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N200LZ: Chapter 11


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I'm planning on cutting the elevator cores this weekend.

Any tips?


I think someone mentioned something about the best order to make my cuts.

Any suggestions?

Inside, Top, Bottom?

Top, Bottom, Inside?

Bottom, Inside, Top?

....... what works best?

T Mann - Loooong-EZ/20B Infinity R/G Chpts 18

Velocity/RG N951TM

Mann's Airplane Factory

We add rocket's to everything!

4, 5, 6, 7, 8. 9, 10, 14, 19, 20 Done

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Here is what I have learned after cutting three sets....


TOP front to back

Inside bottom to top

Bottom front to back


Here is my process:


You will need two hotwire bows, a long one around 30 - 36 inches and a shorter one longer than 10 inches. 6 - 8 short 1 - 1 1/2 inch dry wall screws. 2 metal yard sticks with holes drilled every 5 inches.


Draw the level line on both sides of the foam with a sharpe.


Place the template on both ends with 1 - 1 1/2 inch dry wall screws (I used three in each. I also made the foam cores about 30 - 32 inches.)


Put several weights on the foam core to hold it in place.


Inset two nails, one on each side of the cores, at the level line. The nail should intersect the template at the top and inside (torque tube) cuts.


With a partner set up the long bow to cut the foam. Place the hotwire on top of the nails and enter the foam at the same time.


Cut the TOP First. Count the numbers and keep pace with each other. Remember the wire will lag so don't go to fast.


Move the nails so they align with the bottom of the template and the bottom of the torque tube circle.


Cut the INSIDE of the torque tube cirle Second. Place the hotwire on the newly placed nail and cut from BOTTOM to TOP. The numbers will be reversed, but this worked best for me. This method reduces the lag problem.


Cut the BOTTOM. Place the Hotwire on the bottom of the nail this time and then cut accross the bottom of the template.


Inspect the core for waves or if the wire burned through the thin sections if the cutting speed was to slow.


I found that measuring down 1 inch from the bottom of the elevator I could place the next Level line. Repeat above process until you have the desired number of cores.


After I cut five (5) cores (one spare). I then used masking or painter tape to tape the block(s) together. I then measured them for the 26.1 inch section. I marked the blocks with a sharpie.


Then I used the two metal rulers and several dry wall screws in the drilled holes to hold the rulers. I placed the rulers to align with the line and then cut with the short bow. This provides a very strait cut.


I then marked off the 26.1 inches at the other end of the foam block and repeated the hotwire cut above. This gave me 5 cores. I only needed 4 but if you damage one later you will need to make another and I didn't want to have to start over again.


Hope this helps.



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Might be too late... Neighbor and I just cut mine this evening.


We started at the trailing edge, for both the top and bottom cuts. It was easier calling off the "1/2 way to the foam, on the foam, ..." routine when we could rest the wire on the templates before starting. I don't notice any wire lag at the leading edge, but haven't gently spline sanded yet either.


I don't think it makes a diff if the top or bottom is cut first.


I think cutting the 1" hole was the most difficult. You're changing pressure/torque/drag on the template as you complete the circle. They came out "ok", but it's real easy to get ahead/behind of the person on the other end of the saw.


Per Wayne Hicks, in a different thread, I cut 1/4" - 3/8" of both foam 'flags' at the torque tube hole off with an X-acto knife before I 'pressed' the tubes in. The foam groaned a bit, and am fairly sure the sliver of foam on the bottom cracked ever so slightly at the tube, but it went in w/o a problem.


Details at 10,



Rick Hall; MK-IV plans #1477; cozy.zggtr.org

Build status: 1-7, bits of 8-9, 10, 14 done! Working on engine/prop/avionics.
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