Big Smash, P-18 for EAA Family Flight Fest 2020

[jim_buxton]

I was asked to come op with a new model for the One Design event we always run at the EAA indoor contest (AKA EAA Family Flight Fest) this year.  We phased out the Double Whammy and decided to replace it with a model that we equally simple, but could be flown i other events.
To accomplish those goals I decided to come up with a model that would be legal (and useful) for P-18.  The model is inspired by the popular "Mash-Up" that Rob Romash and I came up with for a previous EAA one design event.
I have submitted the plans to the Builders Gallery.

Here are the notes I included with the plans when I sent it out:
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The “Big Smash” is inspired by the popular one design “Mash-Up” designed for the EAA event by Rob Romash.  This larger version is designed to comply with the rules for P-18, which is becoming more popular as an introductory event to indoor flying.

Prototype built with 8-12 pound wood and came in at 7.6 grams. Using the sizes shown on the plan.  For hardware, see sources below.  Note, these are not required items for the one design event, just an idea of what I am doing.

I am using the 6" Igra/Czech prop from Volare:
https://volareproducts.com/index.php?main_page=product_info&cPath=56_42_50&products_id=98
Volare no-cal nose bearing.
https://volareproducts.com/index.php?main_page=product_info&cPath=56_40&products_id=1155
Small Brass washers:
https://volareproducts.com/index.php?main_page=product_info&cPath=56_40&products_id=152
Also using S-hook prop shaft from Peck:
https://www.wind-it-up.com/collections/prop-shafts-and-bearings/products/pa048  

Covering is veggie bags for the main panels, printed tissue for the tips and rudders to add some Romash-esque pizazz.  I adhered it with spray 77, but have since helped some scouts build these models and found that UHU glue stick works great to hold the veggie bag plastic on, and you can slide it around to adjust tautness very nicely on the strong structure of this model.
Wing dihedral can be single as shown or double poly at the tips.  Just so the projected span stays under the 18” P-18 limit you are legal.
I hope to build another one, and John Kagan is building one as well.
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The event is just over a week away I guess, so I need to build another one.  John and I will try to post some pics of our builds here.  Below is a Youtube link to a video of the maiden flight of the prototype.  Enjoy!
Jim Buxton  
https://youtu.be/HlrjHcNKDiQ

[jim_buxton]

A couple shots of the prototype.

[Indoorflyer]

That's a neat design, looking forward to the plan.   I've not used one of those props --what is the mass of the 6"Φ version? How's it compare to a Tern?

[FlyF1D]

Here's some info on my Big Smash

I chose polyhedral tips, because that's the Romash way

Won't crumple the veggie bag as much next time. That works well for the thinner films, but is too much for this thickness

Teflon bushing fills out the prop hole while keeping it "unmodified"

Budget mag board worked nicely. $6 22GA sheet from home depot, $5 magnets from Amazon

[jswain]

Hi Jim,
nice smooth flight and good endurance for first flights in video.

Have you gotten a sense yet what size rubber and how many turns have worked best so far for this model?

For example, .074 rubber,1.8g loop,
@ 1900 turns

Thanks again for sharing, john s.

[FlyF1D]

Test session at the local gym: https://youtu.be/C3H0YIeH7ow

[jswain]

I just finished this model and i am looking forward to flying it within the next 7 days or so.
The build was straight forward and i really liked the LPP type adjustments to either flying surface.
The tip about using smaller wire and teflon tube insert was a new tip i used here. Not having that heavy .040 wire prop shaft saved a lot of final all up weight....maybe .5 gram or more???
The final weight ended up at 7.12g so there is plenty of reserve for repairs and self induced damages/repairs.
I made a number of mistakes but i always expect that will adjust the building techniques to not repeat.
More info to follow and many thanks to Jim for publishing plans and videos, john s

[jswain]

I had my first opportunity to fly the newly completed BigSmash p18
and it flew quite well. This model in this setting easily surpassed
my previous bests of different p18 designs 1:40s~1:50's minutes max!!!

After the first 5  test flights were done, ensuring the BigSmash model was
safe and didn't want to kill itself under higher powered wind counts
the last 4 flights were consistantly in the 2:00 to 2:20 range in a
low ceiling (22~23' range...)dual-basketball court gym setting.

The flights seen in the youtube links below used 1.9gram x .069 rubber
motors wound up to between 2300 and 2500 turns with *no* backoff on torque
other than the winds lost transfering the rubber loop from winder and torque
meter to motor stick.  I have found when using this .069 thinner rubber motor
with p18 i need the higher starting torque to get the model *up* high to the
bottom of the girders. Otherwise my P18 models with lower initial torque burst
will only go about 2/3 of the way up and start the cruise phase at a lower
altitude. The .072 and .075 size motors easily and quickly will put the model
high up BUT in between the rafters and 50/50 with a good chance of  hang ups or
fatal crash after hitting obstacles.

It will be fun to fly this guy at Eager AZ nats in a few months

https://www.youtube.com/watch?v=EOBikWiF4AY

https://www.youtube.com/watch?v=EQVRq_rk9R0

https://www.youtube.com/watch?v=VzYpMuBOybU

[jim_buxton]

Glad you like it!  John and I dueled it out with ours under the 35'-ish ceiling in the EAA Eagle hangar.  At least a dozen of them were flown during the event. 
John had the best flight with a 3:39, I chased him as best i could with a 3:29, H.G. Frautschy was third with a 3:13.  The mass launch was great, I think we had 13 in the air!
John suffered a midair that took him, allowing me the win.
We were flying 26" loops of about .060.
We had so much fun I did not think to get video, wish I would have!

[jswain]

Glad you like it! ....We were flying 26" loops of about .060.
We had so much fun I did not think to get video, wish I would have!

Thank you Jim and congrats on the win.  
Big thanks on the motor size and length combo info.
This is similar in size to John McGrath's "1st Derivative" p-18 specs last year at Eager AZ indoor nats
which i plan to copy and use for the Big Smash model also in a few weeks in AZ.
I just need to build another one as a spare plane and become an 'official participant'.
best wishes, john s.