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Author Topic: Peanut Pilatus Porter  (Read 974 times)
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Peanut3
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« on: December 18, 2013, 05:12:58 AM »

After building a few kits, I figure it's time to have a go at building from a plan. I've had this plan from Aeromodeller magazine for a Peanut scale Pilatus Porter sitting on my hard drive for a while, and according to the text, it is an ideal first subject.

First step was to tape together the 4 sections of printout and copy onto A3.

Then to look through my box of leftover balsa from kits to see what I have on hand, and what I'll need to buy. The plan calls for 1/20"  strip, but I only fly outdoors, so I'll use 1/16 instead. OK, already it's going to be heavier than the plan!

Anyhow, looks like I have enough nice springy strips left over to get started on the tail and fuselage, but I'll need to buy some sheet for the wing ribs and formers.
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rgroener
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« Reply #1 on: December 18, 2013, 06:43:17 AM »

Peanut3, will follow your Pilatus build closely. Not sure if you are aware, but there is a "Worldwide Free Flight Postal Scale Build" going on on HPA.
http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=15168.0
Your Porter would fit in it nicely.

Roman

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Peanut3
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« Reply #2 on: December 18, 2013, 04:06:50 PM »

Started with the tailplane and rudder. No problems, but it is quite fiddly with those small sticks. I think I need some longer pins if I'm going to build this small.

Once off the plan I gave them a light sanding. I use a 240 grit sheet which I have glued to a board and a small wood block.

The stab especially feels very flimsy. Hopefully it will be strengthened by the tissue coating.

Hi Roman, hope it will be interesting. I'll email the times in to the "Worldwide Free Flight Postal Scale Build" if I can get it built and flying in time!

-Ivan
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Peanut3
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« Reply #3 on: December 19, 2013, 06:29:11 AM »

On to the fuselage.

I selected the springiest strip for the longerons for both sides at once. I also shaped the nose piece and shaped and drilled the rear rubber peg holder piece as stacked pairs so they would be as identical as possible.

Forming the lower logeron around the nose was difficult, as there is quite a tight curve. I used a lot of pins, but it ended up a bit crushed. Maybe I should have soaked the strip first.

Cracking the longerons at the middle went OK. I always wonder, is a cracked bend stronger than a cut and glue, or do we do it because we are lazy?

Once the first side was dry, I gave it a light sanding to remove the inevitable excess glue blobs.

As recommended in all of the articles I've read, I tried to use the same pin holes when building the second side. This I was able to mostly do.

Second side got a light sanding as well, and I now have two fuselage sides, the stabilizer, and rudder.

Attached pictures show the progress, first side started, first side complete, first side sanded, second side complete, and the framework so far.

-Ivan
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Peanut3
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« Reply #4 on: December 28, 2013, 02:22:24 AM »

More fuselage.

A minor bit of rework was required -- I had to remove a gusset on both sides of the fuselage to make way for the undercarriage wire. It attaches at the top of the fuselage.

I cut all of the horizontal strips and sanded them as a stack, again to try to get things as symmetrical as possible.

I also drew the formers for the nose section, based on measurements from the plan. These were trimmed and sanded to final shape.

The very front is supposed to be 1/64" ply. I looked for this in my local hobby shop. They had a sheet, it was $35! It was very flexible, in fact it felt more like covering than a structural piece!

There was some thicker ply, but it was just as expensive. I figure I will use balsa, and just harden it up with cyanoacrylate glue.

Glued the two fuselage halves together with the horizontal strips, then pinched the tail together with a peg, and glued the nose section, holding it in place with pins.

-Ivan
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Peanut3
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« Reply #5 on: December 29, 2013, 06:20:41 PM »

Undercarriage

The plan does not have a lot of detail about how to attach the undercarriage wire, so I have decided to use a scheme that was used in a Dumas kit I built.

The undercarriage wire is bent with a "V" in the middle top, and this is sandwiched between two balsa plates with packing in-between. I glued with epoxy.

The whole assembly then goes into the fuselage, glued in front of the upper former. I used white glue for this as I think it will be a bit more forgiving than balsa cement. Finally, I replaced the gussets. The whole thing feels nice and strong, but is also quite heavy. Maybe overkill for such a light model?

-Ivan
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Peanut3
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« Reply #6 on: December 29, 2013, 06:23:11 PM »

The Wing.

I cut out the wing rib template from the plan, and stuck it using a glue stick to a stack of rectangular blanks of 1.5mm sheet. I pushed two pins through to hold the stack together. I then shaped the stack, first with a knife and then with sandpaper, until I had the basic rib shape.

In order to cut the slot for the spar, I built a tool from a scrap of sheet balsa and a strip of 240 grit sandpaper glued on with super glue. This worked really well. I also used it to finish off the diamond cut out for the leading edge.

Pulling out the pin, I had 10 nice ribs. The template came off after a little dampening with water.

-Ivan
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Peanut3
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« Reply #7 on: December 30, 2013, 04:51:51 PM »

More Wing.

The trailing edge is a strip of 1.5mm sheet. This will be sanded to a wedge shape.

The plan calls for a 1/16" strip leading edge, set at 45 degrees. I have lots of 1/8 strip, so I will use that, just sand it down more. The spar is a nice springy 1/16" strip.

I cut the spar, leading, and trailing edges at the centre section and glued each section of wing separately. Once the three sections were dry, I glued them together with the recommended dihedral angle, using gussets to give it strength. The dihedral jigs are just made up from cardboard. I added some washout to the wing tips.

You can probably see from the images that it looks like I built the wing a bit wider than the plan. This is, I think, due to a problem with the printing of the plan (either that or the plan is inaccurate).

The wing rib is as drawn on the plan, but this is longer than the top view. It matches the fuselage side view, so I think that the longer width was the correct one to use.

-Ivan
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Peanut3
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« Reply #8 on: January 03, 2014, 08:58:24 PM »

Having finished all of the frames, it was time to start covering.

First I cobbled the frames together and did a weigh-in. The scales do not have fine resolution, but I think 3g is OK for now.

I used white tissue left over from a kit. In the past I have used a glue stick to adhere the tissue, and this worked well, but was a bit fiddly to get an even coat onto the frames.

So this time I decided to try using 50% diluted white glue, applied with a small paint brush. It seemed to work just as well, and I found this to be easier than the glue stick for a smaller model.

The top of the nose was covered with 80 gsm paper and then black tissue.

The tissue was shrunk with a spray of 50% water/isopropal alcohol. It tightened up nicely.

Finally, I laminated several pieces of sheet balsa cross grained and carved out a nose block. The hole for the prop shaft was drilled for 3 degrees down thrust, and the back surface (as well as the front of the fuselage) was hardened with a layer of cyanoacrylate glue.

-Ivan
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« Reply #9 on: January 04, 2014, 06:24:44 AM »

It's looking very good,Ivan.

Scott
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Peanut3
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« Reply #10 on: January 05, 2014, 05:05:53 PM »

Thanks for the comment Scott.

A little bit of progress was made with the main gear wheels. This is the first time I have made wheels from balsa, rather than use plastic molded ones.

I laminated two pieces of balsa at crossed grain, roughly cut out the shape and drilled a center hole. This allowed me to mount it in the Dremel cutting disc holder bit.

I made a gauge to help me get both wheels the same size. The wheels were shaped on the Dremel with an emery nail file stick.

Final photo shows both wheels ready for painting. I will use a piece of 3mm aluminium tube for the axle.

-Ivan
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Peanut3
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« Reply #11 on: January 10, 2014, 07:39:59 PM »

Oops - broke the wing spar  Roll Eyes

While twisting to correct a wing warp, I ended up snapping the spar. So I had to strip the tissue from the top side on one bay, repair the spar and then re-cover.

The last image shows the tissue wet, being shrunk. After drying out, the repair was almost unnoticeable.

-Ivan
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