Jack Stafford Chipmunk build

octagon · March 17, 2020, 07:25:16 PM

So, looks like I will be spending a lot of time at home in the next little while. I was lucky to be able to pick up a Jack Stafford kit of the Chipmunk. The kit is very nice and complete and the newspaper that was in the box as cushioning was dated 1998, so I recon the kit is that old. It has foam core wings which I have never build before. I got it out of the garage this afternoon and started work on the fuse. It goes together pretty nicely with great plans and balsa and plywood cutting. I am hoping to have it done and flying by the end of the month, as I can work on it every day now.

Frank v B · March 17, 2020, 08:39:11 PM

Rob,

Are you building model airplanes or running an airplane factory??

Keep building!

Frank

bweaver · March 17, 2020, 10:06:38 PM

Looking great Rob. No doubt you are well on the way to meet your timeline.

Polecat · March 17, 2020, 10:44:08 PM

Rob That kit is a nice fined. There is a new company in the US making that kit now, I have been thinking about getting one.
When you are doing the sheeting of the foam cores send me a PM, over the years I have sheeted close to 50 wings now. Did a couple this winter for the E F 1's.
I use epoxy to glue the sheeting on, put the sheeted core's back in the shocks, put on a flat surface, a sheet of 1/2 inch piywood on top and weighted down with 2 cement blocks and let it set over night. You can use a 24 of beer for weight to.lol
Each wing planel will come out straight and no twists.

Ken

octagon · March 17, 2020, 11:07:44 PM

Thanks guys. Ken, I will give you a call when I get to the wings. Thanks for the advice. I was thinking Gorilla glue, but maybe epoxy is better?

Polecat · March 18, 2020, 09:18:02 AM

Quote from: octagon on March 17, 2020, 11:07:44 PM
Thanks guys. Ken, I will give you a call when I get to the wings. Thanks for the advice. I was thinking Gorilla glue, but maybe epoxy is better?

Rob Over the years Epoxy is the glue to use, the wood sticks really well to the foam and also adds some strength. When I started doing sheeted foam wing cores, I use a 3M contact glue, it worked OK but didn't add any strength and could develop some twists.
I wouldn't use the Gorilla glue as it is much like the white carpenter glue and could add a lot of weight.
When you are ready just give me a call.

Ken

octagon · March 18, 2020, 09:26:53 AM

Thanks Ken, I will. Can you PM me your phone number?

octagon · March 18, 2020, 06:48:34 PM

Got a chance to do a bit more today. The plans call for two separate control horns, one for the rudder and the other for the tail wheel. I figured I could combine the two so I silver soldered up what I think will work well. Got the control rods in and made the battery hatch. The plane is quite light at this point, and I am thinking 4 s, but if necessary should be able to get 5 s in. Thinking a Rimfire 46 and about a 70 amp ESC turning about a 13 inch prop. I also managed to slip with an allen driver and drove it half way through my finger. It has taken me 10 minutes to type this due to the bandage on my finger!

octagon · March 23, 2020, 06:49:51 PM

So like most people I have been spending a lot of time at home, and for me it has been in the workshop. I have built a lot of kits over the years, but I must say, this Jack Stafford Chipmunk is very rewarding. The kit itself is at least 20 years old and Jack Stafford kits are hard to find. I was lucky that Ron at Pinnacle got this and offered it to me. I decided to build, at least the tail, with internal control rods. required a bit of engineering but I find when I do get something original working, it is really rewarding. I also had to make the mount for the 46 motor I am using, as when this kit was produced, electric was at best in it's infancy. That was fun, but took a long time to engineer to get just right. But I think it is good. I now have to start on the foam core wings. I have never built this kind of wing before. Ken Flunney who builds a lot of this kind of wings, kindly offered the give me his method. I might start that on Wednesday as we are tied up tomorrow.

octagon · March 28, 2020, 06:23:50 PM

Back to work on the Chippy today. I am really enjoying this build as the plans are good, the wood, although at least 22 years old, better, and because the building instructions were kind of vague and non-existant for any electric conversion, it has meant some engineering to make it all work. The wings are foam core, and I have never build foam core wings, so I was happy and thankful when Ken Fluney got in touch and shared his method of doing them. They require a bit different thinking as things like the pockets for the servos and how to run the servo wires have to be decided upon and created. The plans call for and the kit supplies bell cranks for the ailerons. I cut pockets for so I have separate servos. I think I am going to build a structure inside the servo pocket door and then build a plate with the servo glued to it. I have found a product that should negate the need to fiberglass the plane before painting. It is a product from Wowplanes and it is called liquid sheeting. It is used in place of fiberglass and resin and there are a few threads on it. I really hate the mess and more the sanding that is required with glass, so I will give this a try. I have decided not to fly until after the threat of this damn virus is past us. I wish this was not the case as I have a whole fleet of planes I want to maiden. The picture in the basement shows a few of them.

Polecat · March 29, 2020, 10:39:25 AM

Looks good Rob, the wings came out OK with no problems doing the sheeting.
Keep up the good work.

octagon · March 29, 2020, 04:21:10 PM

After carving out the pockets for the servos I removed a think strip of wood leading from the pocket to the root. Then cut a slit down the middle and inserted the servo wire. Then covered it again. I embedded 2 pieces of basswood into the foam to act as anchors for the servo hatches. The 30 minute epoxy I used to glue the servo to the hatches is curing as I write this. I have to hinge the ailerons and then join the wing so I can get the right shape for the wing saddle. The roots of the wings have to be cut so that they match properly when the proper dihedral is set. I have to make sure I get a good fit as the wing only has a 5 inch hardwood main spar, so the joint needs to be perfect. I have been experimenting with how to do this.

octagon · April 08, 2020, 09:53:07 AM

Have been quietly working away. The wing fiberglassing is finished . I had to redo one panel as I was not satisfied with the way it looked. I am using quite light glass, probably 1/2 ounce, and it is harder to work with than heavier glass I find. The centre joint of the wing was re enforced with an 8 inch wide strip of 2 ounce material. With the wing saddle and the fillets being the last bits to finish, I will move on to glassing the fuse. After the glass and sanding I run into a problem, because I have no glazing compound that I use to fill any uneven spots that show up after a coat of primer. It comes from Canadian Tire and I am not going to go there just to get it. I also have no primer paint so the final finish may have to wait until after we get past this.
Stay safe everyone

piker · April 08, 2020, 11:39:09 AM

Hey Rob, The Chipmunk is looking great!

What happened to your idea of trying the Liquid Sheeting?

Robert

octagon · April 08, 2020, 12:20:22 PM

I liked the idea but the product is made by a company in Texas, and that place has closed down due to the Virus. There was another source at Wowplanes, but his website does not allow ordering anymore. I found in a forum somewhere that his wife was quite ill and that was a post from a couple of years ago. I would like to try it someday though.