Aeronca Sedan

[Erfolg]

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.

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).

Hmm, these are the first thoughts.

[Peter Miller]

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

[kc]

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 Leighfield]

Good one Erfolg, great project for a model I’ve admired since my school days in the fifties.

[Erfolg]

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 Chandrayan]

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

[Erfolg]

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,

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

[PatMc]

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 Ovenden]

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 R]

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.

[Erfolg]

The feed back is very useful.

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

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.

[Erfolg]

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.

[PatMc]

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.

[PatMc]

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 R]

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 Miller]

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.

[PatMc]

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.

[Erfolg]

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.

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.

[PatMc]

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.

[Erfolg]

Patmac, I thought I had mentioned that it is my intention to alter the wing structure quite extensively.

The spar arrangement on the original kit, is not dissimilar to what would be found on a Rubber or towline glider for the period. A single 1/82* 5/16" balsa strip for the upper (compression spar) and couple of same size strip on the lower side (in tension). From a structural point of view not what I would have expected, as I would expect the wing spars to be liable to crippling, as it is the wing ribs that lend all the resistance to the crippling forces, no bout it was found that that form of construction was warp resistant, or that any warps forming were favourable (washing out).

My intention is to form a "I" beam of 3/8" or 1/2 spruce spars top and bottom, separated by shear webs to resist crippling. Fully sheeting the wing will also considerably improve the wing strength. The weight increase I expect to be pretty modest. If I use brass and drawn wire rods to join, I think that will be more significant, especially the changes to distribute the bending forces into the root structure.

I know that the Eppler 205 section works really well at both slow speed and quite high speeds, loosing little in altitude. However I will think of the wing loading to ensure that it is not unacceptable. I have used it with wing loadings from 9oz ft-^2 up to 15oz ft-^2( ballasted).

No decisions have been taken yet, mainly due to demands on my time. I need to access how 2" triangular TE stock will fit in, also commercial LE. Then be better positioned to see how it all looks.

The one thing i have found with most kits (the sort I buy) that at best they are pretty approx. In the case of the Balsacraft Fw190, the wings were at a totally different scale to the body, In the case of the Sterling PT19, the tailpalne is massively oversize, I did not check the wing.

In the case of the Sterling kit, RC was basic rudder, pretty much as I think the Sedan was, when designed. Both designers I suspect tried to design models, that flew well, inspite of the person controlling and the limitations of the RC equipment and engine (single speed).

[brokenenglish]

Respectfully, I'm always amazed when builders take a super old model, that's been flying perfectly well for decades, and decide, for no clear reason, that the plane is "liable" to all sorts of problems (that no-one has ever experienced), and therefore needs to be extensively modified.

IMO, the Sedan built exactly to plan, with minimum mods for radio, and a PAW 15 or 19, would be superb.

With a competition glider wing section (!), you're going to end up with a high-speed powered glider. There must be other designs that are more suitable for that kind of flying.

Sorry, please don't take offence, it's only my opinion!

[John Bisset]

Lovely easy handling machines, Aeroncas.

Speaking as the owner of a vintage Aeronca - a Champion rather than a Sedan - the earlier comments about handling and speeds are broadly correct. The wing section of the original provides a tractable, easy handling aircraft with excellent low speed characteristics for short landings. The useful speed range is small, like any relatively low powered aircraft of its era with the wing sections of the time.

I also have flown modern section sailplanes and motor gliders; with much higher performance, they are also more likely to bite if mishandled.

It will be interesting to see what the results of your modifications are, though it will not be a Sedan !   (Personally I'd start afresh rather than modify the kit, but each to his own - I wonder if the changes will make the model more sensitive near the stall? )

Around 2 degrees of dihedral is right for a Champion by my memory of the drawings.

Edited By John Bisset on 15/01/2018 21:55:05

[PatMc]

Erf, ff the kit's unstarted, IMO the best plan would be to carefuly repack all the parts in the box after taking a few good photos then put it on Ebay. It's a highly desirable item as it is & would probably fetch enough to finance two of the kind of model you want.

[Erfolg]

Brokenenglish.

if the site I fly at was more often than not subject to a wind speed that is probably in excess of 10 mph, a slow flying high drag type section would not probably be an issue. Or if I was able to allow the model to fly downwind, as the FF models does.

I need a model that going upwind will need an airspeed of at least the wind speed + 5-10 mph, relative to me on the ground. That is so I can see and make progress in a circuit.

Going downwind is much the same, now it is the wind speed + stall speed (by some margin), just to keep the model flying. It probably will look fast.

However I have been thinking I can always build both type of wing.

Patmac, I have done very little so far and not touched the kit. In some ways it is tempting to sell the kit. Yet at the end of the day, is there any value in a kit sitting on some one elses shelf? Money is not everything, although I do prefer to have some.

I did have to alter the Sterling Kit quite extensively, to make it viable as an everyday RC model. It is a little nearer the full size in that dihedral is as near scale as I could make it. I added ailerons. Sparred using standard engineering type arrangements and sheeted the wing (as full size). Also changes were required on the UC, although initially I got this wrong, trying to adopt something nearer to the kit. Now is standard RC type blocks in the wing. Where I failed is that the ball park 100w per ib, was not enough for safe flight. The drag forces from the thick wing never allowing the model to get far from the statl. Re-motoring to 150 w per lb has resulted in a good flying model through the complete flight envelope, yet does not look excessively fast, when compared to similar sized trainers.

I may put it to one side for now.

Edited By Erfolg on 18/01/2018 14:00:31

[brokenenglish]

Yeah, but as PatMc and myself suggested, if you're looking for a tough all-weather model with a fairly high airspeed, then a vintage free flight Aeronca Sedan may not be an ideal starting point.

The beauty (charm) of such models is that they're light and fly slowly (around scale speed), and are both aesthetically pleasing and relaxing to fly. Your proposed mods will destroy all that, and bring you back to the conclusion that you've picked the wrong model for rough weather, high speed flying.

Only my opinion of course, but I think you'd be disappointed with the result and you'd completely miss out on the real qualities of the model.