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Aeronca Sedan

Mercury Kit

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Erfolg06/01/2018 15:44:47
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Now that I am coming to the completion of the Coverite Gee Bee, my desire to keep on building has grown.

For some time I have put of building the Mercury Aeronca Sedan. A kit I was aware of when even I was a child. I naturally knew I could build one, even though my efforts with a Frog Minx and a Veron Sea Mew where perhaps not anything approaching good, although a very high mediocre score was achieved, after great effort. Anyway, I had difficulty in getting my parents to buy me a KK Spectre which was expensive enough. Never mind the Sedan.

Many years later I passed on a Mercury Aeronca, being satisfied with my RC Trainer, although the sedan was there at the back of my mind. Then by chance a kit came my way. Even with it in my possession there were other fish to fry.

A change of club, and a realisation that I was not motivated by many of the obvious, that is speed, nor precision aerobatics, has consolidated my self awareness of what i like doing. I pootle around the sky, no great flight plan, I do not care one jot how good my loops, inverted flights etc are, certainly I have no desire to link sequences, I just pootle, enjoy the model flying along.

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As can be seen some of the pictures are pretty much the same, as I took two in the distant past, another two to start the build, not even suspecting repetition.

The kit was designed as FF or simple RC, when RC was more of a title than a reality. When the gear weighed a ton, and enthusiast, convinced each other that gyrations in the air and vertical landings where planned.

On that basis I have started the process of deciding what to do. Originally the kit calls fo a 2.5cc Deisel or similar. The wings were knock of. The wings appear to have dihedral, no ailrons.

My current field more often and not ahs a 10-15 mph wind. On that basis the model must cope with that. No evening light air flying in my operating regime.

I will have ailerons, and no dihedral, as at present the indications are the full size did not have it. I will sheet the wings as the full size was aluminium covered wings with a tubular fuz. I will either use steel round dowels as per glider models, in a two peice wing. Also the knock of wings were defiantly not designed to take a cantilever load, so the spar arrangements will be rearranged to provide graduated strength along the span.

My experience with the Sterling PT19 indicates that marginal power at take of and even during flight, makes for a difficult, nerve jangling experience. So a decent sized motor will be needed. Oh, it will be electric, I have no time for all the frigging about starting, the residual mess after a flight. It seems that the relatively high camber and possibly the thicker wing circa 12% sucks up power (high induced drag).

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Hmm, these are the first thoughts.

Peter Miller06/01/2018 18:46:41
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Some pictures show a very slight amount of dihedral.

If you are sheeting the wing and adding joiner tubes etc and not having calm conditions I think I would go for a 30 four stroke. It might stick out the side a little but it would be ideal power ans would sound more realistic

I had one with an ED Racer but that was standard. Some in the Club had one free flight in Aden and that was a dream out in the desert strip

kc07/01/2018 18:09:32
5285 forum posts
159 photos

Erfolg, have you seen the David Deadman article from Flying Scale Models some years ago about this model? Also the info in BMFA News a year or two ago? Quite a lot of useful info there especially about wing strut improvement.

One of my clubmates built this decades back and still flies it but with electric power now. Following a rebuild caused by strut/wing failure he now has ailerons fitted and very little dihedral. Beautiful flying model.

For anyone else without the actual kit, the plans are still available- see BMFA News (last year or the year before)

Colin Leighfield07/01/2018 18:22:14
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5308 forum posts
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Good one Erfolg, great project for a model I’ve admired since my school days in the fifties.

Tom Sharp 208/01/2018 00:47:18
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2579 forum posts
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I had one back in the 1950's, due to poor building skills the outcome was not good. I think Mercury was a Ripmax brand.

Erfolg08/01/2018 20:49:00
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10617 forum posts
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I do believe you are pretty much spot on Peter. visually there is a hint of Dihedral. I have found a drawing of the Champion where the dihedral is 2 degrees per side.

I will not be using an IC engine, all of my engines are now in retirement. It will be electric.

KC I have not read the article you mention. Although i will endeavour to find it later. For now I am looking at the design from my own perspective, as to what needs modifying, then see what others have done. It is apparent that when kitted and designed these models were flown completely differently. The idea of knock of wings, is very much a large FF idea. The wing reflects this in that the struts were meant to work,. The design of the spars and the plug in arrangements, is pretty light weight, no real acknowledgement that there varying bending moments with the stresses distributed through out the wing. It could be that a flexible wing was seen as desirable.

Looking at the TE, it is not an arrangement that I like, in that I built a glider with such an arrangement, where the TE warped with age. Also it probable does not obviously lend itself to having ailerons. I keep reminding myself, that FF models took of, by a number of low level circles, at pretty low speed, slowly gaining height, whilst we all ducked and dived whilst admiring a few minutes of flight, whilst chasing down wind, negotiating fences, running around hedgerows and so on, as the model departed our field. Although not seeing much RC in the 60s, what I saw did not really impress, in that control was any where near the order we have today.

I do not really know who actually owned the Mercury brand, although I thought it was a Henry J Nicolls or some one else in London. Perhaps Ripmax just acquired the assets at some point.

Like many at the moment time is nor as freely available as I had hoped, as i am busy doing work for others.

Manish Chandrayan09/01/2018 13:57:26
330 forum posts
50 photos

From what I understand Mercury brand was indeed owned by HJN. Aurora of India had rights to kit the Mercury models in India, and initially were even selling the UK made Mercury kits.

Have one of the much later Aurora produced Mercury Sedan kit stashed for that maybe one day project

Erfolg09/01/2018 15:18:40
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10617 forum posts
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Being busy, does allow you to ponder in those quieter moments, or is that boring , but must continue moments.

I have been thinking a bit more as to how many FF types were flown. Unlike RC models, particularly contests RC Gliders, a wide speed range was not required. I imagine that what really was wanted was a model that self regulated its airspeed. In that if starting to go a bit fast, or perhaps diving/zooming. the drag increased limiting speed, tending to bring back to a normal airspeed. In a similar manner, if the model slowed, the profile encouraged a general mushing, at worst in a stall a self regulating recovery.

Looking at the airfoil used, it is 13%, pretty chunky by todays RC standards. Also the the LE is pretty low, with apparently a quite high camber line. As you would expect a really well rounded, large radius LE.

I have just printed out a E205 for comparison. It is very obvious that the LE is much smaller radius, although well rounded and much higher set. At 10.5% is a bit thinner. I have used E205 widely on gliders and quite a few power models, finding it generally very good. I will try and find the section that TH used on the Clean Sweep as that also works well, I think it is E387.

It does seem that the wing does need a dose of looking at for our present general way of operating. Perhaps an anathema to vintage buffs, to todays modellers perhaps almost a necessity,

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This photo perhaps says far more succinctly with respect to the various airfoil sections than I can write.

Edited By Erfolg on 09/01/2018 15:19:25

Edited By Erfolg on 09/01/2018 16:26:38

PatMc09/01/2018 16:57:03
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The full size Sedan used NACA 4412 airfoil - i.e. 12% thickness.
BTW I've seen a factory GA drawing of the Sedan giving the dihedral as 1° each side, other drawings show the Aeronca Champ & Chief dihedral as 2°.

David Ovenden09/01/2018 18:02:19
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Built one of these in the early 80's for 3 channel rc. I used a Fuji 25 schneurle ported 2 stroke glow engine. Wing was built in one piece (incorporating the fus centre section) with ply dihedral braces. Wings were sheeted at the LE with webbing on the spars to form a D box structure. Struts were hinged at the wing and had quick links to connect at the fuselage. Wings were covered in Solarfilm and fuselage in Solartex and paint.Other than that it was built much as the kit.

It had plenty of power and flew nicely enough in an "old timer" sort of fashion, but would have been better with reduced dihedral and ailerons as you propose. In the end I sold it on as it wasn't very exciting when compared to my Graupner Middle Stick with its HP40!

Graham R09/01/2018 18:08:13
238 forum posts
6 photos

We have one flying in our club. It has been enlarged to around 120%. It flies very well with a small brushless motor. I’m very interested in your build especially the fitting of aeilerons as I have the plan sitting on my todo list.

Erfolg11/01/2018 15:00:22
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10617 forum posts
997 photos

The feed back is very useful.

I have printed out NACA 4412, in addition to to the Eppler sections.

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I have to say that NACA 44i2 looks a far better bet than the section used in the kit. The most obvious difference is the massive LE radius in the kit, then this is followed by the camber which i will measure, the last aspect is the thickness of 13% kit, 12% Naca 4412, 10.5% with E205. It is interesting that the camber with the NACA is higher than Eppler although 10% further back (when compared to E205), reminiscent of many of the laminar flow sections. As I never achieve anything approaching accuracy, laminar flow or a true profile is a pipe dream with me.

It will be a toss up between NACA 4412 and E205 (which i favour as I know it works well).

Patmac, can you point me towards a good picture of the plan of the wing, as the drawings I have come across suggest approx 50% of semi span, stopping just at the wing tip. It is the aileron chord i am keen to fix on. I do appreciate that most drawings are thumbnail, prone to significant differences from the full size, due to line width, just slight variation on line placement etc.

Erfolg11/01/2018 16:40:38
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10617 forum posts
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I have just done the measure and calc on the kit camber which is approx 4.7%, I could nudge it up to about 5%, dependant on how i placed the Nose and more variable TE. It is perhaps what I thought, ball park wise. The max camber is probably just less than 30% point. A much larger change in rate ( the tangential slope) of the velocity than is the case for many of the more popular airfoils that I am familiar with (which in reality is not many, just fashionable).

I am pretty much decided that a more fashionable airfoil will be used. Principally just because these older kits I have built seem to be more a one speed affair, without a lot of power being used. Although I am amazed how stall resistant my Nobler with a NACA 0012, rather than the original 0018 is. Its leading edge is very large radius.

PatMc13/01/2018 23:24:02
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Posted by Erfolg on 11/01/2018 15:00:22:

Patmac, can you point me towards a good picture of the plan of the wing, as the drawings I have come across suggest approx 50% of semi span, stopping just at the wing tip. It is the aileron chord i am keen to fix on. I do appreciate that most drawings are thumbnail, prone to significant differences from the full size, due to line width, just slight variation on line placement etc.

I've had the Replikit short kit stashed away waiting it's turn to be built for some time. In anticipation of bulding it I did some research online & found an Aeronca factory dimensioned GA drawing [IIRC it was in copy of an old sales brochure]. I copied the drawing & stored them with the kit. Unfortunately the kit's in the loft & for the time being not readily accessible. However I later came across a copy of the same GA drawing within one of two or three plans of model Sedans that are held in Outerzone.co.uk. A quick search & browse through these should get you what you're looking for.

PatMc13/01/2018 23:39:34
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Posted by Erfolg on 11/01/2018 16:40:38:
Although I am amazed how stall resistant my Nobler with a NACA 0012, rather than the original 0018 is. Its leading edge is very large radius.

A blunt LE causes the point that the air seperates to vary as the AoA is raised [or lowered]. In effect the AoA lags behind the angle that the wing is raised by.

Graham R14/01/2018 10:01:29
238 forum posts
6 photos
Posted by Erfolg on 11/01/2018 16:40:38:

I am pretty much decided that a more fashionable airfoil will be used. Principally just because these older kits I have built seem to be more a one speed affair, without a lot of power being used.

You are absolutely correct with the flying characteristics. The one in our club as mentioned before is some 120%(wingspan is around 78" 3 channel. Flies on a 2820/10 with very little throttle. Perhaps that is the charm of this great model.

Peter Miller14/01/2018 12:44:24
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Basically it is a free flight model and a superb one at that.

Needing something just to occupy my time I am toying with the Aeronca Sedan from Vintage kits. I would definitely stay with the original section but make it a one piece wing and add ailerons and an SC 30FS

I see no need to change the section at all.

PatMc14/01/2018 14:18:56
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I see no reason to change the wing section. The full size would have been flown at one speed apart from landing approach & take off anyway.
The mods I intend are ailerons, fully sheeted wings with scale dihedral, flat plate taiplane & scale thrustline. Might go for one piece wing as well.

Erfolg14/01/2018 15:01:26
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10617 forum posts
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From your input Patmac, the model uses a very different section to the full size of (Naca 4412). which I have no reason to doubt.

I do expect my models to fly in a 10 up towards the 20 mph. That is without using large amounts of energy or power.

In many respects I see no issue with plug in wings, as model RC gliders use, again as the original full size were bolted on. This is apparent when looking at what drawings are available at full size. Having said that, I have been considering a one peice wing, from the simplicty point of view.

With respect to my Nobler with the Naca0012 wing. I have been very surprised at the apparent AOA that can be reached, at slow speed, with no hint of a stall. The downside is, the model is pretty much one speed, whatever it is doing. A speed machine it is not. Building one again I would do Naca 0010. Which I think I used with my Pushy Cat, a really good turn of speed, with good low speed handling.

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Nothing is as yet set in stone, although I do like a nice handling model, with a good speed range.

Peter, a number of people have said at the club, it is a pity that your Cassut (that is your design electrified)is so small, at twice the size it would be great. Again because it flies and looks really well.

PatMc15/01/2018 13:42:43
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Posted by Erfolg on 14/01/2018 15:01:26:

From your input Patmac, the model uses a very different section to the full size of (Naca 4412). which I have no reason to doubt.

I do expect my models to fly in a 10 up towards the 20 mph. That is without using large amounts of energy or power...

...Nothing is as yet set in stone, although I do like a nice handling model, with a good speed range.

The same aerfoil on a full size will perform very differently with a model.

I'd say whatever section you use the Sedan isn't going to meet the above requirements unless it's built much heavier than designed & the stucture beefed up to take the increased stresses. The operating speed range will always be fairly narrow so it would fly more like a WW2 fighter than a light touring aircraft.

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