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Feb 13, 2019, 09:02 PM
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Jim.Thompson's Avatar
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Build Log

Spacewalker 1/4 scale build thread.


I am building a 1/4 scale copy of this aircraft that was designed for the home builder.........so I have read.
It will not be totally to scale, as I will probably hack the fuse shape a bit..........I hope to fly this plane as a tug for gliders........this will make the fitting of the tow release just that little bit easier.
I started just a week ago today. This is the progress so far...........starting with the tail surfaces.
I am using a hot wire cut foam rib construction method sometimes referred to as the "laser method", but I don't know why.
The pictures will tell the story so far, I hope.

Jim.
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Feb 22, 2019, 04:45 AM
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Motor now converted and running.


I have been distracted from the airframe construction work as I have been working on the motor.
It is another one that a friend gave me and came out of an agricultural blower. It just needed cutting down and converting for aero application: CDI, propeller hub, some increase in compression ratio and port timing adjusted to suit. I also made an adapter to fit a Walbro carburettor.

The stab and elevators are now framed up. Pics will tell the story.
I hope to get started in the fin/rudder over the weekend.
Mar 17, 2019, 05:17 AM
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Tail surfaces framed up.


The tail surfaces are framed and have threaded hard points to take two 1/4 inch nylon bolts to retain them.
Fuselage and wings next!
Mar 17, 2019, 12:17 PM
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kenh3497's Avatar
IIRC the Pauwlonia is a substitute for balsa. How does it compare in real life to balsa? Looking good so far!


Ken
Mar 17, 2019, 03:55 PM
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Pauwlonia.


Quote:
Originally Posted by kenh3497
IIRC the Pauwlonia is a substitute for balsa. How does it compare in real life to balsa? Looking good so far!

Ken
Ken,

The Pauwlonia is a substitute for balsa; it has a better strength weight ratio, allegedly. Used judicially, it serves the task well, in most cases but not all.
"IIRC"? What is that..............early in the morning here and I am acronym challenged!....................
Thanks for the reply, I was wondering if someone was reading.

Jim.
Last edited by Jim.Thompson; Mar 18, 2019 at 12:07 AM.
Mar 17, 2019, 11:03 PM
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kenh3497's Avatar
IIRC..... If I Remember Correctly.

Ken
Mar 20, 2019, 06:17 AM
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Some progress........


I now have all the wing rib slabbed out, hot melt glued to separate moveable building boards, and the top hot wire cut done on all three panels.
Yes, it will be a three panel wing.
One of the reasons is that this will allow me to use full length (915mm) long balsa and/or ply for the sheeting without any scarf joins being required.
the outer panels will be 915 plus the wing tips and the centre panel will be 400 mm.
There will be two dihedral breaks, each at the fuselage sides.
I have fitted two ribs at these points, for ease of sheeting when the time comes.

(1 min 35 sec)
Mar 29, 2019, 04:24 AM
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Spars............fuselage framing etc.


I have made full depth tapered spar system. Foam core with vertical timber shear webs on each side; Pauwlonia on the center section and out to around 1/3 span, then balsa.
This sandwich is capped with carbon spar caps, also tapered. Dimensions at the root, nominall 1.8 mm x 14 mm tapering to around 1.5 x 8 mm at the tips.
The entire assembly is wrapped with Dyneema braid. Wound with my battery drill on its slowest setting.
Three piece wing with carbon joiners in 2 mm ply boxes also wrapped as above. The joiners are 10mmx 20 mm in section, 300 long.

Meanwhile, I have started work on the fuselage. I made a late decision to make it out of sticks of Pauwlonia as I figured it would actually be lighter than the composite method I had planned for a long time. Besides, its a bit of fun; this is the first stick construction I have done for over 50 years.

More later............


Jim.
Apr 02, 2019, 09:21 PM
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Some work on the wings.


I now have the spars and joiner tubes glued in place.
Next will be some of the top sheeting and drag spars. Then it will be time to cut the entire wing assemblies (or part thereoff) off the board and proceed with the sheeting of the bottom of them.
I am planning on making a carbon/glass/epoxy undercarriage. It will be a bit of guesswork in choosing the layup thickness.

I am not going into much detail with my build method, as there seems to be very few people reading this.
I am more than happy to provide more information if the need is there. Please advise if so.

Jim.
Apr 03, 2019, 07:30 AM
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kenh3497's Avatar
Your wing build has inspired me! The wing on my Zlin is quite tapered. The tip is undercambered and has six degrees of washout while the root is set to positive four degrees. The wing is built with the trailing edge of the wing 1" off the building surface to accomplish all this geometry. That leaves the spars off the table at the tip and most of the way back to the root.

So the point of this description is; I'm going to use my foam cutting rig to cut some foam saddles for the ribs to set in. That will support the spars and provide all the correct geometry...... I hope Should also help when it comes time to sheet the bottom of the wing.

Thank you Jim for posting your build!!!!

Ken
Apr 03, 2019, 01:37 PM
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Quote:
Originally Posted by kenh3497
Your wing build has inspired me! The wing on my Zlin is quite tapered. The tip is undercambered and has six degrees of washout while the root is set to positive four degrees. ......................
Wow! That is a lot of washout. Is this a tailless aircraft?

Quote:
The wing is built with the trailing edge of the wing 1" off the building surface to accomplish all this geometry. That leaves the spars off the table at the tip and most of the way back to the root.

So the point of this description is; I'm going to use my foam cutting rig to cut some foam saddles for the ribs to set in. That will support the spars and provide all the correct geometry...... I hope Should also help when it comes time to sheet the bottom of the wing.

Ken
Do you have a build thread or blog for this build?

Meanwhile, my wings are almost ready for the hot wire cut off the board. Each wing will be then inverted and sat back down on the blanks. This is one of the reasons I chose a symmetrical airfoil for this model. To facilitate the support for the second side construction.
Apr 03, 2019, 02:00 PM
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ErcoupeEd's Avatar
I find your build thread interesting!
I have read both of Keith SParks books "Building With Foam" versioon 1 and the revised edition
Very interesting.
He has a website www.parkflyerplastics.com

The revised edition of Building With Foam is on his website

He has a 1/4 scale P-40 kit available.

I am interested in what your AUW comes out to be vs a full wood build Spacewalker !! .
Last edited by ErcoupeEd; Apr 03, 2019 at 02:06 PM.
Apr 03, 2019, 06:38 PM
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Jim.Thompson's Avatar
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Quote:
Originally Posted by ErcoupeEd
I find your build thread interesting!
I have read both of Keith SParks books "Building With Foam" versioon 1 and the revised edition
Very interesting.
He has a website www.parkflyerplastics.com..................
Does he describe this so called "laser method"?

Quote:
.........................................
I am interested in what your AUW comes out to be vs a full wood build Spacewalker !! .
Watch this space.
Thanks for the post.
Apr 03, 2019, 09:51 PM
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kenh3497's Avatar
Quote:
Originally Posted by Jim.Thompson
Wow! That is a lot of washout. Is this a tailless aircraft?



Do you have a build thread or blog for this build?

Meanwhile, my wings are almost ready for the hot wire cut off the board. Each wing will be then inverted and sat back down on the blanks. This is one of the reasons I chose a symmetrical airfoil for this model. To facilitate the support for the second side construction.
In this forum "Zlin 526 AS" Just three or four threads down from this one. It's a sad start but I've made up my mind I'm going to build this thing come hell or high water.

Ken
Apr 03, 2019, 10:45 PM
High-power Rocket Gliders
iter's Avatar
Quote:
Originally Posted by Jim.Thompson
I am not going into much detail with my build method, as there seems to be very few people reading this.
I am reading this with great interest. Your builds are so interesting to watch--you're building bigger things than most, and the ingenuity that goes into bigger builds is inspiring. Everything you do is bespoke, in contrast with the average "how I put together a kit" thread.

Please continue to share your work. The more detail, the better.

Ari.


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