How Strong Should a Model Plane's Spar Be to Survive Mid-Air Collisions?

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Discussion Overview

The discussion centers around the construction of a model plane's wing spar designed to withstand mid-air collisions during combat flying. Participants explore the necessary strength of the spar, considering the materials involved and the dynamics of impact between two model planes traveling at high speeds.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant, goony, seeks to determine the required strength of a carbon spar for a wing made of EPP foam, specifically for impacts at 50 mph.
  • Goony proposes that two objects colliding at 50 mph is equivalent to one object hitting a solid wall at 100 mph, but expresses uncertainty about the calculations involved.
  • Another participant suggests that the design of the wing should be optimized for combat, referencing various models and their characteristics.
  • It is noted that if both models are similar in size, the impact dynamics may not differ significantly from a crash into a solid wall, but larger size discrepancies could alter the impact experience.
  • Goony clarifies that the models are powered by methanol engines and are designed to engage in streamer cutting, which influences the wing design.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the exact strength required for the spar or the impact dynamics involved, indicating that multiple views and uncertainties remain in the discussion.

Contextual Notes

Participants have not fully addressed the absorption characteristics of EPP foam, which may influence the impact force calculations. There is also an assumption that the impact area is uniform, which may not account for variations in wing design and size.

goony
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Hi all I fly model planes in combat and need to build a wing that will withstand a head on impact! I am going to use epp foam to form the wing and a carbon spar
the foam will be cut at the spar line and the spar will be a H rotated 90deg so that the foam slots in either side
what I need to know is how strong do I need to make the spar

so its 2 objects both traveling at 50 mph impacting on a surface area of 1 inch
I assume that's the same as 1 object impacting an imovable object of 1 inch at 100 mph
but that's all I know as I am a rather thick so if you could tell me the answer and also explain the calculation Id really appreciate it

kind regards goony
 
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please ignore the absortion of the epp foam i just need to know what the impact force would be

regards goony
 
The closer the model is to a "combat" wing, the better the chance of survival. The "classics" are getting harder to find:

http://www.zagi.com
http://www.fatlion.com/sailplanes/boomerang.html

The newer ones are still around:

http://www.combatwings.com/catalog/product_info.php?cPath=22&products_id=32&product_name=Ready%20to%20Fly%20XL%20Slope%20Glider

Link to videos (plenty of these at other web sites as well):

http://www.combatwings.com/catalog/video_electric.php

Also note that if the two models are virtually identical then a 50mph head on isn't much different than a 50mph crash into a solid wall. If one of the models is much larger, then the smaller model starts experiencing the effects approaching a 100mph crash into a solid wall.
 
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Hi these arnt gliders they are powerd by 30cubic inch methanol engines and we attatch a 30ft streamer to them the idea is to cut the other streamers but midair impacts are quite common and we use a straight leading edge to snag streamers if they were swept back the streamer would slide off
the wing will be 6ft span and made from EPP foam the opposition are 4ft and made from correx

goony
 

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