Sig Akromaster Wing Weight
 

Hello im just getting back into building and my first kit in about 10 years and its an Akromaster. I was wondering if anyone has any recomendations on how much weight i should put in the wing? Im looking for something fairly stable and easy to fly. It will have an OS 15LA-S in it and im gonna cover with monocote just because I think its easier to repair and slightly sturdier than a dope and silk covering. The kit is being build to the plans specs and if i can get the old U-Reely to work i plan on flying on about 52' lines.

Just so i could quickly get out to fly i also put together an flightstreak ARF and it has an OS 35FP-S. I flew it with a 10x6 prop and it was quite fast and unstable. I limited the control throws and went down to a 10x4 prop so im hoping when the weather gets better i can try it again and maybe be a little more successful. I also have a 10x3 prop im thinking about trying. Any other tips for this one would be great too.......I balanced it to the point called for in the instructions but that required a lot of weight on the tail. I guess the 35 is on the heavy side.

Thanks

RE: Sig Akromaster Wing Weight
 

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Check out the above thread for Flite Steak info. I think the general concensus is that the balance point in the instruction book that comes with the FS ARF is considerably too far back. I think the OS .35 is quite a bit more motor than you need, too. I'd try setting it up pretty rich, at first.

Sorry, I can't help you with the Akromaster. Doesn't the plan tell you the tip weight?

Phil

RE: Sig Akromaster Wing Weight
 

I agree with Phlip, sounds like the Flight Streak may be a little tail heavy. It's the rearward C.G. that makes them twitchy, not the control surface throws. Just my thoughts, give it a try with a little weight removed from the tail, I'm sure you'll find it more pleasant to handle.........John

RE: Sig Akromaster Wing Weight
 

Just finished the Sig Akromaster with Thunder Tiger 15. I cut about 3/4 inch off nose so I could move the engine towards the leading edge a bit to help with CG control (little or no tail weight).

I used about 1/2 ounce tip weight and also used the heavy pieces (leading/trailing edges/spars) for the outboard wing.

Have not flown yet, however.

RE: Sig Akromaster Wing Weight
 

I can't remember what the wing should or will weigh, but SIG's Akromasters tend to build heavy when using the supplied in kit wood. A really great flyer, but with a smallish wing area (250in²) for a contemporary .15.

As memory serves, 3 U.S. pennies worth of weight epoxied together and onto the wingtip should be about right. :) Cheap tip weights too.

A perennial favourite, I've kit and scratch built a stack of them over the past 17 years, but because of that critical wing area they need to come in under 17ozs dry AUW as a maximum to retain ½ reasonable aerobatic performance. Ideally, 14oz is the target, but unachievable with kit wood and a muffler fitted IME. 15½oz can be achieved scratchbuilt but 16oz is reasonable and more realistically achievable target. At 16oz with a 2oz tank for a release weight of 18oz they will fly quite well with an O.S. 15LA, TT .15 or similar.

Lighter is better, but a realistic 16oz should be your ideal target. A 2oz bloat overweight can turn this model from a nimble ship into an acrobatic dog.

Because of the smaller wing and thinner section, the Akro tends to fly fastish anyway even with an 8x4 prop with an O.S. 15. They will fly well at any weight in S&L, but when you manoeuvre so the prop loads up and the model slows down, if you're overweight you'll know all about it.

Tips to keep it light. Everywhere you can save weight counts. It all adds up in a model of this size.

1. Do Monokote the wings, and if you must paint the fuselage - less is better. Paint is heavy, you would be surprised how heavy even on a model this size if you go the whole undercoat thing etc.
2. 52' lines are perfect for the Akromaster/.15 combo. .0012 SIG or Brodak will offer less drag, smoother control and are adequate for sport flying this combo.
3. Keep the tank mounting system (hardware) light.
4. Use CA and remember, where you have to use it, more epoxy doesn't = stronger, just heavier.
5. If using the supplied U/C which works well, use broad lightwight wheels. The drag isn't a issue. The weight is.
6. Soldering them in place is lighter.
7. Plastic clevises are lighter, and adequate for this model. Use with fuel tube safety band.
8. Ditching that glue on clear canopy for a solid piece of identically shaped monocoated or painted lightweight balsa glued on to become an integral part of the fuselage can save upwards of ¼oz alone.

To give you an idea of what is achievable with good wood selection and prudent use of glue and acessories, I build similar profile George Aldrich Peacemakers of 300in² area and thicker section which I cover (wings only) in either Monokote or Oracover. Rest of surface including empennage gets seal doped, sanded and lightweight sprayed cote of clear polyurethane fuelproofing - Lustrekote or Pactra Formula-U (no longer available) They get a single leg U/C with lightweight slimline wheel and Perfect 1¾oz or 2oz tank (can't remember which it is, but it easily runs them for 4½ mins on a .15). I turn them out at a flying weight of 14¼oz dry AUW with an O.S. 15FP fitted with muffler. Very nice turners for .15 slow combat, and they'll execute the basic pattern with ease.

IME Akromaster is as much fun and a great flyer if it's kept light and under the critical 16oz+-/½oz. Harder to achieve that performance boosting low wing loading though (which makes all the difference in manoeuvre) because they tend to buld at least as heavy as as the Peacemaker (*heavier with the dual U/C,canopy and kit wood) with lesser area. The drag afforded by the Peacemaker's extra wing area and section is inconsequential to speed, but a huge boost to acrobatic performance. (Peacemaker is smaller version of Flitestreak for those who don't know, and fits in between Flitestreak and Flite Streak Jnr, which is marginally smaller again intended for an old Fox .15 and similar powered .15's of the 50's. George designed the Peacemaker for the Brits who used more powerful .15 diesels of the day, which is just about perfect for a modern Schnuerled .15 like the TT or LA .15s.

BTW, stick a .15 TBR diesel on an Akromaster and watch it perform at any weight given the excess power available and torque. :) Mind you it sperforms even better when lighter.

That's about it. For the O.S. 15LA, keep it light. Enjoy your flying.