Fly-guy

Hi guys
I am currently drawing up some planes for a .30 size powered 3DX. I have used the Foamy Factory plans but I am having a little trouble redesigning the wings(this is my first attempt at scratch building[&:]) The fuse will be profile so thats nice and easy. I have redrawn the wings with all the ribs and spars and stuff in place but I cant work out how to do the wing ribs. The innermost rib is 210mm long and I have a rough shape but the next six ribs are each shorter by 10mm. How do I keep the same LE shape and TE shape without the middle of the rib chaniging while making then 10mm smaller?

HELP ME PLEASE

Fly-guy

David Cutler

I believe you can download a program for your computer that handles this very problem.

Trouble is, I can't remember where it is!

Try putting 'wing ribs' in Google and searching. The program will be perfect for what you want.

I will search for it, and come back if I find it.

-David C.

Fly-guy

Thanks Dave the porgram is profili but it is going to takee me over an hour to download it

David Cutler

Try this:-

http://www.profili2.com/eng/default.htm

-DC

David Cutler

or this:-

http://www.dchobby.com/airfoil/design7.html

David Cutler

Try putting:-


wing ribs drawing software

in Google.

-David C.

Fly-guy

Cool thanks dave

Fly-guy

ThunderAI-RCU

Since the wing airfoil will remain constant, with only the size decreasing you just need to find a way to rescale the other ribs. The easiest and most simple way for you for you do do this would be on a photocopier.

Wingroot = 210mm
1 = 200mm (95.2%) (95%) (.2) error: .42mm
2 = 190mm (90.5%) (90%) (.5) error: .95mm
3 = 180mm (85.7%) (86%) (.3) error: .54mm
4 = 170mm (80.9%) (81%) (.1) error: .17mm
5 = 160mm (76.2%) (76%) (.2) error: .32mm
6 = 150mm (71.4%) (71%) (.4) error: .60mm
Total scaling error is 3mm (not something to really worry about)

I doubt a photocopier will have a percent to the hundreths, but you should be able to get away with using just the tens. You will have a margien of error of cource in the total length ranging from .17mm to .95mm.

If this doen't answer the question, I dont understand the question

David Cutler

Excellent idea! I wish I had thought of this when I was building a wing!

However, I think you'll find the LE and TE have to remain the same size, so they should not be reducing in the way a photocopier would.

Great idea though!

-David C.

ThunderAI-RCU

I fail to see why the LE and TE need to remain the same size? Is this a square wing?

Fly-guy

ThunderAI-RCU that is the best idea ever

(note to self think harder before you come to RCU next time)

Really thanks heaps tha should get it pretty damn close now.

Fly-guy

David Cutler

I just found the program I was talking about.

It's called 'rib design' and is about 250k in size.

Would you like me to email it to you?

PM me if you do.

It's perfect for what you want.

-David C.

Fly-guy

ThunderAI-RCU
i mean that the curve of the LE should be constant all the way down the wing, I don't want it to get narrower(for ease of building) Also the way I'm doing the wing will be a good fun-fly design. Great for aerobatics.

Fly-guy

Fly-guy

yep Dave I'll take that

250k isnt too big is it.

Anyway email it to me at [email protected] (don't ask)

Fly-guy

Fly-guy

Profili is 90% done almost there. Dave could you please send that file to ASAP.

Fly-guy

David Cutler

I just emailed you with it attached.

It took about 20 seconds to send using DSL, so, if you have a modem it shouldn't take much more than 5 minutes to download.

reply if you have problems.

-David C.

Fly-guy

Uh Dave we have a slight problem.

I got the attatchment but it only has the setup part where you choose your measurement unit. What happend???

Fly-guy

David Cutler

No, I think you'll find it is now installed on your machine. Try

Start---> Programs and you should find it installed.

-D

Fly-guy

Opps
I'm an idiot here it is. I have profili now to so I have two programs to slove my problems

Fly-guy

David Cutler

Does it do what you wanted?

-D

Fly-guy

Sure does Dave
That has to be my fastest ever answer form RCU Under an hour and a half

Fly-guy

BMatthews

If you keep that forward section back to the high point constant on a tapered wing then your wing section at the tip will be very odd. The high point will be moved back and the rear half will be forshortened. The aerodynamics will be very nasty if the taper ratio is much at all.

First and foremost you must make the airfoils do what they are meant to. THEN worry about building. Besides I don't see what the issue is. It's not that hard to form leading edge sheeting even if the taper ratio is quite high. For an extreme situation it may require that you precut the sheeting to a tapered section first so the grain in the center follows the curve better but that's not that big a deal.

As far as the drawing goes you need to scale the airfoils and THEN add the leading, trailing, spars and sheeting to each rib. You can't scale this stuff like the section. The only exception to this is capstrips and sheeting thickness. If you use a double line tool the spec for the double line width does not scale, or at least it doesn't in TurboCAD, so the sheeting stays the same thickness. However leading edges and spars will change.

David Cutler

And it's tomorrow there in Oz!

I'm in Los Angeles!

BTW, since it's tomorrow there, what are the numbers for tomorrow's lottery?



-David C.

Fly-guy

BMatthews trust me, what I'm doing will work, I probably just havent explained it very well. Go to www.foamyfactory.com and have a look at the 3DX plans and picture the wing that shape but the same sort of look as a trainer. I'm not completly stupid you know(i think)
Anyway I'll let you know on my progress while I build the plane and WHEN it flies.

Fly-guy

David Cutler

Yes, all good points but it's not that unusual to have a tapering wing with a constant shape LE and TE.

-David C.