2025-2026 P-18 Online Indoor Postal Contest

Current Standings

Many thanks to all who participated last year, it was a great success and is back on for the next flying season!

Last Years Final Standings (with ceiling factor scoring)

What is an online Postal Contest? It is a contest where everyone around the world gets to build a P-18, go fly it, then submit their scores by email to see how their flights compares to other modelers.

What are the rules?  P-18 is an offical AMA event (#227) and the rules are in the current AMA rulebook. To save you the effort I have refomateed the rules and they are below.

P-18
1. The model shall be a rubber powered monoplane covered with either tissue or plastic shopping bag material.
2. The wing shall not exceed 4.5 inch chord and projected span of 18 inches.
3. Horizontal stabilizer shall not exceed maximum span of 9 inches with a maximum chord of 3.5 inches.
4. Maximum overall length, including the propeller shall not exceed 18 inches.
5. The propeller shall be an unmodified commercially available plastic prop with a nominally maximum diameter of 6". Weight may be added for balancing.
6. The maximum hook to hook distance shall not exceed 10 inches.
7. The minimum weight of the completed model, less rubber, shall be 7.5 grams
8. The maximum length of the rubber strip before tying into a loop shall be 40" ***

***For this postal contest, this additional rule has been added to P18. So before the rubber loop is tied, the strip of rubber cannot be longer than 40". So that means your tied loop will be about 19 3/4" long. The loop can be any thickness rubber you choose.  A rubber widths around .050"-.055" (seems to be about right for this class. Why this rule? Becasue P18s can fly on very long loops, well over 40"  long with flight times up to 5 minutes. Limiting the rubber length is an easy way to keep flight times resonable without worrying about motor bunching, neededing motor "sleeves" on the rubber to prevent bunching etc. The purpose of this postal is to get people flying at the local level and also allowing some experimentation in rubber selection to enhance flight times.   

Some translations of the rules.
1. "shopping bag" material means go to the produce section of your local grocery store and take a few of the thin veggie bags on the rolls, use 3M 77 spray to adhere.
2. "unmodified plastic prop" means no sanding, scraping, re-twisted pitch, to the prop. You can add your own prop shaft and add ballast to statically balance the prop.
3. Some plastic props come as an assembly with a plastic thrust bearing and wire shaft. You do not have to use the attached shaft and bearing, you can remove those and use just the prop.

Here are some online P18 designs: (when printing out plans, make sure the printed plan meets the chord and span limitations.
Big Smash (11" x 17" paper)
P18 Cruiser (11" x 17" paper)
P18 Pursuit (11" x 17" paper)


Here are some P18 kits for purchase:
https://jhaerospace.com/product/squatty-p-18-contest-model/
https://jhaerospace.com/product/flat-top-p-18/

How do I enter my flight times into the Postal Contest? To enter your flight times, send an email to don@indoorfreeflight.com
Your postal entry must include the following items:
1. Your Name
2. Flight time in minutes and seconds (e.g. 1:17 = one minute and seventeen seconds)
3. Date of your flight
4. Ceiling height of the building you are flying in (e.g. 24ft 5inches) FAI ceiling measurment should be used, that is ceiling height measured at a 50ft diameter circle.
5. Age classification: There willbe two age categories, "Junior Class" and "Open Class"
    if the contestant is 15 years old or younger then please note they are in "Junior Class"
    if no age classification is included in the entry then it will be assumed they are in the "Open Class"

You may enter as many times as you like. As your flight time increases, send in your new scores. Fly in a new venue, send in the score. All flights must be submitted by May 31th, 2026

Why are you requiring the ceiling height where I fly?
The ceiling height will have an effect on how long the model can fly. A higher ceiling generally means longer flight time can be achieved. Knowing the ceiling height can help me graph the flight time based on ceiling height to try and come up with an appropriate correction factor. This is a method I used years ago when I use to run online postals.

Winners will be announced the first week of June 2026. 

Latest update to this page: September, 20th, 2025

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