RCU Forums - deleted topic

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- RC Pattern Flying (https://www.rcuniverse.com/forum/rc-pattern-flying-101/)

- - deleted topic (https://www.rcuniverse.com/forum/rc-pattern-flying-101/9355323-deleted-topic.html)

I have removed the posting, I have decided not to create a build thread here.

Apologies to those that have responded, and thanks for your insights!

RE: deleted topic

Hezik,

A lot of good planes came from the TLAR (that looks about right) concept. At the very least you will have fun and learn quite a bit about designing. Put me down for a set of plans if and when you get them done. I'd offer free laser cutting, but seeing that you live overseas it would be a hassle. Good luck with the design. I'll be eagerly watching.

Pedro

RE: deleted topic

I like it

what about the wood structure for the wing tube? looks very slim and in the middle of the fuse, or the drawings are incomplete?

anyway i like it!

RE: deleted topic

Hedzig,

Your stab area is way way too large. We don't use stabs this large for several aerodynamic and manueverability reasons. If you are building a trainer, then a 32% stab is fine. Reduce the area to around 20-25% of the wing area. ...smaller area (20%) for all out F3A capability or larger area (25%) for more stability in pitch and groovier performance

You wing section at 9% is also fine. Try to get a taper ratio as close to 3:1 (tip chord 1/3 the root chord; 2.5:1 works well andmay be easier to make built up) as you can and still build the wings straight and flat.

1 degree of dihedral should be very close for as low as you show the wing relative to the thrust vector. We generally raise the wing a little and reduce dihedral for better rolling character and elimination of roll coupling with applied rudder

I like the general side view shape

MattK

RE: deleted topic

Quote:

ORIGINAL: hezik

Thanks for your comments!

The stab area is something one could argue about.

For instance: Sebart's new WindS 2m: 21 dm^2. Larger than my stab. CPLR enlarged the stab on the Osmose Evolution, and the Axiome. Both have a bigger stab than this bird.

See also Chad Northeast's blog:

Quote:

Secondly, the stab and fin are very large relative to the wing, and also to other F3A models. Christophe said he was not happy with the directional stability in the Osmose, so he made a similar change to the Osmose Evolution and it was improved. So this is a carry over of that, my next question was obviously does that not make it more difficult in the snap, to which he smiled and said there are always compromises Indeed.

However, you are right.. it's a large stab, and a large fin, for that matter. If it turns out to be too large, I will build a smaller one!

The wing is 10% all the way, from root to tip. Since there's a fillet near the fuse, the chord gets very big at the fuse, so it's 9% at the fuse.

So overall, its like this:

fuse: 9% (chord: 57cm)
6cm outward from fuse: 10% (chord: ~45cm)
tip: 10% (chord: 16.5cm)

The root chord at the fuse is 57cm because of the fillet. If one leaves out the fillet, the chord would be 47cm. Since the tip chord is 16.5cm; that means there's a 2.8:1 ratio, which is close to what you mention.

The dihedral on the wing is practically the same as on the Axiome, after CPLR cut it and increased the dihedral. I'm hoping it is correct indeed, but the proof of the pudding is in the eating :)

You're welcome. You asked for help and comments so those were mine. It's your choice whether to use them or not.

Christophe is a great flier and he could make anything fly well including compromised designs. I have flown a couple of his designs and I think these are not particularly good for the average fliers.... too many mixes needed. But in his hands, they fly fine and are world beaters due to his flying skill and ability to set them up electronically. A better design would trully leave everyone else in the dust.

The fact is that we can design a pattern model that has virtually no practical compromises. Look up and study Bryan Hebert's latest, which is being offered by CompArf. There should be photos in their website. No need to copy it... just pay particular attention to the relationships in areas, location of wing relative to thrust vector, dihedral, etc. There is an awful lot more of course but it sounds like you are very early in your learning curve so these variables are a very good place to start

MattK

RE: deleted topic