Some thoughts on the production of smaller gliders...

[B Sharp]

Chris, I couldn't help noticing that some of your webs don't connect with the ribs. I have always assumed that there had to be contact all round to achieve perfect strength in the structure.
Brian.

[chris williams]

Not really, Brian...it's the job of the spars to accommodate the bending loads: the web plates accommodate the torsional loads, preventing the top and bottom spars moving laterally when the wing tries to twist. It's the contact between the ribs, the spars & the sheeting that's important. In theory, the webs could be even narrower than they are; I can remember wings designs from years ago wherein the web plates were balsa and only half the width of the rib spacing...

[B Sharp]

Mmmmmmmmmm. No too sure about that Chris. When I was being taught to design structures I was always told to make sure that all components of the structure were properly tied together in order to avoid twist in the structure.
Brian.

[John Vella]

Brian I am afraid Mr Williams is right again. In 1984 I built a wood wing on a Jantar 1 and the outer balsa webs only covered the middle 50% between ribs. The wings have held together since ! John.

[B Sharp]

I knew my comments would start a discussion. Yes John you are very probably right. However in my defence, the roofs and steel structures that I helped design are all still standing and none of the roofs have collapsed or blown off and that is after 40 years
I think I will continue fitting my webs to the spars and also to the webs, it makes me happier.
Brian

[chris williams]

Oh dear, Brian...can open, worms all over the place! Your comment speaks to the heart of this and many other matters regarding the building of wooden gliders. The nub if the thing is, and it's as much about philosophy as it is about artisanship: Perfection can be the enemy of the Good.
If you were to take your wings, the ones with the perfectly-fitting web plates, and fly them to a 1000', push over into a vertical dive and then pull a square loop 20' above the deck, you might well be glad you took the extra trouble. (Although by then several other things might have fallen off!)
The thing is, wooden structured scale gliders, even when cowboy-ed about a bit, are designed to accept more modest loads than the average F3F model might experience. Therefore the upshot is that these structures don't have to be perfect, or even (gulp) good, they merely have to be suitably functional, or adequate, given the loads to which they can be reasonably expected to endure.
Spending too much time making perfect those things that aren't structurally important eats into the time you have to build more gliders. Now you can see why I have so many...!

[chris williams]

It can be tempting to think of Small Glider/Large Glider as a binary choice, but there's no reason not to enjoy both... In the 18 months since I built the 7th scale Wolf, I have learned that there's a whole new dimension to scale soaring. This model will fly in just about anything, from 5-30mph and give tremendous aeronautical satisfaction in the process. The 1/4 scale Minimoa, at a mere 12lbs AUW, leaves even the F3F'ers with their jaws hanging thanks to it's ability to stay up with almost no wind on the slope. So here is what I have learned...

1: Choose a subject with plenty of wing area, if possible. If not, increase the wing chord by at least 5%

2: Keep the structure as light as possible. The most significant way to do this is cover the flying surfaces with film

3: Use the HQ 35 cambered wing sections, which have proved ideal for our purposes over the years. (Dr Quabeck produced this section specifically for scale gliders). You can thicken up the root to 15% to accommodate a straight wing joiner if necessary, tapering down to 12% at the root, with no washout.

Be prepared for lots of fun...

[chris williams]

Here's the video of the Lightweight Minimoa committing aviation...[youtube][/youtube]

[StephenB]

Lovely, you build them fast Chris!

What's the wing loading, somewhere around 15 - 16ozs?

[paulj]

Fabulous - Thanks for sharing this Chris!