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General control line discussion => Open Forum => Topic started by: Paul Taylor on December 21, 2024, 03:01:47 PM

Title: Fuel cell location? On the thrust line?
Post by: Paul Taylor on December 21, 2024, 03:01:47 PM
Ok I’m building a Pathfinder and going electric. I want to recess the
Battery compartment into the fuselage. Should I put it in between the motor mount cut out or lower it down on the thrust line?(https://uploads.tapatalk-cdn.com/20241221/ecccafa3133f04957683492167ac1c9b.jpg)


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Title: Re: Fuel cell location? On the thrust line?
Post by: Ken Culbertson on December 21, 2024, 05:12:52 PM
Here are two examples of with the battery on the thrust line.  I make the cavity larger than the battery by 1/4" top/bottom and at least 1" on the front/end.  That lets me position the battery to fine tune the CG.  The Pathfinder is Crist Rigotti's, and the Trifecta is my design.  These are old pictures.  I use the foldback Velcro strips like Crist now.  I put my battery on the outboard side to slightly lessen tip weight, but it can go on either side.

Ken
Title: Re: Fuel cell location? On the thrust line?
Post by: Paul Taylor on December 21, 2024, 06:09:24 PM
Here are two examples of with the battery on the thrust line.  I make the cavity larger than the battery by 1/4" top/bottom and at least 1" on the front/end.  That lets me position the battery to fine tune the CG.  The Pathfinder is Crist Rigotti's, and the Trifecta is my design.  These are old pictures.  I use the foldback Velcro strips like Crist now.  I put my battery on the outboard side to slightly lessen tip weight, but it can go on either side.

Ken

Thanks Ken
Going to steal your idea. 😎
And Merry Christmas!
Title: Re: Fuel cell location? On the thrust line?
Post by: John Rist on December 22, 2024, 09:02:24 AM
I now place all of my batteries on the inboard side.  I had one on the outboard side come loose and fly out. the airplane crashed on the spot.  Tail heave aircraft don't glide, they just fall.    y1
Title: Re: Fuel cell location? On the thrust line?
Post by: Dennis Toth on December 22, 2024, 09:25:34 AM
Since the motor is just above the wing center line, with a long/skinny battery I would go with between the mounts to help the vertical CG (off sets the weight of the wing and gear). I like going through the mounts load from the inside with an inboard cover plate held on with magnets ( https://www.kjmagnetics.com). If your pack does not fit between the mounts (like a 5 or 6 cell) then do flat against the outside nose but still inline with the motor to start. If you use the plate mounted to the fuse then straps to hold the pack you can adjust the height (like you would a tank) to fine tune the vertical CG.

Best,  DennisT
Title: Re: Fuel cell location? On the thrust line?
Post by: Ken Culbertson on December 22, 2024, 09:28:48 AM
I now place all of my batteries on the inboard side.  I had one on the outboard side come loose and fly out. the airplane crashed on the spot.  Tail heave aircraft don't glide, they just fall.    y1
I used to do the same until I found the right kind of strap.  IMHO having that much weight on the inboard side means more tip weight.  I have never had one of these come off.

https://www.ebay.com/itm/404616786894?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=404616786894&targetid=4580909053911843&device=c&mktype=&googleloc=&poi=&campaignid=603247654&mkgroupid=1236951625700523&rlsatarget=pla-4580909053911843&abcId=9316139&merchantid=51291&msclkid=1b6bb345bb841bd9a90dd42d8651f24a

Ken
Title: Re: Fuel cell location? On the thrust line?
Post by: John Rist on December 22, 2024, 12:30:23 PM
I used to do the same until I found the right kind of strap.  IMHO having that much weight on the inboard side means more tip weight.  I have never had one of these come off.

https://www.ebay.com/itm/404616786894?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=404616786894&targetid=4580909053911843&device=c&mktype=&googleloc=&poi=&campaignid=603247654&mkgroupid=1236951625700523&rlsatarget=pla-4580909053911843&abcId=9316139&merchantid=51291&msclkid=1b6bb345bb841bd9a90dd42d8651f24a

Ken
That is the type of straps I used.  In hast, one did not get hooked well enough.  With the batteries recessed into the fuselage and almost at the center line between the wing tips it makes very little difference on wing tip weight.
Title: Re: Fuel cell location? On the thrust line?
Post by: Brent Williams on December 22, 2024, 12:46:21 PM
Roger Kramar's method.  Lightweight and keeps the battery secure.  The velcro isn't doing much heavy lifting. 
Locate the battery anywhere you want with the depth of the aluminum cage, ie, on the centerline or biased outboard.

(https://stunthanger.com/smf/index.php?action=dlattach;topic=61865.0;attach=335232;image)
(https://stunthanger.com/smf/index.php?action=dlattach;topic=61865.0;attach=335230;image)
Title: Re: Fuel cell location? On the thrust line?
Post by: jerry v on January 03, 2025, 08:20:20 AM
In line electric motor, battery and wing.

Jerry
Title: Re: Fuel cell location? On the thrust line?
Post by: Ken Culbertson on January 03, 2025, 03:36:46 PM
Jerry, very interesting motor mount.  Simply converts an IC fuselage into an Electric. You might consider rounding the fuselage at the rear of the mount. 

Ken