Eddie vs. Otto: Cartoon style WW1 Combat biplanes free plan - Page 24 - RC Groups
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Feb 20, 2018, 02:28 PM
Registered User
FIFI1969's Avatar
Thank you Squall
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Feb 24, 2018, 01:31 PM
Scratch building addict
rotagen's Avatar

skeptical on cg

Finally got around to making a little albatros with these plans.

This will be my first scratch bipe with no airfoil or undercamber so who knows how it will fly probably twitchier than most.

Could some folks with nice flying planes chime in on their actual cg? I'm quite skeptical of the cg as printed on the plan, seems too far back.

I have tons of planes, and I have found a great starting point is to use the 12% MAC figure on online calculators.

Messed with 4 different calculators today and got some weird results, somewhat conflicting.

In general for bipes I pretend there is one large wing with leading edge at front's and trailing edge at bottom's.

Using the different online calcs I actually got different results, I am inclined to believe these are close, one gave 3cm behind leading edge and one gave 3.99 cm.

Others actually gave me negative numbers.

So I'd like a consensus... also I will determine cg location: the percent back on my nice-flying scratch built fokker and I may just resort to the same percentage.

Feb 24, 2018, 02:06 PM
Scratch building addict
rotagen's Avatar
OK if you go to my inactive RCgroups blog you will see my little fokker. I made the lower wing equivalent to upper in size so not scale. The wingspan is around 28 inches and I actually attached the lower wing with strong magnets and little magnets in the wing struts, it rolls and loops just fine.

Anyways the cg on that one I just tested and it's 4.4cm back from upper leading edge. Taking the wings as one single larger chord wing I calculated this at 22.3% back. Putting my new cartoon bipe at same puts the cg at 5.5 cm back from upper leading edge.

I'm thinking this is a good figure to start with since it is between what some cg calcs gave and what people are using here?
Feb 24, 2018, 02:17 PM
Registered User
FIFI1969's Avatar
Hello Rotagene,

I confirm that the center of gravity is 28mm from the leading edge of the lower wing.

My Eddie flyes very well with this seeting.

Best regards.

Mar 05, 2018, 12:29 PM
Scratch building addict
rotagen's Avatar
Thanks for the input. I have a feeling that there is a nice big range of possible CG due to the fat wing?

I finally finished my Otto albatros, I sorta copied the paint scheme someone made on this thread.

I put my CG at around 5.5cm back from top wing leading edge, which puts it actually in front of bottom wing on mine.

Maiden went very well, with 1400kv motor and 3S 500maH battery, I think the prop is 8-inch.

There is one issue - it wants to climb and pitch up. Even though there is a good size downthrust on the motor when following the plan - something I rarely add on biplanes.

I am almost certain this is due to the large incidence angle of the wing - I noticed this when I was assembling from the plan, it looks like more than 2 degrees of incidence relative to the horizontal stab?

Just a note to builders, it may be a good idea to lower the front of the wings. I find that around 1 to 1.2 degrees of incidence is perfect, at least for my scratch-built warbirds.

Would be interesting to see if someone tries this and notes the results.

A really fun easy build that flies well- thanks for these plans!

I have lots of trouble making a biplane that flies well, this one flies great due to the larger wing area I think.

Mine has a funny pilot not seen in this pic. Sven from Ren and Stimpy cartoon, hence the S.

I have no 6mm depron and it is too expensive in the US, so mine is dollar tree foam and bluecor wings (very stiff and nice)
Mar 05, 2018, 01:22 PM
Rampage's Avatar
Is there a kit for these anywhere? I'd love to get a few of them for our field! I bet that'd be a ton of fun.
Mar 12, 2018, 03:15 PM
Registered User
FIFI1969's Avatar

One more Eddie for the patrol of our club.

This one belongs to Christion.
Weight with battery: 326 grams

We arrive at about fifteen aircraft for air combat.

luckily spring is coming soon.

Best regards.

Mar 13, 2018, 04:42 AM
Registered User
Squall's Avatar
Nice looking color scheme!

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