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Jul 25, 2018, 12:04 PM
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Build Log

Citabria, 54" Wingspan, #1.3 EPP, prototype


I finally finished the design on the Citabria wing.

Wing is hotwire cut on my CNC from #1.3 White EPP Foam.

This was challenging due to the wing tips having a compound taper. My CNC was at itís limitations for the majority of the hotwire cut. It took a lot of CAD work and tinkering to finally get the wing tip to fit in the machine and properly cut out. I think I cut over 10 different wing tips before I finally got it. I also had other challenges like buggy software, loss of files on my computer, and in general several (Iíll spare you the long story!) unexpected external events that pulled me away from the project.

Iím really excited about the Citabria. It is finally coming together and I canít wait to fly it. Iím still shooting for a target of about a 480 size motor, 3s-2200mah battery, and the wing span will be 54″ with a removable wing. If you want a clipped wing version, then donít add the wing tips to have a 48″ wingspan. Or just cut off the ends of the main wing to make it shorter. I think this will have some silly STOL capabilities with a 54″ wingspan and flaps. I canít wait to play with it. With the EPP, you can afford to horse around a little and not worry about damage.

I am now getting over a cold, so the fuselage may take a few extra days to complete. Iím trying to decide exactly how I will make it. One thought is to do a clam shell style design with a left and right shell that is hollowed out with my mill. The downside of this is that the entire fuselage will need to be cut out with the mill which means rougher cuts and longer CNC time. The other option, which I might actually go for, will be to have the fuselage made in three different sections. Weíll have the main center section sandwiched between a thinner left and right sheet. This will allow me to use the mill to hollow out the center section, but the outside pieces from the sheet will leave the outside of the fuselage smoother. Do you have another idea? Let me know.

Once I am finished with the complete Citabria design, the EPP kit will be available for sale on my website: www.windcatcherrc.com

If you would like to purchase EPP foam, please head over to my website www.windcatcherrc.com
Or message me to make arrangements.
Last edited by iCrash2; Jul 26, 2018 at 07:17 PM. Reason: renaming the title.
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Jul 26, 2018, 07:20 PM
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I've been sick this week, so progress is slow. Today I managed to work on the CAD for the fuselage. I hope to cut this out tomorrow on the CNC.

I did some rough estimates and think this will be less than 30 ounces ready to fly with a 3s-2200mah battery and a 480 Plus Powerup motor.

The wings weigh less than 6 ounces and span 54" across.

I'll post fuselage photos tomorrow after I get it off the CNC.... assuming it all works right as expected. ha! we know how that goes, right?
Aug 05, 2018, 04:44 PM
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I have all the parts cut out with the CNC hotwire and mill. This evening I'm working on assembling and documenting part of the process. Things are going together quick now. It took less than 30 minutes to glue up the wings completely and the front and back of the fuselage.

I'm using the yellow/brown Gorilla Glue because that's what I have on hand due to all my wood working. The white version (not clear) would have looked better.

My process is to put a hint of water on one piece. Then on the other piece I apply the Gorilla Glue and smear it all around for good coverage. Then I use a few dabs of hot glue in a few strategic places to tack the two pieces together. Once I have the pieces together, I will add a little more hot glue to the outside, smeared down flat, to help hold the parts. The hot glue is not necessary, however I found it allows me to work faster and I can set the parts to the side while the Gorilla Glue sets up.
Aug 24, 2018, 10:46 AM
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Research and development of the Citabria was put on hold recently in order to work out the details for the Spec Wing I plan to sell. I was able to fully assemble the Citabria and give it a toss about a week ago. Iím using a PowerUp 480+ electric motor on a 3s-2200mah battery. I think it is over powered, but I didnít have enough time to really know for sure. 🙂

I knew the motor mount was weak, however I was in a hurry to get it out to the field for testing. I didnít realize just how weak until about 10s into the flight I gave it up elevator and hammered the throttle. The plane didnít go very far, but the motor sure did! haha The plane then flipped over inverted and amazingly floated gently to the ground. There were only 2 small pieces of foam that came off the plane where the motor ripped out. I already have a new plan in place to have my CNC cut out a proper firewall with reinforcements that go back into the fuselage like it should have been in the first place. This will most likely happen sometime next week. I might even get proper landing gear on the plane too.


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