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FT Commuter Enduro Build

JennyC6

Well-known member
#1


4oz fuel tank, one Cox 0.049 engine swinging a 5x3x3 prop. If she'll lift a full fuel load I'm looking at something like 45-60 minutes of flight time. Won't know till ya try! If she won't carry it, oh well, I'll run a smaller tank, but hopefully she'll carry a full fuel load.


Don't let me forget to document the modifications I have to make to the nose! I might just make an article about it.
 

JennyC6

Well-known member
#3
Thanks! My biggest problem is going to be mounting the engine in a way that allows for servicing, fuelling, adjusting, exhaust residue control, and engine startup. Was laughably easy in my FT Spear; the engines just sorta hang off the back nothing in the way. Mini Sportster; bit more cramped, but access still doable. The Commuter has a fully cowled nose, though. Won't be easy, but that's half the fun of Flite Test aircraft, innit? Make 'em your own~
 

JennyC6

Well-known member
#5
This will definitely be cool!!!!!
Hehe. My main concern is gonna be lifting a full fuel load. Glow fuel's heavy stuff, after all. I have no question it'd carry 2oz without issue, but a full load...almost wonder if I'll need flaps on it. It's certainly going to fly in a highly scale manner, though!

Will be mounting the tank on CG so I'm not concerned about CG shift.
 

Ketchup

4s mini mustang
#6
Flaps would be cool and they could help in some situations. Also, for your problem with engine access you could make a removable cowl or put a hatch in it.
 

JennyC6

Well-known member
#7
Flaps would be cool and they could help in some situations.
If it feels like it's only barely able to lift a full tank I'll probably install flaps instead of downsize. Testing on my Mini Sportster, which uses the same engine swinging a 6x4 2-blade on a 2oz fuel tank, shows ~20 minutes at full throttle. Twice the fuel reserve in this thing, in theory, means a 40 minute full throttle flight isn't out of the question.

But the Commuter isn't the type of plane you fly at WOT all the time, so in all likelihood I'll be tickling an hour with enough left in reserve for a powered landing.

Would be especially cool if I have it flying before I go up to FPVFest, could launch it and explore the entire airpark in one flight hahaha.


Also, for your problem with engine access you could make a removable cowl or put a hatch in it.
yeah that's what I'm thinking I'll do. The top of the head will poke out anyway...likely to one side as I want to FPV the thing and I don't need castor oil getting on the lens...so startup won't be too much trouble. Getting to the mixture needle...I can slip some fuel tubing over that as an extension, so also not too big a deal. But I'll need to be able to get in there to do piston socket resets which involve removing the engine outright and fully dismantling it, and I'll need to make a much sturdier firewall than what the plane's equipped with because the stock firewall isn't up to the vibration of ICE power. Happily the nose of the Commuter is chock full of structural bits and bobs so I shouldn't have much trouble getting an ICE-compatible firewall set in.


Frankly, I'm surprised FT themselves didn't put a hatch on the top of the cowl, considering they recommend you shove the battery right up to the front anyway. Would have made more sense to me to make the top panel of the cowling magnetically attached so it could be easily removed for battery swaps.
 

Jackson T

Well-known member
#9
This will be very interesting. An article about it would be cool too! Have you ever thought about making a control line plane with the cox .049 and foamboard? That would be really cool!
 

JennyC6

Well-known member
#10
This will be very interesting. An article about it would be cool too! Have you ever thought about making a control line plane with the cox .049 and foamboard? That would be really cool!
CL doesn't really interest me any, but I don't see why you couldn't. The guys actually did that with brushless power a while back, fun fact!
 

JennyC6

Well-known member
#12
Update: Took my Spear, my Mini Sportster, my SC10GT, and my NexSTAR 46 to a local field. STruck out pretty bad; the Spear only had one engine running right so it didn't really move, the Sportster just groundlooped, the SC10 ran great for a few minutes, flipped, died, never re-fired. But the NexSTAR flew graet!

In light of that, I'm borrowing parts from the other two. The Spear's cooperative engine, a convention tractor 5x3x3 prop, a conventional rotation spring starter got yoinked, and from the Mini Sportster I borrowed the receiver and receiver batt. Did a mock-up of engine, fuel tank.


Should put fuel load right on CG and put the fuel right next to the needle! Promising! Will commence full assembly tomorrow afternoon~
 

JennyC6

Well-known member
#13
Current status: Under active construction as I type this. Engine is in!

Engine mount details:





That plywood is found in my local WM at the craft department right near the DTFB! Convenient. And the stuff is STRONK. I will not tear those screws out. Only need two, can fine tune thrust angles if need be but the motor mount has right and down built in.




Here it is chooched in nice and solid. Can see the thrust angles already present. Oh, right, one last thing: A Schmoo Drain!



Onwards I go! Prolly gonna mount the elevator and rudder servos in the tail to help balance this thing. That firewall and a Cox 0.049 weigh a fair bit more than the factory firewall and an 1806 outrunner, plus I kinda want to put the fuel tank right where the stock servo mounts are.
 

JennyC6

Well-known member
#16

Throttle servo, linkage is set up, and I have a stopper on the throttle arm where I can adjust it externally.


Moved the tail feather servos back here 'cause the massive $*%(ing fuel tank sits right where they would otherwise be. Also this thing is stupid nose heavy; needs grams aft.


Radio gear will live here, mostly because there's space here and because this is where Ben put the battery hatch anyway.


4 US FL Ounce fuel tank crammed into the cockpit. REal tight confines in here, but the tank is more or less centered on CG, so I shouldn't have too much trouble with the plane changing tendencies mid-flight. Crucial, when the fuel load is so much of the total plane weight, as it will be on a full tank. Fingers crossed she'll carry it, cause if she does, I'm looking at >30 minute flights!
 

JennyC6

Well-known member
#19
Welp, it took me from 4pm to 12:30AM, and it's heavily modified. But it's done. I've put a Cox 0.049 on an FT Commuter.



She's not painted, but she's a pretty bird. Especially from this side, with the jug visible poking out the side of the nose like that.

Bit of a closeup of the nose as a whole. Can see the vent/fill like poking up. Throttle's at about 75% here; it was pure coincidence but I love how it ended up with the throttle being more open the more of the throttle arm pokes up into the breeze. 'Course with these Cox engines and the choketube throttles it isn't like you've got a full, linear power curve, but eh. You've got roughly a few points between idle and full blast. It's enough.

I can access all necessary adjustments for engine operation, too. Repositioning the throttle arm, adjusting the throttle linkage, fuel mixture, and glow head servicing all easily done. Should cover most operations.


Top down of the intake area. Silicone line is attached to the vent of the tank, fuel chooches in here, and then air, and perhaps fuel again if I leave it on the bench upside down haha. Don't plan on doing much inverted shenanigans with this one so I'm not overly concerned if it's a bit incontinent when inverted. Can also see the firewall/engine mount I made for it.

I ended up using the battery hatch as a battery hatch after all! And in fact, it's carrying a 2s 850mAh LiFE pack under there. Not too far removed from what's *supposed* to be there. Got it sitting sideways and the CG's dead nuts perfect on an empty tank. Will be slightly nose heavy on a full tank, but not by much. Tank's CG is maybe half an inch ahead of the airplane's if that.