RE: Cold Duck - Build
 

Started work on the fuselage MonoKote. I did a final sanding of the fuselage and looked it over for any dents in the balsa. I find that a spot of water on a balsa dent and then heating the area with the hot MonoKote iron steams them out nicely.

I did the lower front of the fuselage first and the lower back.

RE: Cold Duck - Build
 

I decided to do the remaining fuselage with a right and left piece of MonoKote with an overlapping seam along the top center of the fuselage. I did the left side first leaving the right side with the engine opening last so I could use the engine opening area to gather MonoKote to work the nose compound curves.

RE: Cold Duck - Build
 

View of the center fuselage seams. I took these images with lighting that enhances ability to see the seam but they are mostly invisible in normal lighting. I’ll be filling in the area under the canopy with black MonoKote.

RE: Cold Duck - Build
 

View of the completed MonoKote work.

RE: Cold Duck - Build
 

I've got a couple of Super Kaos's that need covered, and I am no match for your work. Give me an address. All kiddin aside, that is beautiful work. Keep the pics coming.

John

RE: Cold Duck - Build
 

Always impressed by your threads. Very nice work on the monokote. Was it only two full rolls to complete the wing and fuselage. How fine do you final sand your balsa? 400 grit paper? Just some extra trim work on the sides and the canopy to install?

Looking forward to the completion.

Jim

RE: Cold Duck - Build
 

Thanks for the positive comments guys! Of course they always look better in pictures don’t they, but I’m very happy with how it looks.

Yes, with careful planning you can do it with only two rolls.

I find sanding balsa for MonoKote covering pretty forgiving. I usually finish up the sanding with extra fine 220. Balsa will always show grain no mater how fine the paper used is, but MonoKote easily bridges over the grain pattern using 220. The hard part is getting the surfaces true for the MonoKote application. Because balsa does not have a reflective surface like you have when you are using primer and paint and it is hard to see imperfections in the balsa. I do a lot of my sanding with a wood board that has sandpaper glued to it and the unpadded side of a commercially made sanding block.

I use the straightedge and shadow method to help see and compare curves like along the length of the fuselage top. I find that it helps if you work it and then put it away for a day you often get a fresh view when you start again. As you know it is a step-by-step building process from the quality fitting the parts and gluing it together, razor plane shaping, sanding, etc.

For some unknown reason there is always a big debate on RCU about the best film covering, but for me MonoKote has always worked great. For 37 years its had consistent excellent quality and color and makes what I think is the best looking film finish.

I usually keep my aircraft for many years so I feel like my workmanship needs to pass the test of time.

RE: Cold Duck - Build
 

8178,

Very Nice Work!!! I agree with you on the Monokote... the only way to go. I have got to quit putting more time in the day job and start building. You thread is definitely an incentive to get going. Great project!!!


Dan

Carolina Custom Aircraft

RE: Cold Duck - Build
 

Just simply fantastic 8178. If you hadn't posted pics it would never occur to me that it's not a painted glass fuse. Two questions: Do you have the main gear canted outwards and what happens if your engine drips castor oil on that carpet!

RE: Cold Duck - Build
 

*Beautiful* work 8178! If the lighting really does accent the seam, then either you're the guru god of covering or I need glasses. Besides your obvious building skills, you've got good taste in reading material too, judging from your books in the background (Ferrari, DeTomaso, etc). It doesn't get much better than airplanes and exotics!

Tim

RE: Cold Duck - Build
 

Thanks rainedav! Yes the gear is canted out a little and gives the gear a little more flex on take offs and landings. It also allows the gear blocks to be in further toward the center of the wing. It is an idea that a friend pioneered and I borrowed. The RJL K.61 engine is brand new so it doesn’t have a bunch of oil in it and I’d be in big trouble if it dripped out on the carpet.

Thanks Tim! You’re right, nothing better than classic RC aircraft and classic exotic Italian cars. Especially the 5.7 liter V-8 mid-engine ones!

RE: Cold Duck - Build
 

You’re right, nothing better than classic RC aircraft and classic exotic Italian cars. Especially the 5.7 liter V-8 mid-engine ones!

OT - but.... speaking of mid-engine Italian exotics, did you happen to see the Lambo Miura concept that they just unveiled in Detroit? Faithful to the original (one of the most beautiful in my book), but fully updated w/ technology.

RE: Cold Duck - Build
 

Yes, I saw it and thought it was pretty nice work.

RE: Cold Duck - Build
 

Looks like this Cold Duck is going to be a rocket machine! I put it on the scales including everything to be installed, push rods, linkage, etc and the all up weight is only 5 lbs 3 oz. I’m sure that I’ll add a little more weight gluing the stabs on and etc. but it’s going to be light! At 5 lbs 3 oz the wing loading is only 18.38 oz and a power to weight ratio of .021 HP per ounce. Yikes! As a comparison, the wing loading on my Tiporare is 24.9 oz and has a power to weight ratio of .016. That’s assuming the Tiporare engine is making 2 HP but it might be more when it is on the pipe. The wing on the Cold Duck tapers down to a 15% airfoil at the tips so there is not a lot of drag. It’s going to be a fun machine to fly!

RE: Cold Duck - Build
 

How are you planning to attach the canopy to the fuselage and finish it? It's been a long time since I've done a build. I like your techniques. The forum is great for this step by step building.

Jim

RE: Cold Duck - Build
 

I’m working on the tail group installation next and then I’ll show the canopy installation work.

RE: Cold Duck - Build
 

I forgot to mention a hint about the MonoKote seams. Sometimes after you have scored the top MonoKote piece at an overlapping seam and you are carefully pulling off the excess cut away piece, a small chunk may stay glued down at the seam and tear loose from the piece that you are removing. To remove these small stuck pieces, I use MonoKote solvent and carefully use a razor blade to lift off the stuck piece from the lower MonoKote piece.

RE: Cold Duck - Build
 

I started work to install the stabs. I find it helpful to use a square on the stab trailing edge to draw the center line on the horizontal stab before adding the MonoKote. You want to check the center line from both sides of the trailing edge. From the center line I mark off lines for the thickness of the vertical stab less about 1/64”. I use the outer lines to align the edge of the MonoKote. I do this because I do not like trimming the MonoKote off the center of the stab because of the possibility of scoring the top of the balsa and creating a week point on the stab. I do the same thing on the bottom of the stab.

Before covering the fuselage with MonoKote I checked to make sure the stab fit correctly on the fuselage and was level with the wing. As you recall I also checked the wing incidence.

I like to use an alignment thread attached to center line of the fuselage up front to help align the stab as well as the normal measuring from the center nose of the fuselage to the back tip of each side of the stab. To check the horizontal alignmen I make sure the wing is bolted on and use the eye ball method by viewing the aircraft from behind and making sure the wing and stab are parallel. I used 30 minute epoxy to glue the stab to the top of the fuselage and the front of the stab to the back edge of the fuselage top piece.

All this alignment checking seems like a pain in the neck but very necessary if you wan a true flying pattern aircraft.

RE: Cold Duck - Build
 

Because this Cold Duck is going to be so fast I decided to further lock the horizontal stab to the fuselage with a couple of round hardwood tooth picks. I drilled a hole toward the back of the stab and one in the front that intersects the fuselage top piece. I worked some 30 minute epoxy into the holes and slid the tight fitting tooth picks in place. The epoxy soaks into the hardwood and the surrounding balsa and adds a good amount of strength.

RE: Cold Duck - Build
 

Most epoxy glues have a lap shear strength > 3000 psi. Lap shear is defined by ASTM D3163. Tooth picks are typically made from birch, and the shear parallel to the grain for birch is a maximum of 1880 psi. The cross sectional area of a 1/16 diameter toothpick is 0.0031sqin. it would take only 5 lbs of force to shear the tooth pick. Your glue is spread over a greater area and would provide greater strength than the two tooth pick. Might help with alignment, but the stab is already glued in place. The epoxy is probably holding more of the structure together. If your tail section ever broke off, I'm sure the joint would fail at the wood than the epoxy. Balsa has a typical tensile strength of 1000psi, but a shear strength of 230psi. Ok enough of the technical stuff, lets get back to the fun.

RE: Cold Duck - Build
 

Thanks jpurcha! I agree and remember they are soaked in epoxy so let’s give them 10 lbs each! The vertical stab is also glued to the top of the fuselage and over the top of the stab and that adds some strength too.

RE: Cold Duck - Build
 

The Monokote on top of the fuselage and under the front of the vertical stab was cut away using the thread as a guide. The vertical stab was then glued on with epoxy. The piece of masking tape in front of the stab was used for aligning the front of the stab. The stab bottom needed a little sanding to create a gapless seam along the bottom. Before the epoxy is fully setup I will use some alcohol to clean up the epoxy joint.

RE: Cold Duck - Build
 

View of progress so far. The canopy install is next and then the, control arms, push rod exits, push rods, glue all hinges and finish off the radio install. Notice, that by countersinking the Du-bro hinges and beveling the leading edge of the control surfaces a zero gap is achieved at the hinge line.

RE: Cold Duck - Build
 

In-between sanding the canopy for a good fit on the fuselage I installed the push rod exits and the rudder and elevator control arms. The exit guides were glued in with CA and the control arms were glued into control surface's round cutout holes with epoxy. The last image shows the 4/40 socket head bolt used for the control arm.

RE: Cold Duck - Build
 

Completed control arms.