Introduction: DHC-1 Chipmunk

Dumas KIT NO. 335

30'' Wingspan Scale Rubber Powered Flying model converted to full RC.

Max weight once finished 250 grams (everything included)

RC equipment details:

Engine: E-flite park 260

Receiver: 4 Channel Spectrum AR400

ESC: Talon 15 Amp castle.

Elevator/rudder servo: Hitec HS-55

Aileron Servo: Hitec Digital Micro HS-5055MG

Step 1:

This plane doesn’t come with pre-cut spar to make sure the wings have the right amount of dihedral, they want you to raise the wingtips to a set height on the plans 2-⅜” and glue the wings together. That would be enough for a free flight plane, but in order to convert this pane into a full RC one I was going to need more strength in the middle of the wing.

With the help of a protractor, I figured out that according to plans the wing dihedral was 9 degrees. I cut a piece of basswood, which is stronger/heavier than balsa wood. later on I realized that indeed 9 degrees was way too much and created another one, more details on this later.

Step 2:

The first pieces of the wing together lying flat on the table. The intersection pieces are not glued together yet.

Step 3:

I realized that 9 degrees of dihedral would make the wingtips pretty much touch each other. I did my research and made the decision to cut another basswood piece, this time with 6 degrees of dihedral. What you can see on the picture is the template I used to cut the wood piece.

The reason the plans use 9 degrees is because a free flight rubber band plane needs to be stable. lots of dihedral means the plane would have tendency to keep the wings level. although the less responsive the ailerons will be.

WW2 planes had a little bit of dihedral. so pilots didn't have to keep their hands on the stick on long missions. but not too much so the plane was still maneuverable during dogfights.

Step 4:

Center part detail. I planked the center bottom. I was thinking to put the aileron servo around that area but I thought it would be a good idea to add some reinforcement (Wings are glued now. You can see the dihedral spar.)

Step 5:

Making sure both wingtips were the same height.

Step 6:

Starting with the fuselage, the hardest part for me is getting both sections (you can only see one here) to align straight together once you are gluing them. I need to find a gadget or something to help me out with that.

Step 7:

I planked the top part of the nose, I decided to add the battery plus ESC there, so I needed some kind of lid/compartment.

Also, I cut out one of the formers so I had space to put the elevator and rudder servos. Trying to keep the weight as forward as possible!

Step 8:

After sanding the nose. I cut/opened the compartment (did that with a little saw) where i am going to put the battery and ESC. You can also see that I added the firewall made of basswood.

Step 9:

Put two pieces of wood on each side of the lid to make a better fit.

Step 10:

put another two pieces of balsa front and back of the compartment.

Step 11:

Added magnets to the lid and fuselage.

Step 12:

I am not super happy about the way I built the ailerons. I could have used way less wood and been more careful on the finish. I put too much unnecessary wood and glue, but anyway they turned out to be alright.

You can see I cut out the aileron from the wing and added a piece of wood across. Couldn't find the right height so i glued a 1/16 at the bottom

Step 13:

Here some details about the piece of wood that goes across diagonally and where the hinges will be glued

Step 14:

I should have used CA hinges, way less heavy and simpler, but for some reason i decided to go with normal hinges. I had to add 2 pieces of wood so the hinges would have a place to be glued.

Step 15:

It might be hard to see, but the aileron is made of 2 pieces of wood. The flat bottom and a square piece right in front, Front piece will be sanded round. More details on next steps.

Step 16:

Adding the continuation of the ribs

Step 17:

Bottom part and the front square piece sanded. Tried to sand 45 degrees bottom and top so the aileron would be able to move once attached to the wing.

Step 18:

Here is the finished aileron. It does the job but it can be improved.

Step 19:

To move the ailerons I ran Sullivan cable through the wing and put the servo in the middle. Wings are thin so this is pretty much the only way, it also saves weight.

Step 20:

I needed a way to get the cable out of the wing, like i said maybe not the most finest work here

Step 21:

Elevator pieces

Step 22:

Joined both elevator pieces with a U shaped wire. I tried to use a flat piece of wire first and it didn't work out, I had to fill the gap and try again

Step 23:

Rudder

Step 24:

Dry fitting the Servos to see where the cables to control rudder and elevator should go.

Step 25:

Wing covered with tissue, I would also like to say that I didn't use the tissue that comes with the kit, I really like the tissue Guillows kits come with, you can also buy it separately

tissue

Step 26:

Glued the empennage to the tail.

Step 27:

Wing and ailerons covered. I gave the tissue a fine coat of easy-dope to give it some strength.

Step 28:

Tail covered.

Step 29:

Gluing the rudder. Used some scrap wood I had lying around to try to keep the rudder straight, worked better that I expected.

Step 30:

For the Elevator and rudder I used CA hinges instead of regular hinges. After my work on the ailerons, I decided to give them a go. This was my first time using them and I have to say that from now on, this is all i am going to be using for these types of planes.

Step 31:

Glued the servos with CA so I could set the cables. I will put some screws at the end to hold the servos in place.

Step 32:

Had to come up with a solution for the canopy so I could take it off to reach the electronics. To do that I added 4 pieces of wood and glued some magnets on them.

Added some washers to the canopy so it would stay in place. Neodymium magnets are freaking strong by the way.

Step 33:

So this is the engine cowl, “for a rubber-band engine”. There is no way I can fit the brush-less engine there. So I decided to add more wood, and make a mold out of it. later I could use the mold on a vacuum forming machine and get a plastic version of it

Step 34:

Time to cover the plane,

Step 35:

I changed the servo on the wing for a digital metal geared one. I found that the cable was putting quite a bit of stress on the old servo. Didn’t want that servo to slip the gears while flying, so I decided to change it for something better. Of course I glued the old one with Epoxy, so I had to break the base where it was sitting and make a new one for the new servo.

I added a little box of wood around it too keep it in place,. Didn't glue it this time, I put a very good double side tape underneath. and surround the servo with a wood

Step 36:

Painting the canopy

Step 37:

Priming the model with Tamiya spray, fine white.

Step 38:

Painted the whole thing with chrome yellow Tamiya TS-47

Step 39:

Put the decals in place, it really comes alive

Step 40:

Main gear and Tail

Step 41:

Masking work to paint the “black stripes” used by the pilots to get in and out of the cockpit. I used an airbrush and Tamiya XF-1 flat black.

Step 42:

I have done some weathering on the plane with dark grey pastels. you can also see it on the fuselage and tail, very subtle.

Step 43:

This is the frame I am going to use to hold the plastic for the vacuum machine. The pieces are put together with those 90 degrees angled pieces and few nuts and bolts.

plastic is styrene

Step 44:

Mold of the engine cowl. I added a couple more layers at the bottom. The grey stuff is putty.

Step 45:

Few plastic cowls made with the vacuum forming machine

Step 46:

Picked the best one and made the engine and vent holes.

Step 47:

Put the engine in place. I Added a 1mm piece of plywood as a firewall, basswood wasn't strong enough

Step 48:

Some more masking to paint the nose.

Step 49:

Cowl finished!

Step 50:

260 grams

Step 51:

If I measured correctly the CG should be 5 cm from the leading edge of the wing. The plane looks quite nose heavy in that configuration.

If I move the CG a bit forward until the plane is just a tad less nose heavy the CG is 4 cm from the leading edge.

Step 52:

The finished plane. If you are reading this, thanks for making it all the way through.

now I just need to find some time and a calm day!

Comments

author
MiraJ3 (author)2017-08-15

how nice

author
exVista (author)2017-08-06

Really good clear instructable. Wish more were like this. Would love to see it fly.

author
DavidB685 (author)exVista2017-08-08

Thanks!

author
rickharris (author)2017-07-31

Impressive. Would make a good DTFB plan.

author
DavidB685 (author)rickharris2017-08-01

Thanks!!

author
Mehadi_Saki (author)2017-07-25

Can you share the design

author
DavidB685 (author)Mehadi_Saki2017-07-25

Hi Mehadi_Saki, this is a Rubber band powered plane from Dumas, it comes with plans and some laser cut wood,

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=L...

what you can see in this instructable is how to convert the plane from a free flight rubber band plane to a Full RC airplane, lots of modifications are needed.

thanks

author
Altoidian (author)2017-07-27

I have been building RC models for almost 30 years and your skills are fantastic. I've thought about doing this but shied away because these little balsa strip rubber powered AC models are so fragile and re-engineering them to stand up to electric flight weight and stress seemed too much of a challenge for the reward. But, the beauty of your model and the intelligent re-design decisions you made have convinced me it's worth a try. Thanks for a really good instructable.

author
DavidB685 (author)Altoidian2017-07-27

Thanks so much Altoidian.

You are right, it takes quite a bit of thinking to build one, always thinking ahead.
In the end, the reward an experience makes it worth it, even if it crashes on the maiden flight!

thanks again and let me know if you start a project like this!

author
pr1 (author)2017-07-27

How strong is painted tissue?

author
DavidB685 (author)pr12017-07-27

Hi pr1,

I apply eze-dope https://www.amazon.ca/Eze-Dope-Tissue-Shrink-250ml... right from the bottle. That makes the tissue shrink and strong, quite strong to the touch. once the eze-dope is dried you can paint on it but that doesn't make any stronger.

I would also like to say that I didn't use the tissue that comes with the kit, I really like the tissue Guillows kits come with, you can also buy it separately
https://www.amazon.com/Tissue-Paper-15-Sheets-Guil...

author
rickharris (author)DavidB6852017-07-31

Yellow monocoat would add that much weight.

author
UFOdriver (author)2017-07-30

Awesome! Great work! Can you upload a plans?

author
rickharris (author)UFOdriver2017-07-31

try https://aerofred.com/

for suitable convertable plans.

author
DavidB685 (author)UFOdriver2017-07-30

Hi UFOdriver,
Thanks! Plans come with the kit. Here you can see the conversion process from free flight rubber band plane to Full Radio Control.

author
carolineb143 (author)2017-07-28

Great work!!!!

author
DavidB685 (author)carolineb1432017-07-28

Thanks!

author
Filmdesigner (author)2017-07-27

Very clear presentation. There are a quite of modelling tips you skipped (simply because its an article about conversion, not your skilled modelling) but your conversion is excellent. I often see these rubber kits on sale at hobby shops, covered in dust. I haven't found a good conversion kit. Maybe you could offer this? I really love the older kits as they have an honesty about them.

Thanks! I will go and buy one.

author
DavidB685 (author)Filmdesigner2017-07-28

Thanks Filmdesigner,
True, this is as you say a guide so anybody can pick some ideas if they start something similar to this. I don't think there are any conversion kits available anywhere that I know.
Some Dumas/Guillows planes are also meant to be flown as U-control, but you still have to figure out how to put ailerons and all the other pieces.

author
dotbox (author)2017-07-27

Build, adaptation and presentation, very nicely done (even if it doesn't fly!). Good to see this is still being done. Thanks for the memories.

author
DavidB685 (author)dotbox2017-07-27

Thanks dotbox four your kind words!

author
locojoel (author)2017-07-27

Very sweet, thanks for sharing!

author
DavidB685 (author)locojoel2017-07-27

Thanks locojoel!

author
FrancescoK2 (author)2017-07-27

Outstanding craftsmanship !!! I would also like a video of this great RC plane flying. Please post one as soon as you are able to.

author
DavidB685 (author)FrancescoK22017-07-27

Thanks FrancescoK2,

I am pretty excited and terrified to fly this plane, will see how it goes!

author
pr1 (author)2017-07-27

Love the build it will help me with my guillows me 109 build

author
DavidB685 (author)pr12017-07-27

Thanks pr1!

Nice, glad that I can help building the me109, I actually have the kit too waiting in my stash. one day!

Thanks.

author
N36 (author)2017-07-27

Amazing! And great documentation + visuals of the process. Well done.

I would also love to see a video of this flying. As a young kid I tried to do the exact same thing with a P-51 wooden kit like this. I fitted in what ever electronics equipment I could into it and it was horribly off-balance and didn't fly at all. So would love to see a success of it!

author
DavidB685 (author)N362017-07-27

Hi N36,

Thanks for your kind words!

Indeed getting the CG right it is not an easy task. I tried to put all the weight as forward as I could because I always end up building tail heavy planes. this time though plane seems to be nose heavy so will see how it flies.

like they say, a nose heavy airplane will fly poorly, a tail heavy plane won't fly at all.

Thanks again.

author
TURBOTECHNOLOGY (author)2017-07-25

Very Nice work
Do you have video of flying it???
I want to see great RC Plane Flying!

author

Thanks TURBOTECHNOLOGY,

Haven't flown the plane yet, the local filed i usually go is having some construction work, I will have to wait a bit, I would think 2/3 weeks.

author
seamster (author)2017-07-24

Very nicely done!

You should enter this in the make it fly contest that just opened to today! https://www.instructables.com/contest/mif2017

author
DavidB685 (author)seamster2017-07-24

Thanks will do!

author
seamster (author)DavidB6852017-07-24

You got a vote from me - good luck in the contest.

And well done on this little rc conversion. I haven't made a balsa/tissue plane for many years, and this was inspiring and really fun to see - thanks for sharing all the details!

author
DavidB685 (author)seamster2017-07-24

Thanks for your vote, really appreciated.

Thanks for your kind words, it is hard to see balsa/tissue RC airplanes these days!

author
gm280 (author)2017-07-24

Nice build. Back years ago when I was flying R/C, we use to reinforce the center of the wings using fiberglass material and epoxy. Anything less and you were asking for the main wing to fold in a dive and pull out. Don't ask me how I know that. The more dihedral the model has, the easier it is to fly and semi-correct itself when first learning to fly. The flatter the wing, the easier it stays in any angle you set it when flying. And that is because the more dihedral the lower the center of gravity of the plane and that makes the plane balance out easier when flying. Either way, Enjoy your new plane. It looks great.

author
DavidB685 (author)gm2802017-07-24

Yes, you are correct, I have also used fiberglass back in the day when I used to fly big planes with glow engines, as a matter of fact I learned the hard way, but that was long ago.

plane only weights 250 grams (all included) hopefully the wing will be strong enough, the basswood spar I made keeps the wing really strong, although I don't have and exact number on how hard i can pull, so I will be gently flying it, here is hoping!

You are also correct about dihedral. Plane was designed for free flight and powered by a rubber band so it made sense to have lots of dihedral in that case. In my case, putting ailerons, 6 degrees should be more than enough.

author
ArachnisDeathicus (author)2017-07-24

Very well done. Mind blowing.

author

thanks!

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