FTFC23: Build-ruary by Inq: Inq'd F-8 Crusader with Training Wheels
- Thread starter Inq
- Start date
Inq
Elite member
Put a fork in it!
This one is done... ready for maiden. The last thing was to install the inlet door. I wanted to get thrust tests, but it's raining today and the test stand is not weather proof. There is a little twist in the foamboard fuselage, but I'll just have to get over it.
A couple things are left to do, but can be done after the verification maiden... if it survives.
This one is done... ready for maiden. The last thing was to install the inlet door. I wanted to get thrust tests, but it's raining today and the test stand is not weather proof. There is a little twist in the foamboard fuselage, but I'll just have to get over it.
A couple things are left to do, but can be done after the verification maiden... if it survives.
- Ventral fins - cosmetic
- Saw-tooth wing
- Pitot tube for the DIY Telemetry and Control project
- Painting with my Dad's squadron colors
- Sidewinders.
telnar1236
Elite member
That looks incredible! I hope its flight characteristics are as good as its looks!Put a fork in it!
This one is done... ready for maiden. The last thing was to install the inlet door. I wanted to get thrust tests, but it's raining today and the test stand is not weather proof. There is a little twist in the foamboard fuselage, but I'll just have to get over it.
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A couple things are left to do, but can be done after the verification maiden... if it survives.
- Ventral fins - cosmetic
- Saw-tooth wing View attachment 235666
- Pitot tube for the DIY Telemetry and Control project
- Painting with my Dad's squadron colors
- Sidewinders.
If you have the time, the ventral fins definitely help stability so they might be a good idea to install.
Inq
Elite member
You think they will help that much??? My first thought was the vertical stab is huge (relative) compared to your F-104... I should have thought directional would be overkill as it is. My books say they only added them on the C models and later for directional stability over Mach 1.5. Not sure, I'll try to go for supersonic on the maiden flight like they did on the F-8.
telnar1236
Elite member
It's just from personal experience, but I found they help prevent stall spins. I built a foam board and tissue F-8 a couple of years ago and didn't install ventral fins to start off with since it was belly landing and I didn't want them to break off. However, it had severe spin issues until I installed them (and then about 3 flights after that, I crashed it into a tree). The CG was definitely tail heavy for an F-8 and I think I might have been getting issues with aeroelasticity in the wings, so it's definitely a different plane, but it (and the Freewing F-8) has informed a lot of my opinions on the airframe.You think they will help that much??? My first thought was the vertical stab is huge (relative) compared to your F-104... I should have thought directional would be overkill as it is. My books say they only added them on the C models and later for directional stability over Mach 1.5. Not sure, I'll try to go for supersonic on the maiden flight like they did on the F-8.
Inq
Elite member
An hour later... Dismal...
Is all I can say.
The EDF starts out with 1160 grams here in free air. Note - All these tests are without any cheater inlet... just the scale inlet.
Test 1 - 509 grams
This test was with the wing removed and the nose off. This lets in the maximum air even if the insides are cluttered with equipment... no internal ducting.
Test 2 - 410 grams
This test was with the wing on, but the nose off.
View attachment 235413
Test 3 - 130 grams
This test was with the wing and nose on.
View attachment 235414
Not that I had any doubts ahead of time, but I think that is conclusive evidence that a cheater inlet is mandatory!
Test 4 - 580 grams
Did the final testbed test with the inlet door. Even with the smallest crack of the throttle position and the door snaps full open. And cutting the motor and it slams closed. This tells me that the semi vacuum caused the small nose inlet way up front is of almost no use. I'm very leery about flying this plane now. It doesn't have better than 1:1 thrust : weight and I doubt I can throw it hard enough for it to get enough speed and thus lift to do its own flying before crashing. I was trying to keep it light enough, but it looks like I'll need to add landing gear to even give this thing a chance.
telnar1236
Elite member
One option is a bungee launch or similar. They are pretty easy to build and use, and there are a ton of great plans out there. Depending on the final AUW, 580 g thrust might be enough to hand launch, but you're right that it might be risky.
Did you ever get the chance to install a thrust tube behind the EDF? I don't see one mentioned, although it's not a major milestone and you might well have not posted it. If you don't have one, just adding a straight tube should recover a decent bit of thrust on its own by cutting down dramatically on turbulence.
Did you ever get the chance to install a thrust tube behind the EDF? I don't see one mentioned, although it's not a major milestone and you might well have not posted it. If you don't have one, just adding a straight tube should recover a decent bit of thrust on its own by cutting down dramatically on turbulence.
Inq
Elite member
The 50% loss is pretty disappointing. I hadn't, but I will before I try to fly it.
Inq
Elite member
Thrust Tube
While at the field someone flew one of these - https://www.horizonhobby.com/produc...-basic-with-safe-select-and-as3x/EFL0950.html. It had a 12 blade 70 mm and 6S. It did not have any special thrust tube that I could see. In fact the plastic exit piece was decidedly tacked-on with a big internal lip. I'm assuming this puts out a lot more power than what I have, but I also noted that the exit piece was quite a bit smaller than 70 mm. What do you recommend for an exit tube diameter? Mine currently is 70mm... a strait shot behind the EDF. Do you have a ballpark percentage improvement I might see?
While at the field someone flew one of these - https://www.horizonhobby.com/produc...-basic-with-safe-select-and-as3x/EFL0950.html. It had a 12 blade 70 mm and 6S. It did not have any special thrust tube that I could see. In fact the plastic exit piece was decidedly tacked-on with a big internal lip. I'm assuming this puts out a lot more power than what I have, but I also noted that the exit piece was quite a bit smaller than 70 mm. What do you recommend for an exit tube diameter? Mine currently is 70mm... a strait shot behind the EDF. Do you have a ballpark percentage improvement I might see?
telnar1236
Elite member
I'm not sure about the E-Flite plane. I know that some of the Freewing and FMS ones have bad nozzle geometry and that people put masking tape in them to improve them and get pretty notable improvements, so it might be a case like that.
Typically, you want the nozzle to be between 85% and 95% of the FSA which is somewhere around 65mm for a 70mm EDF. I don't know how much improvement you'll get but I would guess it would be pretty noticeable. Somewhere north of 50 g of extra thrust, possibly going quite a bit higher, but it's hard to say. Unless your inlet is way too small, the losses shouldn't be 50% so I'm guessing an appreciable portion of the losses comes from the lack of thrust tube.
