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