Covering tailboom on Affodaplane?

Discussion in 'The light stuff area' started by ChuckyJeager, Nov 14, 2006.

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  1. Nov 14, 2006 #1

    ChuckyJeager

    ChuckyJeager

    ChuckyJeager

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    So the website says that covering the tailboom part of the fuselage would impart undue stress on the airframe that it's not built to handle.
    Well I'm not sure how well I like that. I'm sure you could do some simple cable based reinforcments. I'd like to make an enclosure out of some aluminum tubing and clear vynil for a bushplane look.
    So saying that I reinforce where needed, and cover the tailboom, do you think the flight characteristics would be altered? I think if at all, it would be minor, and I'm finding it hard to believe it would hinder anything.
    Any input? What are your thoughts?
     
  2. Dec 6, 2006 #2

    mstull

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    Chucky,

    Everything in aircraft design is a compromise. On a true, Part 103 legal U/L, light weight has to take priority in most of the compromises. You're right, covering the tail boom won't hinder the aerodynamics. It will actually help, both by decreasing drag, and by adding some side area that helps the vertical stabilizer and rudder keep your plane yaw stable.

    The covering the web site talks about is dacron fabric, that when heat shruk, pulls extremely hard. That would tend to bend in your frame. Cable bracing would not help this problem. But you wouldn't have to beef up the structure if you covered it with a different material that doesn't pull so hard.

    I wouldn't recommend using clear vinyl. It is heavy and/or weak, depending on thickness. Hobby stores sell iron-on coverings (Super Monocoat) for R/C planes in all opaque and translucent colors and clear, that are extremely light and well proven. I don't think it's strong enough to cover aerodynamically essential parts. But it could last a while on your tail boom. And it's easily repaired or replaced.

    Covering with anything else could add enough weight back there to move your CG back enough that you'd need other modifications to compensate.

    I'm not trying to discourage you from covering your tail boom. I would probably seriously consider covering it myself. Let me know how long Super Monocoat lasts back there, if you end up using it. I have a little on my U/L just for visibility. I'm using the opaque, chrome color.
     
  3. Dec 6, 2006 #3

    Nilsen

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    This is from the affordaplane FAQ.

    Can you cover the rear of the fuselage with fabric?

    Answer: The short answer is no. Covering the rear fuselage adds weight, and during maneuvers such as a slip to landing, imposes stresses on the frame it was not designed for.


    Chucky, I know you quote that in your question but in my eye it's very important to heed that advice. If covered, that tail boom will be too weak in a cross wind kind of situation. I'm no expert but if you want a covered tail I'd say find a ship that is designed with a covered tail. As mstull mentioned, aircraft design is a compromise. Any simple reinforcing you do will add stress to another part of the plane so that in turn that part where your have transfered new loads to will need to be reinforced. It's a domino effect.
     
    Last edited: Dec 6, 2006
  4. Dec 6, 2006 #4

    mstull

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    Chucky,

    While Nilson's "domino effect" is something to consider... I doubt that it applies in this situation. The side loads on the tail boom from covering it, won't increase the total side load of the vertical stabilizer, rudder and tail boom combined. It could even decrease it by making your plane more spin resistant.

    I would have to see photos of your frame before covering, to be definitive. Many U/Ls are designed to be extremely spin resistant, to save the weight of making the structure strong enough to withstand spins. This is usually accomplished by making the empennage surfaces amply large and far enough aft that they have good leverage. That's how I designed my U/L.

    I had a nice flight today. I'm glad I moved to Texas where winters are short and mild. I've started my next project... a self-designed, semi-aerobatic, U/L biplane, with direct drive pusher engine.
     
  5. Dec 7, 2006 #5

    Peter V

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    If it's just for cosmetic purposes, then there's no need for the la-dee-da poly/vinyl/ester/blah blah stuff. Too heavy, too stiff.
    A pound of nylon fabric stretched and sewn over 9 feet of tail boom would hardly add weight - just don't paint it. Microfibre would be better as it repels water, but I can't find any in a camoflauge design :gig: (would you fly in the rain anyway?)

    I mean the designers arn't fussed about what engine you use, and isn't that a source of far greater CG and weight consideration?

    As for stresses? What the ????

    You'd be able to lay a boot into that tail without causing any undue stress, it would have more flex than a Vegas showgirl.

    Look at the surface area of that section, 9 by 3 feet? the amount of wind it would take for it to be a problem would be too much wind for an ultralight friendly flight in the first place.
     
  6. Dec 8, 2006 #6

    ChuckyJeager

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    That's pretty much what I was thinking, but I 'm just wanting a few more opinions.

    My goal is to enclose the whole plane, and have that bush plane type look to it like I mentioned above.
    I was brainstorming (my 3 braincells got into an argument) and came up with he idea that, hey, I'm not going to fly this on an overly windy day. I'm going to use the best quality aluminum. I'm going to beef up the airframe as it is, reinforcing wherever I see fit. If I come out a few pounds over the limit, that doesn't really concern me. I drive 5mph over the speed limit too on most occasions. :p:
    Besides, it'll have a ballistic parachute ;)
     
  7. Dec 8, 2006 #7

    Topaz

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    I think this subject has been discussed more than once here, so a search might be a good way to get even more opinions, already expressed earlier.
     

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