RC DeltaGliderIV project

[RisingFury]

Well, for the simple test of the nose aerodynamics, I could use a makeshift trial, like a fan at a distance and burning something... but an actual wind tunnel is a desirable thing to have, so I might look into making one for real.

My town has a considerable RC community and if we ever start up a RC club for kids again, might be useful...

 

[Dig Gil]

Better buy some large pipes then!

 

[RisingFury]

I'm thinking of just some bendable sheet metal that I could bend around into a tube and weld or solder together... the pipe is not the problem... it's the air propulsion. The problem will be getting a laminar flow.

 

[Arrowstar]

I'm thinking of just some bendable sheet metal that I could bend around into a tube and weld or solder together... the pipe is not the problem... it's the air propulsion. The problem will be getting a laminar flow.

You won't get this with air, don't bother trying. It's alright, though, since your flight conditions are probably in the low turbulent region, anyway. Best way to get a uniform velocity field, which I think is what you may have been really asking about, is to use a series of closely-packed screens upstream of your test chamber and then use a fan to suck air through the screens (and thus test chamber). This will eliminate some of the chaos otherwise associated with flowing air. It might help if you nozzle the section right after the screened inlet, as well. That is, make the inlet to the wind tunnel larger than the test chamber and then narrow down to the test chamber diameter (you can narrow fairly rapidly without noticeable stagnation pressure losses).

 

[RisingFury]

You won't get this with air, don't bother trying. It's alright, though, since your flight conditions are probably in the low turbulent region, anyway. Best way to get a uniform velocity field, which I think is what you may have been really asking about, is to use a series of closely-packed screens upstream of your test chamber and then use a fan to suck air through the screens (and thus test chamber). This will eliminate some of the chaos otherwise associated with flowing air. It might help if you nozzle the section right after the screened inlet, as well. That is, make the inlet to the wind tunnel larger than the test chamber and then narrow down to the test chamber diameter (you can narrow fairly rapidly without noticeable stagnation pressure losses).

Ah yes, a pulling fan might do it!

I think I'll use one of those house fans for cooling, but unlikelly I'll use any narrowing. The problem is that I have to keep this thing small... I'm thinking maybe a 30 cm diameter tube, with a slit where you can insert the wing or whatever you're testing.

We'll see... I'll have a look through wing tunnel designes when I'm done with the DGIV.





Speaking of the DGIV, here's a bit of an update:

I started covering the thing in foil before the end of the holidays, but badly underestimated the time it will take me to finish the process. I've already spent 20+ hours covering the thing and might need another 10...

Hopefully I'll have the thing done by tomorrow, if not, next weekend it is.

After that, the only big task is to build the main landing gear and do the tinkering... this thing will be finished soon. You'll get pics when the foil is done.

 

[Kaito]

Or, to make a wind tunnel, use a "pushing" fan, but immediately after it, have a bunch of tightly packed drinking straws, which should make a uniform air-flow (not turbulent). The mythbusters did this, and it seemed to work well for what they were doing

 

[Zatnikitelman]

Actually Kaito, a pulling fan is better because you won't get the turbulent fan-blade wash you do with a pushing fan. The drinking straws though are a good idea either way.

 

[Skookum]

I've done some RC aviating in my time. I wouldn't worry about whether or not the pusher prop will generate enough thrust. The greater majority of the thrust is generated in the half of the blades closest to the tips.

Check out this site.

http://www.casr.ca/bg-uav-cu162-vindicator.htm

 

[RisingFury]

Wow! Very nice! Thanks for the link.

 

[RisingFury]

Alright! Took me a long time to do the foil on this plane. A lot longer then I had estimated. I think I spent 30 - 40 hours working on the foil alone so that brings the current build time to around 270 hours.

So, here are some pics:

I was gonna do hollow letters for the DeltaGliderIV font, but quickly realized cutting them out would be a nightmare. Spent 2 hours just cutting out the 4 fonts with full letters. But looks good too, so nothing to complain about.

I still have to clean the yellow foil off of the cabin. The yellow foil that I bought is not Oracover, so not as high quality. Seems to melt at a lower temperature. But as long as it can be cleaned off, it's ok.

Other then that, I think the windows look good. It was pretty hard making them. Didn't wanna burn my fingers...

For the photo-op, I have the elevons and rudders stuck on with tape...

I made a 5 cm thick black edge at the back. I think it looks nice. Other then that, I wanna leave the back plate white. Might help me see how the prop is rotated before landing, so I don't smack it on the ground.

Underside:

Anyways... that's it for now.

The build has now gone into the final phase. Only have to build the main landing gear, make the connections, glue in the servo tray, make electrical connections, pick out the right battery and so on...

Should be between 10 to 15 hours of work, no more.

 

[Arrowstar]

...wow. That's fantastic! Love the paint scheme. Can't wait to see it in action.

 

[Brycesv1]

that is a beautiful craft, my friend. im holding my breath till i see her fly...

 

[Sky Captain]

RisingFury you have done an AWESOME work:thumbup: I can`t wait to see it fly. And please please please be careful when taking off for a first time, it would be such a shame to smack the DG into ground after all that hard work you have done.

 

[Juanelm]

Wow, awesome job!

Will the prop have enough ground clearance when taking off?

 

[RisingFury]

Thanks everyone!

Yea, the first takeoff and landing will be the challenge. I'll have my landing gear in the drop configuration and land in tall grass, so if I stall it right in the end, it won't be a problem.

The ground clearence is a real issue... the landing gear will have to be really tall, around 20 cm, so that might cause some problems. That's why I've held off making the main landing gear until I consult with some other RC guys.


All in all, I think the foil came out pretty nice. I did make a few mistakes that aren't obvious on the cam, but hey, that's proof it's hand made
Nothing major, just I'm a perfectionist and it bothers me. The white and yellow foil is a little transparent and you can see the under layer... in some places where the layers meet, the under layer is seen through and since I didn't know it was gonna show, I didn't trim the under layer too much.

Also, in some places, the foil is wrinkled a bit. It was a really difficult job because of all the curved surfaces (try sticking a flat piece of paper over a small ball and you'll see...). Compared to my trainer, covering this this was a few magnitudes harder...

But the result is good and I'm sattisfied.

I did want to do some more blak - mainly thin black lines over the wings and body for some detail, but I think that would have ruined the look, so I didn't go for it.

 

[dougkeenan]

Oh man that's SWEET! Excellent job sir!

 

[Dig Gil]

Also, in some places, the foil is wrinkled a bit. It was a really difficult job because of all the curved surfaces (try sticking a flat piece of paper over a small ball and you'll see...). Compared to my trainer, covering this this was a few magnitudes harder...

I understand you, I've even made an entry in one of my blogs about that: http://scciencia.blogspot.com/2009/07/mapas-numa-superficie-esferica.html :thumbup:

Good job, ehm! So how's the wind tunnel now? When are you planning the first lift off?

 

[Jarvitä]

Awesome, can't wait to see it fly.

 

[RisingFury]

Thanks!

 

[ikrase]

Now if only it had an RCS,a dn hover thrusters...

lol. Awsome build!