2.6m Extra 330 Hints, Tips & Information

This page contains items that may help you whilst building and flying your Composite-ARF 2.6m Extra330. The items are in no particular order.


It should be noted that you will still have a 100% capable model should you choose to build your Extra exactly as per the standard instructions.


Check the gallery here and equipment list here


Item Description
Latest Instructions The latest set of 2.6m Instructions and photosheets can be downloaded here (they are in .pdf format):

2.6m Extra 330 Manual

2.6m Extra 330 Photosheet


Cowl Baffle Template In order to ensure that your engine runs cool whilst cowled in, it is important to fit a 'baffle'. This directs the airflow up and over the cylinders rather than taking the quickest route which is under them and out the cowl exit hole. Forcing the air over the cylinders will ensure that your engines runs as cool as possible on hot days. The baffle can be constructed from 3/16" balsa in order to keep the weight to a minimum.

Thanks to Morten Laugesen for this template


Aileron Servo Bay Boxing The instructions clearly state that the aileron servo bays be strengthened by gluing 'ribs' in place so as to connect the top skin to the bottom wing skin. This ensures a very strong area to absorb the loads generated by the servo and stops the wing skins flexing which could otherwise lead to flutter. These ribs are generally made by a trial by error basis but using the template below will avoid such annoyances!

Thanks again to Morten Laugesen for this template

Cannister Muffler Installation The latest 2.6m Extra kits come prepared for the MTW cannister installation that you can also buy from Comp-ARF however, many older kits did not. For the older kits, each installation will be ever so slightly different but the concept of mounting the cannister mufflers stays consistent. Build a supporting former and attach this former to the front u/c support former. Here are some good examples of nicely carried out solutions..


Morten Laugesen (again!!) has a similar idea carried out to an equally high level of workmanship...


These pictures also give you a good idea of the holes required in the fuselage for the headers/cannisters to fit through...


These installations both use the MTW 75K cannisters and headers from MTW. For my installation (leftmost 2 pictures) I found the MTW straight headers with a 60mm 'drop' fitted very nicely. Rather than use the spring clips I would use small jubilee clips and tighten them right up! The spring clips cannot exert enough pressure to stop leaks.


Fuselage cooling vents If you have installed the cannister mufflers it is very important to allow the heat that they generate inside the fuselage to escape. This is best done by cutting some cooling vents in the underside of the fuselage. Below is a series of pictures showing how I cut my cooling vents. First two shots show the template tacked in place, the next two show the slots roughly cut whilst the final two show the slots tidied up and finished.


The CorelDraw template that I used for this cooling vent setup is below...

CorelDraw Template - Right click and choose 'Save Target As' to download this file. You will need CorelDraw to open it.

However you choose to implement 'cooling' vents please do not cut through the centre seam of the fuselage - this will weaken it considerably!!


Undercarriage Mounting Bolts In order to absorb some of your more 'bumpy' landings it is highly recommend that you use four very large washers on the four u/c leg mounting bolts. These help to spread the loads and stop the bolt head and otherwise small washer from crushing into the carbon leg. It's a highly recommended mod!

The photo on the left shows the standard bolts and washers used in the kit. The photo on the right shows the washers I would recommend you install to spread the landing loads.



Spinner Size? Whilst Comp-ARF recommend a 5" spinner for this model, many pilots prefer the look of a 4.5" model. If you choose to fit a 4.5" spinner then make sure that when you mount the engine you raise it 1/4" higher than the standard mounting position shown in the instructions. This will ensure that your 4.5" spinner lines up nicely with the cowl. The raised engine position has not been known to cause any adverse flying characteristics.


Cowl Mounting Warning On the 2.6m Extra the cowling is held in place with 9 M3x12 bolts. Earlier versions of the instruction manual showed the incorrect position for these holes. Please ensure that all cowl mounting holes are drilled 8mm from the rear edge of the cowl. If you drill further forward you will find your cowl bolts hang in mid air where the gap between the cowl and the angled engine mounting dome is formed.

The instructions have been corrected in all newer kits.


Wing roots rubbing on the fuselage Many pilots have noticed that after several flights the wing roots 'dig in' to the fuselage sides and leave indentations. The picture below shows such indents after 280+ flights....

These indentations are cosmetic and do not affect the strength of the model. If you really want to avoid these then you have 2 avenues to go down. Firstly, you can fit some very thin wing seating tape around the area (may not look to good unless you are very accurate with the placement) or secondly, you can use clear silicone on the wing root. This can be done my taping some cling film to the fuselage where the wing meets it, applying a bead of clear silicone all around the wingroot, tightening the wing in position and allowing to dry. Once dry, remove the wing (it should come off because the silicone shouldn't have stuck to the cling film) and, using a scalpel, tidy up the silicone. This should hopefully give you a slightly soft wing root that won't dig in to the fuselage too much.


Protecting the spars from cannister heat If you go down the route of installing cannister mufflers then it is very important to remember to protect the spars from the heat generated by the cannisters (which will only be an inch or so in front of the spars). It is possible, in extreme cases, for the heat from the cannisters to soften the epoxy in the spars resulting in the spars themselves softening.

A simple balsa box can be built around the spars to protect them. The newer kits contain the parts required for this mod whilst the older kits require you to supply and fit them yourself.

If you own an older kit and wish to make this modification then here are some good examples: