magilla12

I am in the process of building a Great planes 33% Extra 330L and am wondering what engine to use. Is anyone using a AVIOmac 70cc as was used in the prototype? This is my first giant plane and will be sport flying mostly and would like to try 3D.

ronk1

My Feedback: (25)

The AVIOmac is a no. I have a FPE 5.8 in my GP 330L and has more then enough power for hovering. It is a less expensive way to go and balances very well. A 85-100cc class twin would be a excellent choice also, like a 3w, DA, BME, FPE 6.8. Be careful of the cap to cap dimension, I don't think you would want the spark plug cap outside the cowl. Most will fit with no problem other then some of the 3w 100cc class engines.

3D Joy

A lot of guys use the ZDZ 80 RV. You must take into account that it is lighter than most other engine choices so you must be careful not to add too much weight in the back of the plane.

korky

I have a 3W 80 in mine and my friend had a Fox 6.2 in his both have exelent power as the plane is very light. My friend recently bought a composite and did not want to cut out the cowl for the spark plugs so bought a desert aircraft 100. As he has no plane for his Fox I think he would be interested in selling for a reasonable price. He is very fussy about his motors so it has had exelent care. If you are interested EMail me at [email protected] good luck.

ronk1

My Feedback: (25)

The ZDZ 80 is a fine engine also but for this airplane you would need to go with a pull-pull rudder for sure and most likely some nose weight. By the time you add the cost of a muffler the price would be very close to a FPE 5.8 and not have as much power. For the right price the fox 6.2 that korky has available would work. There is one question I would ask though about the fox. Does it have electronic spark advance (Syncro Spark) or mechanical? The mechanical works very well but you have the maintenance of the ring and linkage. Some people love it because of it being proportional to the throttle but in a dusty environment it can be a pain. If you notice I have not mentioned the Brison 5.8. Check out the thread in the gas engine forum.

Dick T.

My Feedback: (243)

The prototype using the AvioMac 70 only weighed slightly over 19 pounds RTF so it's performance was excellent. They later changed to the AvioMac 85 which bumped the weight up to roughly 21 pounds. Both performed 3D well at those weights/power.

Built from kit versions average 21 to 24 pounds so the 70 will be limited for 3D but the 85 will do well. AvioMacs are heavier than comparable engines because of the magneto ignition but they are smooth as glass and very powerful. I currently have an 85 in a H9 Sukhoi weighing 26.5 pounds and it pretty much matches a friends DA 100 powered version weighing 27 pounds. Several years ago I watched a Lanier Staudacher with a Mac 70 hover and rocket around with the rest of the 3D'ers. His weighed 18 pounds RTF.

I have a Mac 70 that will be going into a Lanier 1/3 Laser 200. Shooting for the 17-18 pound range. Also have the GP 300 kit which will have a Moki 90cc twin installed.

AvioMacs are available now with either mag or electronic ignitions and are agood value for their cost.

rmh

If you are an accomplished builder - you can do the plane with the ZDZ80 well under 18 lbs.
BUT If this is still fairly new ground for you - the weight will go into the 20's easily.
The prototype was built /flown by a good builder.
I am referring to Mike Cross.
3D is based on a power to weight relationship of aprox 1.25-to 1 as a bare minimum- Most of my own stuff is upwards of 2-1
My own suggestion is blow a few bucks on a small electric foamie and do the 3D with that -
Make the EXTRA into a nice , precision aerobatic setup.
I have both and frankly I have found that 3D is much more fun with the little stuff.

Tim_Indy

The key word there is "prototype". The plane apparently gained weight in its production models (as you stated). I used a BME 102 twin which was significantly lighter than the AvioMac 85 and still ended up with a 24 pound plane.
Hmmmm...... same plane and same approximate weight but your 85cc MacMinarelli matches a DA 100? What's wrong with THAT picture?

Dick T.

My Feedback: (243)

Hard to believe. The Mac pulls two more inches of pitch (26x12 vs 26X10 if I recall as I haven't flown in a while, might be 24X12 vs 24X10) at slightly less RPM. I don't have any other explanation. The planes perform about the same, we have flown each others and they feel the same. Go figure!

cygnet

My Feedback: (33)

Hey Dick did Mike you use any glue when you built that 18 pounder, I have built two now and the best I can do is 21lbs 8oz and I used CF gear wing tube and TW. One other thing with a ZDZ 80 single on a full length pipe the thing is out of control it is way over powered to the point that if you don't learn throtle management very quickly you find your self in a whole pile of throuble. Just my .02

rmh

Glue?
some - wings and entire tail group was 1/16" balsa over solid foam - NO carbon fibre anywhere -
I don/t use structures typically seen on ARFS-- they are in my opinion, overweight.
The GP 300 has good construction but it can be done much lighter than stock setup.
Am I familiar with it - yes- I bought one - looked it over , thought it was a bit heavier (but very strong) construction than I like - sold it to a friend -he built two of em - both with 80 singles - great flyers.

ronk1

My Feedback: (25)

We are talking about a Great Planes 330L 33% kit. Your reference to a GP 300 and ARF's makes me think your talking about a different airplane.

rmh

same plane--

SLINGSHOT-RCU

Any pics of the kit.

ben beyer

My Feedback: (23)

Could you do 3D well with this airplane and a ZDZ 80 single (pitts muffler)?

3D Joy

I will try to answer the last 2 questions with this photo.

It shows the kit as it arrived home. Most of the wood is die-cut of very good quality and some, where precision is critical such as ribs with wing tube holes etc. are laser-cut. The quality of the wood is very good to me and allows me to build this plane fast, as I don't need to change everything IMO. It is also easy to modify for a canister installation for my ZDZ 80 RV. It will "have to" have enough power for 3D.

I agree with Dick as for the sturdy construction. It is a solid aircraft. The only thing I don't know is how to remove weight. It seems like the kit is strong where it ha to be and weaker where it has to be at the same extent. I try to say that if I remove some weight here, I just created a weak point because the rest becomes stronger than this point. One way is to change everything and get it real lighter, another way is to build it as is like me, and the other way is to sell the kit as Dick did.

I would think that a carbon LG would be great as the stock one is somewhat heavy (more than 1 lb).

Hope this helps.

ben beyer

My Feedback: (23)

Let me know where you can get some carbon fiber gear for this bad boy.