Doors for a CHallenger

[Morph]

Seeing as I fly a tandem type aerie, and the PAX gets wind blasted, a blow job of sorts , I decided to build AUKie a set of doors for winter. I hunted the internet and this is the plan from Quad City, the Challenger manufacturers. Very sophisticated and detailed as you can see



I did all the calculation and found I would need one 1250X2500mm sheet of Lexan(the SA equivalent at R360 per sheet), 2 X 5m 12mm aluminium tubes (92), a sh!tload of rivets (R10) and some patience. After cutting the sheet to fit I temporarily mounted it on the plane to assist in getting the curvature of the tubing right.

Here is the LH Door, still with protective coating on and artists impression of Morph and PAX


I needed to bend the tubing and a knee, some leather gloved hands , a gas burner for heat and a wooden pole were used to get the curvature of the tubes right. The tubes were fitted onto the plane and the lexan attached with a few rivets. I then removed the door and had to make up a number of gussets out of aluminium sheeting to strengthen the corners.

Finally I had to devise a method of keeping the doors shut when in flight (a wise thing to do I am told)

This is the end result




Now to see what she will fly like.

This is AUK before the doors



I really enjoyed this little exercise and am now keen to start exploring building a complete kit Bushbaby, or Savannah, or..... who knows, soon

[Aerosan]

Morp
If I assume that the drawing of you wearing glasses is correct, am I then correct in assuming that the drawing of your pax is also correct?
Ive seen the post on a topless trike but Challenger??

[Morph]

You are absolutely correct wrt the glasses part. Now for the PAX I am trying to elicit a favourable response but so far no takers. However I will not give up. :D

[GR8-DAD]

Morph,

Let me know how she flies and how the 35 mph crosswind capability is affected.

My doors arrives tommorrow but is unlikely that I will fit them before 2007.

Looks like a good fit. BTW, I see all the CGS Hawks comes fitted with enclosed doors as well.

[Morph]

GR8-dad

I do expect the doors to affect the cross wind landing capability of the plane to a degree, however, in all the time I have been in the Cape and with all the times I have flown in the wind I have yet to experience a 35MPH cross-wind landing. Besides we all know the wind doesn't blow during winter :D which is what it's for

[RV4ker (RIP)]

Baie mooi. Nice job...

[Morph]

I test flew AUK with the doors on today. The manufacturers stated that the doors change the flying characteristics of the plane. The addition of the doors increases the adverse yaw effect because they act like a large tail ahead of the CG. Another way of looking at it is the side of the body now acts like a wing and when the plane will tend to drift towards the side that has the highest airflow across it.

I was told to expect to use more rudder than previously and the plane would require a finer control during co-ordinated turns etc. If you are slightly out on the ball-type slip indicator , or yaw string, the plane will tend to skid more than previously, so a little more concentration is required to keep the ball/yaw string centered. (BTW if you do use the traditional ball type slip indicator, chuck it out, and go the yaw string route. Much more sensitive and is the cheapest instrument you would ever buy.)

I started by just doing crow-hops, i.e. taking off, flying along the runway to experience the required rudder inputs and then landing again. I did this 4 times and I was satisfied that I still had significant directional control for the take-off and landings.

Next, it was circuit time. I took off on full power and noticed the max RPM had increased by 100 rpm. This must be bacause the wind flow across the prop is cleaner, without the turbulance the open cockpit generates. Climb out was uneventful with no major rudder movements required except of course the normal right rudder to compensate for the rotational effect the prop has when at max rpm.

Left turn on to crosswind and I noticed the tendency to yaw into the turn if you don't control the rudder inputs correctly. At first I got a skrik but the second turn on to base was much better. Reduced throttle down to 5000 rpm and trimmed for level flight. The plane is flying 8mph IAS faster than previously (I used to get 60mph IAS at 5000, now it's hovering around 68. I thought it was my imagination but after 5 or 6 circuits I was still getting the same.) Must be due to reduced drag, and cleaner airflow across the prop.

Turning finals, I reduced throttle to 3000rpm, set up for a 65mph approach and lined up. Sufficient rudder authority was still available at it was a simple process to keep it on the center line for a smooth landing.

By the time I completed 6 circuits I was getting the hang of this. It does require you to be more active on the rudder, but I would say a 5 to 10% rudder deflection in a co-ordinated turn previously would now require and 15 to 20% deflection and more control straight and level, where previously you could fly feet off.

I would not receommend this to in-experienced Challenger Pilots because the initial sensation can scare you and you could end up getting into cross control situations etc. If you want to try this, get an instructor to fly the plane first to check that he is happy and then get him to spend an hour or two with you with the doors on.

There are mechanisms to reduce the adverse yaw such as installing a larger tail, or installing additional vertical fins on the sides of the tail wings. The second option will reduce the cross-wind capabilities of the plane and the rudder authority. Other guys install vortex generators on the doors the increase the turbulance around the doors and reduce the lift they potentially could create.

Personally, I feel it is flyable, and comfortably so. Give me a month and I'll let you know the developments.