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KeilKraft Gazelle Scratch Build;
Topic Started: Tuesday Jul 28 2015, 09:53 PM (1,598 Views)
Tony Leong
Avid builder of models
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Just back from break in the UK learning how to fly gliders - the full sized ones, in my case an ASK 23. Sort of like flying a big RC model except that you are in it. This makes it a lot easier (because you can feel the lift when riding a thermal but can be more difficult at the same time because that is the ground rushing at you and you can't afford to go and do something stupid like stalling out. Anyway, I digress. Now that my last build - the little Baby Ringmaster has been completed and flying, I've been itching to build a childhood favourite of mine - the KK Gazelle. I built two of these when I was a kid and they were a blast to fly.

As usual I started with preparing the patterns for the parts needed. The plans were downloaded from the web.


The stats for the Gazelle are 28 in wingspan, 163 sq. in wing area, All Up Weight about 10 ozs, and powered by 1.5cc class engine.

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I'm thinking of powering the Gazelle with a 0.11 ci (1.5cc) diesel from Enya - the Enya Ultra 11CXD. This is a pretty powerful unit - probably much more than what this model needs, so I may consider another power plant like the Enya Quicky 09. Have got some thinking to do. This particular unit is brand new, straight out of the box. Its an RC engine meant for an RC Old Timer plane I intend to build shortly but I bought the venturi and spare needle valves to convert it back to a control line engine.

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Tony Leong
Avid builder of models
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Project is on hold at the moment as my Proxxon Jigsaw, after more than a decade of service has decided to go kaput. Will need to see if it can be repaired or get a replacement. Very sad.
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Tony Leong
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I have made a kit of parts needed for the build. The only change I have made at this point is to substitute the use of a hard lightwood (don't know the name of the wood) - 9 mm thickness, available from the the Japanese $2 shop in place of 1/4 balsa for the fuselage. I find this wood to be only very slightly heavier than hard balsa and very strong. The Enya 11 Ultra CX up front is a much heavier engine than the typical diesel engines that the Gazelle was originally designed for, the slightly heavier tail will come in handy to achieve balance. Better to put the weight to use (additional strength) rather than to stick dead weight in the form of lead at the tail.
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Tony Leong
Avid builder of models
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I usually start with the wing first so that I can get the most difficult part of the build out of the way. I am starting with glueing the ribs to the first half of the trailing edge first. The ribs are not yet glued (friction fit only) to the spar as the trailing edge and the ribs have to be flipped around to allow the second half of the trailing edge to be glued. The spar just provides the key to ensure that the ribs are properly aligned before glueing the ribs to the first half of the trailing edge. I am using aliphatic resin (Titebond) hence the need for pins to secure the glued parts in position while it cures over night. It sounds slow but in reality its not much slower than using CA because I allocate only a a short time to building at a time and once the parts are glued and pinned down, I move on to doing the many other things I have to do. By the time I get back to the project again later in the day, the glue would have cured - so it won't be faster for me even if I had used CA. It would be different if one were to be building for several hours at a stretch and using CA would be faster as it cures instantly, allowing the next step to progress immediately. I don't like using CA and will only use it when it is absolutely needed as I do not like the fumes that it gives off. I work in an enclosed air-conditioned room and I don't think that it is a good idea to be breathing in that stuff as it seems to linger in the room even after you have ventilated the room for hours.

The wing is flipped over to allow the second half of the trailing edge strip to be glued on. Again, the ribs are only friction fitted on to the spar just to key them into position while the Titebond is cures. I am using the leading edge beneath the ribs to act as an alignment support.

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Once the Titebond has cured, I have flipped the wing back again - note that the port wing has holes cut into ribs to allow the lead outs to be threaded through whilst the starboard wing hasn't. I am using the leading edge strip as a support at the trailing edge position. The wing is pinned in position before the spars are glued on. This is to ensure that the wing comes out straight and true. It is very easy at this point to end up with a bowed wing (laterally) or a warped (twisted) wing which will be near impossible to remove later. Note that the ply bell crank supports have also been glued on at the same time.

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Tony Leong
Avid builder of models
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Second wing spar glued into place. If you look carefully, you will know that I screwed up with the 2 middle (W1) ribs and had installed them with the ribs swapped around. The rib with the holes should be on the other side and the rib without the holes should be on the starboard wing. Ah well, things like that happen when you are not concentrating ie. watching TV while building. Since I discovered it after the glue had already dried, it was not feasible to remove and swap them around. No big problem. I just need to cut the holes on the rib without the holes so that the bell crank leads can go through. It won't have any effect on the completion or the strength of the wing.

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Edited by Tony Leong, Friday Sep 25 2015, 06:11 PM.
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Tony Leong
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With the leading edge glued on, the basic wing framework is completed.

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A deviation from the plans, I have added spar webs using 1/16 in balsa cutoffs from the trailing edge. This strengthens the wing considerably with negligible added weight. Ideally, the grain of the web should be vertical for maximum strength but this will mean that I will have use a fresh plank of balsa. The balsa cutoffs were just the right size so I used it instead of committing it to the scrap box. For this size of model, there is more than sufficient strength even with the grain running horizontally.

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Tony Leong
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Fuselage has been completed with 3/8 x 1/4 in hardwood engine bearers mounted and 1/32 in birch ply fuselage doublers glued to each side of the nose area.

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Tony Leong
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I made a bell crank out of G10. 4 nuts locked into position held it in position. As added security, blue thread lock was applied.

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As it is difficult to centre the bell crank after it has been covered up by the centre sheeting, I opted to prepare the lead outs prior to the completing the centre sheeting. I've not yet installed the wing tips as they will get in the way of the sanding and carving of the leading edge. They will be glued in after the leading edge is sanded and the trailing edge is installed.

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The then commenced sheeting the centre wing panel.

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The wing is then left over night for the Titebond to cure.

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Edited by Tony Leong, Thursday Oct 22 2015, 05:23 PM.
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Tony Leong
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Lead out guides have been epoxied to the wing tip, followed by the wing tip gussets. The wing then received a final sanding.

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The fin and tail are given a final sanding.

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Here we have the components ready for covering and final assembly.

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Tony Leong
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Covering with Oracover Lite on the way.

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Tony Leong
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The plane has been covered and final assembly completed. Next is to make the water slide decals to complete the finish. I haven't got a tank to suit this plane so I shall have to make this up from tin plate before bolting on the engine.

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Tony Leong
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I could not find a commercially available tank that could fit the space and the capacity needed, so had to make one up from scratch. Worked out the dimensions for a tank the came out at 40 cc capacity. Printed out the pattern and transferred it to the tin plate for cutting and then bending to shape.

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Trial fitting of the parts.

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Tack soldering to get the alignment right.

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Soldered up all the seams.

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Here is the completed tank body with the plumbing (1/2" brass tubing) bent to shape prior to soldering. I may decide to go with straight vents instead of the forward facing vents shown here as the limited clearance with the small size of the fuselage may cause the vents (particularly the bottom vent) to come into contact with ground/grass and cause crap to be ingested into the vent on landing.

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Tony Leong
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Here, a piece of balsa wood scrap is used as a stay to ensure that the vent tubing is held with the appropriate clearance between the bottom of the tubing and the tank to allow the vent properly. It also leave both hands free to handle the soldering iron and the flux/solder.

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Et Voila! one vent in place, two more to go.

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The completed tank just after leak testing. Its leak free and time now for a final de-burring and removal of sharp corners.

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Tony Leong
Avid builder of models
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With the Enya 09 Quicky up front, the plane came out very nose heavy. The original design most likely was for a smaller and lighter engine. Adding 3/4 oz of lead weight to the tail still wasn't enough. t didn't want to add more lead weight so the only way around this problem is to shift the engine further back. This necessitated making a new shorter tank. For the new tank, I had the tube exit further back and higher on the tank. There is not a lot of clearance between the bottom of the tank and the ground and my concern was that the feed and over flow tubes would end up scraping the ground on landing. The first tank I made had a capacity of 40 cc. This smaller one is 35cc. Should still be sufficient to provide a decent flight duration. I will use the 40cc tank for my next build - a KeilKraft Firebird. With a Fora diesel up front - the 40 cc tank will be a perfect fit.

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Edited by Tony Leong, Thursday Nov 19 2015, 02:20 AM.
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Tony Leong
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Well, here she is ready to fly.

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