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Introductory post and a question on the Sportsters CG

#1
Hi I am new to the forum but have been watching flitetest for a good few years now.
I recently did my first foam board model and I chose the sportster

Now I am using a propdrive 28 30 1200kv with a 10X4.5 slowfly and a 3s 2200mah battery

The problem is that the CG is way far to the rear and I have to move my fingers about an inch and a half behind the CG to balance it this is with the battery all the way to the front.
Now I know this is too bad to fly im guessing I need to add weight to the nose till it balances I was just wondering if anyone else had this issue?

Thanks
Tom
 

foamtest

Toothpick glider kid
#2
I have not build this particular version of the sportster but I have had a similar issue with the mini. If you can use a bigger battery to balance it I would recommend that over adding dead weight, but in this case it looks like you might have too. Also did you buy the speed build kit or did you scratch build it?
 
#3
Thanks for the reply

I scratch built it but it looks identical so not sure thats the issue and yes I would rather balance up with a bigger battery but unfortunately the next size up is a 16000mah 6s I use for my ebikelack

Well ill go get the hot glue and the rocks then
 

foamtest

Toothpick glider kid
#4
Yeah rocks, coins, washers, anything heavy and small really will due for nose weight. What brand of foam did you happen to use? They all weight differently. The foam they sell at dollar tree is Adams readiboard, others that people commonly use are Ross foam board and Elmer's craft board. If you used Ross or Elmers that could be the cause of your CG issue. Those foam boards are more durable than Adams but I believe that they are almost twice the weight, this is what causes CG issues like this. Another way to fix this issue is to make the nose longer to bring the GC forward. Lots of people who use these other foam boards tend to have to do that with short nosed models like the sportster and the speedster.

P.S. I think the 6s would make the maiden a lot more interesting ;)
 
#5
indeed 6s would be interesting :D

i live in the uk so had to hunt for some foam-board i eventually found the right thickness but it is construction paper backed so that must make the difference it didn't cross my mind before.

(in case anyone in the uk is interested its the A1 size foam-board from hobbycraft)
 

foamtest

Toothpick glider kid
#6
I am not familiar with this brand, how large is a sheet and how much does it weigh? Also can you remove the paper from the foam core?
 

daxian

Well-known member
#8
here in the uk ..i find adding 3-4 inches to the nose is the best solution ,due to the weight difference in the uk foamboard.
nearly all the ft models need this ,or a lot more weight ,typically between 40 and 100 grams for the sportster was what i found !