smaller battery means less power ... means the only solution is smaller prop ... it will be much better to find way how to move battery back ... even on cost of splitting to 2x 2s

Robert,

How much do your Hyperion packs weigh?  Also, what is the kv rating on your E Flite 25?  If it is the 870 kv version then you would likely be out of the governor range with a 5 cell pack unless you went to a much smaller propellor.  It seems that electrics tend to be happier with a slightly more forward CG as well.

A 5S, 3200mAh pack will be thicker and shorter -- that would move your CG back a bit.

If I'm doing my math right, and this is your 60oz stunter (and using the 70W/oz rule and the 75% charge left at the end of the flight rule) then your 4S 4000mAh pack is correctly sized, as would be a 5S 3200mAh pack.

Can you notch the wing without causing too much grief?

I hate to say it, but is that motor big enough for 60 ounces?

Actually a 4Sx4000 sounds like more battery than you will use.  The 5Sx2700 should be comfy, the equivalent 4S size would be 3375, you could probably use a 3300 or 3600 and save a little weight.

Remember that you will want it to balance a little foreward of what you are used to - because your tank is "full".

Sparky,
When you say extremely nose heavy could you be more specific?  Measure from the flap hinge line at the root.  On a Crossfire, the balance point should be at about 7 3/8" from the hinge line.  If you notched the wing out, locate the battery at the extreme back of the bay.  My last years plane had  the battery as far forward as possible while this years has the battery all the way back.  You will probably find that electrics seem to work better with a more forward CG than what the modern piped ship did.  Most competition Electric flyers in the Northwest have found this to be true including Mr. Walker.
Alan

Sparky.
May be a little real-time information from this weekend's flying will help you get a better feel for what you're up against as far as the CG situation. So far many people have given you sound advice to work from. I'll give you some actual specifications that my Crossfire/Finesse is flying at in regards to the CG.

Alan gave you a dimension to work from, nominally 7 3/8 from the trailing edge, my ship is currently flying at 7 3/4 from the trailing edge. Look closely at the picture that I've included you'll see the red lines on either side of the fuse, this is the current CG as I am flying it. My power system is E flight 25, 12/6 APC P prop, 4S 3000 batteries, KR timer. The ship is 655 in.², ready to fly weight is 60 ounces. This ship incorporates the same nose and tail moments as Mr. Hunt's Crossfire (just different overall construction).

I've followed your thread since you started with a Crossfire, my weights may be on the low side, I think Allen's new Crossfire will be very similar in flight characteristics to mine . There are many good sources for different sized batteries, leadership hobby, hobby King, hobby partz, etc. Ideally, you would like to have a battery that allows you some movement, gives you ample milliamps and doesn't break the bank.

I'm sure you will truly enjoy the flying characteristics of the Crossfire.

Regards
Dave

ama 41041

My ballance poing now is around 8.5 from the TE. Way too nose heavy. Plane is at 59 OZ no clear.

Hi Sparky,
What's the actual weight on those Hyperions you are using right now?
Can they be moved any farther aft?

Dean P.

Sparky,
Why not drop the E-flite 25 and add the 32 instead.  Adds 10g, but you could then go to the 5S 2700 mAh Thunderpower 25C Pro Lite battery that weighs only 300g.  I was a bit nose heavy, but due to the small size of the TP, I was able to move it aft by over 4".  Running a 13" APC prop I never use more than 1950 mAh.  Saving the extra 3 oz of nose weight might mean you wouldn't even have to shift the battery position.  It also would reduce the overall weight.
Alan Resinger

My ballance poing now is around 8.5 from the TE. Way too nose heavy. Plane is at 59 OZ no clear.

Sparky,,
you will move the CG aft when you clear it. betweeen that and a slightly lighter battery you may still be just fine