Yellow Planes Spitfire MK XIV

[Paul Williams]

One thing I said I would never do is build for a friend, it’s ok for me to make a mistake on something that belongs to me but I would worry about somebody else’s pride and joy. However after seeing this spitfire kit sitting in a mates garage since 1066 I figured It deserved to fly. Plus I was on the sick for 4 weeks and bored silly.

Its a Yellow Planes Mk XIV and can be viewed here

I Have struggled to find a good build blog with detailed pictures so if you have seen one please send me a link. First impressions remain neutral fibre glass fuse and foam veneered wing, the kit boasts a lot of scale detail (air intakes, guns, scale hinges) the panel lines are present on the fuse. Its those foam wings I am concerned about. This will weigh in around 25lb and the span is 90” I don’t think I would design it with foam. But what do I know I can’t find any negatives on the net other than a bit of cracking ERRRR.

The works done so far was to join the wing sections and glass up then cover with glass and poly C resin. The tail section has been fitted then elevator and rudder built as standard with balsa ribs. These are covered with cream solatex. A pair of yellow’s own air retracts have been screwed in. Now this really is a builder’s kit as far as there are no servo trays, tank mounts ect you are left to design your own. Plan shows suggested position that is all the help you get.

The model shop sold him a Zenoah 38cc petrol on the grounds it would fit into the cowl without too much cutting Mmmmm. My Thunderbolt is roughly the same size and weight and I run a 65cc so I felt very much it would need more power. After some deliberation we settled on a Turnigy 50cc petrol. They claim it will deliver 5.5hp and spin a 22x10 prop, rev range 1500 to 10,000rpm that is the same as my RCG 65cc only I know for a fact 22x10 gives me 6500rpm.

I have never used Turnigy so look forward to testing it.

The plane is noted to be tail heavy with some reports using 3.5lb of lead up front! So to keep weight down at the rear I have dismissed a tail retract and made up a steering tail wheel for now.

No need to be pretty its under the tail wheel door so can't be seen

Hinging the control sections was the next challenge, I have never done scale hinges but soon worked out the hinge point needs to be at the centre of the leading edge diameter this is how I did it. Measure the width of the leading edge where you wish to hinge. Remember this will reduce if the section is tapered so all hinges will have a different depth. Lets say the LE is 30mm the fulcrum point needs to be half the distance 15mm (the radius) if your hinge measures 30mm from the end to the pin (hinge point) the depth you will drill in would be 45mm.

Ok now we need clearance for the hinge to move. Offer the elevator to the tail and scribe a line top and bottom all along the lenth where it meets the female radius on the tail. The slots you cut across the LE should not exceed this line or they will be visible when its put together. With a fine tooth saw or sharp knife cut slots at 90 deg to the LE where you have drilled the hinge holes don’t cut past your pencil marks.

This will still not be enough clearance for the hinge so now with a sharp pointed knife cut away so the slots are tapered into the hole at 45 degrees. Its made clearer on the pictures. Now the hinge will swing through 90 degrees (45 up and 45 down) Glue in the hinge being careful not to get epoxy on the pin, work them till dry to ensure they are free. When dry fit to female radius on tail and slide some paper between the sections to ensure clearance. Glue in hinges and hey presto control surfaces with no gaps. you can still see slots when the surface is moved but I cant figure a way round this. Any ideas guys?

[Danny Fenton]

Looks great Paul, always difficult building for somebody else

The way I hid mine was to take the elevator off, insert the hinge and move the hinge the maximum amount you will need. Then fill in between the hinge and the upper and lower leading edges of the elevator, ie the slots are too large in angle. Does that make any sense at all? lolol

Doesn't eliminate it completely but lessens it

 

If you look closely you will see I didn't fill it in, I just didn't cut it open so much same end result though.

 

Cheers

Danny

Edited By Danny Fenton on 16/10/2012 12:44:57

[Paul Williams]

Thanks Danny, I must remember to ask before I do the job

[Paul Williams]

The cockpit kit was no problem after cleaning and rubbing with sandpaper I tacked it in with cyano then epoxy’ed around a few points, it was at this point I discovered both glues had not stuck well., it took very little effort to pull it away from the fibre glass Mmmmmm. I am glad I found out now I intended to glue in the servo tray supports in the same manner. The book recommends some make of glue I have never heard of Stabilit but goes on to say reinforce with glass cloth. So a fibre glass kit from Halfords and that bonds well. I am now thinking what a pain to have to bond everything to the fuse in this manner I have got lazy using cyano.

I have decided to hold on the roofy bit with self tappers its gonna need painting and a brave fella in there to drive it. All fitted well, very little fettling needed.

Onto the servo tray, please take this advice, draw it out scale size first. Better still cut it out of card and take some time to weigh up where all the components are going to live, make a list so you dont forget to give any item a home. There is no more a disappointment then after you have handcrafted a support tray to discover the air canister will have to be taped to the rudder because all room is used!!

Even after hours of deliberation I discovered when all the stuff is screwed on I can’t get the tray through the opening Grrrrrrr

Still when I get frustrated I go see what Malcolm next door is doing. Often in the freezing cold and wet he solders on what on earth could establish such a bond of unity between man and land rover is not within my understanding. I salute you Malcolm. Oh you have set fire to your cat !!

Having walked away and returned I now see if I split the tray into 2 sections I can get it in, proven by taping the stuff on first. Yepeee onwards we go.

Making a cradle for the air canister.

The RCGK engine arrived I could not resist firing it up, I have to make up some mineral oil fuel for running in although the instructions say it will happily run in on synthetic. Sure there is a debate to be had there but just for a short run I used synthetic at 40;1. I was impressed how quickly it started I read somewhere about priming the motor why waste all the time and energy revolving the prop a full rotation. Simply take the prop through top dead centre and back so its like operating a water pump. The pulse required is still transmitted to the pump wow it certainly worked here the engine fired first flick then off with choke and one flick had her running, well impressed. I kept the revs well down but all seems good, I will get some fuel made up and post some figures later.

[Paul Williams]

More work done on the servo tray and control lines made up.

Only the bulk head connectors to go

Edited By Paul Williams on 25/10/2012 10:10:46

Edited By Chris Bott - Moderator on 25/10/2012 11:17:45

[Phill @ Elite Workwear UK]

That is very nice!

[Paul Williams]

Cheers Phill, could not resist having a look at the plane with the wing on.

Its that gorgeous outline that draws me to the spitfire cant wait to get it painted.

[Stephen Grigg]

Brilliant thread anf model.Kept seeong yellow spitfire which didnt click,mightely impressed.

[Danny Fenton]

that looks fabulous Paul, well done

cheers

Danny

[Paul Williams]

I am still worried about putting a 5hp engine in a fuse you can see through !

I was thinking ahead regarding painting, It would be ideal to spray it but I dont fancy paint fumes and overspray all round the newly finished workshop, has anyone handpainted such a beast? Can you acheive a good finish with a brush? What about covering instead. love to hear ya thoughts guys.

[stu knowles]

I usually wait for a dry bright day, spray outside and then whip it back in side to a warm workshop.

I'm sure that you could brush paint it but spraying is more likely to end in a satisfactory finish

[Paul Williams]

Sure your right spraying will bring a better finish might try the outside thing.

had a go at fitting the carb intake

I thought it would look naff, but a quick coat of primer and I was quite pleased.

[Stephen Grigg]

The real ones were hand painted with a broom,think you should do the same for realism and scale.Then fire a shotgun at it for battle wounds.

[Danny Fenton]

Hi Paul looking good, I love this stage of the build

A good quality airbrush (IWAATA) is my weapon of choice, I find the overspray is nowhere near as great as with an aersol, and just throw dust sheets on most things. The huge clear polythene dust sheets are really peanuts to buy on ebay too.

I really wouldn't advise spraying outdoors as it is a sure way to end up with all sorts of foreign matter in your finish. Not to mention the humidity is out of your control. Okay for primer as you are going to attack that with wet and dry anyway.

Cheers

Danny

[Paul Williams]

Going to look into a HVLP spray gun, if any one has information please get in touch.

OK the turnigy engine has now run for 45mins I am happy with it starts great always within a couple of flicks. Time to show it its new home.

The weight in the huge spinner is concerning me, it will act like a flywheel the engine will tick over about 500rpm ! but will it prevent it from getting up to max rpm or worse still make it over rev?

I keep wondering how the hell am I going to get an exhaust in there?

Might as well finish the spinner whilst I ponder that problem. First up drill out back plate to suit prop bolts.

I have seen one or examples of spinners where the attempt to cut out the prop clearance is terrible. I figured out a way to keep things looking ok. Using a cheap profile finder B&Q or most hardware stores get the prop shape (make sure this is the largest prop in the engine range)

Transfer the profile onto a bit of sticky tape lay the prop onto the backing plate centred and mark where the leading edge will be.

Remove prop and position spinner on plate mark where both leading edges of prop should come to. Going back to your sticky tape cut out the profile and stick to the spinner. Mark around the tape with a marker pen then remove tape to reveal the scrap section needed to be cut out.

I then chain drilled using a 2.5mm drill staying 2mm on the inside of the line.

Then using a file saw cut out

File or grind back to the line and hey presto

I can live with that result. I now have to fix the spinner to the back plate and try to remember every prop fixed must have the drill holes in the same place or things will not line up.

 

 

Edited By Paul Williams on 03/11/2012 12:08:04

[Paul Williams]

cowl fitting is easy enough I will cut out more so the engine gets better cooling but fit some mesh.

I have to address the exhaust problem and it is going to be a nightmare. There is nothing I can find on the market that will fit. I could draw up some thing and have it fabricated but that is going to be expensive and if my drawings are not spot on no doubt will interfere somewhere. So make it myself is the challenge ! It would be great to finish with the exhaust gases leaving via the stacks on the fuse. I dont know much about exhaust systems other than the more you restrict the flow the more the engine suffers and straight away there is the first problem. I have only 25mm clearance from the engine port to the cowl and to leave some clearance so the paint don't blister that brings it down even more. I can only think to come straight off the port into an expansion chamber as wide as I can get it. So I cut out a foam block to use as a template.

The next problem is without a tig welder what is the best way to fabricate the shape and get it gas tight. Weight is not a problem with this model it will need lead up front so the more heavy the exhaust the better. With that in mind I ordered some copper sheet offcuts from ebay. The theory is I can cut it with tin snips and braze it with a gas blowtorch. Plus any pipe work to the stacks can be done with copper elbows cheaply. That is the plan so far please jump in if you feel I am out of the ball park with this.

[Paul Williams]

The copper arrived and I tried to braze a scrap piece thats the plan out of the window I simply can't create enough heat with a plumbers blow torch. I rang round some fabrication shops and found a place happy to weld it up for me. So I will have to swallow the cost Grrrr.

Making it up as I go along I followed the foam template shape and ended up with several pieces

The next problem was how to hold it all together so it could be welded. I figured small self tappers so starting with the baffle plates

I cut out the exhaust port and drilled the flange holes bolting them together for brazing, I bent some strip for brackets and screwed them on

Now you can see how the system will work boncing the gases of the side walls before exiting the chamber will I HOPE silence the engine enough. Because there is no restriction it should not effect engine revs. Well thats the plan.

I cocked up making the top forgetting I would lose lenth after bending so without enough materal to make another I had to make another small section to close the bottom.

the exit tube 22mm copper elbow looks just about right.

[Paul Williams]

I could not swallow the £150 estimate to weld up the exhaust so taking advice I decided to silver solder it. I got some MAPP gas which burns hotter than normal butane and fingers crossed tried that.

First joint done

I was so chuffed at being able to fabricate it I forgot to take any pics of the end result I will take some later (after its painted Ha Ha)

The best news is I took the spit out for a ground run and it not only allows full revs but sounds great not to noisy.

I also discovered it is far to easy to nose over while taxing I will have to canter the retracts forwards to avoid embarrassing landings.

We were going to test fly at this stage but even making the worlds most heavy muffler and having a spinner that weighs in at a sack of spuds its still 600 grams tail heavy. I am beginning to believe the only way to get this to balance is to put in a full size griffon engine.

Back to tea and biscuits

Brain waive the fibreglass exhaust stacks supplied are a bit delicate and I envisioned them getting hanger rash before long. So in a bid to get more weight up front lets change them for copper ones. A quick trip to the plumbers shop and bought some 45 deg elbows next unscrewed the managers door plate to get some brass plate and bingo.

Dill through holes in plate so air can still exit cowl and using lead solder this time (no heat here) join up to make stacks.

Screw to fuse with another ally plate on inside these will not damage easily.

I cant believe it still does not balance! so I removed them and filled the first stack on each side by melting lead into it with a blow lamp.

At last it sits on the balance beam correctly at 5.5 in from leading edge. Yeppee. I will pack up the retracts on one side to canter them forward and then I have run out of excuses it must fly before the paint job.

 

Edited By Paul Williams on 27/11/2012 11:32:53

[Engine Doctor]

Hello Paul . Exhaust looks good. Good idea filling with lead to balance CG . My spitfire is still slightly tail heavy even with the exhaust as I removed a lot of the solid spinner back plate to reduce any giro effect .once iits painted i'll re-check CG and adjust as paint can make a big difference to the balance .

good luck with the build and test flight.

Phil

PS I would have to fit floats to test anything in our field !

[Stephen Grigg]

Still enjoying this model and its thread.

[Paul Williams]

Sorry for not keeping up with the blog for those following, so did it fly?

[Colin Leighfield]

That is wonderful. Spitfires always look special in the air and the late Griffon engined Marks exceptionally so. Captures the full size beautifully, really well done.

[John Turner]

Hi P ail, I just came across your thread and found it interesting, I am finishing off an 88" Pica spi and plan to fit my 3w50 engine in it, my prob is same as yours with exhaust, what gauge copper did you use and looking at the pic I can't see how you tighten screws into engine exhaust port with your curved sheet of copper covering the bolts? Has the exhaust held up after time?

Thanks Paul,

John