Hi everyone, especially free flighters.

Over 50 years ago, Frank Ehling, then the Technical Director of the Academy of Model Aeronautics, USA, designed this model.
It was initially considered too simple to interest anyone.
But the AMA used it to successfully introduce thousands of youngsters to the joys of aeromodelling.

You can find the plan and description if you go to:
Outerzone.co.uk
and search for Delta Dart.

To build it you need balsa strips, the prop and the prop hub, suitable rubber, tissue, glue stick and Feviquik.

Which I'll try to provide.

I'm going to build it tomorrow and see if it flies!

Plans (from outerzone.co.uk) are attached.

Mr. Iyer picked another good model. I would have guessed you would pick Bobni, but this one is famous the world over.

Over some summer time, my RC club invites kids  to build this one. We give the full kit and help them build it at the field. Under me I have had about 30 plus students over the years. We take kids from grades 4th standard to 8th for the Delta bash.

We make jigs so they can move faster and use thin CA so everyone can be in the air after lunch. Hot air is quite abundant at 1 PM and a few kids have lost it in Thermals over in their second trim flights. So awesome to see the kids really enjoy the build and fly.

Late afternoon we have what is called "All Up , Last Down" and give special prizes for the first second and third longest flight but all get to take their model home.

Have fun! Very enjoyable.

Here is a good source on discussions :

http://customers.hbci.com/~bkuhl/building_tips.htm

Look up outerzone.co.uk
Type 'Delta Dart' in the search box.
You'll get 3 plans.
Select the middle one (18" span)
Scroll down.
Download plan.
Print it at home on A4 paper.
It's 4 pages. The full size plan is on pages 2&3.

All the wing and tail parts use 1/16" x1/8" (1.5x3mm) strips.
The longest pieces (wing leading edge) are just under 10" long.
I had a piece of 1.5mm sheet just over 10" long.
So I cut a few strips from it using a 3mm spacer.
Then made the angle cuts at the strip ends.
Notice that I added a base piece for the fin, though not shown in the plan.

Had some very old tissue paper,
But a warm iron took out most of the wrinkles.

A bit hard to see the plan throughthe red tissue.
Should be easier with plain white tissue.

Rubbed the tissue with a glue stick where the structure is.
A bit messy.
With the second wing, found it much better to rub the glue stick on the wood instead of on the tissue.

Then just tiny dots of Feviquik on the joints...

Poor workmanship!
Jagged edges due to using a dull blade for cutting the tissue 

A bit surprised and disappointed that it's possible to make a mess of the covering on such a simple model.
For the stab I used the traditional method. Built the structure first and covered thereafter.
Notice that I added a centre rib, not shown on the plan.
And used a NEW blade!

Sprayed with 80% alcohol, instead of water...

Completed.
Surprised at how well it flies (at least indoors)
Will try outdoors tomorrow.

Why is the wing covered at the top, and the stab at the bottom?

Quote from: sanjayrai55 on January 30, 2021, 05:47:23 PM
Why is the wing covered at the top, and the stab at the bottom?

It actually says so on the plan!
To get a balsa to balsa joint without paper in between, I guess.
(This model was intended for kids. I built it now as I'm in my second childhood  )

Incidentally, as per the plan, there's no central rib in the stab, and no base rib in the fin, both of which I added.

I think because the stab is stuck to the bottom, wing on top. Long may you un-age Iyer sir!

Quote from: sanjayrai55 on January 30, 2021, 07:06:16 PM
I think because the stab is stuck to the bottom, wing on top. Long may you un-age Iyer sir!

Not to forget the DECALAGE, that I kept talking about in the Lunchbox Build and Contest threads...

For a beginner the best option is what the instructions suggest.
Print the plans, and build it directly on the plan, ie, stick the balsa strips with gum on the plan itself!
The plan paper becomes the covering.
No need to mess with tissue etc.
It won't add more than 1gm or so to the weight.

Nice Home made prop. Lighter and probably more efficient.

What is your all up weight minus the rubber?

At about 36 square inch wing area an overall weight of 18 grams  puts you at the 0.5 grams per square inches. Looking at your pictures, you must be well under that, I think?

Get the motorcycle tuned up, it will be a long chase in the afternoon flight.

Quote from: Free Flight on January 31, 2021, 07:36:12 AM
Nice Home made prop. Lighter and probably more efficient.

What is your all up weight minus the rubber?

At about 36 square inch wing area an overall weight of 18 grams  puts you at the 0.5 grams per square inches. Looking at your pictures, you must be well under that, I think?

18gms?
This one is 6 gms with a 6" loop of 1/8" rubber.

Wow! at 6 grams with rubber is very nice light weight.

When we have a building session with the kids, it usually comes out at 9 to 10 grams using the plastic prop with bearing (about 3 grams) , packaging tissue, hardest wood for strength and resist warps. Then the weight of the rubber. The convention followed here is that we speak of the rubbered model weight always without the rubber.

Take a look at the Bobni video posted here. It does a nice ROG and model weight of 7 grams not including the rubber.

Vey much looking forward to your outdoor flight video at such a low weight. Should be great.

@Free Flight,
There are 2 short videos on the Whatsapp group.
At 150 and 250 turns.
Didn't dare go beyond that!

But then I found this chart (see pic)

So can I really go to 600 turns on a 6" loop of 1/8" TAN?

That table is a good approximation. I would use 80 to 90 percent of the turn per inch suggested in the table. I would  do a sacrificial break on a 5 inch rubber and go 90 to 95% of that many turns in flight. My last batch of 1/8 rubber breaks at 97 turn per inch. So I go to 90 winds per inch. Of course as you know this is based on the rubber being well lubed and about 4 times the length of stretch winding for the first 50 percent of the turns. I find that home made torque meter is more reliable to get consistent torque for each flight and so usually  I no longer count my turns.

One more thing I found out is that the max turns varies within the batch of the rubber that I purchase. Hence 80 to 85 % of break torque is what works safe or me.

Would very much enjoy seeing your WhatsApp videos if you can mail it when you get a chance. Thanks.

Quote from: SI74 on January 09, 2021, 03:53:16 PM
First set of gifts arrived from @FreeFlight ( Malav sir) . Thank you !

Malav Sir's gift  inspired me for more builds ... so I built this one - Initially built a "Hangar Rat" , but flight duration was not great , so replaced its wings with foam . And here's the result - this is just a test flight - only very few turns (250-300) , I am sure it'll fly forever if the winds are increased . Thank you @Freeflight and Glidiator (Anant sir) for the proper guidance .



https://m.youtube.com/watch?v=IJd5ro_2JAA&feature=youtu.be

Some pics...

More pics

I think Hangar Rat is more challenging(build, trimming and flight duration) -needs so much patience) . So if we are targeting beginners ( who are just into the hobby ) Delta dart would be a better choice .