Magnum Models F5 sloper to Foamboard
- Thread starter thenated0g
- Start date
I was just talking about a T-38 build. Except I was looking at using a single 64mm edf I have laying around. I'm going to keep tabs on this. It seems every project I want to try and build someone always beats me to it. I'm going to have to go way obscure if I don't want to copy someone.
Userofmuchtape&glue
Posted a thousand or more times
I love that F-5! I have wanted one for a loooong time now.
Like I said before, I still don't even know where the CG wants to be!
What is the length/span of the model? We've done a lot of math and a fair amount of testing around the T-38 CG and I'd expect the F-5 to be very similar. On the 81" T-38 the math and testing is converging at 6.59" aft of the leading edge where the wing meets the fuse. That is on a 47" span. The wing strakes will have some effect but that might get you in the ballpark. I know with Jetset44's T-38 and F-5 the CG didn't change noticeably with the strakes but your mileage may vary. His parkjet model didn't really have an airfoil to speak of.
BTW... looks awesome!
Michael9865
Elite member
This is great. Quick engineering and great looking plane. Looking forward to the maiden and then plans...I guess I need to pick up some 50mm EDFs now. Mid7nights do you have a link to the EDFs you are using? Thank You!
Edit - I found the link in your C-17 Thread. Where they 4500kv or 5400kv version?
Edit - I found the link in your C-17 Thread. Where they 4500kv or 5400kv version?
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wilmracer: Thanks! That definitely will help me as a starting point, or at least a sanity-check reference. My dimensions are 42" long, 24.2" span. Another thing I've noticed from my previous scale foamboard aircraft, is that the RC-scale CG is forward of the full-scale CG due to the blocky/boxy nature of square-fuse builds. The actual flyable CG on my A-4 is considerably forward of what I had calculated based on the wing planform, so much so that on maiden (with the 'full-scale CG') it flipped around like a crazy 3D plane. I'm hoping this works in my favor, because as of now the balance of all the components is putting the CG quite a bit forward.
Michael763: They are 50mm FMS 4S units from Banggood.
Michael763: They are 50mm FMS 4S units from Banggood.
I'm hoping this works in my favor, because as of now the balance of all the components is putting the CG quite a bit forward.
That has been a challenge with my model as well. I swear I built the nose as light as I'm comfortable with and crammed the batteries as far back between the inlets as I can reach and I'm still looking to see if I can trim weight from the nose. I can fly her today with a bit of lead in the tail but I'd really like to shave that off as she is already a heavy model.
My first T-38 was a pusher jet and hanging the motor off the tail solved all the balance issues.
Spent last night working on how to actually fit the electronics in this little thing, I was able to get everything except the battery under the rear turtle-deck over the center fuselage. I cut access holes to poke the ESC heat sinks out the side for cooling, shortened the ESC signal wires, and hooked up all the servos to the Rx. In future plans I'll include the ESC cutouts, and I also think I'll try and figure out how to make the rear deck a removable hatch for access.
At some point I'll add pushrods and actually cut the control surfaces.
At some point I'll add pushrods and actually cut the control surfaces.
One thing i havent done yet on foam board is the split elevator. If i was using coroplast (which i may in my slope version) i would bend a U shaped piece of metal and glue it in to transfer the movement to the other side. How are you planning on setting yours up?
Im having a "squirrel" moment currently. I have 2 other projects i should be working on but this one is just looking so BA.
Im having a "squirrel" moment currently. I have 2 other projects i should be working on but this one is just looking so BA.
You can see two servos in each wing; the outboard servos are for ailerons. The inboard servos are for the elevators, and I plan on running simple independent pushrods down the side of the fuselage to the elevator surfaces.
I thought about using a torque rod and center pushrod, but there wasn't room in the middle. I suppose I could've still used a torque rod to connect the two sides, and just had one servo, but I like the symmetry and simplicity of one-servo-per surface.
What % area are you tapering down to on your thrust tubes?
Ok i see it now. I guess if i wanted a super light build i could taper the bottom of the back and keep the elevator solid. Looking great. I want to get a pair of these in different colors made up for some sloping with my friend.
I'm not sure what he's doing with this one, but I figured I'd share this free tool for creating cones. It makes thrust tubes dead simple. You just fiddle with a few variables and out prints a template to cut and roll your tube.
https://www.conelayout.com/
I was shooting for 80%-85% of the swept area, but it turns out my scaling did not work out as such. I just measured, and my nozzle exit area is 73% of FSA. Probably a bit over constricted, but it is what it is for now. I could widen the rear fuse a bit to open up the nozzle in the future. Might actually simplify the fuse construction if I did that anyway....
As far as interest in this project we are hitting like 295 likes 12 shares on facebook and about 320 likes on my IG account. I basically had to turn off all notifications on my phone last few days. Im sure you will have any number of testers once you get the plans out
