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I had a dream and Im building it.

Liemavick

Member
Mentor
#1
Seriously guys I saw this plane in a dream I had. I guess Ive had a little to much FT lately and its following me into my sleep. Long story short is im not a plane designer and what limited understanding I have on scratch building has come from FT and Josh B's designs. So here's where Im at: DSCN0025.JPG The wingspan is 60" and the fuse is 40" which seems long to me. DSCN0026.JPG The wing has a balsa and foamboard combo spar and I snaked some gold n wire through the wings for the elevators, they will attach to the servos under the wing. The tail body is actually triangle. One thing I already know is Im going to flip the tail, somehow I dont think my dream planned on landing this thing but I do. So what do you think? Will it fly? is the Fus to long? I plan on putting a small motor on the nose to give it a chance. If I had been thinking and not following my dream I would have made it a swappable :)

Brian
 

Liemavick

Member
Mentor
#3
One thing Ive never been clear on with scratch builds and CG. Do you build your plane and find the CG before adding as much as a servo? Then work around that point while installing your motor, battery, servo's, etc...?
 

OutcastZeroOne

Fly, yes... Land, no
#4
once you find your CG point from doing test glides, you have to add on your motor. once thats on its a fixed weight. I try to give as much room as posible to move the battery around on my planes to adjust the CG. Servos and motors are fixed weights. The motor you dont really have many options for where to stick it. But the servos you can play around with their final spot to try and deal with CG if its a major issue.

Ive heard of guys adding several washers as weight before too.
 

OutcastZeroOne

Fly, yes... Land, no
#5
on a side note, I do question the small size of your horizontal stabilizer. It dose seem very small. Over all it seems to have similar proportions to those foam gliders you can get from hobby stores. May want to take a look at one of those for some ideas about CG and such.
 

Bolvon72

Senior Member
Mentor
#7
One interesting tip I got from Ed at ex-air is to mount your motor esc servos etc in the fuse to get the weight distribution right. He then rests the fuse on top of the wing's airfoil. Where the fuse balances on the highest point in the chord of the wing gives him his wing mounting point. Good luck
 

Liemavick

Member
Mentor
#8
I noticed your horizontal stab points down, what is the advantage of this setup? BTW looks like it would be a fast flyer!
Bernie the downward pointing stabs are for after the wings rip off in mid air. That way I can still have a controlled descent like a lawn dart :) Seriously, the tube I built for the rear fus is triangular, I cut 3 slots centered on each side. The Stabs pointed up in my dream, they pointed down after I cut the slots lol Adjustments will be made, thanks to everyones input. Larger stab ( Thanks Outcast) and the foward fuse needs tweeking, did I mention Ive never done this before?

Bolvon Thanks for sharing Ed's method, makes perfect sense in balancing the plane fully loaded.
 

earthsciteach

Moderator
Moderator
#11
You want the cg to be slightly forward of the center of lift. Figure the center of lift to be the mid-point of the wing from the leading edge of wing to trailing edge of wing (this distance is called the wing chord). So, if you install the components such that the cg is about 1/4 to 1/3 the wing chord (back from the leading edge of the wing) then you should be fairly close. Since you have such a long fuselage, you may be ok with horizontal stabilizer size.
 

Liemavick

Member
Mentor
#12
After much inner fighting with myself I decided I needed to make thie dream a "swappable". I cut the front of the fuselage off and started from scratch. I used Josh B's bloody wonder fus design and after much trimming and sanding was able to get it to work. So it's becoming more of a improvised dream design, but hopefully with decent results in the air.

I rigged it and put it on my balancing rig and it wasnt bad. The only question I have is my CG is just about 50/50 on the wing. I know from what Ive read up to this point it's best to be in the upper 30% neighborhood from the leading edge. For what its worth the stripped weight is 246 grams, loaded its 391 grams. Its either going to fly, die, or something in-between! :)
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