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Zero for surestart

Old 09-19-2007, 02:54 PM
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lz-23
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Default Zero for surestart

Few days ago I start new model for surestart that I have laying around. It is scratch build from peanut scale plans enlarged to 29".
Here is few shots of the building so far:






Weight of the fuse is so far 24 gr. (0.89 oz)
How much should be the AUW for that engine? I was thinking somewhere of 12-14 oz range, but not really sure since this is my first 1/2A.
Old 09-19-2007, 09:24 PM
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Default RE: Zero for surestart

In that size range, a pound is a good goal. A tissue and doper might say that it has been done for less. All I got to say to that is show me that model after 100 flights, especially flown from my field.
Old 09-20-2007, 11:11 AM
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lz-23
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Default RE: Zero for surestart

I'm going to use doculam for this model. Very light and strong covering. Will try to stay under pound AUW.
Old 09-20-2007, 06:51 PM
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Default RE: Zero for surestart

I think that stuff is great. Easy to fix at the field with packing tape. One of the best flying "Guillows type" 1/2A planes I ever saw was a Zero about 20 years ago with a .049 Medallion.
Old 09-20-2007, 09:29 PM
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lz-23
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Default RE: Zero for surestart

Little progress on tail. All weight is 6 gr (0.21oz).

Old 09-20-2007, 09:54 PM
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Default RE: Zero for surestart

So far so good. Your basic airframe weight is the hardest area to save weight. A 1/2 oz of balsa is a lot of wood. It sure is nice to see a plane being built from scratch, keep up the good work!
Old 09-20-2007, 10:02 PM
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lz-23
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Default RE: Zero for surestart

Thanks a lot! Raw wood for wing is 22gr (0.78oz), so I hope to come out little over 1.5oz. This is including 3 basswood spars on the wing and I used one on the stab too - it really make difference!
Old 09-20-2007, 11:17 PM
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Default RE: Zero for surestart

Besides crashing, the roughest handling that airframe will ever see [with a surestart pulling it around], will be when you are starting the engine. It is possible to go so light that the firewall rips out. Building these stick models is a game of deciding when enough is enough to just withstand the forces of flight and normal handling...without going too far.

After flying a fair amount of 1/2A combat with planes that have taken lots of damage, you can really see how little strength is required to keep things together.
Old 09-20-2007, 11:34 PM
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lz-23
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Default RE: Zero for surestart

Thanks for the advices! I really need them. The smallest airframe I was dealing with was for 0.09, so this is really new world for me. Right now the firewall is 1/8 lite ply, and I have prepared another 1/16 birch ply to go up front for additional strengthening. All spars are 1/8x1/8, and certainly there will be planking between first 3 to 4 formers. Hope to handle the small power plant well.
Old 09-21-2007, 01:37 AM
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Default RE: Zero for surestart

I hope I'm wrong but I think you're going to find that the tail surfaces will need to be a touch stronger than what you'll get from using just the 1/8 sq stock. If it was me I'd have used 1/8 by 1/4 for the spanwise parts of the horizontal tail. A flexy tail will allow the hinge line to bind and prevent you inputing elevator commands in a smooth manner.

Otherwise I like what you've done so far and what you're planning on. The fuselage being done with the 1/8 square stock and plank fill for the first three bays should provide a light but suitably strong structure.

The wing will need to be done with a bit more attention to a proper spar setup. The peanut plan scaled up won't cut it. For stunt worthiness I'd also suggest a different airfoil. Something either symetrical or "semi symetrical" to run with little or no camber so it can fly upside down more neutrally.
Old 09-21-2007, 10:13 AM
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lz-23
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Default RE: Zero for surestart

Tail have basswood spar which give me much stronger tail than just balsa. Also I'll have to add little more wood here and there. On previous my model (Bristol Scout) I make this mistake to rely on balsa wood only, and her tail is pretty flexible. But being electro model she is flying very well. Also doculam covering give extra strength. Wing use flat bottom airfoil, similar to Clark Y, which I hope will be useful, even if is not the best for the task. There I have 3 basswood spars 1/8x1/8 and 1/4x1/4 leading and 1/4x1/8 trailing edges. So far wing consoles are 20 gr (0.71oz) total. Since this is my first 1/2A, I'm not planing on much stunt for this model. Also I'll have to use a way of shutting down the engine without throttle. What I have done before successfully was to use metal fuel tank with all fuel lines soldered in place. Usually when model is inverted for longer than few seconds, engine shuts down. This approach always require some gliding abilities of the airframe and some extra hight when you perform it. Hope that airframe will be light enough for that.
Old 09-21-2007, 04:20 PM
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Default RE: Zero for surestart

Basswood in the tail would make up for any issues. Good call on that one. Oddly enough you only really need the basswood (or larger balsa) for the fixed forward part. The elevator halves can still use balsa since they get their support from the forward stabilizer section.

If you won't be flying inverted very often then you can use the flat bottom section. But if you enjoy a wider range of options I still say you'd be better off with a quick build thicker and lower camber airfoil. With a less than 16 oz weight it'll still glide just fine.

Here's an example of what I'm suggesting. This is a slight mod to ptulmer's DNU airfoil to allow it to be built on a flat surface more easily. It uses a flat lower rear area. You just make it with the leading edge sticking up in the air. As a side benifit the spar placement and arrangement allows you to use balsa and still get a stiffer and stronger wing than just copying the rubber model arrangement even with bass substituted.

If you're not planning on using ailerons then be sure to use enough dihedral that the wing tips are up even with the base of the canopy in order to have good rolling effect when you apply the rudder.

Here's the airfoil I'd suggest....
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Old 09-22-2007, 06:05 PM
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Default RE: Zero for surestart

Really I have basswood only in stabilizer but elevator halves are pure balsa build. I decided that is not worth putting basswood in them and just firm stab should do the trick. Wing is almost ready, and at this point I'm more concerned about taking at least one bird in the air on such small engine than about her aerobatic abilities. Next one will be more carefully designed.
Old 09-22-2007, 06:24 PM
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Default RE: Zero for surestart

lz-23, that is what it took for me to really see how much strength was needed and how various ideas worked.......seeing the plane in the air and sensing what it felt like to fly it. The only other consideration about the heavyness of the airframe besides normal handling is whether or not it can take a heat shrink covering without buckling or caving in. You have to automatically figure that the lightly built wings will warp, so the covering job isn't complete until all the warps are corrected...no big deal. It is good to see you approach scratch building from the light end of the building spectrum, if you start out building too heavy it will take much more time to figure out how light you can go.
I started in 1/2A RC building kits that were too heavy and with heavier onboard equipment, so those models weren't too thrilling to fly compared to a .40 sized model.
Old 09-22-2007, 07:02 PM
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Default RE: Zero for surestart

Here is the wing. Ailerons are still gluing, and bottom part of the wing is not covered, so I add some extra material on the scale for general estimate of the weight. All in all it is 32gr (1.14 oz). Center section is 1/32 sheet, ailerons are pink foam covered with 1/32 balsa and 5/16 balsa spar upfront. They where leftovers from another model (0.15 RC combat) that use solid balsa ailerons but here they give me some weight savings compared to solid balsa. Spars of the wing are 1/8 square basswood. In any case I'll be happy if final weight of covered airframe is doubled compared to what it is so far.



Old 09-24-2007, 08:30 AM
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Default RE: Zero for surestart

lz:
Wing looks great. Good craftsmanship. My two cents, if you can continue with the light construction, then you will have a heck of a nice flyer!

Really enjoying your thread!
Old 09-25-2007, 11:47 AM
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Default RE: Zero for surestart

Thanks a lot. Usually after the basic airframe is done, my models start to gain weight. Let's hope that this will be light enough to fly well.
Old 09-28-2007, 12:16 AM
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Default RE: Zero for surestart

Update on building. Fuse is sheeted, wing mount dowel and bolt are done. Having on mind that this will be IC model, i went over board and used 3/32 balsa for sheeting the fuse. Weight after that is doubled (52 gr - 1.85 oz), but strength is probably quadrupled. Whole airframe is at this moment 82 gr (2.93 oz), and with engine and prop installed is 140 gr (5 oz). So far I'm very happy with this build. Still have to install the fuel tank, push rods, servos, covering. Really I did not expect dramatic gain of weight during this stages, but even if it happen, I believe will be possible to fit under 10 oz. For awhile I will be returning to other projects, so this build will be frozen for at least 2 weeks, unless I have to stop again due shortages of materials for my other planes.
Here are the pics:






Old 09-28-2007, 12:44 AM
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Default RE: Zero for surestart

Did you glue that copit sheeting down? How are you going to get the gear in there?
Old 09-28-2007, 09:54 AM
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Default RE: Zero for surestart

How is it balancing?
Old 09-28-2007, 10:25 AM
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Default RE: Zero for surestart

The wing is removable, is hod in place with hardwood dowel in front and bolt in back, so all equipment will go under the wing. At the moment the balance is on first spar of the wing which is 26% of the wing chord. Here is the plan if someone is interested: [link]http://www.rcgroups.com/forums/showthread.php?t=745155[/link]
Old 11-03-2007, 08:21 PM
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Default RE: Zero for surestart

Here is a little progress:
Pushrods for ailerons are in place.

I start covering too. It is Doculam paintend on adhesive side.




Old 11-04-2007, 07:05 AM
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Default RE: Zero for surestart

Very nice project, you are a good builder.
Those sheet fill-ins are very well done look really nice, thanks for sharing.

I built the original peanut version some years ago and it flew surprisingly well. The kit is still available from Peck Polymers;
http://www.peck-polymers.com/store/Category.asp?Cguid={13AF3F86-81D9-4519-B6C0-41BCF991F283}&Category=ModelKits%3AFF+Rubber+Powered

I tried a twice size 26" version too (for rubber FF), and it was delightful too.
Bob PeckĀ“s designs are great - he could simplify structure just enough to make a practical & flyable free flight model, and yet retain good scale fidelity.

Good choice of subject, it will look great in the air, will be very interesting to hear how it flies with radio control
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