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My New Plastex Delta (picture heavy) Empty My New Plastex Delta (picture heavy)

Post  batjac Sat Mar 21, 2015 9:02 pm

Well, the first time I saw the 1959 Duplex Delta design, I thought, “Meh.”  But, for some reason, last week I looked at it again and thought, “Hmmmm”.  I have all this coroplast, and was thinking that it might make a evening’s quick build, with a couple of modifications.  It’ll be a little heavier, as it’s made out of coroplast instead of balsa, but the coroplast is free.  The plans are here:  
My New Plastex Delta (picture heavy) 3399a_zpsfum5i8o7
http://www.outerzone.co.uk/plan_details.asp?ID=3399

Changes from the plans:
1) The plans call for a .75cc to 1.5cc diesel engine.  I don’t have any diesels, so a Cox it is.  But, an .09 seems awfully big for a little plane with a total area of 100 sq.in. to it.  So it’ll be a tanked Bee, then.  
2) The plans call for a 1/8 firewall, but I have some 3/32 scrap, so that gets used.
3) The plan has both 1/16” balsa fuselage sides full length out to the fin, but that’d be too heavy and thick back there.  So, the right side fuse stops before the elevator, and the left side fuselage goes all the way back.  This eliminates some weight, builds in right rudder, and still comes out to a 1/8” fin.
4) The plans have the bellcrank on the bottom, with no landing gear.  So I put the bellcrank on top of the lower wing.


With the initial thoughts out of the way, I cut some coroplast and ply to make my Plastex Delta kit.  As you can see, there's really not much to it.

My New Plastex Delta (picture heavy) DSCN3244_zpsxypyad8j

The first decision was how to glue the firewall to the plane.  Many ways popped up.  But what is the minimalist way of doing it?  After a few minutes of thinking, I figured the best way would be to slit the coroplast flutes to recess the firewall into the coroplast sheet.
My New Plastex Delta (picture heavy) DSCN3274_zps5mmmzphy
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My New Plastex Delta (picture heavy) DSCN3250_zpshihs3qp4


Test fitting showed it all looked good.
My New Plastex Delta (picture heavy) DSCN3252_zpsqqrprzix
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My New Plastex Delta (picture heavy) DSCN3269_zps5dafjqgn


Some people say that CA isn’t good for these coroplast planes, but using thick slow setting CA to bond roughed up surfaces has worked for me so far.  So, I went ahead and glued everything together.  
My New Plastex Delta (picture heavy) DSCN3280_zpsqp3vvsz6
My New Plastex Delta (picture heavy) DSCN3282_zpsybax4fbi
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My New Plastex Delta (picture heavy) DSCN3291_zpsgflaeaen


A little blue electrical tape to close up the exposed flutes and provide some trim, and it’s done.
My New Plastex Delta (picture heavy) DSCN3302_zpsb3dytqge
My New Plastex Delta (picture heavy) DSCN3306_zps7r3bjqoj
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My New Plastex Delta (picture heavy) DSCN3321_zpsjqt3aavh


I still don’t like the leadout guide, but we’ll see how it goes.  Now that it’s all done, I can see the desirability of a .09 engine.  Not that it needs the power.  Like I said, it’s only 100 sq.in. total area.  But, it’s terribly tail heavy.  An .09 would help with that, even if it is overkill.  If I ever did another one of these, I’d move the engine about ¾” forward.  It wouldn’t look as good, but it would balance better.  I used a weighted spinner to help offset the tail-heavy condition.  I’ll have to live with the weight penalty.  I suppose 6.3 ounces isn’t that bad.  We’ll see.
My New Plastex Delta (picture heavy) DSCN3325_zpsewbty2pw
My New Plastex Delta (picture heavy) DSCN3329_zpslr5dpceu


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Post  NEW222 Sat Mar 21, 2015 10:21 pm

That looks great. I had downloaded that plan many years ago and had always wanted to build it, just that I was always worried at how it will turn out, as well as the finishing would be a p.i.t.a. But you now showed how easy to make it and look good indeed, without the worry of refinishing it.
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Post  OVERLORD Sun Mar 22, 2015 5:20 am

Very nice Mark. Is that 1/8 Coroplast you use? it's good to see that these older models live on built with today materials!
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Post  getback Sun Mar 22, 2015 6:24 am

Great Job Mark , but is'nt tail heavy a recipe for desaistor ? were the heck did my spell ck. goo // I love watching your builds , Thanks , Eric
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Post  pkrankow Sun Mar 22, 2015 11:40 am

http://outerzone.co.uk/download_this_plan.asp?ID=3399

I don't see where it says 1.5cc, I read .75cc to 1cc, which is .061

Fluted plastic typically weighs more than balsa.  This may account for your tail heavy results.  

It is nice looking. I would put a spacer in behind the engine, 1/4 inch might be enough to make it balance.

Phil
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Post  batjac Sun Mar 22, 2015 1:54 pm

Leiven, yes it's 1/8" coroplast.  Sometimes I can get used boxes from work made from 2mm coroplast, but now that our company bonuses are tied to recycling goals, it's rare to get trash boxes anymore.


Eric, that's why I have that ugly spinner on the nose.  It brings the c.g. forward to a decent position.


Phil, if you look at the upper right of the plans, it says .75cc to 1.5cc engines.  I don't know why the body of the article says .75 to 1.0.  After test flying, if I don't like it, I'll move the firewall forward by making a recess in the lower wing where I want the new firewall, and then cut a slot in the upper wing and drop a new firewall down.  Honestly, with the plane being all wing area, I don't think 1/8" is that critical.

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Post  GallopingGhostler Mon Mar 23, 2015 1:07 am

Very creative use of alternative construction materials, batjac. In the 1950's, engines with .049-like power were the McCoy .099 "9" or Fox .09 Rocket and etc.
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Post  pkrankow Mon Mar 23, 2015 7:30 am

I see now.

I await your test flight to decide if I am going to build one for myself.

Phil
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