Kema 90 (oz10082)

 

Kema 90 (oz10082) by Keith Humber from Radio Modeller 1990 - plan thumbnail

About this Plan

Kema 90. Radio control sailplane model, for 3 channels.

Quote: "Kema. Try this traditional construction aerobatic soarer, by Keith Humber.

Having not designed an acrobatic slope soarer since my old 'Kema 84' I thought it was about time I came up with a more up-to-date design using more current design thoughts but still with conventional ply/balsa construction.

The wing is semi-symmetrical progressive sectioned, ie the tip is slightly different to the root. Using the sandwich method of rib construction, this produces a slightly differing section throughout the whole wing. The fuselage is 1/16 ply, rear boomed; this incorporates the wing and tail mounts so the incidence alignment is easy and it's a simple matter to obtain the correct relationship between the wing and tailplane when building same.

Let's get started. The boom is constructed first as a ply/ balsa box. Then 3/16 balsa pod sides are fixed to the boom, and the 1/2 inch sheet bottom glued in position with the laminated nose block rebated into place then carved and sanded to shape. The pod is lined with glass fibre laminate; this is optional - mine is lined thus but I am not really convinced that it is strictly necessary. Look on it as a form of insurance!

The wing is spruce sparred top and bottom with 1/16 sheet 'D' box leading edge and 3/8 sheet leading edge capping to the box and ditto the trailing edge (see the plan - all will be revealed!). All the rear sections of ribs at the open area of the wing are capped with 1/16 x 1/4 cap strips. The 3/8 sheet ailerons are shaped and hinged with either Mylar or Magic Tape used in the manner of the old control-line hinges of the fifties and sixties. Believe me, it works fine on a soarer and is cheap and neat. In fact, I now use this method on all my non-scale gliders. You occasionally have to replace the odd hinge after a heavier than normal landing but this can be done very quickly and easily.

The wing has approximately 1/2 inch dihedral under each tip; this is not really essential but I think that it improves the appearance of the wing and is worth the trouble. To my eye, straight wings always tend to look as though they have anhedral. There is no washout used at all.

Tail matters. The tail group is from 1/4 sheet, hinged again with Magic Tape - or Mylar, for those not totally convinced! The rudder has a bottom Mylar hinge mounted in a shaped balsa tailskid, pinned and epoxied. This is my solution to wing/elevator joiners. By hinging the rudder thus you can use a one-piece elevator with thin ply saddles. Cut both the rudder and the elevator to allow clearance and there you have it, a nicely balanced rudder (for stall-turns and spins) without the hassle of split elevators and joining wire bridge..."

Kema 90, Radio Modeller, October 1990.

Note this is a low resolution plan.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction

Kema 90 (oz10082) by Keith Humber from Radio Modeller 1990 - model pic

Datafile:
  • (oz10082)
    Kema 90
    by Keith Humber
    from Radio Modeller
    October 1990 
    68in span
    Glider R/C
    all formers complete :)
    got article :)
  • Submitted: 10/05/2018
    Filesize: 479KB
    Format: • PDFbitmap
    Credit*: Circlip, RFJ

Kema 90 (oz10082) by Keith Humber from Radio Modeller 1990 - pic 003.jpg
003.jpg
Kema 90 (oz10082) by Keith Humber from Radio Modeller 1990 - pic 004.jpg
004.jpg

Do you have a photo you'd like to submit for this page? Then email admin@outerzone.co.uk

User comments

Great to see the Kema 90 published by OZ. I built this model over 22 years ago; to me, it looked like a good plan-built alternative to the the excellent but ubiquitous Phase 6. The Kema 90 is really good design and I still fly it now; although it can't match more modern gliders for performance, it's tough, simple to build, docile with rates or exponential 'on', fully aerobatic and it looks good in the air. I would thoroughly recommend it to a beginner moving on from rudder/elevator to 3-axis control, and/or to an RTF flyer who would like to try an easy self-build.
In the light of experience I made three modifications: two to the wing and one to the rudder. The wing is held on by a single central bolt, which is concealed by the hatch. This is very clean arrangement but I found that, when landing on roughish sites with grass tussocks or clumps of heather, the wing would sometimes pivot and damage the central servo mounting. Occasionally the bolt would break. Also, the bottom of the rudder would sometimes catch on these obstructions, which pulled out the hinges. Eventually I removed the central servo and replaced it with two wing-mounted mini-servos, modified the wing and hatch so that the wing could be banded on, and increased the upward angle on the bottom of the rudder. With these mods, the model isn't quite so pretty and it's probably a little slower, but it hasn't sustained any damage for the last 20 years.
Thank you Keith Humber.
Simon Burch - 02/07/2020
Add a comment

 

 
 

Download File(s):
 

Notes

* Credit field

The Credit field in the Outerzone database is designed to recognise and credit the hard work done in scanning and digitally cleaning these vintage and old timer model aircraft plans to get them into a usable format. Currently, it is also used to credit people simply for uploading the plan to a forum on the internet. Which is not quite the same thing. This will change soon. Probably.

Scaling

This model plan (like all plans on Outerzone) is supposedly scaled correctly and supposedly will print out nicely at the right size. But that doesn't always happen. If you are about to start building a model plane using this free plan, you are strongly advised to check the scaling very, very carefully before cutting any balsa wood.

 

Terms of Use

© Outerzone, 2011-2020.

All content is free to download for personal use.

For non-personal use and/or publication: plans, photos, excerpts, links etc may be used, provided that full and clear credit is given to Outerzone with appropriate and specific direction to the original content i.e. a direct hyperlink back to the Outerzone source page.

Unauthorized use and/or duplication of this material without express and written permission from this site's owner is strictly prohibited. If we discover that content is being stolen, we will consider filing a formal DMCA notice.