dmajchrzak

My Feedback: (17)

I did post this in the ARF section and realized that's probably not the most appropriate place to get feedback. My apologies.

I'm looking for a good aerobatic, low cost ARF to be powered by a low cost 25cc conversion engine to get into gassers.
I welcome your opinions. The attached picture is a spreadsheet of what I think might be suitable airframes...

captinjohn

dma: You done a very good job. Must have took some time. I have the Giles 202 1.4 size. I think the Katana 1.4 size for $10 more is a very ...very...good choice too. How about it Guys....drop your opinions in here!!! Thanks Capt,n

carlosponti

My Feedback: (1)

eventually i want to try it on my hanger 9 120 size cap 232. the thing is sitting in my garage and i just havent had time yet to work on it.

dmajchrzak

My Feedback: (17)

Updated with CAP 232 from H9.
Updated with some 25cc conversions and comparable glow engines...

av8tor1977

My Feedback: (6)

Hey, nice work on the lists. I had an idea to do this a while back, but then I came to my senses! It's a lot of work!

It really depends on exactly what you want. If you want an aerobatic knock around plane that's easy to work on and fairly cheap, I recommend either the Great Planes Giant Stik or the Hangar 9 Ultra Lite Stick 120. If you want a more serious aerobatic plane, I'm sure happy with my Giant Scale Planes Katana 72" with it's Kioritz 23.6cc. If you want a warbird, the Great Planes Fokker Triplane is fun with a 25cc engine.

Thanks,
AV8TOR

BillS

You have gone to a lot of trouble and I can’t help much. But some design issues that should be considered are:
1. Less than 15 pounds all up airplane weight for 25cc engines.
2. The engine can be expected to weigh around 4 pounds.
3. Gas engines are sometimes 2 pounds heavier than the glow engine being replaced.
4. When substituting gas for glow structural support will likely be needed in the firewall area. The added structure will increase weight.
5. Prop, spinner, and muffler will be bigger and slightly heaver.
6. Up front weight can often be countered by servos in the tail.
7. Airplanes intended for 120 (and up) glow engines seem to be the most likely and most often converted to gas.

Planning a design takes a lot of thought but is a rewarding exercise. Since it is mandatory to maintain the balance point it is helpful if see-saw (moment of inertia) calculations are easy.

As a personal preference I would avoid airplanes that are capable of flying on glow engines less than 120. All too often the need for additional structural support is not recognized until after the breakage. Your building experience and skills are probably better than mine.

Bill

dmajchrzak

My Feedback: (17)

AV8TOR,

Thanks for the feedback, Is the 23cc in your Katana magneto or electronic ignition? Any idea of the engine weight? Since I'm new to gas, I'm a bit nervous about CG. The price of the magneto versions is attractive, but the weight of the EI versions is attractive also. My experience in .90 sized glow aircraft is that often times nose weight is needed. Question is, on a 1.20 aerobatic aircraft, is the extra 1lb of the magneto version too much?

Thanks,
Dave

av8tor1977

My Feedback: (6)

Hi,

You know, I've been doing this for several years now, and I've yet to come across serious weight and balance problems. I presently have 3 planes flying with conversion engines, and none of them needed any tail weight to get the c.g. right. My Great Planes Giant Stik needed the battery mounted about 6 inches behind the servos in the tail to balance, but that's with a big Poulan 42cc on it and a smoke system in front!

I never run magnetos, instead preferring the lighter weight , easier starting, and better power of using an ignition system. The ignition system costs a few bucks, but you can always transfer it from plane to plane; not needing to buy several. However, lately I've been running what we call "Gas/Glow" on all my planes. It works great and I'm happy with it. You use an adapter to install a glow plug in place of the spark plug, and then run a mix of 10% nitro/10% oil glow fuel with gasoline. (Two parts high test gasoline to 1 part glow fuel.) You can find more info on this here: http://www.rcuniverse.com/forum/m_12...page_28/tm.htm

The Echo/Kioritz engines work great, having good power and light weight. Mine come out at about 2 lbs. 8 oz. ready to fly including mounting. The Homelites work well too though. I have a 30cc Homelite that I hopped up that turns an APC 16 x 8 prop at over 9400 rpms, and only weighs about 2 lbs. 14 oz.

The Katana is a great aerobatic plane, and I love mine. If you decide to do one, look it up in one of the other forums. The plane comes with a hatch in the bottom that is a pain to work through. If I did another one, I would modify it to open up in the canopy area like an Extra. The forum posts detail that. The early ones had a problem with the wings folding, but that has since been addressed by the manufacturer.

Good luck,
AV8TOR

av8tor1977

My Feedback: (6)

Post script: Some people bad mouth the GSP Katana 72", saying it's a bit too heavy for good 3D performance. Doesn't bother me, as I don't do 3D. The plane does normal aerobatics beautifully, and my hopped up Kioritz 23.6cc hauls it vertically until it I get tired and hammer head out, or throw it into a spin to get it back down. I rigged mine with flaperons, but I never use them as it lands nice and slow without them.

AV8TOR

DALE PABAJO

av8tor1977 I have a lanier 1/4 Lazer 200 it's 855 sq.in. wing area, I also have a craftsman 25cc engine, it's on a blower wich I plan on stripping from so I could mount it on my lazer. I might need to reinforce the fire wall a bit that's no biggie, my question is do you think the 25cc blower engine is ok for this plane?

BillS

An airplane that is often seen with a converted engine is a 4* 120. I have a fuselage but no wing although it appears the airplane could readily accept a gas engine. Giant Stingers will often have a gas conversion.

Bill

grumpE

My Feedback: (6)

Hey guys,

I have a HEAVILY modified 4*60 with a power problem. It has been bashed into a crop duster look alike with smoke system. I have a mag 91 FS in it running Magnum 1 fuel (approx 20% nitro). I have solid performance but little emergency reserve. The thought of a bigger glow engine is not appealing as it would just need to carry more fuel and negate most fo the gain IMHO. Plus I think I could get better smoke from a gasser. Do not have an all up weight but will look tonight.

Here is how the stock version (mine is easily 2 pounds heavier) compares to the stock 4*120.

4 Star 60
Recommended Engines:
.60-.75 in³ (10.0 - 12.3 cm³) 2-Stroke Glow
.65-.90 in³ (10.7 - 14.8 cm³) 4-Stroke Glow
Wingspan: 71 in (1803 mm)
Wing Area: 920 in² (60.3 dm²)
Wing Area: 6.388 ft²
Weight: 7 - 8 lbs (112-128 oz)
Wing Loading: 17.5 - 20.037oz/sq ft
Length: 57 in (1448 mm)

Estimates of my bird:
Weight: 9 -10 lbs (144 - 160 oz)
Wing Loading: 22.54 - 25oz/sq ft


4 Star 120
Recommended Engines:
0.90-1.20 cu. in. 2-Stroke
1.20-1.60 cu. in. 4-Stroke
Wingspan: 81 in.
Wing Area: 1205 sq. in.
Wing Area: 8.368 sq. ft.
Weight: 10 1/2 - 12lbs.
Wing Loading: 20 - 22.9 oz/sq ft
Length: 65 in.


My bashed 60 flies really well and will glide like a kite when deadsticked (read as run out of glow fuel having fun). I have three 4.8v packs under the tank (one for flight pack, one for smoke and one as dead weight) and the smoke system crammed as far forward as possible and I still needed a Higly heavy prop nut to balance so I have room to loose weight.

I just happen to have a Homie 25 wacker that is seven years old and needs a new cutter head. Easy to convince the Missus we just need a new wacker.

Do you think this is just too far over the top?

Eric

BillS

Not sure of the question. But I would put a gas engine in a 120 but never in a 60.

Bill

grumpE

My Feedback: (6)

That was my question. The size diferences looked really small to me but having never used a gasser I was looking for more experienced users advice.

Thanks Bill.

Eric