siclick33

Following on from the fun I've been having with my Ducty I've decided to try and make my own P20 powered delta model. It won't be anything special (which is part of its appeal), just a simple wooden box with wings. Hopefully, it will end up being a bit of a hybrid of the Balsa USA Enforcer, Mick Reeves Super Reaper, and Ducty I'm going to try to have a play with CAD (which is a big learning process in itself) and maybe get some formers laser cut. I am also trying to get someone to make me a set of foam wings.

One of my main goals is to make it completely disassemble so that I can take it to Florida Jets. The Ducty is actually a little awkward to transport even though it is tiny.

To that end I have decided on the following:
[ul][*] About 1 metre (39 Inches) long[*] Wingspan about 39 Inches[*] Plug-in (removable) wings[*] Twin removable fins[*] Fixed main gear (easily unbolted for transport)[*] Retractable nose gear
[/ul]

To make it super easy to maintain, I want to make the fuselage in separate partitions, each with their own function. There will be a separate partition for fuel tank, turbine electronics, receiver, air (for brakes if necessary) and batteries.

The first job is to find someone to make the wings (or find a suitable set from another model that I can use). The first manufacturer couldn't help as the sweep was too great. I did think about trying to adapt a set of Grumania Eurofighter wings but the sizes don't work[] If anyone can point me in the direction of someone suitable that would be great!

siclick33

I have managed to change the wing profile to fit within the manufacturers capabilities (and still look ok) and am just about to order a foam wing set. Can anyone suggest a suitable wing section? I have searched the web and found various threads but still don't really know what will work. I have seen reflexed sections such as the MH60 or maybe just a NACA symmetrical section. I then looked at my Ducty and it is flat-bottomed!!

How much washout do I need to add for a delta?

craigdyer

Hi Siclick33,

I dont think a NACA section would be suitable on a delta maybe a semi symetrical or symetrical would be better. Maybe the SD series.

Regards, Craig.

mick15

Neither do I, you should be looking at reflex sections for a delta.

m

siclick33

Thanks for the info.

The NACA 00?? series are fully symmetrical and can have 'forced' reflex by adding up elevon.

The native reflexed sections (such as the MH60 listed above) would be better if selected correctly but am not sure which one to pick. From what I've read, the reflexed aerofoils seem quite critical whereas the symmetrical ones appear pretty straightforwards (although not as efficient).

Any suggestions of sections known to have worked in similar shaped models would be greatly appreciated.

Jgwright

I used MH60 for the Junkers EF128 flying wing that performed well. It had 2.5% wash out and 2mm of elevon reflex.

http://www.youtube.com/watch?v=MBmLPIPepL0

John

erbroens

Yes, you can use a airfoil without reflex in a flying wing, but the elevons will need to be raised to keep level flight, making a ugly sight like in the Hotspot.

Another solution is adding canards. This will make the design concept jump about 50 years ahead in time.

Enrique

siclick33

I've gone for a MH60 section at the tip and a thinned MH60 at the root to keep the wing thickness at sensible levels. It may not be required but I've also specified 2 degrees of washout. The wing has been ordered but it may be a while for it to be delivered.

I'm very happy with the options that I've been offered for the wing and it will be vac bag cured with glass reinforcement and come with servo cut-outs, wire channels, wing tubes and retaining blind nuts installed and will have the elevons cut out and all facings finished

John,

Where did you put the c.g. on your Junkers EF 128? I know how to calculate the MAC based on area but do I need to make any adjustments for the aerofoil section being used? I've made a 1/3 scale cardboard chuck glider and it seems ok with the c.g. at 15-20% MAC but this is obviously just a flate plate. I will do some more trials with it over the next couple of days.

siclick33

Whilst waiting for my wing to be delivered I have made a 2/3 scale test model from Depron. The aim here was to identify any potential issues and play with various c.g's. The first thing I have identified is that the fuselage will have to be longer to avoid nose weight.

I test flew it this morning and it does fly. However, I may have confused myself even further with the choice of c.g. location. The initial stability at at 15% MAC was ok but the model climbed significantly at speed. Moving the c.g. back appeared to make no difference apart from eventually making the model unstable in pitch.

I then tried moving the c.g. forward and was surprised how far it would go without problems. I ended up with it forward of 10% MAC with no issues. The climb at speed seemed to be slightly better (but still there) with forward c.g. but I might have just been imagining it.

Is the climb at speed an inherent problem with a flat plate delta or is it an indication of incorrect c.g.?

These trials may be irrelevant as the turbine wing will have an aerofoil section but I'm trying to learn as much as possible before risking the P20[X(]

proline8000

My Feedback: (12)

try Bob at Flyingfoam.com. He is cutting the foam parts to my own design jet.