's a dashboard I found; http://www.rcgroups.com/forums/showt...agonfly&page=3

My hands are too covered in foam dust, resin, or wet sanding to pick up a camera!

From a 3 view I cut out a block of foam, sanded it round, covered it in tape, glassed it, acetone dissolved the core, sand, fill, sand, fill, prime,sand, finish putty, sand prime.

It was my first time thermoforming the canopy.

Bagged the wing with a "sport nylon" material as a live hinge. 55" span (stretched probably 10 inches past scale size) and it slopes just fine.

Won't you stretch the span some?

Dave

Dave
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Last edited by Tick Point; Jan 08, 2015 at 09:31 PM.
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Old Jan 08, 2015, 08:21 PM
Crafter of flying plugs
Owen Hedger's Avatar
Armidale, NSW
Joined Feb 2007
1,278 Posts
I just can't imagine just carving it out of a foam block.

Scale span would be 79". Span will depend of weight of the fuse. Fuse looks like it will be a decent lifting body. I think my Aerostar is a little light so I am aiming for a higher loading this time but I won't to go past 95" (2.4M).

Sorry Glenn, transport considerations are my upper limit
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Old Jan 15, 2015, 02:46 AM
Crafter of flying plugs
Owen Hedger's Avatar
Armidale, NSW
Joined Feb 2007
1,278 Posts
Only a bit of foam to go in now. Have to shape and sheet the rudder before that can be finished.

Might get to the snow making this weekend!
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Old Jan 15, 2015, 05:09 AM
Registered User
Australia, NSW, Hornsby
Joined Jul 2005
1,105 Posts
And here's the pilot.


Interesting build method. I'm enjoying the build pic & it's looking good.
Do you cut/ trim the foam & then sand or just sand it all down & is this how you built the Skyknight?

Al
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Old Jan 15, 2015, 05:40 AM
Aerotow and sloping Holland
MaartenX's Avatar
Joined Mar 2012
605 Posts
Quote:
Originally Posted by Owen Hedger View Post
Only a bit of foam to go in now. Have to shape and sheet the rudder before that can be finished.

Might get to the snow making this weekend!
I see you have the vacuum cleaner ready for all the snow you're gonna create.
It would be nice if you could make some pictures of the shaping process.
I'd like to see the process and tools you use.
For me it is just a rasp and sandpaper...

Good luck with this wonderful project.

Maarten
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