Flapper oz4346

 

Flapper - plan thumbnail image

Flapper - completed model photo

Submitted to Outerzone: 07/05/2013
Outerzone planID: oz4346 | Filesize: 251KB | Format: • PDFbitmap | Credit*: ErikJohnson

   

About this Plan

The Flapper. Ornithopter. National record holder.

Quote: "Junior and Senior Record Holder Ornithopter. The Flapper, by Robert Horak.

AFTER designing and building several ornithopters following the general indoor trend of design, I reached the conclusion that indoor types were not adaptable for outdoor flying. I then set about trying to develop an ornithopter which would turn in successful outdoor flights. After trying various ideas and different aero-dynamic setups I finally arrived at the following conclusions:

1. It must have a large stationary sur-face with a high lift airfoil set at a high angle of incidence.
2. It must be extremely light but strong in the right places.
3. It must be streamlined in order to permit fast flights. Speed is essential since lift increases with the square of the velocity. In other words, a model producing 5 oz of lift at 5 mph will produce 25 oz of lift at only 10 mph.
4. It must have sufficient flap area to obtain the very necessary forward speed.

I designed the model presented here with these ideas in mind. The model presently holds both Junior and Senior National Records.

Read the article carefully, studying plans until all details of construction are clear. Lightness should be paramount throughout the entire model. Select materials indicated. Original model only weighed 1-1/2 oz.

Fuselage. Select four pieces of 3/32 sq medium hard balsa for the longerons. Pin longerons in position placing pins on either side of the wood and not through it as this weakens the structure. Next select a length of soft 3/32 sq stock. This is to be used for the crossbraces and uprights. Finish one side of the body and let it dry thoroughly; then place a piece of wax paper over it and build the second side directly over the first..."

Direct submission to Outerzone.

Update 28/02/2017: Added article pages, thanks to George.

Supplementary files

Article.

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oz4346 datafile

Flapper  
by Art Horak
from Model Airplane News
July 1945 
38in span
Tags: Rubber F/F
all formers complete :)
got article :)

 

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User comments

Having built Dr. Lippisch's 48 inch version, which probably preceded Horak's version by 10 or 20 years (unlikely he was a Dr. yet), I'm naturally interested in the Flapper. I can plod my way thru it, but a text would be really helpful if there were any available.
ArtHoltzman - 13/08/2013
This plan (and article) is in the July 1945 Model Airplane News.
George - 28/02/2017
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Notes

* Credit field

The Credit field in the Outerzone database is designed to recognise and credit the hard work done in scanning and digitally cleaning these vintage and old timer model aircraft plans to get them into a usable format. Currently, it is also used to credit people simply for uploading the plan to a forum on the internet. Which is not quite the same thing. This will change soon. Probably.

Scaling

This model plan (like all plans on Outerzone) is supposedly scaled correctly and supposedly will print out nicely at the right size. But that doesn't always happen. If you are about to start building a model plane using this free plan, you are strongly advised to check the scaling very, very carefully before cutting any balsa wood.

 

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