Topic: Hawker P1121 EDF Build

I have been following this build with great interest. I can't believe what I've been seeing! It looks fantastic, the mind boggles how you've done it as well. I can't wait to see her fly. You are going to video the maiden right?

patiently waiting.

Cheers

I have been following this build with great interest. I can't believe what I've been seeing! It looks fantastic, the mind boggles how you've done it as well. I can't wait to see her fly. You are going to video the maiden right?

patiently waiting.

Cheers

Thanks.  We will get video and photos, but I have a reputation for taking ages in getting around to trying a first flight, so hope you are every patient! 

This morning I filled the dinks and rubbed down the high spots to get a smooth following fuselage.   I attacked the rear section of fuselage tunnel with a razor plane and Dremel and inserted a bit of 1/16” sheet to force the air down over the ESC through the enlarged vent.  It weighed 48g when CNC cut from 19mm sheet, but after shaping, hollowing and glassing it now weighs 16g.  Sealed surfaces with 50:50 thinned dope and rubbed back again with 600 wet & dry then started glassing.  I like Z-poxy finishing epoxy as it starts to go off in about 30 minutes, is hard enough to handle in about 3 hours and is easy to sand (for the first 3 days), although I also sometimes use Fibretech resin for a flow coat when I need more working time.  Just finished glassing the bottom of the fuselage, hope to be able to get the flow coat on and rubbed down on Tuesday (day off  ). 

Well like all of my plans other things got in the way (work, family and 4 AGMs!) and I'm only getting the flow coat on today.  Have got the heating on and hoping that the first application will go off by this evening so I can do the other sides done - club meeting Tuesday and I would like to take it along to scare the gliderists
Pete

PS
Understand some potentially suitable 60C packs will become available in a month or two.  As I'm happy to trade endurance for weight a 3300 6S might provide the solution.

Hi Pete,
That is good progress. I have yet to buy any flight packs for mine: the prospect of higher voltage under load is certainly worth waiting for.
Paul W.

Hi Paul
How is yours going?  Any photos?
Pretty boring picture, but the first lot of epoxy went on at lunchtime.  The label says 24-36 hours to cure, so no way will I be able to finish it off tonight    Luckily I finish early tomorrow so should still be able to take it along on Tuesday evening.
When I do the flow coat I usually add some Fibretech epoxy colour to help see where I have been and where it is too thick - I used grey today.

Pete

I like the look of whats in the top left corner of the pic Pete 

Tiggs

How is yours going?  Any photos?

Hi Pete,
I too have been at the ding/seam removal and surface preparation stage for a while. I'm applying sanding sealer at the moment to all the various parts, prior to them getting a misting of grey primer, when all sins will be revealed!
The time-consuming bits have been the hatches & wing-root fairings - especially as someone  managed in-design to ignore the L/E root-shape implications of the wing-sweep...  All fixed now, electronically and actually.  Lots of work and v. little to show for it basically!
Given the weather, I've not taken it out into natural light, so no assembled piccies since the last. I did take it up to last months club meeting. We have some jet-jockies on strength, both model and full-size, so it got some interest.  "What, they cancelled that..?!
You bet...
Paul W.

I like the look of whats in the top left corner of the pic Pete  

Tiggs

Just a chuckie to check C of G, just in case I find myself with some time available next year after the big bomber

Just a chuckie to check C of G, just in case I find myself with some time available next year after the big bomber

I know what you mean 



Sorry about the size, maybe the mods could reduce it ?

Hi Pete,
I too have been at the ding/seam removal and surface preparation stage for a while. I'm applying sanding sealer at the moment to all the various parts, prior to them getting a misting of grey primer, when all sins will be revealed!
The time-consuming bits have been the hatches & wing-root fairings - especially as someone   managed in-design to ignore the L/E root-shape implications of the wing-sweep...  All fixed now, electronically and actually.  Lots of work and v. little to show for it basically!
Given the weather, I've not taken it out into natural light, so no assembled piccies since the last. I did take it up to last months club meeting. We have some jet-jockies on strength, both model and full-size, so it got some interest.  "What, they cancelled that..?!
You bet...
Paul W.

Am going to try a different way of making the hatch this time which will not require so much faffing - learnt from the M52  
Given the power figures it was suggested to me that I build a thinner wings and go for a speed machine, but that would also require changing the fuselage formers that carry the stub spars, so fortunately it is a non-starter  

I know what you mean 

I like to have a few projects on the burners too    There are V-1 and FD2 EDFs lurking somewhere on the memory stick, plus a Harrier  prop-jet fun fighter.

Applied the flow coat earlier in the week and have been making slow progress sanding flat this evening.  Should have something to show on Sunday

Finished sanding flat the flow coat today and then cut the battery hatch free.  I beefed up the hatch with additional formers and made good the edges with car body filler and strips of 1/64” ply.  When the spine goes on I will add a peg and catch to secure it.  Because I could get at the ESC, etc again I couldn’t resist a quick test.  On a 3S pack I got approx 580g thrust, but nothing was held properly and the scales were on the carpet, so I think it was actually more than that.  I’ll do a better test tomorrow and post the results. All the parts have been primed and rubbed back, paint left to harden off tonight.
As I am not going to open up the fan bay I glued on some 3mm 1/64” ply strips to mark where to cut if I need to get in there.

I applied another layer of glass cloth to the hatch before bed and sanded/primed this morning.  Glued the spine on with 5 minute epoxy.  Spine cut with a razor saw, thin cyano run into the end grain and sanded smooth. Latch was from Robotbirds (I think) epoxied into a suitably sized slot cut/dremeled.  Made good with scrap balsa, filler and a smear of medium cyano.

Ailerons hinged and glued to the wings, horns added and 3M control rods made up. 
The fin was epoxied in place with some 3mm diameter bamboo dowels for added security. 
The tunnel/spine combo was also glued in place with 5 minute epoxy.
I have started to add a little cockpit detail, will paint and add a seat + pilot tomorrow.

Dizz, that's looking good. 

Dizz, that's looking good. 

Thanks Stuey, should be baaaa-listic when I get around to flying it (I hope!)
Merry Christmas
Pete

I would love to know if you ever flew that Miles M52. Any way this is looking fabulous, amazing attention to detail being employed to get this just so. I really admire that quality, hope it doesn't mean the weight is ramping up.

Have only been able to add a little weight cockpit detail today.

TSR
Hopefully not too much weight though because that is just a Pete's Pilots latex head and a few scraps of balsa.
Afraid to say that the M52 hasn't flown - hence my 2 year comment earlier 
pete

I added an extra canopy frame and made a new one the other evening from thicker plastic - now fitted using a mix of odourless cyano and canopy glue.  Aileron linkages hidden with some recovered plastic pen packaging.
Couldn’t resist another dry fit.  I glued on the port wing earlier this evening with slow setting epoxy and have left it overnight to cure.  Starboard wing will go on in the morning before my tribe visit.

Jigged the fuselage and glued on the starboard wing this morning.  After lunch I tacked the tail planes in place and (with approx 3 degrees of up trim at neutral) made and fitted some fairings from ¼” balsa, also added a couple of fillets to the wing trailing edge/fuselage join made from 1/8” balsa.  All the seams have been filled with light weight model filler and will be sealed with sanding sealer later.

Had a brilliant present yesterday – Project Cancelled by Derek Wood (Jane’s 1986) and it has several pages of P1121 info in the Hawker Supersonics chapter.  I like the description of the FD2 development fighter and that has now replaced the FD2 on the "to do" list.  

This morning have applied a light dusting of grey primer where required and given the whole structure a final wipe-over with fine wire wool.  Keyed the 3mm tail plane rods with a dremel cut-off disc and glued on the control surfaces.  Weight was1342g at that stage, then I shortened all the servo wires and it now comes in at 1334g – obviously paint, decals and lacquer will add more weight yet, but still roughly in keeping with my initial estimates.  Will get some photos alongside some of my other EDFs for comparison later this afternoon.

Anyway, that is all the construction work complete.  

I have 2 fun fighters to prep for finishing today and am out tomorrow (including a Cosford visit if the weather is ok), so the plan is to paint all 3 aircraft on Tuesday in one big airbrushing session.

Merry Christmas Pete!
You are making good progress - we'll be seeing the final scheme in a few days? Your book collection is beginning to sound like mine by the way..!
Paul W.

Merry Christmas to you too Paul.
Yep, that is the intention to at least start the painting on Tuesday although things today have slipped due to Christmassy things - not that I'm complaining, nice to see people and catch up.

Had to drive up to Stockport today so took a detour and called in at Cosford.  Imagine my surprise when I sat down for a coffee to see this etched in the window glass!

Might not be able to complete the airbrushing tomorrow - will need more paint and I'm not sure I'll be able to get to the (plastic kits) model shop in Paignton.  However, found a scheme to use on the Sabre hanging in the Cold War exhibition.

The 2 days I had available this week for airbrushing were very foggy, far too damp for spraying in my opinion so I made the decals.  That took a long time in the end because I had to make sets for 2 funfighters and 3 x Me163s as well as the 1121.  This morning I had to get the car fixed and when I got home my painting desire had gone, so went for a static thrust check instead.  Nothing sophisticated, just had the plane mounted nose down in a large block of EPP sat on the scales.  All packs had been fully charged last week, I waited about 30 seconds before taking the thrust reading and only bothered to check current on the 6S pack.  (figures in brackets are from the tests I did earlier on the test stand)

4S 4000mAh     740g (926g)
6S 4800mAh     1470g (1734g)  1480W (1374W)

As expected really, the long sharp lipped intake duct is limiting air flow, but I think once the model is moving it will become more efficient.  I wanted to check exhaust velocity on the 6S pack, so throttled up again and then got a loud “pop”.  Thoughts of another Gyron-esque engine failure, but it was only the intake duct splitting at the seam on the first bend.  Fortunately no FOD damage this time.  The plastic vac-forming was pretty thin in that area and I had tried to beef it up a little during the build, but obviously not enough.  I cut away the damaged plastic and have repaired the hole with several layers of glass cloth and tape with an extra patch on the inside.  The epoxy is still curing, but it is already much stiffer/stronger than before.  I’ll have another test whilst keeping an eye on it before I re-instate the battery bay floor and carry on with the painting.  I suppose the other thing I could do is open up a couple of slots on the glass fibre to help relieve the low pressure at the bend.
Now if I could only find some batteries that could give 70Amps and only weigh 135g I would be laughing!

Pete you can now get 65C and 90C burst Lipos from XPS, and Thunder Power are due to release some of these soon which should work out at about the weight for the amperage you crave but capacity will be pretty low.

Pete you can now get 65C and 90C burst Lipos from XPS, and Thunder Power are due to release some of these soon which should work out at about the weight for the amperage you crave but capacity will be pretty low.

Yes I know higher C rating packs are becoming available thanks - do you know who stocks the XPS packs so I can take a look?  Overlander already have a 60C 3200 3S pack which is quoted at 295g.  A mate has 2 on order for his lecky Komet so I'm waiting for them to arrive to check the real weight.  I knocked up another spread sheet (attached) to help me decide what packs to get.  Endurance not necessarily a factor for me though  - my 120mph EF16 should only manage 3 minutes WOT, but timer is set for 4 1/2 minutes flying time because (unusual for me) I use the throttle and tbh, after 4 minutes my legs are like jelly anyway and I'm in need of a lie-down 
I have fallen into the more power means more weight that needs more power vortex! Would have all been a bit easier if I hadn't trashed the original fan.
Weather good for spraying, so that is my day sorted.


Happy New Year!

Found some at Electricwingman, but "only" up to 45C.
Updated the spreadsheet.  Figures in blue are esimates

This is getting to be a habit!
Yesterday’s duct repair has set rock hard, very happy with the repair so time for a test. 
I gingerly opened the throttle and all well at the front so I measured the efflux velocity and ran at full power for 10-15 seconds – all still fine.  However, on closing the throttle there was a quiet” pop indicating that the duct was collapsing somewhere else.  The area immediately ahead of the fan where I had drilled the holes to induce cooling air over the ESC had failed.  Have cut 2 access holes and carried out the same repair with glass tape and epoxy.  Maybe 5S would be the best route.
That is curing at the moment and when set will get another larger patch of glass cloth extending forwards towards the next former.  If the next test is good I’ll replace the fuselage skin and make good.  Am really rather keen to get this squared away now so I can finish the painting back-log.
The next EDF I build will have the intake duct vac-formings glassed from the start. 

XPS specifications can be found here along with an online store. they are a bit heavier than normal cells and I have never used them, but would be interested in finding out if they are as good as XPS think they are.

Can't see the XPS link - I'll try Google again - I only did XP this afternoon.


Anyway, intake duct repaired and checked out under full power.  Battery tray re-fitted.  Fuselage fixed.  Canopy masked.
Final touch of grey primer on the fuselage patches required before bed and then I am back a square one ready to paint.

http://www.xtremepowersystems.net/products.php?cat=16
Oops forgot the control v.

I have used Humbrol matt enamels again (light aircraft grey, dark green, dark sea grey), thinned with proper thinners and applied with an air brush.  Later this evening I will mask and paint the radome and ECM fairing on the top of the fin.

Hi Pete,
I shall be pleased to get to the paint application stage - yours is looking very business-like indeed. Sorry to read about your ducting/intake issues.  I've just had to carry out my first sheeting repair due to a serious piece of hangar-rash - all better now - oh well..!
Paul W.

Hi Pete,
I shall be pleased to get to the paint application stage - yours is looking very business-like indeed. Sorry to read about your ducting/intake issues.  I've just had to carry out my first sheeting repair due to a serious piece of hangar-rash - all better now - oh well..!
Paul W.

Don't forget some photos when you have painted yours Paul.  From reading other forums I was aware of the potential for the duct to collapse on higher power set-ups and thought I had allowed for it - but not so!
Adding the glass to the outside has made a massive difference and I'll bear that in mind for the future.
 

XPS specifications can be found here along with an online store. they are a bit heavier than normal cells and I have never used them, but would be interested in finding out if they are as good as XPS think they are.

The XPS cells have good press on RCG.  I need to make some thrust/current estimates and plug the weights into my spreadsheet.  Hopefully my mate will get his 65C 3200 3S packs soon and I will be able to borrow them for a quick test.

Black bits painted, just the jet pipe to do in the morning.  The flash is doing something strange to the grey sprayed edge – the bright line isn’t visible to the eye.

Decals on and jet pipe painted.
Was on a roll but the panel lines will have to wait until the morning.

Am increasingly worried about the amount of play in the tailplanes cause by my use of a snake for control.  So, before it gets a coat of Klasskote to seal the surface and decal edges, I have decided to open up a hatch above the tailplane horn and brace the end of the snake more firmly.
Hopefully that will do the job because changing the snake to a push rod would be a major pain.
Still not sure what batteries to go with.
More later.

No progress this week - when I have been at home I have had to spend time on the 2 funfighters.
However, whilst at work I had a flash of inspiration.  Vulcan design has been parked for the time being and I have made a start on something else.   
Keeping this one lower powered and a little smaller than the 1121.  More when I start building.