Kay C Caldwell
  • Gunnison, UT
  • United States
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Aircraft Model
Project Status
Nearly done
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Engine installed (or plan to install)
Building Experience
Have worked on airplanes before
Flying Experience
Private Pilot
Home Airport (ie. KMYJ)

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Posted on May 7, 2018 at 2:57pm 1 Comment

Hey just want to throw this out there, my daughter is the one that did my first flight video from crappy go pro and other clips my buddy filmed.  If any of you would like a video of your projects edited,put to music etc,etc she said she would do it for cheap.  She is a struglging college freshman looking for extra tuition money....Thanks Kay C. Caldwell..

tail dragger

Posted on August 2, 2017 at 6:41pm 2 Comments

Wondering if anyone else thinks Zenith should design an all new STOL that is a tail dragger???  Love the performance but I wish they had a tail dragger version.  Don't much like the looks of the conversions I've seen.....Just a thought..

Kay C

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At 5:53pm on October 16, 2020, CHRISTIAN TREMBLAY said…

Hi Kay,

I suppose, marine plywood permit double curving door frame and cover, very hard to do with aluminium without specialized equipment. I suppose main and windows doors windshield are also double curve form, this is why you re-use piper plexiglass windows ? 

All your photos will be very usefull to everyone.



At 6:59am on October 14, 2020, CHRISTIAN TREMBLAY said…
These explanations give me confidence to try it by myself.
I will kept this money saved for others part in the fuselage, like the main spring support weels or fiberglass cowling, to save time and efforts.
I'am sure, all builders want to see more detail about your canopy. :-)
At 5:37pm on October 13, 2020, CHRISTIAN TREMBLAY said…

Hi Kay,

I was considering buying the canopy kit from Zenith (now offer in carbon fiber) but very expensive). Around 10 000$ in canadian dollars.

When I check my plan 0059, I could see any dimension for making canopy, doors and windows plexiglass, only assembly plan. I am wondering how you did figure that dimensions ?

My other question is about how you did the curving in the plexiglass.

Tks for answering, this could help me to decided if I want and could do the job. I have strong habit for fabrication, I did very good jobs with my wing ribs and spars.



At 6:18pm on October 12, 2020, CHRISTIAN TREMBLAY said…

Hi Kay,

I realize that the plan that I have (0059) contain no information about the canopy (Windows, top and windows) measurements for the Ch640, only assembly plans information. You said that was you big challenge. Have buy the canopy from Zenith or you build it from scratch. If so, How you did that ? Your aircraft is prestine.


At 1:22pm on October 18, 2017, Michael T. said…

This post was long so I had to break it up.

I was looking over this "Complete CH 640 Errata"

Did you find any problems in the plans worth noting?...like lightening holes in the wrong place..etc?

I was looking this list over and maybe its all been fixed over time, Just wanted to check with you before I start cutting and bending...lol

Maybe this list below is outdated

At 1:18pm on October 18, 2017, Michael T. said…

Fuselage Discrepancies

  • Drawing 640F2, Revision 7 - Item 0, H.T. Frame Assembly.
    • An overall reference vertical dimension of 500 mm should be shown on this assembly and the top (L) rivets should be called out to be installed on assembly. The back of the 640F3-1 Rear Side Skin is 500 mm tall. The H.T. Frame needs this same height when installed. The 495 mm height of 640F2-4 implies an assembly height of 495 mm.
  • Drawing 640F4, Revision 17 - Vertical position of the 640F4-3 should be 143 mm from the top of the upper longeron to the center line of the 60F4-3. This is calculated from the positions of the 640-F27 H.T. Tail stops and the required deflections shown on 640M50. This dimension was confirmed by the factory on 21 Sep 2009.
  • Drawing 640F14, Revision 12 - The assembly drawing in the upper-left shows a callout to part 640F24-2. This part does not exist and should not be shown on this drawing. The older hand-drawn drawings do not show this callout or part drawing.
  • Drawing 640F18, Revision 7 - Engine Mounts.
    • Item 1, Lower Engine Mount - End plate overall length should be shown as dl=52, not 44 mm.
    • Item 3, Upper Engin Mount - To achieve the 17 degree angle, the dimension for the angle on the body should be changed from 7 x 35 mm to 11 x 35 mm. The end plate overall length should be shown as dl=56, not 44 mm.
  • Drawing 640F19, Revision 8 - In the upper-left corner, the length of the crossbar is shown as "l=306 +1/-0". This should be "l=301 +1/-0" to end up with the dimension shown on the bottom as [300 +1/-0].
  • Drawing 640F22, Revision 15 - The fuselage assembly dimensions show "(430)" from the firewall to the instrument panel. This should be "(480)" to match the other dimensions and the length of the 640F14-1.
  • Drawing 640F24, Revision 11 - The upper-right corner shows a dimension of "[360]" between the firewall and the 640F24-6. This should be "[410]" from 640F14 assembly detail.
  • Drawing 640F26, Revision 7 - Item 5, Lower Rear Side Skin Stiffener. Experience shows the top width dimension of 142 mm should be 150 mm. This leaves 11 mm, instead of 15 mm, for the width which is cut. The bottom 172 mm width should be 176 mm.
At 1:17pm on October 18, 2017, Michael T. said…

I was looking over this "Complete CH 640 Errata"

Did you find any problems in the plans worth noting?...like lightening holes in the wrong place..etc?

I was looking this list over and maybe its all been fixed over time, Just wanted to check with you before I start cutting and bending...lol

Maybe this list below is outdated

Wing Discrepancies

  • Drawing 640V1, Revision 4 - Item 1, Wing Spar Extension. The plans dimension "~405" to the first lightening hole. Change this to 350 mm.
640V2 wing spar extension assembly shows the lightening hole half-way between the two (L) pieces.
Adding the dimensions: 25 mm for spar cap overlap + 225 mm from overlap bend to first (L) + 100 mm from first (L) to center of lightening hole = 350 mm.
  • Drawing 640V1, Revision 4 - Item 4, Upper Rear Spar Cap. Minor typo on plans. Length should be 3390 mm, not 3391 mm. Lower spar caps should be 21 mm longer than upper spar caps. See 640V6 spar root detail.
  • Drawing 640V4, Revision 10 - Item 4, Rear Spar Upright. The top "dl=87" dimension should be to the left phantom line, not to the left corner of the cut piece.
  • Drawing 640V5, Revision 12 - Center Web and Spar Cap Assembly.
    • Upper assembly drawing has a callout for 640V3-1, yet points to the 640V3-5. Change this callout text to "640V3-5".
    • The lower assembly drawing shows an (L) callout for the short angles riveted to the 640V3-5. An (L) is defined using 0.025 material, yet these angles should be 0.032 thick 640F40-12 material. See 640F41 Rear Floor Support + Tunnel Installation detail.
    • The lower assembly drawing shows a callout for the "rear spar upright 640V4-3". The part number should be 640V4-4.
  • Drawing 640V6, Revision 8 - Wing Spar Assembly.
    • The top-right corner of the drawing shows a dimension of 102 mm from corner of the web to the first rivet hole. This should be 118 mm. See the Spar Root Detail dimension stack-up: 40+30+30+18.
    • A similar error just below the last one. The 103 mm dimension from the bottom corner of the web to the AN5 bolt hole should be 120 mm. See the Spar Root Detail dimension stack-up: 35+30+30+22 to end of cap + 3 to corner of web.

Tail Discrepancies

  • Drawing 640T7, Revision 3 - Items 1 and 2 Rear Skin and Nose Skin. The drawing shows a 2 mm dimension between the ~1277 horizontal dimension on Item 1 and the horizontal dimension of item 2. This implies that the item 2 dimension should be 1275 mm. The item 2 dimension should be 1315 mm, symetrical to the bottom of this piece. The 2 mm dimension should be to a phantom 1317 mm dimension on item 1 before the corner notch is cut.

At 11:52am on October 18, 2017, Michael T. said…

Hi. I was wondering if you would be open to loaning out your CH640 form blocks and any other jigs. for a month to 60 days, I cover all costs. Treat them well and return them not to badly beat up...lol

At 10:38am on October 16, 2017, Michael T. said…

At 10:22am on October 16, 2017, Michael T. said…

I was watching some of the Ch640 videos online on Youtube.. CH-640 presentation (Part 1)

I think its a Video made by Jeff Paden. In that Video he relates that the Alarus originally had a large rudder, in 2003 the Alarus went to a smaller rudder but the CH640 retained the older Alarus large rudder.

Jeff also posted a materials list in the video and parts sheet cut out. Would be great to find those for current or future builders. Do you guys have any contact info for Jeff, does he post here anymore?. Iver tried to email him from the address listed in his old build website but it just bounces back


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