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Old Nov 11, 2012, 08:50 PM
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Hobbistar 60 - Tail dragger conversion

Now that the wing repair is complete, I'm turning my attention to the next project for this plane - converting it from conventional tricycle gear into a tail dragger.

The first step was to remove all of the stock landing gear.





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Old Nov 11, 2012, 09:01 PM
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Next step: Filling in the main gear channel with some scrap.



I went with a Sullivan tail wheel. The original idea was to have it castering, but a closer look at the tail presented a different solution - taking a notch out of the elevator.

The notch was centred, but the stripes weren't.



Re-covered...

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Old Nov 11, 2012, 09:08 PM
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After the notch was cut and covered, I ground off the heads of the plastic tail bolts, possible because the horizontal and vertical stabilizers are epoxied in place. Once that was done, I re-covered the tail.



The tail wheel bracket was mounted with four servo screws...



... and the steering arm was connected to the rudder.

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Old Nov 12, 2012, 02:48 AM
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Innovative spring shock absorbing linkage
Clean job
(confirm CG)
Very nice
Regards
Rick
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Old Nov 12, 2012, 08:52 AM
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I would think that will work just fine. It doesn't take much to steer a tail wheel. Nice clean set up.

Ken
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Old Nov 12, 2012, 09:11 PM
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Thanks, fellas! I will definitely recheck the CG.
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Old Nov 13, 2012, 05:21 AM
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On to the main gear. The first step was to decide on the orientation. I chose to have it sweep back.



There are calculations you can do to determine where the gear should go. After a lot of thought, research and advice I decided that placing the axles directly beneath the leading edge (in a level attitude) was the solution for me. To that end, I followed these steps.
  1. Eyeball the placement of the gear on the fuse
  2. Mark the leading edge of the gear on one side of the bottom, 5mm from the edge
  3. Insert a t-pin at the mark
  4. Roughly across the bottom from the t-pin, make a short line parallel to the edge and 5mm from it
  5. Pick a forward point on the fuse. Measure halfway across the bottom and insert the t-pin there
  6. Measure the distance between the two t-pins
  7. Mark the same distance from the forward -pin to where it intersects the 5mm line drawn in step 4.
  8. Insert a third t-pin at the mark
  9. The line between the two rearmost t-pins forms an accurate leading edge location for the gear



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Old Nov 13, 2012, 05:28 AM
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With the leading and trailing edges of the gear marked, the covering came off the bottom.



There was a small gap at one point where a razor blade could be worked in...



... but first the bottom had to be cut across. A fine-toothed back saw worked well.

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Old Nov 13, 2012, 05:34 AM
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With the crosscuts done, a razor blade fit nicely into the gap.



A small scraper soon followed.



With some gentle encouragement, the bottom plate came off the fuse with little damage.



Turns out I had a hardwood block that was the perfect depth and width - it just had to be cut to length.

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Old Nov 13, 2012, 05:45 AM
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I used 30 minute epoxy to secure the block.



While it was curing, I turned my attention to the gear itself. Drilled out the axle holes...



... test fit the axles...



... and marked the centre line.

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Old Nov 13, 2012, 08:54 AM
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Looking good so far. Your tailwheel has good springing between rudder and wheel - essential to avoid feeding shocks back up to your rudder servo thanks to those odd less than straight roll-outs we all do - very occasionally, of course Main gear location is good too, you can't go far wrong with your placement.

Keeping the main UC and model in tight formation can be a problem. I learned that the hard way back when I first flew higher powered electrics, with 40 ounce batteries...

My favourite reinforcement involves two lengths of 1" alloy 'L' section from a local hardware store. These are epoxied between the UC plywood mount plate and the fuselage sides -which in my models are inevitably doubled up with thin ply. Hope the attached photo makes it all clearer

D
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Old Nov 14, 2012, 02:50 PM
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Quote:
Originally Posted by Dereck View Post
Looking good so far. Your tailwheel has good springing between rudder and wheel - essential to avoid feeding shocks back up to your rudder servo thanks to those odd less than straight roll-outs we all do - very occasionally, of course Main gear location is good too, you can't go far wrong with your placement.
Thanks!

Quote:
Keeping the main UC and model in tight formation can be a problem. I learned that the hard way back when I first flew higher powered electrics, with 40 ounce batteries...

My favourite reinforcement involves two lengths of 1" alloy 'L' section from a local hardware store. These are epoxied between the UC plywood mount plate and the fuselage sides -which in my models are inevitably doubled up with thin ply. Hope the attached photo makes it all clearer

D
Nice approach. In my case, the mains for the tricycle gear were made of music wire and were held in by a little friction and a couple of small straps with tiny wood screws, which did not loosen at all over the life of the plane.

My plan for the new undercarriage is five #8 screws into the hardwood block. I'll keep an eye on them, but I don't think they're going to work loose.
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Old Nov 14, 2012, 03:44 PM
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Nice project, and cleanly executed.

EJWash
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Old Nov 14, 2012, 08:27 PM
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Thanks EJ!

I put the tail wheel on before work this morning - couldn't wait to see how it looked.



I made a drilling template for the main gear based on the location of the hardwood block.





Got the holes marked and ready for drilling.

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Old Nov 14, 2012, 08:43 PM
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With the holes marked it was time to lug my trusty drill press to the bench.



A little protection...



Started with the pilot holes.



Then to an 11/64" bit for the #8 wood screws.

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