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Aug 08, 2019, 11:24 AM
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Sub 250g fpv plane


I'm trying to work towards a sub250g fpv plane. I plan to update my progress here as I go.

Here's my goals:
-Scratch built
-FPV (will tackle this later but for now I'll just try to reserve 20g and space in the nose)
-DTF, or white foam hotwired (can't get depron)
-AUW < 250g.
-15+ minutes minimum flight time.
-Ideally can be disassembled and flat-packed.

I made a plane a little while ago and got some suggestions on how to make it fly longer.
I haven't picked a final motor+prop combo to order yet, so for the moment I'm going to make the best of what I've got.

-6000 kv motor. -seems too small, especially with its current prop, but 4 of these lift the eachine lizard miniquad with its 50g battery.
-3x 3.7g servos
-4ch rx
-8amp opto esc + separate bec
-Battery options on hand:
-600mah 1s 25c (12 total) and spare connectors to possibly make a parallel or series connection.
-900mah 2s 40c? 30g
-500mah 3s 80c 45-50g


I'm trying foam without the paper this time. I haven't got any carbon fiber for spars, but hopefully wood and string stays will be enough.

Current mass of foam (<1 sheet of dtf so far), motor, rx, and two 600mah 1s batteries is about 120g.

I think the nose should have been cut longer, so I will probably be making the fuselage again.


Any thoughts?

Recommendations for a motor+prop? -Seems I'm looking at about 10minutes flying tops unless I can get the current below 3A.
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Aug 08, 2019, 02:11 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by RetepTrun
I'm trying to work towards a sub250g fpv plane. I plan to update my progress here as I go.

Here's my goals:
-Scratch built
-FPV (will tackle this later but for now I'll just try to reserve 20g and space in the nose)
-DTF, or white foam hotwired (can't get depron)
-AUW < 250g.
-15+ minutes minimum flight time.
-Ideally can be disassembled and flat-packed.

I made a plane a little while ago and got some suggestions on how to make it fly longer.
I haven't picked a final motor+prop combo to order yet, so for the moment I'm going to make the best of what I've got.

-6000 kv motor. -seems too small, especially with its current prop, but 4 of these lift the eachine lizard miniquad with its 50g battery.
-3x 3.7g servos
-4ch rx
-8amp opto esc + separate bec
-Battery options on hand:
-600mah 1s 25c (12 total) and spare connectors to possibly make a parallel or series connection.
-900mah 2s 40c? 30g
-500mah 3s 80c 45-50g


I'm trying foam without the paper this time. I haven't got any carbon fiber for spars, but hopefully wood and string stays will be enough.

Current mass of foam (<1 sheet of dtf so far), motor, rx, and two 600mah 1s batteries is about 120g.

I think the nose should have been cut longer, so I will probably be making the fuselage again.


Any thoughts?

Recommendations for a motor+prop? -Seems I'm looking at about 10minutes flying tops unless I can get the current below 3A.

Do you not want to build the EzFly I recommended in your other thread ? The EzFly has been around for 10 years and has been proven to fly well , a self-designed airframe may-or-may-not fly well . One problem I can see immediately with the plane in your photos is : in order for a plane to make left/right turns using only rudder/elevator ( no ailerons ) , it needs dihedral or polyhedral on the wings ( wing ends angled up ) .

A 6000kv motor with a tiny prop will not be efficient for a lightweight slow-flying airplane . It would be like trying to drive around slowly in third or fourth gear in your car or on your motorcycle , not impossible .... but very inefficient . You can get small motors with much lower kv , that can swing a larger prop . That would be like driving around slowly in first or second gear .

If you have wood sticks , you could just use one for a wing spar ..... no need for a lot of struts and strings on a lightweight plane .

Here is a 16gram motor that has several kv choices that are lower ( 1100 , 1300 , 1700 ) , and it comes with an ESC/BEC :
https://www.aliexpress.com/item/32835368274.html
If you can find another 10 - 20 gram motor with a kv under 2000 , that would work also . Those small motors only need small ESCs , like this 6A :
https://hobbyking.com/en_us/turnigy-...B&gclsrc=aw.ds

I noticed some paper shred remnants on your fuselage , you can remove the paper cleanly and easily if you spray the foam board with water or alcohol first :

Remove paper from dollar tree foam board (0 min 35 sec)
Aug 08, 2019, 02:47 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Here is a complete micro power system that includes motor , ESC , servos , props and battery :
http://www.dwhobby.com/free-shipping...ery_p0339.html


For a slow flyer , I recommend using this gearbox motor and a larger prop :
http://www.dwhobby.com/free-shipping...tem_p0594.html
Aug 08, 2019, 07:14 PM
flyin' fool
goldguy's Avatar
Your design is sound. I've seen something similar used as a FPV base …………….

https://www.rcgroups.com/forums/show...Pusher-Trainer
Last edited by goldguy; Aug 09, 2019 at 02:02 PM.
Aug 08, 2019, 07:23 PM
flyin' fool
goldguy's Avatar
Here's my version at 5 ounces RTF. It's sporting a Jedelsky airfoil that's easy to make,light and ridged.

https://www.rcgroups.com/forums/show...postcount=1516
Aug 09, 2019, 07:43 AM
Registered User
Thread OP
Quote:
Originally Posted by balsa or carbon
Do you not want to build the EzFly I recommended in your other thread ?
The EzFly looks like a nice easy build. ...But I felt like having another go at making my own design before going back to building from plans where the kinks are already worked out.

Thanks for the power system suggestions. It seems that I just happen to have a one of those c10 motors here on a little biplane that doesn't fly too good (too heavy I think).

True about the wing. I expected the paperless wing to be really floppy and thought I might just use the natural U bend as my dihedral, but it was not the case. That wing didn't look quite right proportionaly to the rest of the plane either, so I made another. Imo it looks more right.

So far the plane seems ok as a chuck glider when I tape a battery to the nose.

@goldguy
Its good to know I'm on the right track.
Aug 09, 2019, 09:18 AM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by RetepTrun
The EzFly looks like a nice easy build. ...But I felt like having another go at making my own design before going back to building from plans where the kinks are already worked out.

Thanks for the power system suggestions. It seems that I just happen to have a one of those c10 motors here on a little biplane that doesn't fly too good (too heavy I think).

True about the wing. I expected the paperless wing to be really floppy and thought I might just use the natural U bend as my dihedral, but it was not the case. That wing didn't look quite right proportionaly to the rest of the plane either, so I made another. Imo it looks more right.

So far the plane seems ok as a chuck glider when I tape a battery to the nose.

@goldguy
Its good to know I'm on the right track.
The C10 motor would be a better choice for your plane than the 6000kv motor .

The dihedral on your new wing looks good .

Glide testing is a great way to get the kinks worked out of an airframe design !

To increase wing area ( for low wing loading ) , you can increase chord ..... if you feel the span is out of proportion . Here is a plane I've made where the chord is 20" , 1/3 of the span ( 60" ) :



FT Old Fogey-ish with 60" wingspan (1 min 56 sec)
Last edited by balsa or carbon; Aug 10, 2019 at 05:21 PM.
Aug 13, 2019, 08:11 AM
Registered User
Thread OP
Well, during glide testing the tail broke off.
I also noticed that I would need more clearance for my motor.

So, I started a new, taller fuselage, this time it is mostly hollow instead of 4 solid layers to compensate for its larger size. The tail is now slightly longer and 4 layers solid which I will carve down to a cylinder and wrap with tape once the servos have been embedded on the top and side.

With the larger fuselage I think the wing now looks a bit short, so I will be extending that next I think.

Seems like I'm basically converging on the blu-beagle.
Aug 13, 2019, 10:37 AM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
To have a stronger tail boom , you could use a square or round carbon fiber tube :
https://www.ebay.com/i/233276768461?...oaArgDEALw_wcB

or a cheap arrow shaft : https://www.walmart.com/ip/Kryptos-C...AaAvdkEALw_wcB

You may be able to find a free discarded arrow shaft at an archery shop or range .
Aug 13, 2019, 02:05 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Here is a Skywalker with a carbon fiber tail boom :
Aug 16, 2019, 01:47 PM
flyin' fool
goldguy's Avatar
How about a sub 250 gram super simple FPV base design without a tail …………………….

https://www.rcgroups.com/forums/show...n-FPV-and-more
Yesterday, 09:35 AM
Registered User
Here's my mini FPV airplane made out of spare parts. It weight 140g. Has over 100 flights on it now. I use it to train people for FPV flight and to take people up for an FPV ride. I've had it up for about 20 minutes (aided by thermals) with power to spare.


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