Balsa Bandit |  Bandit Special Features

Bandit
Airframe Directive (A.D.)
And other helpful notes

Fin Retention
Bandit's (original)

In flight, there is a very minor vertical force component that is trying to pull the fin up from its fuselage mounting. The proper tightening of the set screw into the side of the fin post is many times more than enough force to overcome the vertical component. But, it must be tightened prior to flight. In the case of the steel post (later kits), it is necessary to file a small flat spot to give the set screw a "seat". With the early carbon fiber posts, the set screw made its own seat.

Two incidents prompted this notice

Hundreds of Bandits have logged thousands of flights over the past 7 years. We know of 2 occurrences of a problem. If the fin can ease upward enough to disengage the forward pin, it is going to leave the model.

The Fix

• Make sure that the set screw is tight before flight. This has been sufficient for thousands of flights.

and / or

• Delete the forward pin and replace it with an additional hold down bolt per the drawing below.

Bandit Rudder linkage

The 1/32" pull-pull wires are sleeved with 1/16" brass tubes (1/2" long), then soldered into a Sullivan 2-56 threaded coupler. This can be attached to the servo arm with a safety clip (Sullivan). This idea and photo from David Ribbe is the best linkage for this critical control system if you plan to go really fast.

BANDIT RUDDER
A Bandit with a standard fin experienced a severe rudder flutter as a result of servo gear failure and the unfortunate result was a crashed model. This is the first time that this has occurred in 4 years and thousands of Bandit flights that we are aware of. Since the standard fin has a larger rudder than the swept fin it would follow that it would be more prone to a flutter problem. Flutter can occur if there is any spring in the control system. This dictates that the servo be very tightly screwed to the mounting rails and that the mounting rails be very securely glued to the internal fin structure.

By switching to a metal gear servo, we also can remove a possible weak link in the system. Worn nylon gears can also be a spring source. We have been using JR 3321 servos for the rudder but these servos do not feature metal gears and currently there are no plans to change it.

We just received a sample 94141 servo from Airtronics that comes with a JR compatible plug. This is a high torque precision unit with a metal gear train and a uniquely variable mounting system. It looks like a great candidate for operating some control surfaces (like the Bandit rudder) on jets. See your Airtronics dealer.

Another consideration: If a control surface gets a hard rap from accidental handling as can happen in transport or just sitting in the pit area, nylon gear trains could be damaged. If undetected, this damage could show up in flight. If there is some concern in this area it is worth the time to change the servo before flight and have it checked out later.