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Feb 09, 2018, 08:23 PM
AndyKunz's Avatar
Build Log

Blitzer! sport

The past few weeks I've been cleaning the shop little by little.

Guess what I found! A half-built kit.

Last edited by AndyKunz; Feb 28, 2018 at 05:47 PM. Reason: Improve opening post for moved thread.
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Feb 09, 2018, 10:55 PM
I just want to go fly!
walter3rd's Avatar
im always a fan of a 109
Feb 17, 2018, 05:35 PM
AndyKunz's Avatar
What I found was a partially-assembled Blitzer that my son Caleb and I had started working on several years ago. We had the fuselage mostly finished, but apparently between moving and "shop rash" it was crushed beyond repair. I cut a new set of fuselage part and started following the manual to build the replacement.

I started by joining the lower wing skins and laminating the fuselage parts. The skins are taped together, then glued on the seam. The instructions mention using CA for everything, but with my allergy I just forged onward using Titebond II. To keep the laminated fuse parts flat while the glue cured, I sandwiched them between two pieces of flat wood and clamped them.

Feb 18, 2018, 07:49 PM
AndyKunz's Avatar
The fuselage sides were joined last night using tape to snug things together and keep everything square.

The manual talks about rolling the underside of the leading edge up, using CA to quickly glue things together. My CA allergy prevents me from even thinking about that anymore, so I go back to Titebond.

I used a toothpick to apply a small amount of glue to the bottom side of each rib and the sheeting. After the glue is all in place, the LE is lifted up by 3/16" sq and 1/8" sq strips inserted under it, while the rest of the wing is held down by a few extra pins. It'll dry overnight, and I'll turn back to the fuselage.

Feb 21, 2018, 10:31 AM
Gravity sucks.
mrittinger's Avatar
Flat bottom or semi section?
Gotta love a simple build!
Feb 21, 2018, 10:41 AM
AndyKunz's Avatar
It's actually S3016. About the last 75% is flat. Almost as easy as the true flat bottom you used on the Python, but with lower drag. I found it worth the effort on my Pythons too.

Feb 21, 2018, 12:36 PM
Registered User
jumo004's Avatar
I like your building board/mat !
Feb 21, 2018, 08:53 PM
AndyKunz's Avatar
After lightly scoring the fuselage/turtledeck edge along the top side of the 1/8" sq, I bent the sides over and glued them down. I then added 1/8" sq along the top edge of both sides to improve glue area.

While that was drying I sanded the lower wing LE and TE to blend smoothly with the airfoil, and then added the top sheeting. I'll get photos of that tomorrow.

Time for a little TV with my wife.

Feb 22, 2018, 09:25 AM
AndyKunz's Avatar
Originally Posted by jumo004
I like your building board/mat !
Right price, any size I'll ever need (I have one 4x8 sheet cut up into several formats), holds pins, sands well, and if I really need a piece of foam in a pinch, I know right where to find it!

Feb 22, 2018, 09:19 PM
AndyKunz's Avatar
My wing top skins are glued on with Titebond, then taped and allowed to dry. This gave me an opportunity to put in a small amount of washout. The manual says to use CA, and it could be easier for some to do that, but I think I've learned a bit since I wrote it 13+ years ago.

I used tape to get the edges down. I used a small amount of water on the front third to help it bend more easily, so the tape needed to wrap farther back to be on dry wood.

I then sanded the root and tip skins flush to the ribs, then sanded the aileron cut-out, LE, and TE to shape. The rounding of the LE is pretty simple, using the "Typical Section" on the plans as a guide. I matched the root and tip ribs between the two wings to ensure symmetry.

I then used a sharpened 3/8" brass tube to cut servo lead holes through R1 and R2, and then down from the top skin.

Joining the wing panels was accomplished by first lining up the bottom edge and LE and taping them in place. A schmutzed the root ribs with epoxy, set the dihedral per the plans, and taped the top edge and weighted until it cured.

Feb 22, 2018, 10:03 PM
AndyKunz's Avatar
The wing tips are balsa blocks. After the glue dries I'll carve and sand them to final shape.

Turning attention back to the fuselage, the rear top and bottom surfaces are sanded flat. A good bit of the 1/8" sq on the top gets turned to dust in order to get the edge down to the balsa sides. Take care not to mess up the area where the stab will be glued on. The bottom side gets similar treatment, but it takes much less sanding.

The top and bottom sheeting are glued and taped in place.

I'm waiting for a spinner to come in at the LHS. I need that before I finish the nose.

Feb 23, 2018, 10:47 PM
AndyKunz's Avatar

Wing Tips!

Wing tip shaping starts by extending the TE from the root outwards. I measure the aileron chord at the root and marked that same distance at the tip, and then used a long straightedge to get the correct angle on the tip block. I then trimmed off the excess length from both LE and TE on the bandsaw.

Next, I rough-carved the airfoil shape using a #26 blade. 2" blue masking tape was applied to the wing about 1/4" from the tip block, and in the center where the sanding bar would be hitting it. This prevented damage to the wing surface.

Then I started sanding. And sanding. And sanding until the tip was an extension of the airfoil. Take care to not make the TE too thin while doing this.

The next step was to apply 2" glass cloth to the top surface using Zap finishing resin. I'll trim off the LE and TE excess cloth tomorrow and sand it in, and then do the bottom side.

Because this isn't a scale model we are free to do whatever we want with the tips. I haven't decided if I'm going to try for a scale appearance or make something that's just pleasing to my eye.

Tail Feathers

Because I want an operating rudder, it's necessary to stiffen the rudder chord. I did this on the top counter-balance area by removing a 3/16" wide section of rudder sheet and replacing it with some hard balsa.

The ply elevator joiner is doubled up and inserted between the elevator halves. This will also need some chord-wise stiffening, but I'll do that with a ply doubler on the inner portion. Gotta let the glue dry here first.

Feb 24, 2018, 03:48 PM
AndyKunz's Avatar
Back to the fuselage & hatch

The kit C3 didn't fit very well at all, so I made a new one that fit into the fuselage better. Doing that properly meant I had to sand the edges of the opening to get the tapered edges needed.

I then put C1 and C2 parts onto the hatch bottom. I taped that into place on the fuselage and then started fitting the other C3 to mate the fuse. After gluing that in, I added the two parts C4.

Because I wasn't using the kit C3 in the fuselage, I had to cut a hole for the magnet. I used sharpened brass tube for that. I then used epoxy to attach the magnets to both the fuselage and hatch at the same time, using cellophane to keep things from getting glued together.

The next step was to add the hatch sides, which for the sides of the canopy area as well as the forward portion.

Meanwhile I attached the rudder and elevator HS-55's to their tray and glued cross-bracing. To ensure a good attachment to the fuselage, I added rails to the fuse sides. I temporarily inserted the servo tray in place so I could make sure the rails were level.

Feb 25, 2018, 05:28 PM
AndyKunz's Avatar
I forgot to show an earlier photo of the wingtip. I opted to go with just rounding the LE of the tip, leaving it about 1" wide and straight back to the TE.

The servo tray was glued into place. Nothing much to see there, just that it's done. There is a very straight shot from the servo horns to the control horns on the surfaces.

I added some 1/64" ply to the rudder and elevator around where the control horns will go. This will stiffen them up for landing stresses as well as in flight.

After those were dry, I added some DAP house filler and later sanded it off. The wing root glass was lightly sanded, and then I decided to give a try to a new product, Perfect Plastic Putty from Deluxe Materials. It seems to be a lot like the Squadron Putty I used for years, but without the (nice) smell. I'll let you know how it goes.

In the last photo you can see some thick wood clamped together. Between those thick pieces of wood are the aileron blanks. These are HARD 1/8" balsa with 1/64" ply doubler. The ply will serve as a stiffener for the sharp TE.

Feb 26, 2018, 09:49 PM
AndyKunz's Avatar
Update on the Perfect Plastic Putty: I like it.

It adhered well to the Zap Finishing Resin on both the wood and the glass cloth. It sanded nicely, much better than Squadron used to do, and it feathered well.

It does seem to be harder than the balsa, so I would be careful about using it directly on bare wood, but on the resin-coated portion it was fine.

I'll be using it again.


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