100mph for under $50!

I wrote this article a while ago, but somehow forgot about it. The plane in the pictures was almost 6 months old at the time I took the pictures so it is rather beat up and doesn't look too good.

Up until now, I had never flown anything that could fly over 100mph. The fastest plane I had was a HK RadJet with an upgraded motor. It satisfied my thirst for speed for a few months, but it got boring after a while. When I saw the new Flite Test Mighty Mini Corsair, I saw an opportunity. The design reminded me of the HK FunFighter Corsair and I happened to have a FunFighter motor on hand.

The day the plans came out for the Flite Test Corsair, I cut out the plans and cut out the parts and started building the plane. The build was very easy and only took about three hours from start to finish. The next morning I woke up and walked to the open space near my house and maidened it. It was snowing, but a little bit of snow wasn't going to stop me. The first flight was on 3s. It flew perfectly with almost no trim needed. It really didn't have any bad tendencies, no bad stalls and would slow down easy which was surprising to me given it is literally a flying brick (375 grams). It honestly reminded me of the RadJet, but easier to launch and with more pitch authority.

It was definitely fast on 3s, but I wanted something faster. I kept the 6x4 prop and went with a 4s. I found the speed I was looking for! It was CRAZY fast. The extra weight had virtually no effect on the flight characteristics, if anything it made it track better! On the first motor, I got an average of 83 mph on 3s and 98 on 4s with a max of 103. I was so happy! I will admit I have never flown a stock mighty mini f4u so I have no idea if this would fly anything like it. My guess is it would fly nothing like it, but who knows.

Naturally there were a few deviations from the recommended power system and stock airframe. The power system is much much bigger than what is recommended. The first motor I chose to use was a HK FunFighter motor which is a 1950kv motor. I used the H-KING 35 amp ESC which has proven to be quite a good ESC to me in the past. The second motor I tried was a D2826-6 2200kv motor, but it had nearly identical performance to the FunFighter motor, just a tad bit faster. One nice thing about the H-KING 35 amp ESC was that I never had to change the timing, it had no stutter even with the high kv motor. I did use 9g servos rather than the smaller ones FT recommended because of the extra stress, although I bet the recommended 5 gram servos would have worked. The batteries I used were the Nanotec 1300 3s and 4s 25-50c batteries. They seem to work ok for the price.

Here Is what I changed on the airframe. The most important modification was before I folded over the wing, I put a thick bead of white Gorilla Glue on each side of the spar. Then I put a BBQ skewer on each side of the spar. Then I folded over the wing. After a few hours, the glue had foamed up and filled all of the space in the wing, making it way stronger. Make sure if you do this you wipe away the glue as it comes out, it can get very messy otherwise. Also install the servos in the wing after the glue is completely dry. I used a dremel to clear the glue for the servos. I don't think this is necessary for 3s, but I would do it if you plan on going 100mph with it.

I didn’t make any changes to the fuselage other than the motor mount, rather than having the mini power pod being removable, I just glued the mount directly to the fuselage and coated the surrounding foam with 5min epoxy. The stock thrust angle built into the power pod was what I used as a starting point, but it seemed to be a decent thrust angle, and I kept it. I did reinforce the elevator after the first 4s flight as per NerdNick’s recomendation. I ran 2 sections of BBQ skewers from the outer edge of the elevator to the fuselage. I did not add a rudder and went with a 3ch setup. If you did add a rudder I am sure it would be cool to do some 100mph pop-tops or snap rolls though! The rest of the build is basically the same as in the build video. All of the pictures are after I re-did the tail because the old one was on its last legs. The one in the video had the stock tail.

I would say for sure the hardest part of the build was getting all the electronics to fit. I ended up cramming the ESC all the way up behind the motor and smushing the receiver behind the battery hatch. There is hardly any cooling for the ESC, but it always comes down just warm to the touch, even after a 4s flight. I used a 6ch dsmx lemon RX receiver for this plane. If you haven't tried these receivers, I would highly recommend them; they work awesome and seem to be far more reliable than the Orange receivers from HK. They are also very compact, which is perfect for this plane.

Although this is completely unrelated to making the plane go fast, I did use this plane as a guinea pig for testing balsa plane covering film on foam. I got a roll of checkered, black and red covering from Hobby King on sale for $5 a roll and a covering iron from them too for $10 on sale. It is actually really easy to do; the only tip I have is keep the heat down or the foam will warp. I ended up using this technique on my 60” Sledge and it turned out sooo good. This is a really great method to make planes look good for really cheap.

You might be asking how I knew the speed. The answer is a German program called WAVEosSCOPE that uses the doppler effect to calculate speed. From what I have heard it can be better than a radar gun if you know how to use the program well, which I sadly do not… The main problem some people might face with this program is that it is written in German, but luckily my mom knows some German so I was ok. Google translate could be of some help to those of us who don’t speak German.

In conclusion, this is a really fun plane for intermediate to advanced pilots who are looking for something fun to keep them on their toes. The main advice I have for anyone who is going to attempt this build is to keep everything as true and straight as you can when you build it. If you have the tail section a little bit crooked on a slower plane, you won't notice it much or at all, but on a really fast plane a crooked wing or tail can make it require tons of trim and even some mixing. If I were going to make this plane again (which I most likely will) the one thing I would change would be to use the new Rhoss foam board or the Flite Test foam. This plane has never had an crash but after a few months of flying and transporting it is already falling apart and paper is peeling off. I have made some planes out of the Rhoss foam and they tend to hold up better and last longer. Thanks for reading. Happy Flying!

Price list:

Motor: HK FunFighter motor 1950kv  ($10.77) or D2826-6 2200kv ($10.21)

ESC: H-KING 35A  ($13.60)

Servos: x3 HXT900 9g servo ($2.69 each)

Battery: Nano-Tec 4s 1300 25-50c  ($11.70) for 100mph+ or Nano-Tec 3s 1300 25-50c ($11.90) for 80mph+

Prop: TGS Precision Propeller 6x4 ($0.77)

Electronics cost total (no radio gear): $44.35

Other needed materials:

1 sheet of DTFB foam ($1)

Packing tape ($1)

1 BBQ skewer ($1 for 100 pack at dollar store)

Music wire ($1)

Poster board ($0.69)

Total for everything except radio gear: $49.04!

Thanks for reading!

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