Notes about the Extra 330L

Dear Valued Extra 300L customers!!
Some of our customers have had problems to get the EXTRA 330L balance easily with the lighter engines. We have flown 3 different prototypes with out any CG Problems, but some production models may have differences due to variances in balsa densities. We are not 100% sure as to why yet.

We have come up with some solutions that we feel are the easiest and most practical.
Click here for details.
We stand by saying that a Moki 1.8 is too much for our Extra!

BUT

This is an excellent engine of capable of about 4.5 horsepower. There have been reports of modelers successfully using this engine. We also have had a couple modelers use it and it has resulted in aileron flutter.

That being said, it appears that the Moki 1.8 could be used if one is very careful. You must use a prop of no higher pitch than 8 inches. Probably about 20 or 21 inch diameter is best.

The idea here is NOT to go fast but have very high thrust for 3D and so on.

We have a really neat custom muffler made by Bisson that directs the exhaust out the cooling duct. This is much better than making holes in your nice cowl!

Before you think about buying a Moki, give us a call...

There are many DPM Extra 330L’s that are being flown with much larger engines than we recommend. Many are being successful, but some are not. The extra speed, power and vibration can lead to aileron flutter. Flutter is a very serious problem and most likely will cause the Model to crash. This is true of any plane. I own a full size that has a past history of the same problem. It is also important to understand that EVERYTHING wants to flutter.

All airplanes have a VNE. (Velocity Never Exceed) Most VNE’s are aileron flutter limited. And since we don’t have airspeed indicators in our models to give us real time information as we fly, we must be even more careful as pilots.

The Extra 330L has very large, light control surfaces for fantastic control at lower airspeeds. Works very well. It was never designed as a high-speed aerobat.

We have seen modelers “improve” the EXTRA 330L by changing aileron hardware. While some of the hardware we have seen used is good hardware, it can make matters worse because we designed the aileron structure specificly for the Sullivan metal horns. Under the aileron control horn is a 1/8th plywood plate. Under the plate is a balsa wood block.

The proper procedure is to install the Sullivan horn with the supplied screws, remove, put a small drop of THIN CA in each hole, let fully cure, then re-install the horn. REPEAT. This process adds tremendous strength to the area and much better grip for the screws. This is important to understand.

Using a Rocket City horn just does not work properly because of the type of structure inside the aileron. Its excellent hardware, I use it on other planes, but not applicable here.

Click any photo to enlarge.

You can raise the VNE of the EXTRA if you like by:

  1. Adding another aileron servo as shown in photo. Even a mini servo will help quite a bit.
  2. Making very sure you use at least the minimum servos we recommend. 100 inch-ounce, the more the better if you are using one, if you go to 2 servos, I think a premium mini is fine such as S9602 Futaba.
  3. Making sure the push rods are straight. The 1/6th rods are plenty strong enough because of the short distance.

Lastly, enjoy!