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Balsa Funbat

colorex

Rotor Riot!
Mentor
#1
So I wanted to make a balsa version of the Funbat - because I like balsa construction, and I like making drawings, and the Funbat is such an awesome plane.

Here is a slightly downscaled Funbat that I built with foam a couple of years ago.

IMG_2808.jpg

I flew it only a couple of times before decommissioning it. It had a Park450 1050kv motor spinning a 8x4.7 prop, a 1300mAh 3S and 9 gram servos in it. It would go vertical, fast, but it was a pig to fly, with very high wing loading!

So now I'm going to make the actual size version in balsa, maybe even upscale it a bit, in order to fit the same hardware but with a 2200mAh 3S battery instead. Some modifications will also be included.

More to follow.
 

Foam Addict

Squirrel member
#3
If you build up the wing, that will have some awesome flight characteristics, be sure to reinforce the fuselage though, Balsa belly landers take a beating.:p
 

colorex

Rotor Riot!
Mentor
#5
Sp0nz: No. I'll do a built up semi- or symmetrical airfoil with ribbed construction.

FA: I have this in mind. I will do a stick frame w/ bulkheads formers and sheet it in critical areas: nose, belly and tail. My biggest concern is the propeller, I don't have a prop saver for this motor. I may put landing gear on it to help protect the prop.

Roversgonemad: Thanks for the link. So that's why it's called Bloody Wonder! However I'm into this more for the design (conversion to balsa) and construction than for the flying. I am outside US so buying kits is expensive for me. If I were to buy a kit, it would be a Sig Seniorita! Most beautiful Trainer ever! Trying to get my hands on a plan to build one of those but it looks like it won't be free.
 
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colorex

Rotor Riot!
Mentor
#7
So here's what I got aside from the original FunBat plan. Not complete yet of course.

So for the modifications / features I am planning to make:

- The motor will not be visible from the sides or from above, like it is in my foam Funbat. The sides and top will stretch to the same length as the motor. In the drawing the motor is represented by a light blue rectangle.

- I want to be able to adjust the position of the fuselage relative to the wing, to counter for any eventual CG issues. For example, if it ends up nose heavy, I can move the wing forward and fairly easily trim the tail portion of the fuse. If it were to be tail heavy I can move the wing back to correct this.

- I may mount the elevator servo on the side of the fuselage under the wing, to free up space on the top for a possible FPV rig - depends on what it flies like. (I've FPV'd the Bixler and find it too lethargic to FPV with - I want to start flying lower and the Bixler just doesn't give me the authority I want. The Funbat will on the other hand go where you point it.)

fubat.progress.1.jpg
 

colorex

Rotor Riot!
Mentor
#8
Some progress. I decided to make only 3 formers and fill the gaps with stick framing.

I stumbled upon a problem - battery size. It seems I won't be able to fit a 2200mAh 3S in the fuselage very easily. Maybe this will be a good reason to scale it up a bit.

I also need to figure out the landing gear and wing mounting.

fubat.progress.2.jpg
 

SP0NZ

FT CAD Gremlin
Mentor
#9
Nice work so far. What CAD program are you using? It's really fun seeing all the different methods the FT community is using to design with.
 

colorex

Rotor Riot!
Mentor
#11
I'm working on a foam board version of the Sig Wonder (I'm calling the 1D3R). Had a prototype at FF2014 that Bixler flew and autographed for me. Flies like it's on rails, and has an awesome glide slope!
Nice :) I wonder what makes it so good.

What airfoil would you recommend using?
 

SP0NZ

FT CAD Gremlin
Mentor
#12
The Sig Wonder has a 37.5" Wing span and has a shorter overall length than the Bloody Wonder. Here is a comparison of my 1D3R in front of the Bloody Wonder MkIII.

2015-01-29 22.50.29.jpg

I haven't calculated out the wing loading for my foam board Wonder yet, but I'm sure it is even lower than the Bloody Wonder. The Sig Wonder (and my foam board version) has a symmetrical airfoil. I found some images on the web that I was able to use to create a foam board airfoil that is as close to the balsa kit version as I could make it. Here is a better look of what the 1D3R looks like.

Prototype 1D3R.jpg

I'll stop hijacking your thread now. :black_eyed:
 

colorex

Rotor Riot!
Mentor
#16
Nice work so far. What CAD program are you using? It's really fun seeing all the different methods the FT community is using to design with.
Sorry - missed this question. I use a bootleg version of AutoCAD 2015. I also know SketchUp but for making printable plans I prefer AutoCAD. For making 3D models it is Sketchup of course :)

I'll be watching this progress. You've motivated me to get back to work on my 1D3R too. ;)
Thank you, I'm back on my work schedule so it may be slow but I'll do a couple of things now and then.

Anxious to see some plans from both of these models. Get to work guys!!
I will definitely make them available for you when they are complete!
 

colorex

Rotor Riot!
Mentor
#17
So I ended up making it 33.5 inches in wingspan. This increases the battery space enough for my slightly swollen 2200mAh's :black_eyed:

The green outline represents the standard FunBat size, the red one is my 33.5" balsa design. This makes it a 122% Funbat. The good thing about scaling up is that wing area increases exponentially - the increase in wing area is close to 150% versus the 122% increase in wingspan :p

In other words, lighter wing loading is good :D

[I don't know if this is your style but I've been listening to this song on repeat for the last hour :)
https://www.youtube.com/watch?v=Kf8pOdTtsT0 ]


fubat.progress.3.jpg
 

colorex

Rotor Riot!
Mentor
#18
So this is what I got done today. This will be the layout of the ribs, although I have not figured out an appropriate airfoil yet. earthsciteach said he would suggest one for me :)

I'm thinking if it would be a good idea to laminate the fuselage... Would be much stronger, but it loses that beautiful semitransparent look that I love...

fubat.progress.4.jpg
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#20
What kind of CAD program do you use for the design work? Years ago I had a free program that allowed me to do some basic layout designs for some truck fabrication I was doing, and it might work OK for some airplane designs I've been thinking about.