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Modified FT Sparrow plans.

#1
Hey Guys,

I'm just so in love with the FT Sparrow. However my own experience with it wasn't as straightforward as some. My maiden with the standard v-tail mix didn't go so well. Basically it seemed to have this tendency to violently spin in either direction which ended up with a poor beaten up sparrow in fairly short order. I am the first to confess I am not the most experienced flyer.

Anyway I decided to modify things a bit to suit a less experienced pilot and the result was just fantastic. My mods were.

Increasing the nose lenght by 1 inch. I found I had to add a lot of noseweight with the standard nose lenght. With this extended nose and a 3S 1000mAh battery it balances perfectly.

That leads to the other question where should the COG be. In the build vid Josh puts his fingers right at the front of the wingspars, but in the original plans the COG is marked more forward than that. I noted SPONZ comments in another thread. MY experience is that where Josh balances in the video is just right

The next thing I did was add ailerons. I felt ailerons were much better suited to a less experienced pilot like me. After I placed them, I noticed that in the original FT Sparrow trailer video some of the guys are using ailerons. Look closely and you'll see. So in my modified plans I marked two locations for ailerons, where mine is and where the guys in the triler have theirs. I'm sure both would work fine.

Lastly I built mine from 3mm foamboard. That's what I have available freely. So in my modified plans the score cuts are marked for both 3mm and 5mm board.

For electronics, I used a Turnigy Park 250 2050kv, 6x4 prop, 9g servos, 1000mAh 3S. I did have a bit of a proplem getting the two installed servos to work as a single elevator. I ended up doing a mix on my DX8 mixing the elevator channel with the gear channel and then reversing one (think it was the elevator channel) to get both moving the elevators up and down together,

I'm so sorry I dont have a video of the maiden of this thing because it was awesome. I launched at just over half throttle and it just flew out of my hand (btw use a wing throw type launch to avoid the pusher prop stripping skin!). It was simple to fly agile, turns on a sixpence. Most of the time I was at 1/3 throttle and it just rips along. At one point I hit full throttle and it went vertical like the space shuttle! At another point some birds took grave offence at this noisy bird entering their airspace so a game of chase ensued. I was worried that one might catch up with the pusher prop and injure itself, however this thing could turn an awful lot faster than they could. It was no contest!! They gave up!

After spending an afternoon flying this baby and brought it home with no more than a grass stain on the nose, i'd definitely recommend this variant to less skilled flyers like myself.

Here's a pic of the extended nose and modified plans attached too.

sparrow_mod.jpg

View attachment FT Mini Sparrow_modified.pdf
 
#4
Hi Foxbodyford, I'd love to hear how you get on if you decide to give this a go. Just one thing I noticed in my modified plans is I forgot to mark the slots in the tail for adding the tailskid in both the 3mm and 5mm sizes, only 5mm is shown. If you use 3mm just cut 1mm inside on both sides of the slot.

The sparrow is well worth the effort in persisting with. Once you get it up there it will put a really big smile on your face for sure!
 
#5
Thanks GremlinRC,

The sparrow plan mods are excellent, I am running a RCX 1804 2400kv, 5 x 4.5 pull nose with a 1000mah 3s but still need about 10g of weight in the nose. AUW is 190g (280g with a battery).

I will post some photos once I have maidened it.
 
#6
Looking forward to that djdazzy. I suspect that the weight difference is down to the differing foams we use (or maybe our interpretation of the balance point). I'm chucking this in the air every opportunity I get and it still brings a smile to my face every time.
 
#7
Looking forward to that djdazzy. I suspect that the weight difference is down to the differing foams we use (or maybe our interpretation of the balance point). I'm chucking this in the air every opportunity I get and it still brings a smile to my face every time.
Maiden wasn't as good as I expected, I glued the power pod in slightly out of line with the thrust angle pointing towards the port side. Right turns were virtually impossible when trimmed out whilst under power.

I have hacked it out now and I will re-glue it in later. Is the thrust angle supposed to be zero on this model?
 
#8
Your using a nose pull instead of a pusher? Assuming standard prop rotation (ccw looking from the front) then you should put a little right thrust. Even 5 degrees would be fine.
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#11
The CG on the sparrow is so very close to the neutral thrust line, neutral ( -----| )wouldn't be bad. If anything, the CG is slightly above, so aiming the motor to point the thrust up SLIGHTLY ( on pushers, it's backwards, so ---/ ) is the direction to go.

I'd build neutral, and if it pitches a bit more than you care for in throttle changes, you can either mix it out in the radio (slight throttle->elevator mix), or soften the hot glue and remount the firewall angled down a few degrees -- it won't take much.
 
#12
Thanks Crafty Dan

If I understand you, start neutral. Then if it wants to pitch up with the throttle, adjust the thrust to push the nose down.

Thanks. I built a Long Beak Sparrow after I accordioned my first regular nose after about 2 minutes. Haven't had the guts to try it again.

Tom
 
#14
Ok so total new guy to this. After asking the FT as well as other forms this was the plane I was told to start with. So after watching both videos first thing I thought was where are the ailerons? Then I found this so question time. So does the position of GremlinRC ailerons vs FT change anything. GremlinRC any way I can get you or someone to post a picture of how they mounted their servo? I can see they are on the spare, but how do you run wires and such. As I come from a mutirotor background will a 2204 2300 be ok. Ok last question. Since I'll be using 5mm foam can I just follow the build video but use your plans? Sorry for so many questions just want to build and fly something that only has one propeller.
 
#16
Hi guys,

It seems like a lot of folks have problems with the sparrow, specifically with balance? I'm not trying to stir anything up, this is just a simple question. Are you following everything exactly? What I mean is that this plane is designed around a specific motor, prop, esc and battery, all of which are sold in the Flite Test store. Given the recommended parts, and following the build video completely, shouldn't we find that the plane is balanced as it should be? Josh does mention in that video that even after installing all of the electronics, you may still have to add some putty to the nose to get it to balance correctly.

Again, I'm not trying to stir anything up or question anybodies ability to follow instructions, I'm just wondering if there's something being overlooked here. I'm starting construction on a Sparrow of my own this weekend and will be installing the electronics recommended to go with it (Power Pack A) and will try it out with an 800mAh 3S 30C. The battery might not be the same weight and dimensions as the recommended 850mAh so I already know I'll probably have to add some nose weight, but want to see how this build goes.

What kind of electronics are people adding to these outside of what is recommended to be used in them?

Thank you.
 
#17
Yup, I followed the guidance and even putting a 1000 3s in the nose it won't balance. This is why this thread is here ! :)

My 2nd build has the nose job - I will upload a picture later.
 
#18
Super late to this party, but Here's my neglected poor little sparrow, added a 10cm extension on the nose to get more leverage for the cog and that has been working a treat for me. This is my first plane that I have finally got to fly without crashing. Also, the added layers are great protection for the battery (which is in the original nose. IMG_20190507_135907.jpg IMG_20190507_135947.jpg