Warbird Replicas Spitfire LF mk IXc

[Andy Gates]

Just pondering about my set up.

 

What have any of you who have flown one of these machines done about cooling for the motor / ESC / Lipo?

 

I currently can't see a way of providing cooling without spoiling the smooth lines so I am hoping none is needed.

[RICHARD WILLS]

I haven't had a problem with cooling Andy . I only use a 60amp esc and a 3300 battery . 

Prop size is Dynam 13x7 three blade which is quite "soft " in performance on a 580KV . 

The master airscrew 14x7 gives a lot more power but throttle needs to be used cautiously . 

I generally do all of the initial flights with the Dynam props as they are cheap and give moderate performance but good battery life . 

If you crave more oomph later , increase the prop size . 

[Andy Gates]

Mine peaked at 945w (60A) static on the ground so I expect it to unload in the air and those figures to drop.

I have 2650 and 5000 packs so I am guessing my 5000's may give too long a flight time so I may well cook the ESC. I will ground test before I fly, should be interesting.

Having said that I did run it up on 3S which seemed to have plenty of power too.

I expect to be flying it around on half throttle if that most of the time.

 

Mine is covered now with Laminating Film and currently weighs 4lb 11oz.

 

Just the painting to do, with an airbrush,  another learning curve for me.

Edited May 14, 2021 by Andy Gates

[RICHARD WILLS]

I am sure yours will be very light Andy , so maybe the even the 2650s will be ok . 

 

[Andy Gates]

Well mine is almost finished now.

 

She is covered with laminating film which seems to be great stuff to use.

 

Painted with an airbrush with enamel paint, underside and upper brown paint went on well and smoothly, not quite so happy with the upper green which seems slightly satin finish, was much grittier to use and kept blocking the airbrush nozzle.

 

A few decals to add, and I want to change the wheels as mine are a little heavy at 28g (1oz) each and could be slightly smaller to increase clearance in the wing bays.

 

With my 4S 2650mAH pack fitted the CoG is on the rearmost recommended position at 95mm with no additional weight. I will add some nose weight for the test flight just to be certain.

 

Weight ready to fly as is ... 5lbs 2oz.

 

Pictures will follow when all the decals attached.

[RICHARD WILLS]

That's very light Andy . Great job . Should fly nicely . 

[Andy Gates]

Finished it and maidened yesterday.

 

 

[Trevor]

Congratulations Andy. Nice landing too!

[Ron Gray]

Very nice Andy.

[Andy Gates]

Thanks gentlemen.

Looks OK at distance but I do need some more practice / training with an airbrush.

Bit close on the landing, later ones were worse with me trying to get into the field a bit more.

Pilot definitely needs practice as this is quite a heavy model for me.

Bit wary of slowing it down as it did show a bit of a tip stall during stall testing on the first flight but that may have been a result of a cross wind

[Graham R]

Nice one Andy. 

Edited June 6, 2021 by Graham R

[David Hazell 1]

I've been lost in my own head for a couple of months. Trying to get myself back into building the spit. I made a little progress by clearing my build desk today, I might have a little tinker tomorrow. 

 

Great job Andy, nice work.

[Andy Gates]

Keep going David, it will all work out.

It is not unusual to need to take a break during a build to regroup, and lets face it - times have NOT been normal recently.

[David Hazell 1]

4 minutes ago, Andy Gates said:

Keep going David, it will all work out.

It is not unusual to need to take a break during a build to regroup, and lets face it - times have NOT been normal recently.

 

Thanks for the encouragement Andy! Yeah I think the last months of working from home have institutionalised me, messed me up more than a bit, but I'm getting through it! Cheers.

[Andy Gates]

Still trying to get to grips with my Spitfire.

 

Damaged the under carriage a few times and have been ploughing the field with the prop both on take off and landing.

 

I have now moved the CoG back from the very front position suggested and tilted the U/C forwards by packing a piece of 1/8" ply under the rear of each retract.

This has helped but I suspect the CoG can go back further still as the nose is still dropping in the turns.

[RICHARD WILLS]

Wheels look small Andy , 

                                        Perhaps go up to 3" .

[Andy Gates]

The original slightly bigger wheels will not go up into the wheel wells with the retract tilted to push the wheel axle forward when extended Richard.

 

During take off and landing the plane is acting like a drunk lady tottering about on high heels after a good Friday night session.

I have been fighting with the elevator to keep it where it should be which makes for an unpredictable start and end of flight, and a fast heart beat.

 

I will see what effect the further rearwards movement of the CoG has. I may have to re-cut and re-sheet the wheel wells for bigger wheels if this change does not help.

[RICHARD WILLS]

Andy ,it may be that if you have a very rough strip , it is better to bend the leg forward when retracted by about 10mm and nibble away the front of the wheel bay . Ok its a small cosmetic deficit , but struggling to hold the tail down with full up elevator will end badly . 

[Andy Gates]

10 hours ago, RICHARD WILLS said:

struggling to hold the tail down with full up elevator will end badly

 

Tell me about it as that is what I have been doing both on take off and landing.

 

Just measured the wheels and they are 2 3/4" so hopefully big enough, as to our field - we do have routine sessions filling in the rabbit / deer scrapes. Grass quality does vary too from bowling green to full on wild habitat although it is weekly cut.

 

As I anticipated, my ESC is getting a bit warmer than I would like as I am getting 2 x 8min flights out of one 5000mAH pack. So I have fitted a heat sink to the ESC to hopefully cool it better.

 

I also have more telemetry coming, a GPS unit for speed and height info and a current detector to see what it is really pulling in flight.

 

[Andy Gates]

Well, I have been having a really torrid time with my Spitfire and its ground handling.

I had not posted too much about this as I did not want to do a disservice to this plane or Warbird Replicas.

 

For some unknown reason it wanted to chew up the airstrip at very possible occasion which makes take off and landing interesting to say the least.

Once in the air she is fine.

I am on my 3 set of retracts having managed to break off the mounting plates on the others.

 

So I e-mailed Richard to get advice.

He phoned me back which was a lovely surprise and the discussion we had bore fruit.

 

Now if you build the plane as per WR instructions, all will be fine. She is a wonderfull aircraft.

 

My machine was modified with a shorter nose and a lighter back end. My machine came out at around 5lbs, so 1lb or so lighter than normal.

None of the above is the cause of my ground handling issues.

 

What I HAD done is created my own oleo U/C legs from aluminium fitted to my heavy duty retracts, which meant I have no spring in the leg mechanism. This is not normally a problem as I have done similar on other machines before.

However with the Spitfire, this lack of spring had altered the leg geometry putting the wheel axles too far to the rear (I had not thought much about it but the spring works in both directions of course).

As can be seen in earlier posts I had packed the rear of the retracts to tilt the leg forwards.

I had also tried moving the CoG rearwards in an attempt to put the weight further behind the wheels. Please, I really suggest you do NOT do this. I got away with it as my machine is lighter than most but it was getting quite twitchy in the air with the CoG at around 110-115mm.

After my chat, the CoG went back to 95mm and another slither of packing added under the read of the retracts. This brought the leg angle to 20 degrees forwards from the vertical where the origional full size Spitfire had 18 degrees.

 

I flew this combination yesterday, and finally I had ground handling I can cope with so there is at least some chance of a propper take off (I am not a full power and yank it off the deck ASAP flier - replica scale takeoffs for me).

 

I have written this so that if someone else does anything similar to what I have with the U/C, then the info is available and hopefully they have a better time than I did.

 

So thank you very much to Richard for the back up. Much appreciated.

[David Hazell 1]

Searching for a bit more detailing info, found this thread which has some nice pictures of a very nicely finished Tamiya kit: https://forum.ww1aircraftmodels.com/index.php?topic=11286.0

 

[David Hazell 1]

I have a question too... 

 

 

I couldn't figure out if I was meant to slice the exhaust manifolds off at that line which is clearly visible...

 

And what's this little triangle bit for between F4 F9 and F6? I've lost it but curious all the same!:

 

 

 

 

 

[RICHARD WILLS]

That must be the Bermuda Triangle . Only appears when you're not looking for it . ....?

Exhausts look alright David . By the time they are painted brick coloured then suitably smoked with dark grey , all will be well . 

We do make some more sophisticated ones by 3d printing 

.  Bit more prone to breaking them though . Depends how well you handle the models in the car etc . 

[David Hazell 1]

I just stuck my not even fully painted spit on the scales and she's a proper fatty.  With the alu spinner, painted pilot, sound system, a big fat 5000mah battery she is coming in at 3.03kg, or 6lb 10oz. This figure is anticipating me adding another 100g of paint, so I might be able to shave a bit off that figure.

 

I'm worried about this!!!

 

I can drop battery size obviously - do have a couple of 3300 batts, but they're only going to shave off 100g too. I guess I am not a light builder!

 

lose Alu spinner: -114g (plus whatever a plastic spinner weights)

Sound system:  -115g

smaller battery: -100g

less paint: -50g?

 

So by dumping the sound system (which I don't want to do!), swapping the spinner for a lightweight plastic jobby (again, don't want to do this), and dropping the size of the battery I might be able to shave off 300 odd grams. 

 

 Will it fly like a drain cover if I go full fat cornish cream?

[RICHARD WILLS]

I don think that is crazy heavy David . 

If you lose nose weight , the C of g will be wrong , My only (very slight ) concern is that I "built up " to the sound system .

What I mean is , that most good Spits start at 6lb . I had flown it lots of times before I retro fitted the sound system , so I knew what it handled like and when to be careful . (zero wind take offs on a warm day for example ) .

If possible (C of G wise ) , Test fly with a smaller battery . And , perhaps leave the speaker out for the first test flight . 

The Spitfire is a little smaller than the P51 or 109 , so we have to be a little more aware . Having said that , Mike Hammersly gave me his to test fly when he was unwell and I performed a text book test flight not knowing that it weighed 7lb .

The wing section is very efficient . 

As always , the big danger is taking off too early or not into wind .  I would usually wait for a 5-8mph breeze and point just right of the wind direction for test flights . If it starts going left , abort . Once in the air , its a doddle.

I also test fly before painting nowadays , if possible . Far less pressure !!!