mclintock

My Feedback: (3)

I have a medallion 15 that needs to fly, and I was wondering if the sig akromaster would be a good airframe for the cox.
Does it have a nose-heavy tendency? Would a tee dee .09 be better? I only want to fly it for fun, but it would be nice if the plane at least was capable of all the old stunts.

What length lines would be right for the akromaster?

Thanks...

Fix-it

My Feedback: (3)

The Med. 15 is plenty of power, maybe even a tad overkill. My buddy has an Akromaster with an OS .15 on it and even with a 7x3 and a slightly rich run it goes like a bat from hades. Currently on 52' lines, gonna try 60' next time out.
I'm sure a Medallion .15 is on par with the OS .15, and probably a bit lighter. I've had a Ringmaster Jr. with a Medallion .09 and it flew fine, the .15 on a slightly bigger / heavier palne should have plenty of power to do the pattern.

One tip I've read about and plan to do to my Akromaster kit when I build it is strech the wing by not cutting the excess material from the leading and trailing edge stock. You would have to make a couple extra center ribs to use the original bellcrank mount, then keep the standard spacing for the rest of the span except the tip ribs would be moved out to the end. That makes the last bay an inch wider, plus the extra inch on each side in the middle gives you a total of 4" more wingspan. There is a thread here about it, or maybe on SSW.

mclintock

My Feedback: (3)

Thanks for the reply Fix-it,
That extended wing mod sounds like the same thing I did on my rc herr sky cruiser, which I was going to set up as two channel, thinking my old cox radio was legal, thus a climb and glide, so the extra span would have helped.. i digress.. but same deal, I just used the full length of leading, trailing and spar stock and made another pair of ribs.

60 foot lines seems like a mile to me- twice as far as 1/2a lines- awesome..

Are you planning on using flaps? I probably won't since this for me will be a trainer, and if I do a move that would be improved by flaps, I probably wouldn't know it. The medallion looks to be a good training engine, with it's more restrictive spray bar type venturi and single bypass. My only big fear is that I have no muffler for it, and most clubs require one on engines bigger than 1cc. Maybe I'll just stay some distance away and say it's just a cox. Most assume .049 when you say it's just a cox..i hope..

Old Sourdough

Clint,

I fly my Akromaster with fixed flaps and an old Fox .15x with an 8×5 Rev-Up on .012" × 52' lines. It flys very well. Your Medallion .15 should do just fine, although you may find that you'll need to add nose weight, as the typical SIG supplied fuselage I've seen tends to be a bit heavy aft of the wing.

I might suggest that you provide for the possibility of making your flaps operable later, should you choose to do so. Mine is built that way and I may change the control set up this winter to permit the flaps to operate this winter. Since the flaps are already hinged, it will be a fairly simple task to accomplish. It was a simple matter to hinge the flaps in the building process and fix them until a later time.

gcb

Clint,

I would suggest building with the wing extension that Fix-it proposed. I built one that way and have a schnuerle .10 on it.
The Medallion weighs slightly more than the baffle Fox .15 without muffler, I think...but not enough to worry about.
Forget movable flaps if you are just flying for fun. More trim adjustments that you don't need.
Try an 8x4 prop, 15% fuel, and .012x52' lines. That should get you in the ballpark.

Good luck with it.

George

Edit: Trying to include a pic, if it works. The lower one is stock with a baffle Fox .15 and the upper one is with extended wings and a TT 10.

mclintock

My Feedback: (3)

I'm getting excited at the prospects of starting yet another project.
I must admit i'm a bit taken in by the pretty finish of the official sig photo of the plane..

Also I have a tee dee .09 that (you're gonna laugh) i bought just so I'd have the full spectrum of cox engine displacements in my possession.....

I'll probably build the kit with the extended wing mod, and hinged but fixed-for-now flaps, and maybe see if I can use the plans to build an "akro-lite" to use with the tee dee .09, perhaps with the stock length wing and careful wood selection. Altho- the last sig kit I built (reagan was prez)had some pretty well selected wood, if they are still that good, I'll be hard-pressed to do better...

Jim Thomerson

I've flown a medallion 15 on a larger and heavier (one would hope) airplane than an Acromaster. As I recall, the Medallion 15 turned a Cox grey 8 x 4 around 13,800 on 10% nitro Sig champion fuel and the Medallion head. I would think you would have a pretty fast airplane on 52 ft lines. I've flown a TD 09 a lot on a Shark 15 and a Jr Flitestreak. 57 ft 012 lines. Still fairly fast on 10% fuel. The TD 09 likes the Cox grey 7 x 3.5 prop which is a rare find these days. I'd run an APC 7 x 3 if I did not have the Cox prop.

Jim

sigrun

mclintock the Akromaster will fly aerobatics reasonably well with any moderately powered .15 provided it is kept under 18ozs wet. Unfortunately the wood SIG supply in Akromaster kits tends to the heavy side, so watch the amount of epoxy used and select an iron-on covering for the wings to assist in keeping it light would be my advice. Similarly with selection of wheels etc. Go with minimum aka light. A couple of ozs either way in a model of this wing area and power can make all the difference between it being a total delight - or a dog.

Don't use bigger than a 2¼oz tank. Not only is greater than that amount of fuel unnecessary, but you don't need any extra wet weight.

The Akromaster is good on 52' lines. .015 are considered the conventional standard for .15³in capacity, but .012 work well enough and offer slightly less drag and inboard weight. 60' foot are too long even in nil wind for either this model or any sport .15 IMO.

If you want to optimise the Akromaster's aerobatic performance, do a an inexpensive and simple mod and flap it. It works well enough without them, but much better with them.

If you're carrying the added weight of a silencer up front, place the engine as far aft as the fuel tank fit will allow.

The Akromaster is really pleasant model for a moderate power .15 when built light, and capable of flying pretty much the whole pattern in a sporty kind of way. I've built and flown several of them over the years. Pretty much brethren of the ubiquitious Flite Streak Jnr or Peacemaker, its the kind of sport .15 one should always have in the C/L hanger. Typically SIG. Flys well.

mclintock

My Feedback: (3)

Thanks for all the replies, this will really help me to get a complete order together for virginiahobbysport, lines, props, tank etc..
it helps to thin the pain of the shipping charges- if I have to break down and buy it myself..

I should at least START on my brodak waco before I get too carried away- but the first person who asks what I want for cristmus-
I'll tell them akromaster with a 'K'.

Jim Thomerson

AMA stunt rules allow 012 cables for 051 to 15-size engines. Bigger than 15 through 40 requires 015 cables. Of course you can run heavier cables, but this is not, I think, a good idea on smaller airplanes.

Jim

cltom

Stick with the Acromaster stock. The newer engines are much more powerful than the old 15's, and a Medallion 15 is old. I'm not surprised if someone is using a 7x3 prop on an OS, that it flys like a Goodyear racer or a quarter-midget - it's probably turning 20,000 rpms. Use an 8x4, 10% nitro, and 0.012 x 52 foot lines (the 15 std for 50 years), and you should be fine. Don't worry about extending the wing - that's another reaction from the more powerful modern engines. Fly it stock.

I also agree about the flaps - they are almost more trouble than they're worth in a 15 size, and will make very little difference in the whole scheme of things at these sizes.

sigrun

Whilst I can't disagree with cltom about sticking with stock unless you're comfortable with construction, speaking from practical experience with several Akromasters, the addition of flaps makes a notable performance difference with this model's aerobatic performance, and they are exceptionally easy to implement.

All you need is a piece of wire, an extra nylon control horn and a bit of fibreglass reinforcing tape and some tape for hinges.

gcb

Finally got a pic on my previous posting that shows the difference between standard and extended wings.

George

mclintock

My Feedback: (3)

George,
Thanks for the picture- looks like a sort of way-overpowered biplane in the thumbnail!

I'll join the akromaster club soon- bought one off ebay for about one whole dollar less than I could have gotten one from a store..
It looks like alotta plane for 22 dollars.

I'm sure that I'll likely wind up making a few of them, in varying configurations.

Is the main (dis)advantage of the larger wing slower flight? Tighter turns? They both look 'right' to me..

fun stuff..
clint

gcb

The plans for the Akromaster shows an unmuffled Fox .15X (slant plug). The plane's size was designed for that type engine. Modern (or even old) engines using a muffler moves the balance point forward. To compensate you add tail weight. All of this adds up to a higher wing loading. The larger wing provides a lower wing loading.
The lower plane in my pic has a Fox .15X with muffler. The upper plane has a TT .10 with muffler...probably about the same weight and power output.

George