Piper Cherokee - RC Groups
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Feb 07, 2018, 09:18 AM
What...how did that happen?
AleRRon's Avatar
Build Log

Piper Cherokee


I have not seen a foamie Piper Cherokee yet so I decided to design and build my own. I did see a balsa one somewhere and I just love the lines of the plane. I think it looks kinda sexy. So I looked at a lot of Google pics and I found and downloaded a 1969 balsa plan from Aerofred.com that I pressed into service for outlines and dimensions. I decided to implement Tony's monobloc fuselage method that I've built before with his designs and like very much. This one is more complicated due to nose side curves though. I will probably make an airfoil wing but I may make a Kfm3 wing too. It'll be 4 channel. Because this plane has a short nose, I tried to cram electronics as close to the front as possible in order to achieve proper CG, which has yet to be determined. Let me know if you have any advice or have built one similar.
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Feb 07, 2018, 09:24 AM
What...how did that happen?
AleRRon's Avatar

Monobloc design and construction


I traced the fuse outline from the downloaded balsa plan. I then trimmed the outline as necessary to accommodate the future cowl, bottom plate, top deck, and canopy. After a lot of trial and error I created the cavities for the electronics that the components would fit in. I glued the paper plan onto posterboard and cut that out as a template. Pics to follow, I'm at work right now!
Feb 07, 2018, 09:48 AM
treefinder
springer's Avatar
You might browse through this thread: https://www.rcgroups.com/forums/show...Piper-Cherokee for ideas. He went after his from a balsa builders standpoint, so built heavy, but I recall some interesting tidbits in the thread. Just don't put too little dihedral in the wing! Low wingers look better with more.
Feb 07, 2018, 10:36 AM
What...how did that happen?
AleRRon's Avatar

heavy build


Oh yeah, now I remember seeing that thread. It looked very nice when finished but yes it was a heavy build. I wanted to do a monobloc and MPF construction to keep it simple and light. I'll look through it again for useful tidbits though, thanks Springer!
Feb 07, 2018, 12:22 PM
treefinder
springer's Avatar
MPF construction, good man!
Feb 07, 2018, 08:14 PM
Registered User
Captain Dunsel's Avatar
Yes, my Cherokee was (is) a good pound heavier than it should be. If I were to do another, I'd paper the wing (with a spar), plus cut a LOT more foam out of the fuse. I'd also paper the tail, plus I'd go a lot lighter on the paint.

It does fly most Classical Pattern manoeuvres okay (considering I'm not a great pilot), but the fat fuse does cause some funny wiggles during stall turns and side slips. It is very stable in flight and is a breeze to land, though.

CD
Feb 08, 2018, 05:44 AM
What...how did that happen?
AleRRon's Avatar

Monobloc


The plan called for a pretty wide fuse to stay consistent with semi-scale proportions and looks, about 4 1/2 inches at the wing root. Taking into account the 6 mm fuse sides, I needed a 4 inch wide monobloc. I glued together two 2 inch thick pieces of Lowes green extruded polystyrene. I’ve used this stuff in the past and it seems to work well. I think it’s essentially the same as the pink kind, but I bought this because I have more Lowes around here than Home Depots . Next step is to square up the raw block. This step wasn’t necessary with Tony’s plans, but for this evil plan it was, in order to cut curves in two planes. I used my bandsaw to cut the long sides straight and parallel and then cut one end square. Next step was to trace the monobloc pattern in two dimensions on this squared up block. The monobloc pattern is also shown.
Last edited by AleRRon; Feb 08, 2018 at 07:54 AM. Reason: Left something out
Feb 08, 2018, 08:31 AM
Registered User
Captain Dunsel's Avatar
Our neighborhood Lowes is about 15 minutes away; the nearest Home Depot is nearly 15 minutes farther. But, that Lowes is always out of foam, otherwise I'd be using green instead of pink, too.

CD
Feb 08, 2018, 09:01 AM
Jer. 29:11
jeffsch's Avatar
Watching with interest @AleRRon. Hoping to learn more about how you designed your monoblock shape and how you tie it into the rest of the airframe.
Feb 08, 2018, 01:24 PM
What...how did that happen?
AleRRon's Avatar

Monobloc construction


After the side and top profiles are drawn I use the bandsaw. This is a great tool for this work. First I cut the side profile. Secondly I put it back together with blue tape like a 3D jigsaw puzzle enough to recreate flat top and bottom. This is needed to cut the top profile. After the top profile is cut you can take it all apart and Wallaa.
Feb 08, 2018, 01:28 PM
What...how did that happen?
AleRRon's Avatar

Test fitting sides


Just to see how it all fit together, I taped the sides to the monobloc
Last edited by AleRRon; Feb 09, 2018 at 09:24 AM. Reason: wording
Feb 09, 2018, 10:05 AM
What...how did that happen?
AleRRon's Avatar

Fuse sides


I laid out bend lines on the MPF fuse sides, made a shallow cut, then widened the cut with a blunt-ish instrument. A pencil works fine. One bend lengthwise and one vertical.
Feb 09, 2018, 10:56 AM
treefinder
springer's Avatar
Looking really good!

Don't forget you can bend MPF cold with careful rolling over a mandrel like gpw's Bendfoam fixture, and pretty tight radius with a little help from a heat gun. Makes even smoother curves!


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