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Author Topic: Cessna Cr3 dimer  (Read 870 times)
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BG
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« on: November 14, 2018, 12:13:29 PM »

Hi All,
I have a new Cessna Cr3 dime scale kit out and am in the midst of a test build to check fit of parts etc. The plans will be published in the NFFS digest in the coming months. This design definitely skirts the edge of Dime scale "spirit of the event" in that it is a more complex design than many original dime scale designs. Mine is similar in complexity to Mike Isermann's drawings but more complex that Mike Nassie's drawings .... I just can't bear to sacrifice scale fidelity to the gods of simplicity .... (my mind will not allow it sadly) so I will apologize profusely to the dime scale hardliners and beg for their indulgence. For the rest of you this might be something you would enjoy trying for yourself so I will load the plans to the plans gallery soonish.
First image is a screen shot of the draft plan .... I will load the final plan to the plans galley.
Next image is the dummy engine assembly  - WARNING Dimescale hardliners please don't freak out this is not required for the dime scale version ...I will provide a paper image engine in the kits. This dummy engine is for the larger 24" version of this kit and the peanut version and for folks who want a smaller model for sport and mass launch flying.
Next image is the completed dummy engine (NOTE: the photos of the CR3 engine do not show cooling fins or valve rods etc. The engine appears smooth, it actually looks like it was covered.
Next image shows the front of the cowl assembled around the dummy engine; just s series of balsa rings.
Next image shows the front end ready for assembly with the cowling sheets, in this case 1/32 balsa with precept holes and marlins to help with cowl bump (rocker cover) installation.
Final image shows the cowl going on. The simple jig aligns the back former with the front end to ensure everything ends up centred and square.

Attached files Thumbnail(s):
Cessna Cr3 dimer
Cessna Cr3 dimer
Cessna Cr3 dimer
Cessna Cr3 dimer
Cessna Cr3 dimer
Cessna Cr3 dimer
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rgroener
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« Reply #1 on: November 14, 2018, 01:21:22 PM »

Looks great. I like the engine and cowling.
Interested in seeing how it looks when finished.
Roman
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BG
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« Reply #2 on: November 29, 2018, 12:07:21 AM »

Hi All,
Here is the update on y Dime scale (16" span) Cessna CR3 racer.
First pictures show the cowling assembled and rough sanded. You can see that the cowl segments include cuts to take little 1/16 alignment pegs for the rocker cover blisters. When assembles I simply carved the blisters to shape with a sharp blade and then sanded to get em round.
The flight surfaces are pretty conventional. I am not using particularly special wood for this just reasonably light balsa in the 5-7# range. I tend to go for harder stringers these days to help with robustity (new word).
The fuselage side assembly is pretty standard with the only thing of potential interest is that I now use packing tape on my plans instead of wax paper or other products. I find the packing tape is CA (and every other glue) proof. I like using a dipper to put tiny drops of very thin CA on each joint which makes for a very fast light build. I also use packing tape between the first and second sides. It works well because it sticks nicely to the first side and its clarity helps with alignment of the pieces for the second side.
Next you see the simple foam jig I assembled to handle the fuselage construction. This fairly extreme trapezoidal fuselage shape with curves all over the place was just easier to build in a jig. It turns out that the jig was very quick to make and worked beautifully to help me make a perfectly straight and symmetrical fuselage. When construction was complete I simply cut the jig along one side to release the fuselage box.
Attached files Thumbnail(s):
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
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flydean1
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« Reply #3 on: November 29, 2018, 06:38:41 AM »

Always liked the CR3.  Lost one in a Mass Launch at Palm Bay many years ago, last seen heading for Orlando.

When is the kit available, and will it have the "full" engine option?  These things typically need nose weight.
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BG
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« Reply #4 on: November 29, 2018, 11:50:29 AM »

Flydean: The kit is already available for purchase and the engine comes standard as part of the kit.

Bernard

 
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BG
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« Reply #5 on: December 10, 2018, 01:08:18 AM »

The Cr3 test build is finally complete. I covered the cowl with printed tissue marked with eh positions of the cowl bumps. Each bump received a small cover patch to ensure everything was evenly covered. Last step was the Canopy. I 3D printed three plugs, one for each of the kits I am supplying (13", 16", 24"), from a CAD 3D model I developed. Once the 3D printed plugs were cleaned up and polished I pulled a canopy and installed it. Last step was to cover the canopy and cover it with tissue. Prop is plastic because it needed nose weight anyway.
Attached files Thumbnail(s):
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
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BG
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Me with F1B - epic retrieval (flew 10km after DT)


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« Reply #6 on: December 10, 2018, 01:14:08 AM »

The weight of my prototype is 33g with 9g of rubber (two strands of 3/32 and two of 1/8th) or 24g empty and including the 2g of nose weight. The wing area is 50 sq. inch so the loading is 0.66g/sq inch which is not bad. I made no special effort to get it as light as possible so lighter loadings are achievable.

Now on to the next project.
BG
Attached files Thumbnail(s):
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
Re: Cessna Cr3 dimer
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Steviedean
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« Reply #7 on: December 19, 2018, 08:29:45 PM »

Thanks BG!
Another favorite racer from the golden age! I haven't built the Mr. Mulligan or Chambermaid(s) yet. Of course, that doesn't mean I won't buy a couple.
I put the neo dime Chambermaid from Volare' away for awhile. Got frustrated with the framework crushing while tissue shrinking-hallmark brand tissue.
The bigger factor there is we got a 7 week old Beagle puppy( now almost 5 month's old) who is full of piss, literally, and vinegar.
Thanks, I'll order after the holidays.
Thanks,
Steve Probelski
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