Twin Boom, Twin Engine, FPV, Cargo Plane Build Thread


Sunny Day Park Flyer
I'm going to build a plane to bring to FliteFest 2015, and I want it to be able to do everything (except combat, I'll bring something else for that) that I want to do there. I've decided that since I've got some matching motors around, I'll build a twin engine, because I haven't made a twin engine before; I also want to give it flaps, Which I've never needed/bothered to include; I'll also give it room for FPV equipment, which I'm new at; and I'm going to give it a cargo bay, because why not? SO: This entire airplane will be a huge learning experience for me, and should provide plenty of entertainment at FTFF.

And I think I found something that fits that tall order: the OV-10 Bronco:
This plane won't be scale, I just think the Bronco is a great platform which I can mess around with.(I think I can even put a rocket on it). Now, I've been thinking about this for a while and I've designed a full airframe and plans in Google Sketchup: (Click image for more Detail)
Front View, might streamline more
Rear View, the inner dimensions are 4.5"x4"
The Wing Layout with some Engine Pod Supports
Plan for the Fuselage
Plan for the Wing Pods, etc.

If you have any questions or suggestions, you can either leave a reply, or ask me in person at FF15!
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Sunny Day Park Flyer
Total Length: 39 inches
Wingspan: 40 Inches
Wing Chord: 8 inches
Anticipated Weight: Up to 2 pounds
Cargo Capacity: 200 Cubic Inches, Without Parachute, 5oz
Motors: 28-26A 1200KV NTM Motors
Prop: 8x4, counter rotating
ESC: Turnigy 25 amp Plush
Battery: 2200
Landing Gear: Custom Foam 3" w/ steel struts (not in design)
Servos: 9g, as many as I need (8 or less)
Spar: Foam/Paint Stirrers
Material: Foamboard (Obviously)
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Senior Member
If youre joining two wing pieces like that I would suggest something like a carbon or fiberglass arrow shaft for a spar instead


Sunny Day Park Flyer
If youre joining two wing pieces like that I would suggest something like a carbon or fiberglass arrow shaft for a spar instead

I was going to make the wingtips (11") removable so I could take it to FTFF more easily.

Does anyone know how to/have experience with removable wing sections?

Also, thanks for the pointer fireguy, I'll put some tube or dowel (or even paint stirrer) to reinforce the wing


Sunny Day Park Flyer
I looked at the episode about Monster Build tips, and Josh was talking about how he attached the wings on the Giant Cruiser. He layered wooden spars and out a screw through, why not do that with paint stirrers? I'll edit the plans. New Wing Picture soon...


Sunny Day Park Flyer
New Wing Design

I've got the new wing, with detachable wingtips, designed.
It uses 9 Paint Stirrers to construct a VERY strong connection, the foam spar will only be needed to form the airfoil and keep the top and bottom together, all other support will be supplied by the wood.
On the top is just the spar,
In the middle is all the sections of the wing,
And on the bottom, the assembled wing is shown.
The two places where lines intersect forming a + is where pins/screws are placed to connect the sections. It should build the same way, no foreseeable problems



Active member
Really liking the idea behind this one.
Only thing bothering me is 3lb with only a 40" span? Seems like it will need to fly pretty fast.
Most of my rc experience has been on the ground, so I may be way off.
it wouldnt hurt to go 60" for a wingspan with 8" want all the heavy lift you can get from any wing,especialy a draggy cargo design.3X20" sections for transport.


Sunny Day Park Flyer
Ok, I hear you guys; here's the thing. I've figured that the absolute maximum takeoff weight would be 2 pounds, the flying weight would most likely be 1.5-2 lb. (UPDATED MTOW=2.5lb)
Also, that's a great part of the modular wing design: YOU CAN ADD LONGER WING SECTIONS FOR LARGER LOADS
But, keep in mind, I won't be carrying anything too big like metal ingots or whatever, just things like mini water bottles. And also, Cargo is only one thing I'm planning to use this plane for, It can also do FPV, and maybe even some mild aerobatics.
But Keep up with the suggestions! It helps. Thanks
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Sunny Day Park Flyer
Pattern Check

Ok, I'm not the best at designing airfoils, so I'd appreciate someone checking my pattern.
Also, the leading edge would be more rounded.

Last, is the spar to complicated for a 40" plane? It might be too thick in the center...


Feedback Helps
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Elite member
A couple of suggestions:

The NTM2826 1200 will easily take 9x6 (I often use 10x6) on 3S and the 25A plush ESC. Try to make the distance between booms accommodate the longer prop sizes, in case you find you need more prop later on. (also note you will need two ESCs to run the motors)

9 Paint stirrers is overkill for this 40 inch and 2-3 lb load. A lot of your allowable weight is going to be eaten up by the spar.

I routinely build 40inch wings, 7 - 8 inch cord, which are inherently weaker than the design you propose (because I remove a lot of paper from inside the wing), and I use a foam spar and 1 stir stick split length-ways (half on top and half on bottom in the middle of the span) without any issues. You can even take 2 of these 40 inch wings and join them tip-to-tip with 12 inches of 1/2 inch dowel (with screws) to make 80 inches which makes for a slightly droopy wing until its in the air. So I would suggest not overdoing the spar on the 40 inches.


Sunny Day Park Flyer
Good Idea

I will move out the Booms to accommodate larger setups in the future. BUT, I will leave the spar as it is in the center to accommodate larger wing additions, on the 40 inch wingtips, I'll take it down a notch and just put one smaller stirrer I'll have left over from making the center section.
This design is really going to be adaptive from sport, to FPV, to cargo; I can't wait to get building!


Sunny Day Park Flyer
Updated Plans

Thanks to everyone's input, I've amended the plans to accommodate up to an 11 inch prop and a huge motor. I will still be using the 28-26A setup with 8x4 because it's what I have around. Thanks to you guys, I'll be able to keep this airframe around for a long time to come and change it to my liking.

I've also designed 20 inch wing additions which I'll probably build at FTFF for heavier lifting. I'll fly FPV off of the 10 inch stubs, but the 20 inchers will be useful. Thanks to everyone for the idea.

The fuselage hasn't changed much, but I might change the plans depending on how the build goes.

The pods/booms are fine, the rudders are good, and the elevator and horizontal stabilizer are a bit wider because the pods were moved outwards.

Thanks to everyone who made suggestions and subsequent improvements!

Once again, if I'm missing something critical SPEAK UP!

New Pictures will be posted later tonight, or early tomorrow
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Sunny Day Park Flyer
I've officially started the build, I'm going to try and get everything traced today and cut tomorrow, then I'll catch up with some pics and stuff. Thanks again, I think this plane is going to be great :)


Sunny Day Park Flyer
Sorry I disappeared for the last 3 days guys, I've been real busy building. I made a mistake and had to rebuild the wing this morning and I have to recut the elevator. But, otherwise the build is going great! the engine pods are on, the fuselage looks great and all wing portions are built. I'll work on the electronics over the weekend (if there's time) but I think there will be enough time to finish the plane and even Minwax it! Pictures will be uploaded once the build is done.


Sunny Day Park Flyer
Airframe Completed

I have officially finished the airframe!
Here are some pics:
Full Airframe

Without Wingtips


Interlocking design



Wingtip Underside-Note under-cambered wingtips

Next: Electronics!

P.S. I'll put some pins in to lock the wingtips in place later, I need to find something suitable.
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Sunny Day Park Flyer

As you can see from my last post, there's plenty of space for mounting FPV equipment, but my FPV stuff is junk. The camera is terrible, so I'll wait until FF15 for mounting it.

(PS the canopy comes off for easy access and is interchangeable for non-FPV versions