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Old Jan 20, 2012, 02:50 PM
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lordmureth's Avatar
United Kingdom, Cnwll
Joined Apr 2010
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hope this is the right thread to beg for help!

In the last few months I've purchased a trio of Spitfires; the FMS 1400mm one, unflown as yet due to a faulty retract; the Parkzone IX (which flies sooo well) AND the GWS one.

The GWS Spitfire is now made in EPO foam, which makes it heavier than the old EPS version - and given that (from what I gather) the old version was always prone to tail heaviness, the EPO version makes this worse.

To compound the problem I've glassed the bloody thing - before I was aware of the weight issue - so I've now an overweight plane that looks great, but I'm not sure it'll fly!!!

I've had to add immense amount of weight to the nose - under the motor in the cowl, and to the sides of the hollowed out battery compartment. The battery is a 3 cell 2200mah lipo, the motor is one of these:

http://www.giantcod.co.uk/cf2822-122...otor-p-53.html

with a 10x3.8 prop for low-end thrust rather than speed.

The total AUW is 32oz, waaaaaaaaaaay heavier than anything I've read for this plane... AND I'm still not at the required CG, haven't measured it exactly but I reckon its somewhere between 65 and 75mm.

Is there any hope for this plane? I want to finish weathing etc, but I'm not sure it's worth the effort... help!!!
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Old Jan 20, 2012, 02:58 PM
always something to learn...
metalguy's Avatar
Tacoma, WA
Joined Jan 2011
2,850 Posts
I got a little flying in today, over all the ice. In some places we had more than 3/4 inch of ice on everything. This is really rare for these parts. I just HAD to get some footage before it melts away! I also found out my Picocub will j-u-s-t not quite keep altitude inverted. The first time, I was lucky, and could loop out of it, but the second, I ran out of altitude, and "landed" upside-down. Broke the prop on that one, wasn't able to kill the throttle quickly enough! It will also knife-edge, but I am not good at that, so it is very iffy. I think I have finally found the right combo for this plane that suits me. LOTS of power, yet ability to throttle back, and touch and go with ease. Probably not too many 3s pico cubs out there. The motor is a slofly 400 I got at heads up R/C. I also flew some packs through the Slow Stick..or is that SNOW stick? I shall post some video I shot with that today. I is very heavy with the new LED strips I put on. ------Metalguy
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Old Jan 20, 2012, 03:38 PM
always something to learn...
metalguy's Avatar
Tacoma, WA
Joined Jan 2011
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Here is the video:
Snow flight over NorthWest ice storm (3 min 17 sec)
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Old Jan 20, 2012, 06:08 PM
My Co-Pilots Rock!!
wolfewinde's Avatar
United States, FL, Clearwater
Joined May 2011
1,665 Posts
Got in a couple of flights on the Formosa 1 with the new more aggressive set up. She has always been an agile airplane, but she is really agile now. And actually, I think I have more control at lower speeds with better aerobatic capability.

She was even more fun that usual to fly today.

Lord - the Spit has always been a tough one to balance even in the old foam. Looking at your pics, you might try using a smaller battery mounted further forward on the bottom of the fuse and up under the cowl - it would take some foam carving, but it would probably be worth it.

Wolfe
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Old Jan 20, 2012, 07:37 PM
My Co-Pilots Rock!!
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United States, FL, Clearwater
Joined May 2011
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Lordmureth,

Looked at your pics again and have given this more thought - don't think my first idea is going to work. I looked up your motor and I am wondering if it is strong enough to pull that much weight.

I am wondering if you put a 450 on her like this one with a 4mm shaft....

http://www.headsuprc.com/servlet/the...0-Sport/Detail

....if then you could use the prop adapter from the PZ Spit - they sell that at horizon - if you could get enough weight out front that you could lose some of the weight under the cowl and make it work. I am not sure if the Spit prop adapter is 4mm or 5 mm, though, you would need to check that out.

Another idea is to cut some vent holes in the bottom rear of the fuse. That would help some, but not a huge amount of weight.

You have a challenge on your hands, but that plane looks so good it would be a shame not to find a way to get her in the air.

Wolfe
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Old Jan 20, 2012, 07:50 PM
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United States, KS, Derby
Joined Mar 2008
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Lordmureth,

Put your specs through this calculator:

http://flbeagle.rchomepage.com/softw.../webocalc.html

I use it, and others, and it will get you close plus tell you info regarding prop size, stall speed, wing loading, watts needed, plus much more. I used your weight with GWS Spitfire specs in this calculator and the results are really interesting. At 30 oz. looks like you will need at least a 250 watt motor. The heavier motor will also help with your CG but will add more weight overall plus you'll need a larger ESC and battery for adequate flight times. As wolfe said, you have a challenge.

Give it a try.

Allan
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Last edited by swimmer; Jan 20, 2012 at 09:27 PM.
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Old Jan 20, 2012, 08:31 PM
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Taiwan, 北市
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Lordmureth,

Your Spitfire looks great !

Try your best to put the ESC at the side of the motor mount, and use a 1300mAh 25C instead for reducing the AUW. Probably this way could let you locate the CG easier, if not, try to move the lipo forward for the CG needed. It might also be helpful if you use the 450 size motor like what Wolfe mentioned.

Chen
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Old Jan 20, 2012, 08:45 PM
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Lordmureth,

Your Spitfire is heavy at 30 oz. At this weight stall speed is increased, wing loading is increased and landing speed is increased. With the work you will have to put out to install the correct motor I'd suggest you use tools available to you that will get you a flyable, albeit heavy, airplane.

Allan
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Last edited by swimmer; Jan 20, 2012 at 09:24 PM.
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Old Jan 20, 2012, 09:19 PM
My Co-Pilots Rock!!
wolfewinde's Avatar
United States, FL, Clearwater
Joined May 2011
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Swimmer,

I have serious doubts that the motor that is on the Spit now will do the job. Some of the PZ warbirds weight in at around 30 oz flying weight, and they all use 480 motors.

And your calc figures agree he needs around 250 watts.

The only way I can see to lose the balance weights in the cowl would be to move the motor forward - less weight further forward will equal more weight further back. That would entail making a new motor mount, so you might as well put on a stronger and heavier motor. And while you are at it you might be able to mount the battery under the cowl and move it forward too. All of that might well let you shave a few ounces off the AUW.

I wonder if anyone else is flying the new foam Spit and what they did to get it to balance?

Wolfe
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Old Jan 20, 2012, 09:27 PM
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Taiwan, 北市
Joined Dec 2010
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Hi Allan,

Agreed ! It's a challenge to fly such heavy GWS Spitfire. Reducing its weight might be the better way to make it flyable. I would sand off 50% glassed cover, cut off anything not in need, if this Spit was mine, and put a 450 size 1000KV motor + prop EP1060 (10x6) instead. Lordmureth worked very hard on it already, hopefully he could try his best to cut down its weight.

Chen
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Old Jan 20, 2012, 09:34 PM
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Hi Wolfe,

One of my buddies flew his new Spit, the EPO one, well by using a 450 size about 2000KV outrunner + prop 7 x 6 + 3S 1300MAH 25C. But he only put decals on it without painting it at all. Its AUW is about 21 oz. It's as fast as a jet Spit in the air. Though I would like to see Spit fly not that fast.

Chen
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Old Jan 20, 2012, 09:47 PM
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I agree, Chen. Making it lighter would be the trick, however, where he is at with it now it may be better to display it and use it as a reminder to build as light as possible from the get go. I've got the tail section displayed from a GWS Corsair, man I loved that plane, as a reminder not to fly close to dusk again. Sanding off the glass is going to be really difficult. Installing the correct motor and components will only make it heavier and then after that considerable amount of work it would be a marginal flyer.

It might be less work just to buy and build another than to get this beautiful Spitfire flight worthy and concentrate on the others he has to build.

Allan
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Old Jan 20, 2012, 10:00 PM
My Co-Pilots Rock!!
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United States, FL, Clearwater
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Well - I can't see sanding down the gorgeous paint job on the top - maybe could sand the bottom - can't see what the paint is there from the pics.

I have to say that in the past I have put hours of effort into a model that would not fly well for one reason or another and it breaks your heart.

I would try things in this order....

Take off the plastic cowl, lose the nose weights, and move the battery under the motor mount stick so it is under the cowl. I would try a 1300 mah 3s battery

Then I would cut 3 vent holes - as large as I could get away with - on the bottom of the fuse between the trailing edge of the main wing and the horizontal stabilzer.

Then recheck the balance and the overall weight.

I would be trying to get the weight back under 25 oz at least.

At this point you haven't wrecked the existing paint job and you have some idea how much you can reduce the weight.

If that was not enough, I would cut the nose and motor mount stick off just in front of the existing firewall. Then I would extend the fuse about 1/2 inch to 1 inch, put in a plywood firewall, and mount a 450 to the new firewall. Then re-attach the nose you cut off to the new fuse extension. Secure that with carbon fiber rods glued under the nose section and into the fuse You could lightly glass over the fuse extension and paint it to match the existing paint job. And then you could put the battery in by taking off the cowl on the underside.

I would bet that you could get the weight down significantly that way, not wreck the work already done on the finish of the plane. and end up with a plane that will fly .

It's a bit more work, but at least you are not undoing too much of the work you have already done.

My goal would be to achieve less over all weight and get her to balance by positioning a lot less weight a lot further forward. If Icould get her under 25 oz I would probably try to fly her. If not, then I would probably just display her as swimmer suggested.

Wolfe
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Old Jan 20, 2012, 10:12 PM
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Taiwan, 北市
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Allan,

I'm afraid that the reminder's idea might NOT be what he really wants to have. The lipo he mentioned, 2200mAh one, is heavier than the 1300mAh one by 2.8 oz. This should be more than enough to cover the extra weight when replacing the motor on it. Tearing off the landing gears will make it lighter too, it might be possible to make it easier to climb up when WOT if he could cut down 2 more ounces.

Chen
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Old Jan 20, 2012, 10:17 PM
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United States, FL, Clearwater
Joined May 2011
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Chen, what is the lowest reasonable weight you could expect to get on a new EPO Spitfire kit?

Wolfe
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