1/2A Helicopter (oz5723)


1/2A Helicopter  (oz5723) by Paul H Stahlhuth 1952 - plan thumbnail

About this Plan

Free flight 1/2A size helicopter design. This plan appeared in combination along with the Everitt Wakefield on thefullsize Magazine plan service drawing.

Quote: "Lively interest shown in 'copter design contest indicates modelers are experimenting with this challenging category.

When a super Half-A engine is screaming its head off at 17,000 rpm it may be developing near one-tenth hp. Assuming 100 per cent theoretical efficiency, this power is able to pick up an 8 oz weight and lift it 110 feet in one second, or 6,600 feet in one minute.

Having so much power in such a small and light package, one wonders why we do not have model helicopters buzzing everywhere since neighborhood horizontal flying space is scarce. Well, if power was all that was needed for success in helicopter flying, we would have seen full-scale helicopters much sooner, and the ones that we see now would have much more spectacular performance.

The number of entries in AT's helicopter design event was surprisingly high. Designs varied from practical to imaginative. That submitted by Paul H Stahlhuth of Speedway, Ind, appeared to have the best flight possibilities. He has had past experience with such models as can be seen from details incorporated in the design.

In examining the plan, you will note how many problems were met in a clever way. To handle torque, Mr Stahlhuth fixed pivoted vanes directly to motor and permits the unit to rotate. He has a contra-rotating system with a minimum of fuss. To provide steady fuel supply without changing balance, he used a fixed tank and transfers fuel through a hollow bearing shaft. His bearing layout is on the substantial side and designed to eliminate as much friction as possible. This all worked splendidly on test model.

The major item on this design is motor base to which practically all parts are fixed or mounted. You may have trouble duplicating it if you do not have a lathe. However, in such case it would pay to have it made outside as it can be used and re-used for years.

The model AT tested is identical to that shown with the exception that we used flat vanes instead of having pitch vary 10 deg. as recommended. The model was first tested indoor. It. was held stationary just to determine how well the rotor system worked. The upward pull proved more than strong enough to lift model. Holding fuselage portion while contra-rotating rotors were turning produced no particular torque reaction. The bearing and fuel supply functioned fine. During outdoor testing, model would take off from ground by itself and start upward with a strong and fast vertical ascent. It was fun just watching it do its realistic and unassisted take-offs—and were they fast!

The only change suggested is enlargement of vanes. The model should be slowed up, and larger vanes should do the trick. Double the area shown on plans. The .049 wire which is used as hinge for vanes was found to be some what weak...."

Quote: "Hi steve ...also, a 1/2a helicopter full size scan... from jeff mccammant, story city iowa"

Direct submission to Outerzone.

Supplementary file notes

Article pages, text and pics, thanks to rchopper56.


Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction

1/2A Helicopter  (oz5723) by Paul H Stahlhuth 1952 - model pic

  • (oz5723)
    1/2A Helicopter
    by Paul H Stahlhuth
    from Air Trails
    February 1952 
    20in span
    IC F/F
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 12/07/2014
    Filesize: 236KB
    Format: • PDFbitmap
    Credit*: JeffMac
    Downloads: 4230

1/2A Helicopter  (oz5723) by Paul H Stahlhuth 1952 - pic 003.jpg

Do you have a photo you'd like to submit for this page? Then email admin@outerzone.co.uk

User comments

No comments yet for this plan. Got something to say about this one?
Add a comment



Download File(s):


* 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.


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.


Terms of Use

© Outerzone, 2011-2024.

All content is free to download for personal use.

For non-personal use and/or publication: plans, photos, excerpts, links etc may be used, provided that full and clear credit is given to Outerzone with appropriate and specific direction to the original content i.e. a direct hyperlink back to the Outerzone source page.

Unauthorized use and/or duplication of this material without express and written permission from this site's owner is strictly prohibited. If we discover that content is being stolen, we will consider filing a formal DMCA notice.