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Author Topic: Comet Aeronca Chief 54" rubber  (Read 7740 times)
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mick66
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« on: April 14, 2014, 02:23:02 AM »

Hello

I'm thinking of building a Comet Aeronca Chief ... the big 54" kit.  I've got no real experience of rubber models at ths size and type.  I fly a Dynamite in mini vintage - badly.  Anyone got any tips on ths one.  The kit wood is like teak.  I figure the plastic prop needs to go.  Maybe replaced with approx 17" x ?.  How much rubber would you squeeze into ths to get a good duration?

There is some chat in forums but mainly about converting to electrc RC.  I want to keep it FF rubber.
i'm sure there was an article in AM a good few years back about similar recomendations.

Any suggestions welcome.

Cheers

Mike
« Last Edit: April 14, 2014, 02:39:10 AM by mick66 » Logged
gossie
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« Reply #1 on: April 14, 2014, 02:32:43 AM »

Choose your own light wood and follow the plan.

I reckon about an 18 to 20 inch carved balsa prop would suit it with about 100 grams X 16 strands of 1/4 rubber to have it fly well.
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billdennis747
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« Reply #2 on: April 14, 2014, 02:37:08 AM »

I recall an article in Aeromodeller by Brian Faulkner, I think, about 25 years ago.  I had the kit but thought better of it. Is it one piece? It would be a handful and not many weather opportunities to fly it in the uk. One thing I remember is that it had no incidence and Brian discussed this. I'll have a look when I recover from the indoor nats. Or is it for kit scale?
Yes the prop must go.
Don't you just hate it when people try to put you off!
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mick66
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« Reply #3 on: April 14, 2014, 02:47:52 AM »

Hello

yeah ... I know ... the weather in the UK is a right pain.  Added to the fact that with the loss of Fenton and now Barkston its a nightmare getting to anywhere decent to fly from 'up North'.  I'll dig out the AM article ... couldn't remember how far back it was.  I just want to build it as per the kit ... unless with a mod or two it woud be useful for low key scale comps of any kind. 

I thought I'd get some experience in on big rubber models with ths one as, after a few pints on Saturday night, I ordered a short kit of the Al Lindberg Ta152.  Don't ask why but one click ecommerce and lager don't go well together ... according to the wife!

Any more suggestions on the Aeronca welcome.

Cheers

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DHnut
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« Reply #4 on: April 14, 2014, 06:48:24 AM »

Mick,
       There is an article in Aeromodeller by Doug McHard on these large rubber models and what is needed to make them into flyable models. He used the Burd Rearwin as an example. The Bob Jones plan of this has the mods. I believe this plan is available from Mike Woodhouse. There are definitely some changes needed to the structure to make a flyable model.
Ricky
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Megowcoupe
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« Reply #5 on: April 14, 2014, 10:44:20 AM »

Hi Mick

A few decades ago (ahem) I built the Comet Taylorcraft in this size.  Here's my hazy recollections...

Weight- ~8 oz.  Prop- 14" (not hazy, I still have it- P/D probably 1.3) rubber- probably 3 loops of 1/4".  Flights were on the order of a minute with maybe 500 turns?  I never came close to winding the model at capacity- I suspect that this was less than half winds.  I was lucky- the airplane trimmed out and I never cartwheeled it.  Not sure if the flights ever got much over 50 feet- the field was too small to risk much more.

Do go to firm wood for the spars and fuse longerons.  I used the kit wood even though heavy on the printed parts because there really wasn't that much of it in the structure.  Covered in Japanese tissue with a couple of coats of nitrate.

Wings were plug in- pretty sure held together with rubber bands on hooks both top and at the bottom of the strut attachment point to the fuse.  Struts are functional!  I might have hinged the rudder- certainly built the stab as one piece.  (No ailerons either!)

If I had to do it again- I'd move the rubber peg further forward- I had to add a bunch of pennies in the snoot for balance.

The problem with FF stuff in this size range is that it gets really delicate- there's a scaling law that makes ants a heck of a lot sturdier than elephants.  Peanuts can take cartwheels with no problem (well most of them)- but once you get over 24-30" (that was Earl Stahl's favorite size) FF airplanes have to be trimmed carefully so that they don't get broken- and you have to restart the trimming process again.  Note- I know a heck of a lot more about trimming now than I did then- so these designs were pretty stable.  I still have a 50" Easy Built P-40 lying around- needs double covered tissue on the bottom of the wings and fuse.

I eventually sold the airplane to a restaurant when I moved- never saw it again- the restaurant closed.

HTH

Sam

PS- I wound up with a laser cut version of this Aeronca from Penn Valley Hobbies...
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IndoorFlyer
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« Reply #6 on: April 14, 2014, 11:06:38 AM »


I eventually sold the airplane to a restaurant when I moved- never saw it again- the restaurant closed.


By any chance--The "Flying Lady"?
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atesus
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« Reply #7 on: April 14, 2014, 11:20:15 AM »


I eventually sold the airplane to a restaurant when I moved- never saw it again- the restaurant closed.


By any chance--The "Flying Lady"?

Aaah, what a beautiful place it was... Sunday brunch with tens of model airplanes making rounds overhead, a delight to a modeler's eyes.

Mick, I'm planning too, to build a jumbo scale rubber powered model this year. It will most probably be a Heston Phoenix from Eric Fearnley's plan enlarged to 150% for a 51" wingspan. I used John Barker's (HepCat on HPA) PropPicker to size up the rubber and the prop, you may want to take a look at that if you haven't already. You can play with the wing area, estimated weight and arrive to useful numbers on the rubber, prop diameter, pitch etc.

Best,

--Ates
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glidermaster
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« Reply #8 on: April 14, 2014, 11:27:40 AM »

One of our guys here in British Columbia built one of these quite a few years ago, when he made a brief return to the sport/hobby (he has since gone back to drag racing!).

Obviously the kit prop was not used, but I think the kit wood was, and I recall it was actually quite good, being on the firm side of ideal.
He made the wings detachable, the nose block a more conventional plug-in type, and beefed up the front fuselage somewhat. It needed noseweight, and negative in the tail (bearing out what Bill said about incidence), but it flew well eventually. It had a plain tissue finish, but it was well done, and looked good - I wish I had pictures to prove it.

At the time our little f/f club wanted a project to follow on from our very successful Sparky club build, and a few of us went for Jumbo rubber flying scale. My Stinson Reliant lies unfinished in a large box in my modelling room, and once in a while I pull out an Aeromodeller with Doug McHard's version on the front cover to give me fresh inspiration. I am a tall guy with a large hand span, and I can only just hold the fuselage across the bottom, where the DT timer is mounted! Bill Brow brings out his large Fairchild 24 once in a while, and glares at those of us who never finished our projects!
John
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applehoney
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« Reply #9 on: April 14, 2014, 02:41:15 PM »

Could that have been at Morgan Hill, CA ... a restaurant I visited in 1980 when on vacation FROM England?   Models continually passing overhead suspended from a track.
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atesus
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« Reply #10 on: April 14, 2014, 05:12:00 PM »

Yup, that's the place. Sadly they closed down in 1994.

http://www.youtube.com/watch?v=NADKQzClE4E

Sorry about hijacking the thread mick66  Embarrassed.

--Ates
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applehoney
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« Reply #11 on: April 14, 2014, 07:49:55 PM »

Ates - many thanks for the link  - really brought back some memories.  Place was larger than I remembered - wonder what happened to all the models when it closed.

back now to the Aeronca Chief, with apologies to mick66 ...
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Marc*G
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« Reply #12 on: April 14, 2014, 10:33:19 PM »

I have heard of people using as little as 4 strands of 3/16th rubber to power this model. These larger models have such minimal wing loading that it really does not take much to keep them moving.
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Megowcoupe
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« Reply #13 on: April 14, 2014, 11:18:25 PM »

Nope- wasn't the Flying Lady- was a restaurant in Hangover, NH.

Marc- the only way I'd see powering this ship with that little rubber would be to use the stock plastic prop....

Cheers,

Sam
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Dave Andreski
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« Reply #14 on: April 20, 2014, 12:36:23 PM »

mick66,
You may be interested in this-
http://www.smallflyingartsforum.com/YaBB.pl?num=1286999556/60

Start at reply # 67.

Have a look at reply # 49.

Dave
« Last Edit: April 20, 2014, 12:49:48 PM by Dave Andreski » Logged

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mick66
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« Reply #15 on: May 05, 2014, 07:11:17 AM »

Hi

thats for the input ... good link Dave. 

Hope to start soon.

Cheers

Mike
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« Reply #16 on: May 05, 2014, 02:08:58 PM »

I've flown my share of scale and non-scale in this size range...

The above advice is good stuff. Pay particular attention to the recommendations about stab incidence. I would recommend going a step further: fit a DT and put an incidence adjustment screw on whatever stop plate or surface you use. Set your CG using Don Deloach's TVo formula, though it might be good to start out about 5% forward of whatever it gives you. You can move the CG aft 5% once you get it trimmed fairly close. Remember that this will require you to go back to glide testing to get the incidence set for the new CG, but it'll get your thrustline and warps set comfortably with minimal risk.

Do move the rear peg forward. These models appreciate being kept light. Also, if you're not building for kit scale, web the wing spars. You need the strength there.

Removable wings are a good idea on a model this size. If they're retained with tongues or something like that, you can have some crash resistance, too.

Do everything you can to prevent warps, but do build in some washout in each wingtip. Don't depend upon steamed in warps. To be realistic, the only warps I've found to stay reliably are ones that are *built* into geodetic wings...which are an option, you know. Wink

For a model this size, I'd think a 16" carved prop is a good starting point. Consider a Henn blank. I'd start with 12 strands of 1/8 and not expect much more than a powered glide. You might get a little climb going. 16 strands will make it more lively, and then you'll know enough to decide whether it's time for an 18" prop and more rubber. Again, take it slow. In the end you'll have a reliable airplane that, if equipped with a DT, will last for years of faithful service.

As an anecdote, my almost full geodetic 52" Spruce Goose has been in a box since 2011. I pulled it out yesterday and made three picture perfect flights with zero adjustments. On the last flight, it threw a prop blade which cause a moment of terror before it returned to happy left circles.

Large scale jobs glide great, too...some will even flare a little as they enter ground effect.
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Dave Andreski
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« Reply #17 on: July 05, 2015, 03:45:50 PM »

Hi

thats for the input ... good link Dave. 

Hope to start soon.

Cheers

Mike

Hi Mike,
Any progress on this project?
Thanks,
Dave
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mick66
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« Reply #18 on: July 06, 2015, 05:25:53 PM »

Hello

funny you should ask but I was looking at the kit today.  Can't believe it was over a year ago I started looking at the Comet.  At the minute i've pretty much cleared the board of competition and sport builds and have vowed not to have 4 or 5 on the go at the same time.  They don't come off the production line at any greater rate!

I'm thinking ERCO Ercoupe power or Comet Aeronca Chief rubber?
LOL ... its a bit depressing really as i have virtually no where to fly them anyway.

Aeronca is winning at the moment!  I've got as far as laminating the wing tips.  Not as per kit but I fancied doing it that way.  

Are you thinking of giving it a go?  Its a bit out of my usual type of build so will be looking for any more
advice!

Cheers

Mike




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Dave Andreski
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« Reply #19 on: July 07, 2015, 06:25:38 PM »

Mike,
Thanks for the response but I have the same problem- NO place to fly!
This is as far as I got for my second one.
Dave
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« Reply #20 on: July 10, 2015, 05:11:26 PM »

I built the Aeronca Chief right out of the kit box, 1972. I lived in Santa Cruz (CA.) and converted it to .049 power, with a built up balsa nose/cowl, and a heavier music wire gear.
 
Never completed it, but it still hangs in my hobby workshop...rubber was/is the obvious best package for this behemoth.
Pretty thing, to be sure...
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mick66
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« Reply #21 on: July 19, 2015, 03:02:53 PM »

Hello

made a start on the Aeronca.  I'll add  -1.5degrees on tail and +1.5degrees on wing.

Not going to build exactly as per plan but close enough.  I want a jumbo rubber sport model rather than a 100% accurate Comet model.  So in that spirit ... I've laminated the wing tips.

This type of model is a bit out of my area so no doubt I'll have plenty of questions.

Cheers

Mike
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Dave Andreski
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« Reply #22 on: July 19, 2015, 05:42:15 PM »

Mike,
The only thing I can recommend is that you use the 'hard/heavy' balsa included in the kit for the NOSE parts.
Don't be tempted to use softer, lighter, weaker wood in the nose.
Dave
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mick66
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« Reply #23 on: July 25, 2015, 01:35:08 PM »

Hello

made a start on the wings.  I've decided to split the single lower spar into a top and bottom.  Also add some 1/8x1/16 spars on the top front (bit of turbulation) and a rear one on lower surface.  As suggested I'll build in 4mm washout.  Carbon/Ali tube wing joiner with magnets at 8g.

I'll keep a track of the weights and see where we get to at the end.  All wood used so far is around the 7Ib mark except the TE which is around 15Ib with a 1/8 strip glued to the from to stiffen it up as even at 15Ib it felt a bit floppy (I tend to make all my TE out of laminated strips anyway).  I also decided to use full ribs where riblets are used in the kit.  Probably a bit of overkill but it only adds around 3g!

Any recomendations on how to make a tip up tail work without it looking too much like a tip up tail per se.  I was thinking of having the whole rear fuse tip up seeing how i'll be moving the motor peg forward anyway.  Works for my Senator and Dinamites.

Cheers

Mike
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« Reply #24 on: July 25, 2015, 05:08:43 PM »

Fascinating discussion.  I'm one of the folks (many folks?) who has one of these monsters new in box.  Every couple of years, I fumble through the printwood (oak?  maple?) mumbling "I really oughta..." as I do so.  Often, beer is involved.  The potential delicacy of this model just terrifies me.  Built a 40" Pac Ace years ago, and where I fly (yucca, all sorts of prickly desert plants) it was like trying to fly a soap bubble.  Poor thing was eventually more patch than paper. Great to see in the air, though.  Please keep us posted!  You know, I really oughta...
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