Jump to content

1/4 scale electric Bell P39 Airacobra build (designed by Jerry Bates)


Recommended Posts

A dry fit followed by gluing in place tonight took up quite a bit of time.
Again the tube section hasn’t been cut big enough so I will have to adapt it tomorrow. I have dremeled out the center holes and will leave the wing ribs as with the tail.

It really is a solid section when all stuck together.

I’m just gutted I won’t be getting much further for a while as I’m waiting for the retracts from the states.
I can’t progress much further until I have the nose retract.

A6788BA1-763F-4FF6-A776-5122AFA44BF5.jpeg

39632EDD-BDF0-40A1-8232-111ED5E77D82.jpeg

27C1D502-BD1C-4F25-8AD5-F9B9362F7272.jpeg

A1B78472-BB1C-47D2-9339-C9CCA38BD35A.jpeg

B588C594-CBFA-4416-A730-3D58806EFC9D.jpeg

EF8CB3FB-A19B-46B6-AD7B-ED730ADC87E7.jpeg

92186AE6-DC11-4534-B1F0-EC7F43E9F2C2.jpeg

59529DED-A0F6-432D-B51F-050293B55CF0.jpeg

05408252-56FC-494A-8483-4327A7F39527.jpeg

  • Like 3
Link to comment
Share on other sites

Slow progress tonight with a lot of pausing for considering options and planning.
All Aft formers glued in place, main wing tube sanded flat and glued in place along with ribs.

Checked alignment between main wing tube and tail tube and thankfully it’s bang on.

Cut a 6” ply spinner backplate for the motor and offered it up, I need to make up standoffs and a backplate for strengthening the firewall.

Nose retract is not due to be complete until the end of April (plus delivery time) so I’ll have to plan to clear the bench at some point to build other parts.
I may try and fit the retract after so I can keep cracking on.

Time will tell.

5213C202-919A-40CE-9990-03F86879E1A9.jpeg

A8295234-780F-4751-9B23-4BFA46697312.jpeg

EF7DE2C7-E6B8-41FE-AF43-C53FE3ACC22E.jpeg

B8F3D153-57F6-4662-9248-EACE97071AE5.jpeg

6659DC9F-B9AD-4C68-9E12-7D7E2458C7B6.jpeg

F1B84E81-0B22-4BFE-8C96-C85C821B229B.jpeg

631A042E-1111-47C7-98E8-051B61E728E6.jpeg

362239EA-D097-4363-B9CC-C8B9FC80F235.jpeg

  • Like 3
Link to comment
Share on other sites

Limited on what I can do tonight as I’m waiting on retracts and I also need to get standoffs sorted (standoffs are being done by a friend in future).

I’ve added the stringers that I can and some of them take a real tight curve and also a twist.
Glued the firewall down in place with epoxy and also the wing tubes.

I’ve also set out for the rudder but quickly come to the realisation that I can’t complete the rudder until I have the rear section of the fin complete because I need that for the profile (have to cut my own ribs for the fin).
I will be able to do the rudder post and hinges so may do that tomorrow?

I may be able to start the stab so that’s probably going to be my next job.

Cheers 

DD532453-B653-4D8C-BA0E-053192A1EE35.jpeg

EA270CBA-762C-4FBB-AFF4-1A0CB2635BED.jpeg

DFE0927D-FD91-4236-B73E-F683AAB081DE.jpeg

B7EF97B2-ED26-4B4C-9189-12177EDCB045.jpeg

1374D9C7-F0C3-45D9-8EF2-C996C62479D5.jpeg

2D8225B5-EAAB-4C77-A87F-B835CECD46E7.jpeg

7485D6BB-EAC2-4014-8966-7C272F6DAF66.jpeg

  • Like 2
Link to comment
Share on other sites

Slowing down now but still have jobs to do.
Cut nose retract rails from 1/4” ply and dry fitted them, a little fettling of the formers but otherwise all good.

Quite happy with the set up as well, it gives good support to the firewall which is otherwise seriously lacking.

Also done a sketch for the standoffs I need and hopefully these shouldn’t be too much bother for my friend to machine.

1D9FA046-3B1C-40B1-A0B9-39C0C09654AD.jpeg

A20C45AA-9B8D-4757-A8D5-FFCEBE09C12B.jpeg

BB54C937-8F57-4D11-A8BF-52D40F69F86D.jpeg

9D9FA58A-24C9-4651-A687-ED1FEAEF4767.jpeg

Link to comment
Share on other sites

17 minutes ago, Nick Cripps said:

The standoffs look to be more work than necessary. Why not cut some lengths of ally bar, drill a clearance hole through and then use 6mm studding?

Thanks Nick, I’ve had similar feedback from a friend regarding this.

So, the holes of the motor back plate are threaded but can’t take a nut.

 

Plan is to tighten the stand-off to the back plate of the motor. If I use stud alone in a threaded sleeve with thread lock there is a possibility it could work loose.

 

I have been considering drilling a hole through an ally sleeve & taping it.

Then install the 6mm thread, drill through sleeve and thread a pin it.

 

Then install bolts through fire wall to threaded stand off sleeve.

 

it’s all about ease of removal/ installation in future, the hole at the front is tiny & through the hatch at the front it’s tight.

 

Always happy for feedback & ideas though ?

Link to comment
Share on other sites

Fair enough. A decent quality studlock compound is unlikely to work loose though, so you could then drill through and tap both ends for 10mm or so which would be sufficient. You could also dispense with the flats and drill through the diameter to take a tommy bar which would be much easier to produce.

 

By the way, I'm impressed with the build and rate of progress so far, should look great in the air.

Link to comment
Share on other sites

12 minutes ago, Nick Cripps said:

Fair enough. A decent quality studlock compound is unlikely to work loose though, so you could then drill through and tap both ends for 10mm or so which would be sufficient. You could also dispense with the flats and drill through the diameter to take a tommy bar which would be much easier to produce.

 

By the way, I'm impressed with the build and rate of progress so far, should look great in the air.

Thanks very much, really appreciate it.

Hopefully I’ll get the bits I need soon & I can start cracking on again.

 

I considered drilling a hole for a Tommy bar as well but wouldn’t have the room, it’s really tight.

Your right about the flats, they’ll be no requirement for them when the design changes again.

Link to comment
Share on other sites

1 hour ago, Graham Davies 3 said:

I think they're a standard size stand off Nick. Try Essentra or TR Fasteners, they have most things

 

Graham

There a standard size but not what I need, sleeved stand offs are no good for the application.

 

Once I get sorted I’ll post pics and you’ll get what I’m on about.

 

I was going to do a frame but it would be inaccessible, it’s a very tight nose area and that’s why I never went IC.

Link to comment
Share on other sites

Due to work commitments I haven’t been able to get on this lately.

Tonight I’ve cut a ply backing plate for the motor, the aim of this is to aid alignment when mounting after I’ve finished the nose and sanded it.
The fire wall holes have been drilled out to 10mm allowing for adjustment when installing. The backing plate will have epoxy smeared on it and when aligned will set in place giving a solid mounting and accurate.

As you can see there is no room in the nose, I can barely get my fist in there meaning I have to allow for plenty of movement. Hence the reason I’m going with the stand off set up I’ve chosen (pictures of that will be up soon).

I’ve also went ahead and glued the nose retract rails in place. The retracts won’t be coming until end of April/ start of May so I won’t be able to sheet it until I’ve installed the retract.

I also have to work out where I’ll be installing the servos for the doors and how I can do it so I can remove if needed for maintenance.

Lastly I installed a pull through tube for servo wires. Not something I normally bother with but this plane really is tight for access in all areas.

I’ll have to have it all strung up with pull throughs for the entire build which is going to be difficult due to the finishes it requires.

Anyway, onwards and upwards, hope fully I get the items sooner rather than later so I’m not delayed too much.

7527F668-130E-4EC4-8556-54278959039B.jpeg

F8D5CEDF-3EAD-4E49-AEF7-7E6A4D3C1D99.jpeg

E590366F-AD6E-46F3-B3B5-8492A5E77605.jpeg

0BE91FE2-ACD1-46FC-84AD-CAA7262F2B10.jpeg

40DE389D-9521-4B08-883E-967AB01C6A0B.jpeg

1EAC1FC4-A46F-4C27-846F-0BE50B6C4189.jpeg

F509C9FD-5F2B-46BB-A0DA-5239B8E8F437.jpeg

6A3E153F-0E12-460B-9B78-663A113DA5B6.jpeg

  • Like 3
Link to comment
Share on other sites

Running out of options I decided to crack on with the rudder.
Good job as well because I needed to do quite a bit to get the deflection I want.

I think this may be a bit of a pig to do and I’ll find out over the weekend.

What’s quite strange tonight is that I took a sheet of 1/4” and 1/2” in the garage straight and when I left they were both warped! Along with the rudder!

The recent cold snap must have a lot of moisture in the air.

Also slightly worrying ? as I have a long time to wait for parts but I’m sure I can sort any issues that arise.

7CC09AE8-F401-4FBC-A41A-0E32343B31AA.jpeg

0778BFB3-9BAC-4CE9-938B-6A4B9BE03602.jpeg

66EF23A8-4E4D-4C2C-9546-B4388928D8E6.jpeg

E58EB781-18F8-4F1D-81A0-F63B8CE90A3E.jpeg

EF766CCB-3F4F-4684-9753-AA708BD22A82.jpeg

84A4A2B5-EE2E-4291-8C10-444E1D3D6A66.jpeg

C1145CA9-A238-400E-82D7-D036D8E345EC.jpeg

BDB1B54E-1708-49F9-B3CF-613D2839E5A7.jpeg

32769D75-497E-495C-9C75-24DAB0C3F509.jpeg

DA6AE927-D986-4344-ACDE-A0C41AD9F473.jpeg

A92DED1A-7BDA-4990-95E9-42B73F109013.jpeg

  • Like 2
Link to comment
Share on other sites

Yesterday and today I’ve been working on the rudder and it’s surprisingly a lot of work! (Far from done).

It’s got a lot of movement which is what I’ve strived for.

I’ve also sheeted part of the tail. Due to the build up of the wing center section I’m able to sheet some areas whilst waiting for parts. This area in particular will be a challenging bit for fairings and openings in the front of the wing.

I’ve also pulled some string through for servos and lights.

 

Ive also added a scale Jack point which will be used for a transport/ assembly frame later.

 

Exhaust dry fitted for a visual.

566A9BE2-E99A-4FC7-B690-89ACD5AE5EF5.jpeg

DC6285BD-0EB9-4425-BB86-FE5601995F7C.jpeg

DC81C0D6-991C-410C-B9A2-98D92B1BCC61.jpeg

DEF25542-3421-4FA3-84FF-FB0E268DD7E8.jpeg

E8647ABE-AC99-428F-9A28-9FE1A9DCE2BC.jpeg

2A83D0F7-1A45-4433-BA94-EAE4B8D6F7A0.jpeg

570A9913-3FE9-4704-9890-F0C1DA41259B.jpeg

88A5AA6B-5203-4165-B196-EEB2378FA787.jpeg

11BF36C8-2C3A-4721-8D49-DEAA743E5105.jpeg

  • Like 1
Link to comment
Share on other sites

Only a little bit of work tonight, dry fitted the ruder closed loop arm and cut out slots for the clevises.

Dry fitted to fuz again and sanded more. Cut and added ribs to stop warping.

This will now be put to one side for a while as I have another area I can sheet whilst waiting for the retract.

CA8E0336-F193-4D86-89CD-40DD68223703.jpeg

316B6AA9-6D18-42A3-89E9-6E70005754D0.jpeg

3E302E98-EA8F-4D75-A7C0-F414ECBC3E0D.jpeg

44C1AA15-235A-4643-AC80-39A3A5268C73.jpeg

EC9D5ECF-B31B-4EBF-97C0-098733A56DFC.jpeg

F91F4BEF-6D3C-4CA6-8BB4-66A4AE30E19D.jpeg

  • Like 2
Link to comment
Share on other sites

Substantial build and great to follow along  Craig. Can you elaborate on materials used for the rudder hinges please. From what I can see you have cut the hinges from carbon plate of some sort and then used a removable carbon rod to run through as a pivot. If the rudder is intended to be removed for transport how is the pivot rod held in place.

  • Like 1
Link to comment
Share on other sites

1 hour ago, Nick Somerville said:

Substantial build and great to follow along  Craig. Can you elaborate on materials used for the rudder hinges please. From what I can see you have cut the hinges from carbon plate of some sort and then used a removable carbon rod to run through as a pivot. If the rudder is intended to be removed for transport how is the pivot rod held in place.

Hi Nick and thanks ?

The rudder hinges are a type of plastic which a bought from America

CB associates I believe and were detailed on the plan.

 

The pin is 3mm carbon rod and will be fixed in place at the bottom with epoxy.

It’s only removed if I need to repair it so would be a case of just drilling out the lower hinge 5mm or so.

 

I still haven’t decided covering material yet but the top of the rudder and bottom will be carved from foam to keep the weight down.

 

The balsa post is quite heavy and it’s a ply former. I will seal the foam with epoxy to make it tougher.

  • Like 1
Link to comment
Share on other sites

It’s official, this is the last bit of the fuselage I can sheet until the retract turns up ?

However, I’m really enjoying this. Some of the curves are a nightmare to get right but I’m sure that these curves will look great once done and sanded in.
The back end of the wing was very tough.

I’ve got a few more small jobs on this before I have to pull my finger out and change the workshop around so I can start on the stab at some point.

122D1CC2-4259-4E0A-94ED-161C08DCCD74.jpeg

91071423-6AAC-425A-A2A7-399AD3FEAB2C.jpeg

19057D43-FB13-4F65-B4F6-63FEE3FA209D.jpeg

F1FF2ADF-B12A-4B8D-B230-F22F64B3CD92.jpeg

2DDD1068-F31A-47D1-B28C-F79D2686D588.jpeg

  • Like 5
Link to comment
Share on other sites

Small update but a lot happening.
Haven’t done much this weekend as I decided to take one of the warbirds out flying (a bit rusty as well but all good).

Moved the fuz so I could start on the stabiliser, again this will be another half finished job ??
I have to wait till the fuz is done before finishing the stab! Anyway.

Had to open up the ribs where the tube passes through and a bit of fiddling about getting the angles right for the tube but it’s all good.

Just need to get some spruce and I can start the other side.
Putting out an order tonight I think.

3294B472-B618-474E-906F-0C9683BD6F10.jpeg

0C27EEE4-2604-465F-8634-28B7DD3454FF.jpeg

D9FC9C39-6506-4883-928E-D36BBB1642B2.jpeg

Edited by Craig Spence
Forgot photos
  • Like 4
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...