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Old Oct 08, 2012, 04:13 PM
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United States, GA, Centerville
Joined Mar 2012
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Question
Micro Telemaster Dihedral

So...I''m building my Micro Telemaster and I'm tot he point where I'm about ready to join the wing panels. Nowhere can I find a the diheral specified in terms of an angle or, the more traditional method, a measurement of one wingtip above the board when the opposite panel is held flat.

I'm built according to plan and canted the inner ribs so they lined up, tot he best of my ability, with the angle of the end of the spar per instructions. Howver, when I hold the panels together, the angle doesn't at all look like enough for a three channel plane.

Common sense and experience tells me that the optimal angle is less the longer the span (more moment) so my Super Cub LLP has less dihedral than my Champ. I've built lots of free flight planes in the past and I could estimate. But I figure that's what forums like this are for; to share experience.

So, if any of you reading this have built your Micro Telemasters, can you plaese share the measurement of your dihedral. Place one panel flat and measure to the bottom of the tip where the slanted tip rib meets the first vertical rib. It would be interesting, if several people could make this measurement so we can compare them.

Thanks,
RR

P.S.
This is the Micro Telemaster V2
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Last edited by RayRangel; Oct 08, 2012 at 05:59 PM.
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Old Oct 08, 2012, 05:28 PM
Reduce the drama...
rick.benjamin's Avatar
USA, OR, Damascus
Joined Apr 2004
4,044 Posts
"the wing joiner sets the proper dihedral"
http://www.rcgroups.com/forums/showthread.php?t=882100
The thread suggests mods to prevent wing warping.
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Old Oct 08, 2012, 05:53 PM
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United States, GA, Centerville
Joined Mar 2012
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Thanks Rick, but this is the Micro Telemaster V2. It doesn't have a "wing joiner". It has a ply rib that extends below the wing and hooks into a bulkhead forward and magnets embedded aft in the trailing edge. The land gear is mounted differently; it's detachable and has provisions for second set of aft legs for mounting floats.

The wing has diagonal ribs between each whole rib. This feature makes for an extraordinarily strong wing. This looks like it's a much upgraded kit from the one in the thread that you referenced (2009). This kit is going to be much heavier than the original version. The weight migh help in the wind though and extra bracing will definitely help prevent warping during covering.

Still looking for that dihedral measurement just as a verification that the angle is, at least, close to correct.
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Old Oct 08, 2012, 06:09 PM
Texas Buzzard
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McAllen,Texas
Joined Mar 2004
1,034 Posts
Comment on dihedral

It's a rudder/elevator plane so you need some dihedral - you NEED dihedral.

If in doubt for a low wing plane use at least 7 dgrees under each wing tip just to be safe. On a high wing ship use about 4 degrees in each panal at the tip.
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Old Oct 08, 2012, 06:51 PM
Reduce the drama...
rick.benjamin's Avatar
USA, OR, Damascus
Joined Apr 2004
4,044 Posts
http://www.rcuniverse.com/forum/m_10...m.htm#10996302
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Old Oct 09, 2012, 07:09 AM
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United States, GA, Centerville
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Ok, using this handy tool; Right triangle calculator, I did some estimating.

As built, the wing (measured with opposite panel flat and from root to the bottom of the last rib) has only about 1". The length of the panel from root to last rib is 16.75". Plugging these into the handy-dandy calculator yeilds 3.42deg which, of course has to be divided by two since the opposite panel is flat, yeilds only 1.71 deg. Way too small.

Looking at some other plans that I have, the dihedral angle looks to be between 4 and 6 degrees (where did I leave my protractor). So, given that range, it looks as though the measurement, performed as above, at the tip rib would be between 2.34" and 3.52". Splitting the difference results in 2.93. Erring on the side of caution, rounding up would seem to make sense, so 3" is the final number.

Now reversing the process to check the angle results in 5.14 degrees of dihedral. So now the question is whether 5 degrees sounds reasonable.
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Old Oct 09, 2012, 06:15 PM
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So I wrote in to Hobby Lobby this morning and got a response very quickly! Kudos to Hobby Lobby for excellent customer service!

Anyway, the official Hobby Lobby answer is 3".

That, as I said in my prevoius post, puts the Micro Telemaster right in middle of the dihedral range (approx 5 degrees) of the range of models that I used for reference.

Interstingly enough, I asked a couple of aero-engineers at work (I work with aero, electrical, mechanical engineers -- and I'm a software engineer -- in a large aircraft program) how one derives the optimal dihedral for any given plane. Let's just say that this is a simple question without a simple answer. Unfortunately there was no time to go into it today--hopefully tomorrow, though I'll get some answers. But as far as the OP is concerned, question answered. Now I can get on with building my plane.
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