DTFB - Radian

[SheppO]

Radian build - will it work ?

Just throwing this out there to the group - very provisional drawing board exercise so far - could this work ?

I've reduced the TT wing chord and lost the 'spar' but chord/span proportion (aspect ratio?) is still not as per as the actual Radian - im assuming the weight/lift ratio (!?) will be not be scalable using DTFB if that makes sense - i.e. its heavier so need a bit more wing surface. Sorry I really dont know much about this stuff!

This is 950mm (37.5") span - so kind of a 50% full size Radian - running mighty mini power unit (pod is slimmed down a bit) I have "lift doesn't always scale down" in my head and i guess weight might be a problem overall....

Not sure if the electronics would fit - or how access would work. Also the tail feathers / push rod routing is tricky.
Surprised how little elevator surface there is on the Radian - is this to do with the short fuse to counteract pitchy ness ?

Anyway - comment and ideas welcome on this.

 

[ScottyWarpNine]

You're right about the weight of DTFB causing issues for it, especially since it is scaled down. That being said, it really does look great! And I'm sure if you scaled it up to a full size radian it would be almost as floaty.

 

[SheppO]

Tanks Scotty - 2m wingspan would be interesting in foam - bigger than the simple soarer...



Bit of drawing board development - trying to copy the Gottingen foil (used on the radian)

Tiny trainer side view for comparison at the bottom
For weight issues maybe 3mm depron with tape would work better than foam board - but them CF/balsa reinforcement would be needed I guess.

 

[dutchmonkey]

here is my foam board glider it glides great has about a 48" span, 5 gram servos, mighty mini power setup on a 2 cell lipo. weight is always be an issue with gliders but they are build-able. http://forum.flitetest.com/showthread.php?19074-foam-thermic-50x

 

[rcspaceflight]

I've played around with the whole wing size versus weight thing. It was from when I was trying to design/build a DTFB DLG.

I have found this calculator absolutely necessary. Use the "Wing Cube Loading" number because it factors in the scaling. That is to say a WCL of 6 is a 6 no matter if it's full scale or micro scale. The chart at the bottom of the calculator is a good guide line and you'd probably want to aim for a Wing Cube Loading of 4. Too light can be just as bad as too heavy.

If you really want light, remember that the paper of DTFB is half of it's weight but it's also a good portion of it's strength. Gorilla Glue is far lighter than Hot Glue, but takes a lot longer to set. And that strategically placing spars can make all the difference (that is, balance where to go light and where to brace it). (Bamboo skewers can make great spars. They're not the lightest, but super cheap.)

 

[dutchmonkey]

I've played around with the whole wing size versus weight thing. It was from when I was trying to design/build a DTFB DLG.

I have found this calculator absolutely necessary. Use the "Wing Cube Loading" number because it factors in the scaling. That is to say a WCL of 6 is a 6 no matter if it's full scale or micro scale. The chart at the bottom of the calculator is a good guide line and you'd probably want to aim for a Wing Cube Loading of 4. Too light can be just as bad as too heavy.

If you really want light, remember that the paper of DTFB is half of it's weight but it's also a good portion of it's strength. Gorilla Glue is far lighter than Hot Glue, but takes a lot longer to set. And that strategically placing spars can make all the difference (that is, balance where to go light and where to brace it). (Bamboo skewers can make great spars. They're not the lightest, but super cheap.)

Thanks for that link my thermic 50x has a cube rading of 3.4 no wonder why it soars so good

 

[SheppO]

here is my foam board glider it glides great has about a 48" span, 5 gram servos, mighty mini power setup on a 2 cell lipo. weight is always be an issue with gliders but they are build-able. http://forum.flitetest.com/showthread.php?19074-foam-thermic-50x

Thanks Dutch - that is awesome - maybe if I do a Radian clone ill move to a faceted tube fuse like your thermic - so nice

 

[SheppO]

I've played around with the whole wing size versus weight thing. It was from when I was trying to design/build a DTFB DLG.

I have found this calculator absolutely necessary. Use the "Wing Cube Loading" number because it factors in the scaling. That is to say a WCL of 6 is a 6 no matter if it's full scale or micro scale. The chart at the bottom of the calculator is a good guide line and you'd probably want to aim for a Wing Cube Loading of 4. Too light can be just as bad as too heavy.

If you really want light, remember that the paper of DTFB is half of it's weight but it's also a good portion of it's strength. Gorilla Glue is far lighter than Hot Glue, but takes a lot longer to set. And that strategically placing spars can make all the difference (that is, balance where to go light and where to brace it). (Bamboo skewers can make great spars. They're not the lightest, but super cheap.)

Thanks RC - super helpful

 

[SheppO]

So my tiny trainer 2ch glider version came out at a 4.1 CWL - so not terrible.
using the Radian wing area I'll need an all up weight under 3.5 oz (100g) to be under the magic WCL of 4
Just ordered a nano qx so that might divert me for a bit ...

 

[rcspaceflight]

I don't think it has to be under 4. But you should aim for around 4.

4.1 certainly is a great number for a glider.

 

[SheppO]

So I didn't get very far with this - but here is how the plans built up - used some of my kid's sticklebricks for nose weight and the glide was good. Not really happy with the look of the thing though and there is a fair bit of work to integrate a powerpod/motor / servos.