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Author Topic: Hergt Monoplane  (Read 415 times)
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DavidJP
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« on: August 11, 2019, 06:55:00 AM »

I thought I would build this Mooney design to replace one of my other models when it can no longer bounce off walls, as it is rather cute and should not take long...... I hope.  Looking at the plan the washout at the tip seems enormous and looks somewhat unreal.  I propose to reduce this considerably.  Could I have your opinion please as to whether or not the amount shown on the plan is necessary.  It is almost 1/2 an inch at the tip. I have a fair idea of the purpose of washout of course but it does not look a particularly unstable model. The CG is quite well forward.
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Hergt Monoplane
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FreeFlightModeller
Russ Lister
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« Reply #1 on: August 11, 2019, 07:13:10 AM »

You'll do as Mr. Mooney says ... or you will be sat on the naughty stooge!  Wink

I think Tim Horne might be someone to ask?
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Tim Horne
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« Reply #2 on: August 11, 2019, 08:04:18 AM »

Hi David, I built the Hergt monoplane about ten years ago and it has been my best ever peanut for flying. It required almost no trimming and has flown consistently ever since.
I just had a look to see what the wings look like now. I don’t remember how much washout I built in originallly but now the starboard wing looks like it has about 3 or 4mm. The port wing appears to have developed washin instead, and instead of 1/2” dihedral which I think is what Walt suggests on the plan, my model wings have drooped to a definite anhedral!

And it still flies like it’s on rails! Smiley Cheesy
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Tim Horne
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« Reply #3 on: August 11, 2019, 08:22:53 AM »

Here are some pics to show you how decrepit it now looks Grin.

And this is a vid of it flying at Clayton Green seven years ago. Launched by Pete Newsom so I could film it.

https://youtu.be/ArzRmAs9Wl4

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DavidJP
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« Reply #4 on: August 12, 2019, 02:51:32 AM »

Stop picking on me Mr Lister!

Tim, I am most grateful - gosh I reckon even I can get it to fly watching that video!!  The washout on the Mooney plan must be 10mm or thereabouts and I think will look a bit odd even though I am not intending it to be a proper scale job - photos etc. like hens teeth!   Otherwise the dihedral will be as it and looks OK I think on the model but most interested to see yours is so steady.  Do do something though about the anhedral - it does look rather sad!

Thanks again. 
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Russ Lister
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« Reply #5 on: August 12, 2019, 10:23:25 AM »

Sorry   Roll Eyes

Yet another model on the wish list!
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« Reply #6 on: August 12, 2019, 10:41:27 AM »

In case you haven't seen this video of Tim's. A bit colour cast.

https://youtu.be/nT_z69wtJDs
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Pete Fardell
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« Reply #7 on: August 12, 2019, 12:26:07 PM »

Or this one...  https://www.youtube.com/watch?v=0euQILvnUOM
It gets about a bit!
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DavidJP
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« Reply #8 on: August 13, 2019, 04:58:06 AM »

Thank you all very much!  I feel somewhat apprehensive - what if mine does not fly like that?  Anyway have reduced the washout and that looks better.

There is little documentation on the fellow - only one was built and it was a flop.  Various descriptions of the finish - “brown” all over because whole airframe was ply covered which might account for it being sluggish.  Don’t fancy that much anyway.  It does not appear to have had any rigging either so assume the “frame” is to protect the pilot in the event of a bad landing. A photo I have seen suggests a ply covered fuselage and plain fabric covered wings and tail/fin. But not too fussed and doubt will enter any scale event of any note. It might be good for a “mass launch” though?
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ChrisH
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« Reply #9 on: August 13, 2019, 09:13:01 AM »

'German Aircraft of the First World War', by Peter Grey and Owen Thetford, published by Putnam 1962, shows a brief description on page 434, and has a rear 3/4 photo credited to Alex Imrie.

Included in the description..."designed and built as a private venture by F.D. Hergt during 1918 and flown by Mario Scherff.   Of interest are the ply-skinned wings, which medium also covered the fuselage.  The sturdy crash pylon is also noteworthy.   Engine 80 hp Gnome, Span 6.0m, Length 5.2m, Speed 125 kmh, Armament none."
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Tiger Tim
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« Reply #10 on: August 13, 2019, 10:33:07 PM »

I read that end-on view of the wing as not being washout but just a depiction of how the end of the wing would look given the planform.  Look at it this way: the trailing edge is longer than the leading edge so when you take into account dihedral the end of the TE will be higher than the end of the LE even if there were no washout.
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Jack Plane
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« Reply #11 on: August 14, 2019, 07:01:07 AM »

Well observed Tim.

I'd still add the usual amount of washout - which isn't shown in the side elevation.
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