Mercury Aeronca Sedan

[Chris Freeman 3]

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 Watkins]

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 Miller]

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.

[brokenenglish]

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 3]

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.

[brokenenglish]

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 2]

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 3]

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.

[Peter Miller]

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.

[brokenenglish]

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...

[PatMc]

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.

[PatMc]

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.

[brokenenglish]

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 3]

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 3]

This is the progress

[Chris Freeman 3]

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

[Chris Freeman 3]

I 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.

[Colin Leighfield]

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 3]

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 .

[Chris Freeman 3]

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.

[Chris Freeman 3]

Most fabric aurcraft have a ver distinctive fuselage to fin fillit that is all done with covering which I hope to do in Solartex.I have used balsa to build up the around the stab to supprt the covering.

[Chris Freeman 3]

Started covering, using some very old blue Solertex with newer Antique on the fuselage as I wanted to ensure better Adheasion and shrink. I diid use some Oracover Stick adheasive to help keep the covering in position. I will use 2 coats of Nitrate dope and then paint with 2k paint. The spats are made but only one sanded so far. I am very pleased with the way it looks so far.

[Chris Freeman 3]

The wing center section was fully sheeted and the real one has stringers so I used the balsa craft trick and added masking tape under the covering to simulate the stringers.

[brokenenglish]

That's everso slightly superb. Lovely model.

[Chris Freeman 3]

The Oldtimer meet is on Sunday so I have had to push to try and get the aircraft finished. Struts were made from 6mm x 20mm obeche sanded to shape with ali plates for attachment points and then covered with Solertex. The spats were also covered and then the whole airframe given 2 coates of Nitrate dope. The spraying was done outside and as luck would have it it was one of the coldest and windiest weekends of the year! The fuselage was given a coat of Sits Polly spray wich was used to give a even color for the blue. The blue was left over from the Mustang and is a 2k paint to covers very well. I spayned this on Saturday. Sunday morning was spent masking for the white and I noticed that the paint was lifting with the tape, not a good sign. I was going to spray the wing registration but decided against it due to this.

The White was sprayed and then the long anxous task of removing all the tape. I had a few areas that the paint was lifted and had to gently paint them with a brush. Lucky this is an Old timer and not a serious scale project. A mate gave me some matt plastic which looks good and hides the empty interior.