Modifying the Top Flite Spitfire I accidentaly bought on ebay.

[David Hazell 1]

Oh Jon, I'm so sorry. There's clearly much love and support here for those who have lost loved ones. Deepest condolences.

[Keith Berriman]

Hello Jon my thoughts are with you I lost my mother suddenly in early November 

God Rest In Piece 

[Andy Gates]

Hi Jon,

 

I too am sorry for your loss and nothing anyone can say will change that feeling.

The feeling of loss will diminish with time, but loosing a parent will always leave a gap.

 

For our family, my mum was Christmas. She was more excited about the gift giving and the celebrations than us kids were. Now she is gone, Xmas is a much emptier occasion for us.

 

I wish you and your family well Jon. Catch up with you in 2023

[John Stainforth]

On 08/12/2022 at 11:32, Jon - Laser Engines said:

 

Yea it can come as a shock if you arent used to warbirds. I fly a number of WWII fighters and adding a few lbs of lead is neither uncommon or a big issue. They are all 80-90 inch and 20-24lbs. I tend to work on 10%. If the model is 20lbs, 2 or less should be ballast. Over 10% it starts to get a little more uncomfortable but at the end of the day the blasted thing has to fly so just add what needs to be added. If its not too heavy for its span/powerplant it really is not important.  

 

I do not have exact numbers for the relevant marks, but the dry weight of a Spit V was 5065lbs and the weight of the engine was around 15-1600lbs. So almost 1/3 the dry weight of the aircraft was the engine. If we assume a 20lb model Spitfire, it would need an engine of around 6-6.6lbs to get the c/g right assuming the structure of the model was as light as the full size once you scale it. My engine is just over 4lbs, and pretty heavy as model engines go but i am still too light so i need some other ballast both to get to my scale engine weight and cover off the heavier than scale airframe. 

 

I did make an error in my calculations yesterday and mounted the engine about 15mm to far back so this will clearly help with balance down the line. It may just offset the weight of things not yet added to the tail but generally i am increasing in confidence that the job can be done should i decide to give it a shot. 

Your estimate of the weight of model engine required to balance the plane is not quite correct, because the centre of gravity of model engines is quite at bit further forward than a scaled Merlin, which is a long engine. What matters is the turning moment of the engine, not its weight, so you won't need so much extra ballast as you think to balance the model with your 4 lb engine.

[Gary Clark 1]

Sorry to hear of your loss Jon, I hope things go as well as can be for you and the family

[EGB 953]

 Very sorry to hear your news Jon. Thoughts with you and your family. 

[Martin McIntosh]

Flog it and buy my original TN 72" Spit for £100, air retracts included, nose weight added and ready for a Laser 180. 18 lbs AUW.You have seen it flying I think.

[Jon H]

Hi Guys. 

 

I have been picking away at the Spitfire from time to time so thought i would update the thread. i didnt take photos of every stage of the work, i just wanted to focus on what i was doing so you might have to fill in a few gaps. 

 

First i sheeted up the FRC wooden cowl formers to make an actual cowl out of it. Yes the sheeting quality is awful, but its not going to be used on the model itself. 

 

 

Bit of a step here, this was built up, filled, sanded etc to blend in. 

 

 

Jumping ahead this form block was bolted to the front of the model

 

 

 

I then covered it in a combination of sellotape and covering film before glasscloth went over the top. The idea was the resin would not stick to the plastic tape/film and i could pop the finished glass cowl off once i was done. 

 

 

Although it was a right pain to get it off it did actually work. Currently the cowl is a bit floppy, the resin isnt rock hard for some reason and is a little bendy, but i can deal with that later and will add a former ring at the front and any other required parts to give it more rigidity. 

 

 

 

The original cowl top is considerably wider than it should be. 

 

 

The other thing i looked at way back when i had the FRC plans out was the wings. 

 

For some reason each panel is 1 inch shorter than it should be and up to 15mm too narrow for scale, especially round the aileron. This was very clear when the wing was overlaid on the FRC plans. The fuselage is exactly 1/5 scale, the wings for some reason are 1/5.09 scale. Why? Luckily i need to modify the centre section anyway so i can restore the span to its correct proportion and add material to make the wing wider as well. Its not a massive job and the only thing that i see as a bit tricky is grafting my existing wings onto the new centre section. But, that is still to come. 

 

[Jon H]

Oh can a mod change the thread title please? 'Modifying the Top Flite Spitfire i accidentally bought on ebay' 

[Jon H]

Well, i have been at it again 

 

Today was the turn of the wing to get some improvement. The first thing was i needed to separate the outer wing from the centre section. The centre section should be flat with dihedral outboard, but the tf design has (not enough) dihedral from the root. So...

 

 

And 45 seconds later 

 

 

Looking at the structure there is no shortage of options for joining spars

 

 

These were slotted though the ribs so i can make some pass through spars

 

 

The undercarriage need to move as well so the mounts were removed in the customary fashion 

 

 

 

With that done i set about widening the wing as its not only too short but too narrow as well. Strips were added to the trailing edge, these were sanded and profiled to not screw up the aerofoil section and any washout. worked out well

 

 

With the changes made the model looks so much better. I am very pleased with the results so far. 

 

 

 

 

I cant do any more until i buy more glue! i also need wood for the spars so i wont be getting much done tomorrow. 

Edited February 5, 2023 by Jon - Laser Engines

[maurice northcott]

Nice precision work in removing the u/c plates John, the hands of a surgeon. I see you have seen the forces of my landings... 🤣🤣🤣.... on a more serious note, I admire your attitude of getting on with it.....

[David Hazell 1]

God you're so bloody brave! I salute you sir. I would be too scared I'd make a destructive change that would ruin any chance of her being airworthy again!

[alan p]

Definitly a Barber Surgeon in a previous life😱

[Jon H]

Its funny as i dont see any of what i am doing to be that big a deal. I know what i want to achieve and just need to cut out all the things in the way of that. 

 

I did smirk to myself during the wing amputation 'surgery' yesterday as i recalled umpteen conversations about moving fuel tanks and being told it was completely impossible as 'there's a former in the way'. A former you say? one whole former? This was about at the  point where the strongest part of the wing was being obliterated by my tenon saw. 

 

I guess i dont worry about it. Its only wood, and i can always glue it back together again if i screw it up. I have done mods like this in the past where i took my Hangar 9 pulse 125 and modified it into a twin. I added retracts, built nacelles for the twin laser 70's and just got it done. The thrust line ended up a bit out as i forgot about the wing incidence (oops), but once that was sorted its one of the best flying twins i have owned. 

 

Also i am not doing anything especially complicated. Moving the wing forward is easy and just returns the model to the way it should be, so there are few concerns there. Adding the strips on the trailing edge is a similar story, and with care i can blend them with existing aerofoil section and hopefully not screw anything up aerodynamically. The fuselage changes are cosmetic only for the most part. 

 

my only real concern is the structural integrity of the wing which is why i spent a bunch of time looking at all those spars and how to tie it all back together. I have pretty good idea of how to do it, i just need to get on with it now. 

 

If you want to have a crack at it David just buy some old beaten pile of junk from a swapmeet and lay into it. You could even buy two and make some sort of monster out of the pair. My advice is always to just have a go at it. 

 

 

[David Ovenden]

My Great Planes 1/5th scale PT19 had a one piece wing. I sawed that in half. Then added wing tubes, put in split flaps, remade the U/C mountings and fitted Robart oleo legs with 4 1/2 wheels. It looked and flew so much better after that.

If we can build planes from plans, kits or from scratch, then surely we can modify an ARTF to match what we want?

Edited February 5, 2023 by David Ovenden

[Jon H]

I would suggest that modifying an artf is a good place to start for people not feeling confident about a kit or plan build. Your undercarriage example is great David as weak undercarriage mounts are a common complaint on artf models so diving in there to beef them up is a worthwhile upgrade. Especially if you can add to the model with, as you say, longer legs or bigger wheels to enhance the scale appearance. 

 

I can understand why someone who bought this Spitfire new would not want to dive in and do the work i am, but it was already in a state where it needed refinishing anyway so i went for it. 

 

 

[Jon H]

Another weekend in the shed working on the wings. 

 

This time its all about dihedral. and making sure the wings do not fall off. 

 

The Spit apparently has 6 degrees of dihedral on the lower surface of the wing outboard of the flat centre section. Using the FRC Spitfire plan and our mate pythagoras it didnt take long to work out that the tips needed to be 4 inches off the bench with the centre section flat on the table. 

 

The first job was to make some dihedral braces. So a trip to wikes got me some decent enough ply for the job. Its not birch, but its also not made of digestive biscuits so it will be fine. I got 5.5 and 3.2mm sheets. 

 

 

The 5.5 was chopped into 4 braces to fit in the slots already cut in the ribs and between the spars. 

 

 

The 3.2 was chopped up to make the other half of the sandwhich

 

 

Old pieces were removed and new ones added. Just as well, the kit ply was shocking and just fell apart. 

 

 

Mocked up ready for glue

 

 

Like this the wing was rigid enough to hold its dihedral angle without clamps. i was pleased with the fit. 

 

To help keep everything straight and make sure i didnt completely screw it all up i draw a chord line on each root rib and added a foot to the trailing edge to hold it level at 0 degrees. Two simple risers poked up for my incidence meter to sit on. Knowing the foot kept the wing at 0 degrees, if my bench was wonkey and i has say 1 degree incidence, that wouldnt matter as long as the wing tips were 1 degree or less. It was more about checking the difference between root and tip than just checking for the actual number. 

 

 

I then glued the spars in two stages. Inner first, and then the outers before final fitting and then gluing the panels together. 

 

 

 

 

The two panels now have their correct dihedral (its very noticeable vs how it was before) and checking incidence at the tip i have -.75 on one side and -1 on the other. More than close enough. This is with the wing root at 0 degrees. i am not joining the two panels yet as its easier to install the retracts and do all my sanding before it comes a 7 foot surf board. 

 

I did mock it up though, and i think it looks much better than it did before. 

 

 

 

Next, time to make wheels that hide. 

 

 

[Jon H]

oh dear. I have discovered a little bit of a cockup on my part when setting the dihedral on the wings. 

 

I based all my work on a flat centre section and then 6 degrees dihedral using the lower spar as a reference as that is how the full size is measured. The bottom of the wing remains flat and the top tapers towards it as in the image below. 

 

 

The problem is i forgot about the fact that the TF wing tapers from the root so the top and bottom of the centre section are not parallel. Its only 2.4 degrees, but when added to my 6 degree dihedral i end up with..yep, 8.4 and a tip nearly 1.7 inches higher than it should be. Its not as apparent in the photos as the wings are just propped up on chairs and sagging a bit. But when i installed the wing joiner i was a bit surprised. As you can imagine, i was not amused by this discovery. 

 

All is not lost however and i already have a plan to fix it. I could chop the wing in half again but that is not happening. Instead i will use the correctly angled lower surfaces of the wing as my new reference and adjust the top surface to suit. In this case, adding about 5mm of material to the top of the wing surface at the dihedral break line levels everything off. I can then taper and blend this into the existing top sheeting of the wing. Not sure how clear it will be, but the drawing below should show the situation with the top drawing of the current state of it and the lower being the proposed revision. 

 

This is not actually a show stopper and will work out ok. The new material will thicken the wing slightly at the root which will actually be more scale, and it will bridge the gap over the wing join for additional strength. On the one hand i am annoyed i missed this issue, but on the other its actually going to work out better in the long run so i guess its a wash. 

 

 

What i need to do next is finish installing the wing joining braces (i have 5 more per side to make and install), then make the centre section joining braces (with correct angle) so i can get the retracts in with the wing as its proper angles. Once all that is done i can work on adding the material needed to square up the top surface of the wing. I then need to find a flat surface long enough to glue the wing together with my 4 inch dihedral braces under the tips to make sure its all spot on. 

 

Sounds like a plan. 

Edited February 14, 2023 by Jon - Laser Engines

[kevin b]

Obviously an "Oh crap, what do I do now ?" moment !

I know the feeling.  

[J D 8]

    I keep this pic as a reminder.

[Jon H]

Well i have so far managed to avoid the old classic of building two left wings or two right fuselage sides so i guess i am not doing too badly. 

 

Never mind, its only wood and the solution is actually quite desirable. 

[kevin b]

I take it that the solution was an alcoholic one ?

[Don Fry]

I took a great deal of time installing a tail wheel today on my in build hack. I installed hard-points into the very soft balsa horizontal stabiliser structure. . Accurately.
In the leading edge!!

I’m going to fake it, put a hook on a spare hard point, and use it a a streamer attachment. Just need 2 more on the wing tips. Mutter, mutter.

 

Have another go tomorrow. 
 

Currently doing the alcohol.

[Jon H]

1 hour ago, kevin b said:

I take it that the solution was an alcoholic one ?

 

Im trying to straighten it out again not make it more crooked! 

 

[Jon H]

Right then, more Spitfire. 

 

I apparently forgot to take photos of a bunch of the work this weekend but my first job was to make wing joining braces which sorted out my dihedral issue. i also made and installed the retract mounts before sticking the whole wing together. 

 

 

Next i needed to lengthen my oleo legs a bit and after some time turning aluminium into swarf the deed was done. 

 

 

Sunday offered some sunshine, which was nice as the model is now too big to fit in the shed and i needed plenty of space to get the wing on and mounted straight. Once satisfied (mostly, final tweaks may come later) i drilled and installed the leading edge dowels and wing bolt plate. 

 

I think my oleos might be a shade long, and my wheels might be a bit big, but the kit wheels made it look like a monster truck they were so large. generally the model looks good and i am pleased with my efforts. I will shorten the legs later if i need to and will rummage through my box of wheels to see if i have anything better suited. I think the undercarriage on the model are a little too far forward for scale, but this was going to be very complicated to fix and not worth it as i mostly care about what it looks like in the air and the wheels will be hidden then. 

 

So heres a few shots of the model basing in the sun.