EzFly free plans for great trainer plane - Page 47 - RC Groups
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Sep 02, 2011, 12:13 AM
Registered User
motorhead's Avatar
Quote:
Originally Posted by larryross
OK motorhead I did the cutouts and it made the tail very felxible. I installed a tail wheel and main landing gear and made a hole for a 2.2AH lipo in the nose see picture below. Doesn't look like a good idea to me, but I can't figure any other way. The foam I used in the nose is a very still large cell foam that is flexible and all most impossible to tare. I slammed the plane nose down on the floor of the shop (very hard) I don't know how to compare it with a nose in crash, but all it did was bounce and didn't appear to hurt the the battery. The CG is still about 1 inch behind where I thought it should be. How can I get it closer? Any ideas?

I am building a smaller one and I think I will move the wing back an inch or so and see if that helps.
Covering the holes with packing tape will help the stiffness. At this point adding weight to the nose or moving the wing back is the next best options. I would add weight next as with the size your wing loading is probably less than stock and also as you get bigger it can handle a higher wing loading easier.
Mike
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Sep 02, 2011, 12:41 AM
Registered FFF Addict
larryross's Avatar
I am over 32 oz now, but it won't take much extra weight to balance now. Packaging tape will add a little weight, but I will need to put it on the vertical at least. Like I said the next build will be a 48" and I will move the wing back about an inch. I like the way the ezfly flies when the CG is right.

How much danger do you think my lipo is in where I have it (none if I don't nose in right).
Sep 02, 2011, 12:56 PM
Registered User
hey larry i know you have a huge experience then me in building , but plz change the idea for the battery placement , battery is more unsafe from side then corners of cover the battery with some thind tuff .
Sep 02, 2011, 02:00 PM
Registered FFF Addict
larryross's Avatar
I really wasn't worried about the ends, because if I mounted in on the side of the plane it would be just as pron to damage. I was only worried about the effect of a hard nose in. I believe the foam has enough give to break the impact. The wings will protect the ends of the battery unless I hit hard enough to break the wing and landing gear and in that case I still believe the impact will be cushioned enough for the battery to survive, besides there is no other way to mount it without having to add a lot more weight to the front. I might cut some small foam cups to put over the ends of the battery. I was always told to build to fly not to crash.
Thanks for the observation vineet.


Quote:
Originally Posted by vineet.aquariu
hey larry i know you have a huge experience then me in building , but plz change the idea for the battery placement , battery is more unsafe from side then corners of cover the battery with some thind tuff .
Sep 02, 2011, 06:28 PM
Sopwith Camel's Cousin
Quote:
Originally Posted by larryross
... I might cut some small foam cups to put over the ends of the battery. I was always told to build to fly not to crash.
...
Covering the ends sounds good in case the crash is an angle (hit the nose and wing at about the same time and the foam bends a bit).

On another not so fast mid-prop plane, I have the lipo directly behind 2 layers of 9mm EPP. The lipo is fine despite nose-in dives at speed into the dirt (it loops easily, but it seems that I need to have less throttle for up elevator to pull out ).
Sep 02, 2011, 07:07 PM
RC Adddict
Wilfor's Avatar
Larry this is my thought on battery placement Name: battery placement.png
Views: 211
Size: 77.7 KB
Description:

Does take away from the look a little but safe and then you could add weight to where it was to get the COG correct
Sep 02, 2011, 07:36 PM
Registered FFF Addict
larryross's Avatar
Even where it is I had to add 2oz weight. This thing is heavy enough without adding even more weight. If I add any more weight I will have to put a bigger motor on it.

OK this is what I did... now I can call it My Hammer Head EzFly. Hope this makes you feel a little better about my battery's chances. Besides this will give me more incentive to not nose it in.



Quote:
Originally Posted by Wilfor
Larry this is my thought on battery placement Attachment 4253225

Does take away from the look a little but safe and then you could add weight to where it was to get the COG correct
Sep 03, 2011, 04:05 AM
Sopwith Camel's Cousin
Quote:
Originally Posted by larryross
...
OK this is what I did... now I can call it My Hammer Head EzFly. Hope this makes you feel a little better about my battery's chances. Besides this will give me more incentive to not nose it in.
Looks good to me.
For the hammerhead look, you could draw some eyes at the ends of that extension
Sep 03, 2011, 08:38 PM
RC Adddict
Wilfor's Avatar
Larry another thought on getting the COG right . That wing looks huge , could you mark and cut say an inch off the LE and then reshape it . Sure you would loose some wing area but with how much it has i dont think it would be enough to make it fly poorly . It looks like you have room to extend the step if needed but i dont think it would be necessary .

This would give it a little longer nose without much work and possibly move the COG back enough to make the weight not needed ?
Sep 04, 2011, 05:04 AM
Sopwith Camel's Cousin
Quote:
Originally Posted by Wilfor
Larry another thought on getting the COG right . That wing looks huge , could you mark and cut say an inch off the LE and then reshape it . Sure you would loose some wing area but with how much it has i dont think it would be enough to make it fly poorly . It looks like you have room to extend the step if needed but i dont think it would be necessary .

This would give it a little longer nose without much work and possibly move the COG back enough to make the weight not needed ?
If you want to maintain the same wing area but move the desirable COG point back, you can take that removed inch from the LE and put it on the trailing edge, so effectively, you have moved the wing back about an inch.

Or if you are interested in being real floaty, you can skip removing from the wing LE, but still adding to the wing trailing edge.
Sep 04, 2011, 08:42 AM
Flying Models for 55 Years
Sixter's Avatar
Larry: Write this one off, hang it up in the ceiling. Build another one per the plan. Build it lite, don't change anything then the CG should not be a problem.

Bobby
Sep 04, 2011, 12:42 PM
Registered User
dear larry , the hammer head technic is nice to see but it wont safe anything as when the plane is coming down on nose with weight of 1 kg at the speed of 40 to 50 kmph the impact would be so hard then to think in practical .

really sorry as i know you are an experienced man more then me , bu this is what i feel practically , if you dont want to add more weight

you can make a rectangular circumfrence of battery with cf 4 mm square hollow tube , or may be
you can put the battery up as we usually see in ezyfly build and add some penny to the nose may this will balance the plane .

last thing what ever you do , do it quickly as i cant wait to see it in sky.

best of lucy cat(luck)
Sep 04, 2011, 10:18 PM
Registered User
motorhead's Avatar
That is more protection than I have on most of my foamies. They just get the battery velcroed to the side and they come off and hit the ground in a hard crash.
Mike
Sep 05, 2011, 12:37 AM
Registered User
Hello all and love this thread...... I am trying to draw a 60" wingspan version using sketchup 8 and i am having trouble with the fuse and the overall length. I used the 31" wing span and scaled it to 60 1/8". But to draw the fuse i need a reference point to start with. Can some one give me some dimensions to use for this Thank you (build mine from 1/2 foam from Home Depot 13 bucks for a 4X8 sheet)
Sep 05, 2011, 08:03 AM
Registered User

Sketchup Dimensions


I hope this is right. Looking for someone with sketch up to check this


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