Challenger Modifications
Mike Round

Challenger Light Sport Aircraft

Experimental Aircraft


Keel Construction for a Challenger Float Plane

By:  Mike Round

Living in S.E. Alaska means you think "water" and how to allow/accommodate 160 inches of rain a year. When I ordered my kit from Quad City, it was a given that it would eventually become a float plane. Ketchikan has one of the highest concentrations of float plane traffic in the world due to the infinite water landing fields available here. It seemed natural to build a "keel" to the fuselage fabric bottom and allow water to escape through sea plane grommets. Although this modification was designed for a watery environment, I would think that all Challengers could benefit from this modification to accommodate rain or conscientious, vigorous wash downs.


mr3 1
mr2 2        
mr4 3

The center 1/2" tubing is made from 1/2" CPVC pipe (non-corroding). Four lengths of 3/4'x 3/4"x 1/16" aluminum angle iron is cut to length and riveted to the bottom 1/2" tubing at the upright aluminum stringer ribs (Photo 1).


A length of 1/2" CPVC pipe is cut and riveted to the cross pieces starting at the 1/2" inch tubing supporting the bottom of the nose cone (Photo 2) and ending just aft of the 1" bottom tubing aft of the forward fuselage brace (Photo 3).
mr5 4
mr6 5
mr7 6

Blind 1/8" rivets are used to attach the tubing to the cross members (Photo 4) and aluminum angle to the 1/2" bottom stringers.

After applying the bottom fabric, the tubing creates a subtle "keel" where water can drain away from the bottom stringer tubing on the sides (Photo 5) and drain out through the seaplane grommets in the bottom (Photo 6).


mr8 7
mr9 8
This modification has worked very well in alleviating the possibility of standing water (i.e. and shifting weight) in the fuselage.
I put in three sets of grommets bracketing the tubing (Photo 7) and a single one in the center at the aft end of the CPVC tubing. (Photo 8)


Rear View Mirrors on a Challenger

Challenger Light Sport Aircraft
These are bicycle mirrors that fit into handle bars or, in this case, 3/4" pvc. I bolted the pvc pipe into the framing of the forward door frame aluminum angle. These mirrors allow me a "visual" fuel gauge, check on my tail strobe operation, check the condition of my passenger, and look aft for "unusual" goings on in the tail/motor area as well as check for large jet engine intakes coming up from behind!! Clearing turns are great but when you are the slowest traffic in high traffic areas even the initiation of a turn could be hazardous when you don't know how far behind your traffic is.


Puddle Jumper Floats - Modification







Here are a couple photos of the plates that Gary Freitag and I made to
protect the longerons from damage when making a less than perfect water
landing on Puddle Jumper floats.

The bearing plate was cut from a 1/2 inch thick nylon sheet. (Photos 438 and 437) The bearing surface of the plate was shaped by using a 2 inch hole cutter on a drill press. I cut about 1/4 inch, or half way, through the
thickness of the bearing plate with the hole cutter for the full length of the contact surface. I added an additional 1/4 inch bolt to stabilize the
plate on the longeron. The size and dimensions of the bearing plate are
arbitrary but the addition of the plate increases the bearing surface on the longeron greatly and provides relief from the concentrated pressure point of the forward stainless steel stabilizer bracket. At the very least, be
advised to put the large fender washer provided by Puddle Jumper between the stabilizer bracket and the longeron. the instructions do not make this clear and I had mistakenly put the fender washer on the inside between the longeron and the nyloc nut. (Another Challenger owner did the very same thing and sustained the exact same damage as I encountered in the first couple of hours of flying on floats.)

I also put a nylon Super-Tough ultra light saddle from Aircraft Spruce on
the longeron on the inside before adding a washer and nyloc nut. (photo 435)

In addition to providing safety from damaging the longerons, it provides and excellent support bracket for the morse control cables which tend to flex and rip the outside fabric. It's an easy modification and I believe that
it's good insurance from damaging the longeron.



Challenger Flaperon Position Indicator

Here is what I did to give a quick check on the position of my flaperons. Trimming in flight is a common necessity but landing with reflex flaperons can be dangerous if you don't know at what speed you'll be stalling the plane. The Challenger II on Puddle Jumper floats with a Rotax DCDI 503 (i.e. heavy) can stall at 50 mph when the flaperons are fully reflexed (trailing edge up). Attached are pictures showing the cable control wire attached to the flaperon control horn and snaked down to the starboard aluminum downtube in the cockpit. The gauge end has a copper sleeve swaged to the wire forming a small loop to which I fastened a spring to keep tension on the cable. The gauge itself was made from printed computer graphics and backing made from velcro was glued to the paper gauge. This adhesive velcro allowed me to adjust the scale to the neutral position after everything was in place. The clear plastic tubing protected everything on the down tube for those times when I needed the "sissy bars" in turbulence! The position of the gauge at eye level gives a quick easy reference to the flaperon position on landing and is on my landing check list. Good flying.   

Mike Round

image challenger flapaeron indicator with insert

image challenger flaperon indicator cable
image challenger flaperon indicator


Stopping Throttle Creep on a Challenger

1) Cut the head off a bolt that is the necessary size and thread to accomodate the threaded insert to the plastic friction knob ( this item I found in specialty hardware at the local hardware store), 2) install a nyloc nut and washer on the inside and sandwich the aluminum throttle bracket between the nyloc and another washer, lock washer and a regular nut and tighten securely 3) Drill out the gray original plastic spacer to allow the nut and washer assembly to fit inside so the spacer sits flat against the aluminum bracket 4) install the throttle arm and a large fender washer followed by the threaded friction knob 5) install the compression spring and washer and finish off with an acorn nut. The spring keeps all the components from vibrating loose. This modification works great and it's low profile and the knurled knob is big enough to be adjusted when wearing gloves.

Mike Round




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