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Spitfire by Cambrian Funfighters Electric Version


Peter Garsden
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I am having difficulty sourcing a folding prop with such a large diameter Spinner. Can you let me know what you used Graham?

 

Anyway I have made up the ailerons, control rods and installed the servos - EMAX 3352 which I am sure will be substantial enough. These types of aileron probably take less torque than wing mounted versions.

 

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I am not altogether happy with the PVA reinforcement of the bandage but have followed the instructions. I used my hot foam cutting pen to dig out the foam and a sharp scalpel to make the indents for the beech servo rails out of 6mm x 3mm. I glued them in with Gorilla glue which is very good for filling gaps in foam. I am not altogether happy with the plastic clevises as I normally use metal. Also not much adjustment. I might change them later. Difficult to be accurate as the ailerons will not be glued in until after covering.

 

I have cut out the fuselage sides from 2mm balsa using the ply originals as a template and I am waiting for my .8mm ply to arrive from SLEC. I had some but nothing long enough to cover from F1 to behind the wing. I am going to finish it as usual with a diagonal cut to avoid the stress of a vertical break point. The carriage cost was £10!

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PVA on wing bandages, normally requires a few coats of PVA/aliphatic, credit card to spread it and push it into the weave, doesn't add any appreciable weight.

 

I find 3 or 4 coats usually gets me to a smooth enough finish for film covering. I do use multiple thin layers of glass though.

 

 

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Looking good Peter,

 

Don't worry about the servos or clevises. I used a single 3352 and it's fine.

 

I used an auronaut folding prop with a boss that was larger than 57mm (I can't remember which). The hole is larger than the prop adapter, so I made some spacers top and bottom and then used a standard 57mm spinner. The prop slots need to be cut out, but it works fine.

 

Graham

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You can see that I have attached the ailerons albeit temporarily, which probably was a mistake because you can't line them up accurately at this stage. Also there is a bit of play in the rods where they meet the servo which can move up and down slightly. It will probably get tighter when everything is glued.

 

I am using Emax 3352 servos for the ailerons which are metal geared and rated at over 2kg. The instructions show the aileron servo sticking up on rods because when this plan was drawn servos were much deeper and would have stuck out the bottom of the wing. You could not have made a cut out thus.

 

Having just soaked the bandage in PVA, it is not very hard, so I think I will remove the servos and add a layer of fibreglass resin. I will lay on some peel ply to soak up any excess. In fact I may leave it until I glass the whole wing, which will make sense.

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The 1/32" ply arrived so I made up some doublers with a scarf joint to take the stress. I am a bit worried about the thickness of the balsa and the lack of strength at the tail. I hope I won't live to regret the abadonment of the 3mm ply as specified by the designers. Heavy landings slope side sometimes mean that what is good for power doesn't work on the slope. As this is a hybrid it is difficult to know what is best. It is a compromise after all.

 

The instructions say apply all the 5mm square longerons before gluing in the formers. I used cyano for the longerons and aliphatic for the formers. The problem is that you cannot abut the engineer's square to F1 because the longeron is in the way, so I have only glued F2 and F4 at this stage. I will add F1 with some epoxy methinks later. It needs the strength. I am also planning to reinforce the nose with glass and epoxy. Any extra weight is going to be needed anyway. If it is a choice of lead or resin, I know I would prefer resin.

 

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This shows that the bottom of F4 should be butted up against the bottom of the wing  rather than the 5mm longeron. The plan is correct when it show the former abutting the longeron because it goes to a point in the middle. It should be pushed up against the top of its slot. Again Engineer's squares come in handy here.

 

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It is tricky to line up the fuselage side which is quite narrow sticking out over the bench because cleverly, F4 contains the side piece for the over wing fairings. The weights help keep it flat.

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On 17/05/2021 at 09:11, Nigel R said:

PVA on wing bandages, normally requires a few coats of PVA/aliphatic, credit card to spread it and push it into the weave, doesn't add any appreciable weight.

 

I find 3 or 4 coats usually gets me to a smooth enough finish for film covering. I do use multiple thin layers of glass though.

 

 

Thanks Nigel, very helpful.

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Some may say this was unnecessary but  I wanted to apply some extra strength to the tail so I made some 1/64" ply doublers each side, which are very light, and hopefully won't affect the balance too much.

 

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I added the 2nd fuselage side and applied some weight in the form of ballast sets for some of my gliders.

 

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Once the fuselage had dried I was able to see that everything was square. I laid the construction over the plan, and brought the tail together. Everything  lined up. I used Epoxy and masking tape to bring everything together.

 

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Next one adds the remaining formers  - as some of them slot in between the fuselage sides with little support until the top sheeting goes on I used engineers squares again to ensure they are vertical. I lined up the angled former to ensure that the top sheet will line up correctly. I then applied clamps until the aliphatic dries.

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  • 2 weeks later...

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Next job is to glue in the control snakes - one supplied with the kit for the elevator only, so I bought another from SLEC. They are quite robust so the extra rudder snake will inevitably add weight to the tail. I am hoping to move the LIPO as far forward as possible. I plan to only attach the bottom cowl piece with dots of cyano so it can be removed to add weight to the engine area if necessary. Difficult once everything is glued in and the nose ring attached. There is more space below the motor than above.

 

I roughed up the snakes with 125 grit sandpaper as they are hard plastic and need something for the epoxy to key to. I mixed in some milled fibres of fibreglass to the glue. If you apply glue before inserting the snake there is a danger that it will go down the tube so the trick is to insert the tube then apply some epoxy 20 minute - you need the time - and move the snakes backwards and forwards to get the glue in the holes. As the joints are inaccessible I used a syringe and blunt ended needles you can get on Ebay.

 

Oh and you can see that I broke the upper former sheeting which is weak near F7 so be careful. Once the side sheeting goes on of course it will become much stronger. I applied some epoxy, as I had some mixed, instead of the original aliphatic resin.

Edited by Peter Garsden
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So on with the top sheeting which is quite a hard selection in my kit, and needs a bit of force to make it follow the formers in a curve. I cut it to size then steamed it to a curve from front to back and to roll over the top. It wasn't bent enough so as you can see I coated it with ammonia to soften the wood and aid the bending. First of all I glued the rear section to the bottom sheeting, then bent the front round and glued the edge of that with aliphatic, then curved over the top, let it dry, then glued it with aliphatic, pinned and rubber banded and clamped it into position.

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Big thanks to Andy Meade for making the most detailed and accurate pilots. A bargain at £10 each. Although they are 1/10th Scale, they are printed very lightly, and smoothly. Just in case there is any doubt, I am only putting one pilot in the cockpit and the other is for my mate Keith, who is also building a Spitfire Funfighter.

 

As the weather was so nice, I took Bill and Ben out onto the patio and painted them in the sun. The Acrylic Paints however do dry very fast in the heat. First I gave them an airbrush coat of grey primer, which was identical to the colour of the plastic but helps the paint adhere. Whilst I used flesh base, I toned it  down as otherwise these chaps look as though they have been using foundation.

 

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Painting, and shading all done

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Whilst we are on cockpits, I have done some Internet research and found a cockpit facia that I will print on photographic paper, glue to a piece of 1.5mm balsa and glue into the cockpit from underneath once I have painted it with cockpit green.

 

SpitfireInstrumentPanel.jpeg.bc706947eb7a80c6f74ea0f7e34ab1d6.jpeg

 

 

 

 

Edited by Peter Garsden
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Next job was to put the lower 2mm sheeting on the bottom of the fuselage cross grain. When I measured up I realised that forcing the upper sheeting to fit had induced a banana warp in the fuselage which hopefully is evident in this photo. Fortunately the twist is only laterally so the tailplane should still line up with the wing but the fin must line up with the central spar not the line of the rear.

 

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This shows the outlet of the elevator snake and parts 11 which sit on top of the fuselage sides to support the tailplane. They weren't quite long enough hence the packer piece at the rear. All looks square. You can see the top fuselage sheeting which needed quite a lot of ammonia to bend it into shape before gluing it.

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Next is the assembly of the battery cover. The instructions show a picture of the formers being attached away from the fuselage but I fear this may result in a wrongly shaped and ill fitting cover so I sealed the join from sticking with plastic and glued the rear in position first. Because the fuselage is a little longer than plan there is a bit of a gap at the back and front which I will fill with slivers of 1.5mm balsa. The part comes precut which is fine but it relies on building to exact tolerances.

 

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Then the front former which fits over the existing longerons and F1. I had to trim both formers to fit.

 

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This shows the gap which will be filled with a balsa sliver.

 

 

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This is the bottom of the hatch - as with the rest of the fuselage, the side 2mm sheeting has to be applied in 2 stages. Whilst I could have used cyano, I don't like to because one cannot position it accurately. It grabs instantly. So a collection of pins and clamps.

 

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You can see how far away the sheeting is, and it is hard balsa, so I coated the outside in ammonia, left it for 10 minutes then wrapped masking tape round it, a clamp and left it to dry. I then applied the aliphatic resin, and re wound the tape and the clamps.

 

I lined it up accurately at the bottom but left the top and the sides proud for trimming. You can never allow enough on a curve. It always uses more balsa than you think - ask me how I know? In fact I used the off cuts from the rear section of fuselage top side which I had already curved with steam.

Edited by Peter Garsden
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Next, the wing bolt holders to take 6mm wing bolts. These, in experience are badly threaded making them stiff. These were no exception. I was going to ream them out with a 6mm bolt but had none to hand. You can see that the screws are proud on the right. The screws are slightly too long, so I could either file the ends down with a metal file or make small holes in the ply inside the fuselage. 

 

I chose the latter course but forgot that there is no right angle access to the screws once inside the fuselage. You can't push them home into the balsa because of the doublers, so I took a dremmel and made a countersunk hole to take the point of the screw without going through to the other side.

 

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This shows the bolts through ready for marking the point on the wing to drill holes for them to pass through.

 

.

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I have decided to reinforce the top and bottom of the nose with fibreglass before the engine  geometry makes impossible to do so. I am laying on 150gram cloth and dabbing it with resin. Wet the balsa first. I decided to cut it in the middle so that you can see what is going on and apply the brush to the bottom of the fuselage which has part 12 to line up the bottom of the nose. The engine mount, motor, spinner and prop all have yet to be added to F1.

 

This shows the battery hatch

 

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This shows how I measured up the cloth then cut it in half to make a piece of cloth which will overlap and stick to the bottom piece of half inch sheeting. I manage to get a brush down the side of the battery platform, which, with hindsight I could have glued in later.

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This shows the under sheeting to the nose and the wing locating dowel, which curiously, is attached to the fuselage rather than the wing. I think this is because the hole in the wing is simply drilled into the leading edge and foam. I am not happy about this method as I can see it ripping through the wing and making a mess of the foam. 

 

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You can see that the hole is not through the leading edge but slightly above in order to line up with the hole. I am simply not happy with this. It is too weak and will rip out. I am going to inset a piece of block, and probably line it with ply. Not a good design methinks. I might even insert a piece of brass tubing to boot. I can just see this breaking on a heavy landing.

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Apologies for not showing the construction of the wing fairings - always a tricky part of the build on any fuselage. The 0.4mm ply covering is good quality birch (part 22) but it is difficult to bend. I glued it on oversize then trimmed it with scissors - easy as it is so thin. I also steamed it to ease the bend. I used cyano, and cannot see any other type of of glue working - if you don't use plastic bags on your fingers you end up stuck to the fuselage! (How do I know this?).

 

The underneath fairing sheeting which is made of the same thickness of ply but cross grain - great idea as it bends more easily under the wing seating profile - is  quite easy to apply. You cover the fuselage dowel hole and the top of the wing with Sellotape to stop it sticking, then glue it on with epoxy. Screw the wing in place and leave it to set. 

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I couldn't work out from the instructions if the wing profile filler should be stuck to the wing or not. I think this is right but am not sure. It was tricky to fit as parts 20 shown are at a different level to the former, so a step has to be filed into it. Epoxy did the rest!

 

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Because the wing is slightly off to one side the aileron push rods foul the former, so I have cut a piece out of it to allow movement

 

 

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Plea for help.

 

There are no clear instructions on how to attach the motor to the ply box engine mount and I am a bit stumped. This is clearly a very old plan which has been adapted for electric motors. It just says assemble the box having made holes for the motor metal cross thingie to attach to it, glue up the box and attach then attach the motor.

 

The problem is that the box has 4 sides and a front, so how do you get access to the motor nuts and bolts if you want to remove the motor at a later stage?

 

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Also, if the bolts pass from the outside to inside, how do you secure blind nuts to the inside and avoid them falling into the space? If the other way round, how do you get access to the head of the bolt to tighten it? Graham you have built one of these so may need some pictures of how you did it.

 

The cross thingie has to sit diagonally with the holes in the corners methinks.

Edited by Peter Garsden
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