Build it light! Build it true! Building tips?

Use ACCURATE measuring devices. Metal etched rulers and scales. Even micrometers and calipers. LEARN how to read these devices. Hold your eye directly over the top of the device to prevent angle inaccuracy. Hold the device flat agasint the item being measured. Use a 0.5mm mechanical pencil to mark lines. Use accurate angles, protractors and squares, clamps and rubber bands to hold pieces in alignment while glueing.

Use only enough glue to do the job. Make the joint mechanically tight so less glue will be required. Do not use epoxy for 99.9% of your joints. I've built

Most kits are drastically overengineered. If it looks heavy, it is. Some balsa is heavier than similar plywood, don't be afraid to substitute.

Finishing is heavy, use only enough paint or dope to cover.

Look at sailplanes, indoor models, and the NCFFA site, those guys can build LIGHT.

That's all for now...

Dr.1 Driver "There's a Hun in the sun!"

I use Titebond II as my gluing agent. It releases water vapor as it cures.

I try to make all my joints mechanically correct BEFORE adding glue to hold them in place. That reduces the amount of glue being used to a minimum. In addition, I frequently will wipe off obvious excess.

I block everything being glued for 12 to 24 hours - that helps keep it straight.

-- Jim Branaum AMA 1428

Six_O'clock_High Target snipped-for-privacy@Guns.com

Pretty much the same things are true today. Select your wood carefully, don't overdo the glue and build on a good, flat surface.

I haven't built a kit in many years. I have designed and built pretty much everything I flew in the last 10 years.

First tip : stop struggling over an extra 1/10 gram here and there. You'll have more hair when the model is flying, and you need the extra sun screen anyway.

On just about any size powered model a few grams weight savings won't arbitrarily make the model fly better, and in fact it may make the model fly worse.

I won't do the full $0.50 lecture on why, but you can find out for yourself.

On your next film-covered-open-bay-wing model, build two wings.

Build one wing by the book, and build the second wing sheeted with balsa and then cover it with film.

When you're all done and have collected two dozen flights on each wing, throw out the wing you don't like to fly.

I'd bet real money you'll likely keep the sheeted version.

Not all added weight is a 'penalty'. Some specific kinds of extra weight can actually make a given model fly _better_, not worse. Cheers, Fred McClellan the dash plumber at mindspring dot com

Lightness...

When you see a stock of good balsa, buy it... keep lots in stock to select from

After designing your structure, half the thickness of the bits of wood you've specified

Use as little ply as possible

Use as little sheet wood as possible

Go and see my building diary on my website

Use built up structures wherever possible

Straightness...

Build on a granite worktop

Select straight wood, or if it needs to be bent, steam it

Never force any joint, and where possible, pre-bend sheeting

I'll repeat, 'cos it's important... never force any joint

-- Philip Rawson

Light?????? True??????????

Sounds like the makings of a scrap pile-o-balsa and covering to me. Build it HEAVY and STRONG! There is no such thing as too much glue. If there is any glue left at the end of your project it's because you haven't reinforced it enough. So what if that .20 sized craft needs a .60 to get off the ground, that's why they make BIG engines. If my plane hits the ground, I want the earth to shudder before I backhoe it out and restart it. As for building "true", what do you think the "TRIMS" are for????? So what if it takes 50% up elevator and full right aileron to keep her in the air, It's flying aint it????????

This is NOT really my opinion, but makes for some interesting reading huh? ;-) Steve

R> What are people's tips for building light, and true?

In a hurricane, maybe. High wing loading is not good. Heavy is bad, bad. Newton's Laws prevail, check'em out. Dr.1 Driver "There's a Hun in the sun!"

Why is it that slope gliders, ballast for better penetration?

General rules are "always wrong"

That is exactly why, and the ONLY reason they use ballast. A heavier plane DOES penetrate and fly in wind better, but that's the ONLY reason to add, or not take out, weight. As I said, "In a hurricane, maybe."

And Newton's Laws are not "general rules". They are scientific facts that every object is affected by. Dr.1 Driver "There's a Hun in the sun!"

I haven't seen any backhoes at model fields yet. How much buried treasure is there as some of the places you've flown? Dan

Very good possibility. On full-scale fabric-covered wings, there is a drag penalty caused by spanwise flow running over the high spots along each rib. The airflow is NOT straight along the chordline from leading to trailing edge if the wing is generating lift; the higher pressure on the bottom is causing the flow to move outward somewhat, and on the top, lower pressure pulls it inward. This is where wingtip vortices come from. Smooth wings cause less drag, and a sheeted and covered wing will be nice and slick. Further, the designed airfoil will be the same anywhere along span, not just over the ribs. The additional lift and lower drag could more than compensate for the extra weight.

Dan

A heavier plane and therefore, a higher wing loading does NOT affect the quality of flight assuming all other aerodynamic factors are correct. Weight translates into a higher wing loading and therefore, a higher stall speed. Consequently, you need more power to get off the ground and more air speed to to get back i.e., land. All other flight characteristics should remain the same.

Sounds like you've never tried it...

-- Philip Rawson

they fly like a brick compared to a decent flying model if memory serves, some full scale planes fly at 100 POUNDS per square foot they also take off and land at speeds well above what most models can reach.

If you don't think weight makes a difference, try just tying a couple of bricks to your favorite flying model, take it out and fly it, and you WILL notice a difference.

WRONG!

Given the same wing area, higher weight means higher loading. This means:

higher takeoff speed higher landing speed higher stall speed slower maneuverability slower response to control movements higher fuel consumption harder crash

Can you say "inertia"? As I suggested in a previous post, study Newton's laws.

Dr.1 Driver "There's a Hun in the sun!"

Dunno... have they got wings?

Sorry, I can't be bothered... go and spend 15 years designing and flying your own models, then look back at what you've learned...

-- Philip Rawson