Another Parnall Elf

Greyhead · 14-10-2004

I'm new to this forum business so if there's a few mistakes along the way please forgive me!!

I hope to make this a thread about the construction and flying of a 1/6th scale Parnall Elf. To hopefully whet your appetite, I'll start at the end and post a photo of the finished model. Here goes:

The project started about 3 years ago when I was given a pile of free plans from various mags one of which was for the Parnall Elf. I was hooked; a pretty biplane, upright engine, folding wings (No fiddly rigging to contend with) and last but by no means least, not a Tiger Moth!

A little bit of research soon revealed that the designer had been stretching the truth a bit when he descibed it as a scale model, so I set about redrawing the plans.

That's enough for now, I'll submit this and if I get any interest shown I'll continue the saga.

Gryphin · 14-10-2004

Please continue this saga, I am interested in hearing more

duncan · 14-10-2004

More,more , yes please...the whole story.!

**wonwinglo** · 15-10-2004

Yes more,we need build and model evolution run downs like this Grahame,I keep thinking this model is so much like my own,more on the construction,wing folding etc please.

Glider Guider · 15-10-2004

Keep it coming Greyhead I look forward to hearing the story. From your posted shots it looks to be very well detailed so let us look at a few closeups please.

Greyhead · 15-10-2004

OK, so what was wrong with the plan? Don't get me wrong, I'm not a "rivet counter", but some things have to be right. The plan had top and bottom wings with the same span and the tip shape was wrong, as you can see from this photo it just wouldn't have looked like an Elf in the air!

After a trip to the Shuttleworth Collection, armed with the digital camera of course, numerous other less obvious errors were found. I'll not list them here but point them out as the thread progresses.

I intend to develop this thread in the cronological order that I built the Elf but if anyone is building a similar project and thinks I might have an answer to a particular problem let me know and I'll try to help.

I always start construction with the fuselage. Wings are usually fairly straight forward, but that didn't prove to be the case this time!

The first thing is the "heart" of the model, the engine bearers, cabane strut, bottom wing and wheel hard points.

Then the sides made from 1/16th ply and the rest of the formers.

The cabane brackets are made from 0.5mm galvanised steel, from B&Q, much stronger then brass for these high stress points, the extra weight is minimal. They are fixed to the fuselage using model railway track fixing pins.

Greyhead · 16-10-2004

The top of the fuselage was covered with 1/16th balsa leaving the luggage compartment open; I use this hatch as a convenient access point for the rudder and elevator servos, the bottom sheeting was left until after the cockpit detailing was finished. The flat just before the cowl was added later.

Next the tail plane, fin and rudder. Not a lot to say really, I used the popular “core and half-ribs method”, the rudder profile needed changing from a typical “Tiger Moth shape” on the plan to incorporate the distinctive straight TE. On a previous model I designed I got the tail incidence wrong so I decided to make this one variable as per full size, of course sod’s law prevailed and having gone to all that trouble it doesn’t need any adjustment.

Anyone who’s made a biplane knows what a pain cabane struts are. I usually end up with 3 or 4 sets in the bin before I get one that’s near enough to be able to fiddle the fixings to get the correct incidence and level wings. I decided there must be a better way, there is, the way the full size do it! But how to model them?

That’s enough writing; let’s have a photo:

The answer proved to be quite simple. They are made from streamlined brass tube with a snake inner going right through the centre, in this case the ends are crimped and then a closed loop adaptor screwed in both ends. The result is a fully adjustable cabane strut ready to be bolted to the brackets using 14BA bolts. Any variation can now be adjusted out and they look a lot more scale.

Greyhead · 16-10-2004

Before I got to the stage shown in the photo above I needed to know how I was going to hinge the wings to the centre section. This is where the plan was seriously wrong; it had flat plate hinges. Whilst it was obvious using simple geometry that the hinges shown wouldn’t work, it wasn’t quite as obvious what would! Luckily the top hinges are visible and I was able to take a photo at Shuttleworth that gave me a good starting point but it wasn’t completely clear how they worked because of course I couldn’t fold the wings.

I made a jig to see what happens as the wings fold.

This confirmed the design; the hinge has to turn in the fuselage fixing. I achieved this by using 4mm bolts with captive nuts in the fuselage and centre section.

The end result. No problem getting this in the car!

The people at Shuttleworth were very helpful and allowed me to “cross the white line” in order to take the necessary photos. However, if you do visit the collection at Old Warden please don’t abuse their generosity, if every other person says, “I’m building a scale model, any chance of getting closer?” they might change their policy.

Greyhead · 16-10-2004

How about a bit of "feed back"? 85 views and only 4 replies. Am I doing it right?

If this is a photo of my Albatros then I've found out how I should have uploaded the earlier photos!

Eureka!!

Would the thumbnails be a better way?

adzam · 16-10-2004

greyhead i have read your thread , i am not an aero modellor but i have found the thread superb !!
very informative m8

more of the same would be great

keep it up !!