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Daz's FT Spitfire build Part 2 - the sequel!

DazDaMan

Elite member
#24
Well, I've had another three flights with the Spitfire since last week.

Sunday's flight didn't go so great because the battery came adrift and sent the Spit into tail-heavy mode! I managed to get it down in one piece, but the wind was too strong for a second test, so home I went to put in a brace to stop the battery from sliding so far back.

(Before anyone asks, yes, I had velcro on the battery, but it obviously wasn't secure enough.)

Tonight's first flight went utterly pear-shaped from the start. From launch, the Spitfire went straight up as though I was trying to loop it. It bottomed out about 18ins from the ground, and after that it was all over the sky. We trimmed it right down and I managed to get it back down on the ground. I checked the battery, and it hadn't shifted, but even with the motor throttled back it was wanting to climb. I'm sure the wind had a part to play in that, but it certainly wasn't helping.


After I added another 30g of nose weight, I tried again, and this flight was much better. The wind shifted her about a bit, but she was nowhere near as skittish as before. We still had the down-trim wound in, but this time it was much more manageable.


The consensus is that there's a warp in the tailplane, making the model want to climb the whole time. A look over the tailplane seems to confirm this.

I might have to try getting some lollypop sticks to try bracing the tail better, unless anyone can suggest something else?
 

danskis

Master member
#25
Daren - as long as its still flying keep working on it - mine is on its 3rd life and its flying better than ever. I use blocks of squishy foam to hold my batteries in. Just cut them to the width of the fuselage and jam them in there around the battery. I've also used sticks to straighten out a warped elevator. Carbon fiber and BBQ skewers work well too. CG is critical - where is your CD after adding the nose weight? Is it close to the CG on the plans or way off. If its way off then something is warped or your decalage is off. How's it glide motor off? It should float pretty well.

Haha - great save by that pilot on the first launch.
 
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Mr NCT

Elite member
#26
Well, I've had another three flights with the Spitfire since last week.

Sunday's flight didn't go so great because the battery came adrift and sent the Spit into tail-heavy mode! I managed to get it down in one piece, but the wind was too strong for a second test, so home I went to put in a brace to stop the battery from sliding so far back.

(Before anyone asks, yes, I had velcro on the battery, but it obviously wasn't secure enough.)

Tonight's first flight went utterly pear-shaped from the start. From launch, the Spitfire went straight up as though I was trying to loop it. It bottomed out about 18ins from the ground, and after that it was all over the sky. We trimmed it right down and I managed to get it back down on the ground. I checked the battery, and it hadn't shifted, but even with the motor throttled back it was wanting to climb. I'm sure the wind had a part to play in that, but it certainly wasn't helping.


After I added another 30g of nose weight, I tried again, and this flight was much better. The wind shifted her about a bit, but she was nowhere near as skittish as before. We still had the down-trim wound in, but this time it was much more manageable.


The consensus is that there's a warp in the tailplane, making the model want to climb the whole time. A look over the tailplane seems to confirm this.

I might have to try getting some lollypop sticks to try bracing the tail better, unless anyone can suggest something else?
Good job getting it back down in one piece on the first flight. Altitude was definitely your friend.
 

DazDaMan

Elite member
#27
Daren - as long as its still flying keep working on it - mine is on its 3rd life and its flying better than ever. I use blocks of squishy foam to hold my batteries in. Just cut them to the width of the fuselage and jam them in there around the battery. I've also used sticks to straighten out a warped elevator. Carbon fiber and BBQ skewers work well too. CG is critical - where is your CD after adding the nose weight? Is it close to the CG on the plans or way off. If its way off then something is warped or your decalage is off. How's it glide motor off? It should float pretty well.

Haha - great save by that pilot on the first launch.
CG is right on the button according to the plans, with all that nose weight in it.

It glides OK with the motor off, but decidedly fast downhill with all the nose weight.

I will have to look closer at the tail to see if it's warped. I have a distinct feeling it is.

That pilot was me - and I have NO idea how I managed to save it like that, although I think the over-arm launch helped give it a bit of extra height!
 

DazDaMan

Elite member
#28
Well, I wasn't sure if I was going to fly the Spit tonight, but fly it I did - and it was fine! No crazy tail-heavy shenanigans, no looping at launch, no porpoising, just straight and level from the off.

I couldn't add the spinner back on like I wanted to (it's too big for the prop, so the spinner won't sit properly on it), so added 10g under the cowling - and then put the lighter battery in it. I know it would have affected it, but it was honestly pretty good from the launch.

It needed some amount of trimming to the left, but I think I know what that issue is - the plastic keeper for the aileron horn went AWOL at some point, so I think the aileron was moving on its own every so often! But I got her back down in one piece after six or seven minutes.

There is definitely light at the end of this particular tunnel!