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Mercury Aeronca Sedan

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Chris Freeman 327/06/2019 06:40:34
192 forum posts
259 photos

I have started building a enlarged Aeronca as I need to play with some balsa after the composite Mustang and the Cub rebuild as they were not much building as such. I am not sure about the incidences on the plan as the wing is about Zero and the stab is very negative and lots of downthrust. Does this not result in the aircraft flying very tail low which makes it look about to stall most of the time. I prefer a tail high look in flight.

Any ideas?

Denis Watkins27/06/2019 07:06:26
3678 forum posts
173 photos

Some, absolute scale builds, range from very difficult to fly, to unflyable Chris

Have had two high wing builds, over the years, not the Sedan

That had flying horizontal stabilisers

That is, a tailplane producing lift, and these had incidence, that I chose not to build in, but still achieved level flight

Full size would have been another story

A recent visit to view a Police helicopter, surprised me with the machine having an up side down horizontal stabiliser

With the flat side of the flying surface on top, and the curved surface on the bottom, for high speed flight

Peter Miller27/06/2019 08:40:20
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9918 forum posts
1160 photos
10 articles

The Mercury Aeronca Sedan is designed as a free flight model.

The downthrust is at the same angle as the tailplane so the model will fly with the wing at positive incidence. but the aircraft will look as if it is flying level which in fact it is.

They fly very well indeed.

brokenenglish27/06/2019 08:47:33
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427 forum posts
28 photos

The "problems" mentioned in the OP are due to the need for free flight stability.

The Mercury Aeronca Sedan, built as per plan, is a great flier, proven over more than 60 years. You don't need to change anything. It will fly very well as drawn, and look very realistic in flight.

However, using modern RC, if you prefer to change incidences and thrust line to something more conventional, no doubt the plane will still fly well, but such changes aren't a necessity.

Whatever you choose to do, within reason (!), it will be a very easy flier, not very different to a J60.

Chris Freeman 327/06/2019 09:38:03
192 forum posts
259 photos

Thanks for the replies, I will continue as the plan shows. I have enlarged to around 80", should be a nice size.

It just looks very strange on the plan view seeing the incedenses compared to the datum line. I will post some pictures on the progress.

brokenenglish27/06/2019 09:53:34
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427 forum posts
28 photos

Chris, Here's something you ought to see. If you look at this great video. After 6 minutes, there's a Mercury Aeronca Sedan, built exactly as per plan, taking off beautifully, and flying free flight.
It's trimmed to fly in circles and only for a relatively short flight (competition rules), but you'll see it's a superb performer.
Link:

colin wray 227/06/2019 13:28:55
2 forum posts

i have the Phil Smith plan of the aeronca sedan ive put off building it because of the wing mounting Have any of the more expreienced builders got any ideas Any sugestions would be most welcome

Chris Freeman 327/06/2019 13:41:50
192 forum posts
259 photos

Thanks for the link, great to watch. I built a Sportwagon last year and it flies quite well but could have done with a taller fin and rudder. sp1.jpeg sp2.jpeg

Peter Miller27/06/2019 18:21:32
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9918 forum posts
1160 photos
10 articles

If you look at photosof the full size in flight you will notice two things. Those aircraft flying slowly will be slightly tail down. THis is normal for any aircraft as it needs to fly at a higher angle of attck when flying slowly. When flying faster you will see the the tail comes up to a more level position.

brokenenglish27/06/2019 18:28:19
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427 forum posts
28 photos
Posted by colin wray 2 on 27/06/2019 13:28:55:

i have the Phil Smith plan of the aeronca sedan ive put off building it because of the wing mounting Have any of the more expreienced builders got any ideas Any sugestions would be most welcome

Colin, my only remark would be that you're being put off by something that's been working perfectly well for sixty-odd years...
Seems like an excellent opportunity to learn new techniques to me.
Of course, the model has to be built more or less like the original, not heavily modified and tons overweight...

PatMc27/06/2019 23:07:00
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4145 forum posts
518 photos
Posted by brokenenglish on 27/06/2019 18:28:19:
Posted by colin wray 2 on 27/06/2019 13:28:55:

i have the Phil Smith plan of the aeronca sedan ive put off building it because of the wing mounting Have any of the more expreienced builders got any ideas Any sugestions would be most welcome

Colin, my only remark would be that you're being put off by something that's been working perfectly well for sixty-odd years...
Seems like an excellent opportunity to learn new techniques to me.
Of course, the model has to be built more or less like the original, not heavily modified and tons overweight...

This article from Flying Scale Models suggests that the working strut fixings are fine for FF but it's necessary to modify them if converting to RC.

PatMc27/06/2019 23:36:33
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4145 forum posts
518 photos
Posted by Chris Freeman 3 on 27/06/2019 06:40:34:

I have started building a enlarged Aeronca as I need to play with some balsa after the composite Mustang and the Cub rebuild as they were not much building as such. I am not sure about the incidences on the plan as the wing is about Zero and the stab is very negative and lots of downthrust. Does this not result in the aircraft flying very tail low which makes it look about to stall most of the time. I prefer a tail high look in flight.

Any ideas?

The rigging angles of the full size Sedan WRT the datum are : wings +1⁰ (note that's through LE to TE, not the section's flat bottom), the tailplane : -3⁰ , thrust line zero.

IMO the full size angles with a flat section tailplane would make a better RC model than the Mercury plan especially when it's being built to a substantially bigger scale.
It would also look so much better if the fin was covered to fair into the fuselage instead of as a discrete unit.

brokenenglish28/06/2019 06:12:01
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427 forum posts
28 photos

I agree.

Re the strut fixings for RC. That's what I meant by "built more or less like the original", i.e. built using the same techniques, to around the FF weight, and not hugely overweight with a big four-stroke...

Chris Freeman 328/06/2019 06:19:40
192 forum posts
259 photos

Thanks for all the replies. I am building this for our annual vintige meet at the end of July so it is being built as an vintage aircraft and not a scale project so that means the structure will be according to the plan.

Dave Boddington would normally design his aircraft to have a tail high look in flight as he said it looked much nicer, the DB Cub is proof of that as it does the best tough and goes with the tail high. I spent many hours with David and built a few prototypes for him so I like his way of doeing things.

The progress is good and I am enjoying the build so far. Hope to get quite a lot done this weekend as my work does impact my building time during the week.

Chris Freeman 328/06/2019 06:24:49
192 forum posts
259 photos

This is the progress

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Chris Freeman 328/06/2019 06:27:16
192 forum posts
259 photos

I am lucky to have 5 workbenches wich really helps speed up the build, I use mainly Cold glue to build.

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Chris Freeman 301/07/2019 05:53:00
192 forum posts
259 photos

as11.jpgas8.jpgI managed to do quite a bit this weekend, The plug in wings was the most important bit done. I do my best work early in the morning so this was done at 04:00 yesterday! I wanted to use wooden dowls but did not have in stock so I used some aluminum tube and glass fibre rod. The hard bit is to get the angles right with the correct dihedral and no twist in the wings. I used the centre section ribs as a jig and then sharpened the ali tube which was then used to make the holes in the ribs. Once happy with the positions the rods were glued in with epoxy and extra support glued in position. The struts will add strength so it should be able to do mild aerobatics if wanted. Loop and stall turns. as7.jpg

Colin Leighfield01/07/2019 09:41:45
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5847 forum posts
2441 photos

I just watched Broken English’s video, hilarious! I always thought that the Mercury Aeronca Sedan was a beautiful model. Still a Mercury fan.

Chris Freeman 302/07/2019 06:00:26
192 forum posts
259 photos

The cowl is the next challenge, plans show lots of thick balsa which will be very expensive in money and labour as it will take a huge amount of sanding. I decided to make up formers and will sheet with 3mm balsa. The noseblock will be with 2 laminations of 8mm balsa. I also have made a hatch under the fuselage for the undercart and servo access .as10.jpgas11.jpgas14.jpg

Chris Freeman 308/07/2019 06:15:00
192 forum posts
259 photos

The construction is now almost complete, I just have to finish the wing mounting and sheeting on the top of the fuselage. I have done most of the sanding and am now busy with the servo and pushrod installation. The cowl came out nicely and the top is removable.

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