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


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Been whittling away at the fairing trailing edge from solid block.
It will take time to get right but this will save a lot of work later as it will be nearly there before final sanding.

I won’t bother hollowing this out as I will actually need weight nearer the tail.

Hopefully I’ll have this side complete this weekend.

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Still a lot of work to do to the aft fairing but it’s enough for a rough shape and has been glued in place now.

I started the top air intake on the fuselage and have hollowed out.
This intake is attached to the rear access hatch.

The idea is that once I glass the model I will layer up glass cloth on the hatch area and replace the wooden hatch with a glass cloth hatch and the intake will form a handle to remove the hatch.

Through the hole I will place a hatch latch and to the rear I will have magnets. Hopefully this will do the trick.

Cheers

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  • 2 weeks later...

Other than retract progress this will be the last update for a while as I’m in the middle of a move.

 

So, received my spinner from Fighteraces and I’ve gotta say the quality is fantastic. Most alloy spinners get dented really easily, this is not only a great finish it’s very strong. I’m future I’ll have to make cut outs for the prop and drill the backplate to suit (Fighteraces normally drill the back plate for you but my prop washer got lost in the post).

 

Also received my retract units from Robart. These are again great quality but it’s an unknown right now as to if there up to the job weight wise.


They are built for 1/2” legs which is quite thin for the weight of plane I will have.

However, they are low profile which is what the model calls for. 

 

Lastly, I have near finished the air intake. This will be stored for a later date when the fuselage hatches are complete.

 

Quite happy now because as soon as I sort the retract legs out I’m good to start finishing the construction of this build - finally!!

Cheers all.

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  • 3 months later...

Haven’t been on here for a long while due to a house move, workshop build, garden renovation etc..

 

Anyway, I have one retract plate glued in now and it’s been a pig.

the only way a scale wheel can fit in here is if you have slight twist and turn retracts.

 

I’ve had to adapt for this and will reduce wheel thickness and diameter.

 

Retract plate was reduced in size from my original choice to reduce weight.

 

more updates to come.

 

cheers 

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3 minutes ago, Ron Gray said:

That’s a fair bit of chopping about Craig!

Yeah I know, it’s been much more difficult than usual 😂

 

Especially when there are no standard parts for the build as well.

 

No retracts on the market, no spinner, no canopy etc…. All these other little bits will add to the time of the build.

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  • 2 weeks later...

Another small update but good progress this week.
Both port and starboard wings have the tips on now, I spent a good few hours sanding the tip and leading edge.

Gotta say I love the curves on this.

Rough sand today and once the Port wing is done I’ll fine down getting ready for glassing.

Although glassing may have to wait until the intakes are done and both wings offered up to the fuselage.
For that to happen I need to finish the other fairing!

Anyhow, progressing well for now.
 

Oh, both retracts are installed as well and I sanded the wheels to fit 

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That looks as though getting the wheels to sit in the bays has been very frustrating!

 

The retract mounts are very small for such a large model. I would consider some carbon cloth in around the area to mitigate the top skin splitting on a hard landing. I have done this retrospectively on my Sea Fury and the weight penalty is minimal. 
 

As you say, lovely curves.

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1 hour ago, Nick Somerville said:

That looks as though getting the wheels to sit in the bays has been very frustrating!

 

The retract mounts are very small for such a large model. I would consider some carbon cloth in around the area to mitigate the top skin splitting on a hard landing. I have done this retrospectively on my Sea Fury and the weight penalty is minimal. 
 

As you say, lovely curves.

Thanks Nick, I have some Kevlar pulp I normally use to beef things up.

I haven’t put as much info on this thread but the layup is;

 

1/4” birch ply laminated to 1/4” lite ply.

Then half inch balsa block as a shoe.

tye leading edge has a 1/4” birch ply sheet web as well.

 

Trouble is with getting these to fit is that no one’s made a commercial set yet so I’ve had to get an engineer to help make the retracts.

 

They should rotate to fit the wheel well but it’s a mod I can’t afford on time so I reduced the wheel thickness.

 

Where do you use the carbon? On the doublers?

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That’s a shame not being able to get the retracts to twist a little, but understand that it would be an expensive thing to engineer bespoke for your model.

 

I just laid some carbon cloth down back to the spar and to the adjacent ribs around the mounts. Just used Gorilla PVA as it works well with Carbon cloth. 
 

BTW compare the length of the mounts on my FW 190. I suppose with such long stalky legs it made sense to spread the load.

 

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4 hours ago, Nick Somerville said:

That’s a shame not being able to get the retracts to twist a little, but understand that it would be an expensive thing to engineer bespoke for your model.

 

I just laid some carbon cloth down back to the spar and to the adjacent ribs around the mounts. Just used Gorilla PVA as it works well with Carbon cloth. 
 

BTW compare the length of the mounts on my FW 190. I suppose with such long stalky legs it made sense to spread the load.

 

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Thanks Nick, my original intention was to spread 3 bays (as I’ve done in my bolt) as you have but I went against in the end to reduce weight and make it simpler.

 

As you said you have long legs whilst mine are relatively short and it’s a tricycle gear plane.

 

I hope it pays off 😂

At present there rock solid but are behind the main spar which is different to what I’m used to. Only time will tell.

 

Thanks for all the info and I’ll have a look into the carbon.

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Looks like you might need to calculate a pintle angle that will allow the extended wheels to point fore and aft, and the retracted wheels to lie flush with the lower surface of the wing. Danny Fenton posted some very useful info in “Brian Taylor Hurricane Project” build topic.
 

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2 hours ago, trevor wood 2 said:

Looks like you might need to calculate a pintle angle that will allow the extended wheels to point fore and aft, and the retracted wheels to lie flush with the lower surface of the wing. Danny Fenton posted some very useful info in “Brian Taylor Hurricane Project” build topic.
 

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Thanks Trevor, I’ll be going with the set up I have now but when Sierra make a set I will adapt to suit them.

Agree with everything above 👍

cheers 

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  • 3 weeks later...

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