My New Plastex Delta (picture heavy)

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:  

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.



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.





Test fitting showed it all looked good.






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.  








A little blue electrical tape to close up the exposed flutes and provide some trim, and it’s done.







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.




The Retro Mark