Spitfire by Cambrian Funfighters Electric Version

[Dad_flyer]

Many electric designs just use small woodscrews from the front. That is quite a chunky firewall, so plenty to bite into. No4 (3mm), countersunk or pan head depending on your X mount. 

I have been surprised seeing this with only an 1/8" firewall (for 28xx motors) where the screws go right through, but I have not seen failures of that fixing.

[Denis Watkins]

Use modelfixings.uk socket head servo screws and washer if necessary, fixed by Allen key finger torque

Drill 1in pilot hole to help the screw go in straight and to reduce stress on the timber

Edited June 20, 2021 by Denis Watkins

[Andrew Calcutt]

Bit late now but you should have fitted blind nuts,drill four holes to suit your mount  and push them through from the back.Be a bit fiddly now but can be done.

[leccyflyer]

Like Andrew said it might have been easier to fit the captive nuts first, but it can be done retrospectively. I made up a simple tool for pulling captive nuts into firewalls from the front and you might be able to adapt the technique? A short length of threaded rod, which you can thread the captive nut onto insert through the hole in the middle of the firewall, hold it with some tweezers, feed the short stub of threaded rod through the motor mount holds and give it a good tug to engage the teeth, Then remove the threaded rod, attach a bolt with a large washer to spread the load and tighten that up to fully engage the captive nut.

 

 

[Ron Gray]

Use threaded inserts, go in from the front and use a bit of cyano on the threads before finally driving them in. I use them on my JU88 build:

 

 

[Graham Davies 3]

Hi Peter,

 

Yes, I remember these frustrations!

 

The instructions for all the electric conversions are poor, and really should be incorporated into the build instructions as they end up out of sequence.

 

I used captive nuts the same as Ron suggested, but you'll have a job to fit them if the box is glued up. All this ends up pretty much 'built in' once the cowl is built up unless you make it detachable, so be conscious of somewhere to add lead if you need it, or you'll need keyhole surgery!

 

I agree about the wing dowel, and to be honest, this has resulted in my model being temporarily retired to think about what it's done. I fitted the dowel to the wing but added a piece of ply false leading edge to support it. Even so, repeated fast belly landings have loosened this several times.

 

Also, those underwing fairings constantly come off. There's hardly anything to glu them to and they tend to be where you grip the model to launch it.

 

What motor/ esc/ prop are you going with? I had a 3536 1200kv in mine on 3S. I had good performance on 10x6, and 5-6 minute flights. However, the constant prop breakages sent me down the folding prop route, but a 10x6 folder draws a heck of a lot more current. I went to 9x6 and launches became a bit more fraught, and the 40A ESC burned out. I'd go at least 50A on the ESC (which will add useful up front weight), or bigger and accept short flights!

 

Graham

[Peter Garsden]

Thanks so much guys for your help. I know the ply mount looks fixed but it is not yet  glued. I just mocked it up for the photo so you would know what I was referring to. All good suggestions. I will have a ponder and look in my spares box to see what is there. I think I favour the blind nut route though the threaded inserts look interesting. Thank you again all of you - helps a lot for a slope soarer who has not a lot of experience with power.

 

Graham, I am going to re-engineer the front dowel - further photos to follow. As for the motor I am using that recommended by Cambrian - the 1500KV motor I think - the Tornado Thumper 3536 with a 40A ESC and a 9x6 prop so hopefully we should be OK with a 3S 2200mah battery. I suspect, however that it may get more used as a PSS sloper. I am going to have 2 spinners - one for slope use with some lead in it, and another for power

[Peter Garsden]

 

This is my amendment for the hole to house the front wing dowel. I have cut out a section of the leading edge to take the block into which I have marked the angle of the hole for the wing dowel, cleared out to take a 6mm internal diameter carbon tube. I really would have preferred a brass tube, but carbon will be fine.

 

 

The beauty of this system is that the front dowel can be lined up exactly whilst the glue dries. I lined the front with selotape so that nothing stuck fast

 

 

This shows the balsa block glued in place and trimmed to shape before the illustrated piece of glass cloth is wetted into place for extra strength. Cloth both sides.

 

 

[Peter Garsden]

 

Next is making holes and grooves in the elevators for the wing joiners. I put tape on a 1.6mm drill which is the right size, and used my pillar drill. Previously I have made holes in the trailing  edge but not this time. I then used a dremmel tool to make the slot after cutting a slot with my balsa knife.

 

 

I was worried about the weakness of the stab which is just a piece of 5mm balsa. I fear it would snap so strengthened it both sides with inset 2mm rods of carbon which should not add much weight but a lot of strength.

Edited June 23, 2021 by Peter Garsden

[Peter Garsden]

 

The tailplane is now a lot stronger with carbon rods albeit only 2mm each top and bottom. I glad I did it. I am sure it  didn't add much weight.

 

The instructions don't say much here but I decided to added the joiner before I glued the tailplane on. It would be very difficult to do this effectively when in situ. I added vaseline to the rods  to stop them sticking, and strapped the plastic tube on with epoxy mixed with microfibres and masking tape. Before I did so, I added the elevators to make sure everything fitted and to ensure it was glued in the right position.

 

The wing was attached to make sure that elevator and wing lined up perfectly. Although the tail is banana shaped, pulled out of shape when the top sheeting was bent into position, the wing and tail lined up perfectly, so it was the fin that had to be glued at right angles to the tail but not the fuselage line.

Edited June 24, 2021 by Peter Garsden

[Peter Garsden]

 

Before adding the elevators and fin, I slotted the parts for the mylar hinges. The mylar provided was glossy. One has to rough it up with a coarse file to aid with sticking it in position with hinge glue I used, which is a water based glue rather like canopy glue. J Perkins supply it. 

 

I am adding a rudder so I cut out the rudder along the marks shown on the plan.

 

 

Tricky to line up the fin accuately as it is so narrow. Because of the banana shape of the rear fuselage in horizontal plane, I had to ensure that the fin was in line with the centre line of the fuselage. This put it slightly off centre when lined up with the centre of the fuselage. Once the gaps are filled either side of the fin to blend in it will not matter.

 

 

It's beginning to look a bit like a Spitfire at last. The piece of 2mm balsa sticking up at the front of the fin is to fill the gap left in front of the fin.

[Rich Griff]

I tend to "pin" the hinges in, mylor strips "rescued" from supermarket hanging products strip.

 

I use BBQ squers cut to length to make the pins. Makes removal for repair etc easy.

 

Never had a control surface come adrift, yet.

 

The holes in the balsa can be toughened using watered down pva and left to dry/go off over night, then slip in hinges and pin, the pin being a slight interference fit.

 

Works for me, and recycled ( intercepted ) waste from supermarket.

 

 

[Peter Garsden]

Thanks Rich. I used to pin hinges the same way and I agree it is more secure. I stopped doing so, however, when, in an impact, the control surface ripped out not only the hinge but also some of the wing with the peg. Recycled waste is a good one though.

[ken anderson.]

hello peter i haven't built this model but if the original was for ic...which i recall they were it's probably over-engineered.....that box looks rather OTT for your electric motor...either change it for some studding or a lighter box c/w access to the nuts...or use captive nuts for the bolts...... 

 

ken anderson...ne..1....nuts dept.

[Graham Davies 3]

You are right Ken, but the model tends to be tail heavy so the extra weight up front is helpful. 

 

Graham

[Peter Garsden]

Been busy but made a bit of progress. Thinking always of Graham saying it needs noseweight and the difficulty with that, I decided to make the cowling removable at least at the top to be glued in permanently once balanced later.

 

 

You can see that I have lined it with some 150gram fibreglass cloth and resin for extra strength. I have also made the ledges to attach the top blocking. I will spot glue it in place to sand it and plane it to shape. First of all I must attach the engine.

 

 

View from the front showing where the nose ring will go.

 

 

Top block a tight fit but removable to add lead and plane to shape.

[Graham Davies 3]

Nice work Peter, and a good idea.

 

My new 42" spit has a full length hatch right up to the spinner. This gives me access to the motor bolts and is now easy to add lead. However, as I incorporated the ideas we have discussed, it didn't need any! If you see the picture below, the 2 black pen marks are where the front of the battery goes for initial flight balance. That was 'safe' and I could move the battery a further 10mm if needed. It turned out about right, so all good. You can also see that I had to mount the servos towards the rear of the hatch or it would have ended up nose heavy!

 

As you've done similar, I'm hoping you'll not need much lead.

 

Not far to go now Peter; we'll see her in the skies before long.

 

Graham

[Peter Garsden]

Thanks Graham, all good ideas. I plan to carve the nose to shape, install all the hardware ie control rods etc, and the battery then see how we go. I will balance it before covering and hope the balance remains the same.  My ideas set out below.

 

 

I have attached the cowling at the front ready for pairing down with the plane and sandpaper and Permagrit files but with only a few spots of cyano. I have also NB, attached some masking tape to the front of the detachable top hatch so that when I use the plane it won't dig into the balsa of the already planed hatch, but just graze the surface of the masking tape.

 

Also note that unfortunately the side cheeks of the cowl have the grain vertical rather than horizontal. This is unfortunate because planing across the grain will be difficult if not impossible. No doubt this is done for economy of balsa cutting but not how I would have cut them out myself ie grain horizontal.

 

So what I am going to do is wait for the blobs of cyano to hold properly - about 9 all the way round then plane it to size. I can then take it off and once the engine is properly in place epoxy it on permanently.

 

I have already had a session with the transmitter, making sure that the motor is rotating in the right direction and marking the wires with coloured masking in case we have to do it again. Also to enable lead to be added is possible. I can also move the servos backwards or forwards.

 

 

As I am using the strong servo screw method to attach the motor, I don't really want to take it off again. I did think of using this as a mould and fabricating a fibreglass thin removable cowl, but I am too lazy to do that. If this breaks I might go that route (probably not)

[Ron Gray]

Cross grain planing - coarse Permagrit file block but good quality grit paper on a sanding block works fine and doesn’t take that long but does generate a lot of dust.

[Peter Garsden]

 

These pictures show the carved nose up to the ply nose ring at the front and the ply former in front of the wing with the propeller attached. It was not as difficult as I thought planing cross grain, the sides of the cowl.

 

 

And one can see that I have added some filler pieces of 1.5mm balsa at the sides to fill out the width.

 

 

I roughly attached all the parts and the battery. Despite previous concerns, the C of G does not seem to far away from that specified on the plan.

Edited August 9, 2021 by Peter Garsden

[Peter Garsden]

The plan was to hook up all the connections and test the C of G so that if weight was needed to the nose, I could add it before the cowl was finally glued and attached.  So the first job was to intall the fuselage servos and snakes.

 

 

You can see that I have installed the servos wher stated on the plan r\ther than further forward either side of where the receiver is next to the battery hatch. I tested the C of G without the wing on and it seemed to be in roughly the correct place with the propeller and spinner attached.

 

I then set up the Vanessa balance machine to find out if the nose needed any weight. I needed to add a little bit, so I tapped the cowl to relieve the cyano spot glue. I then glued the lead to the bottom front of the cowl.

 

 

I left the top of the cowl unglued and not fibreglassed, so I epoxied it on, and have now wrapped fibreglass round the inside.

 

 

[Peter Garsden]

Having added the fibreglass cloth to the top inside of the cowl, I had to make a few easing adjustments before gluing on the cowl permanently. I must admit I did consider making a fibreglass version which I could screw into position, the motor being quite a permanent feature but didn't do so in the end.

 

Next is cutting the cockpit to size and painting the inside before glassing. I never know whether it is meant to stretch so much to get it into position or not. I have some cockpit green which I am dying to use.

 

Can't remember if I showed you Reg, my trusty 3/4 pilot which I have painted - thank you to Andy Meade for supplying the 3D Print  - but in case not here he is

 

[john stones 1 - Moderator]

How do Reg. ?

[leccyflyer]

Nice work Peter - one thing though, I don't understand why you are balancing the model before it's been covered and finished?

[Peter Garsden]

Plea for help guys. The motor exhausts have to be glued on the sides of the fuselage. The position is bang over the edges of the battery access hatch. So

1.  Do I glue the exhaust to the hatch and not the front fus so that the hatch will come off easily. Graham what did you do?
2. I have always had 3D printed items or ABS plastic before so as these are in clear perspex presumably one uses canopy glue to attach them?
3. They are printed with a border round the edge with some screw indents. Presumably one trims right up to the exhausts and glues the edge to the battery hatch? Or does one leave say 3mm all round the edge and use that as a purchase for the glue?

 

One could of course cut it in 2 and glue a section to each ie cowl and hatch but as the hatch opens upwards I am concerned that this might foul the opening action. Graham you will know what I am talking about.