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1/18 Curtiss P40C


airscale

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Just joined for a ride along.  P-40 is a favorite of mine.  Jumpei's drawings are very good and I'm glad you have them.

Seems like he may have missed the shape of the intake diverter as he perhaps used a drawing reference that had an older prototype shape there.  Who knows but glad you caught it early!!!

 

Nice job so far.  That intake exit trunking is nicknamed the "nun's hat" for obvious reasons!

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7 hours ago, airscale said:

Hi all, thanks for your kind comments :)

 

not back at work yet after a long Xmas break so got some good benchtime in

 

Wanted to get the rear of the chin intake sorted - a few things to note..

 

see the big natural metal duct that takes the air out of the upper two radiators to the exit

 

2XDL7k.jpg

 

..and the rads themselves are mounted in a bulkhead behind the lower ring former that holds the cowl flaps.. you can also see the ducting here with holes in for the cowl flap control rods..

 

1tOsed.jpg

 

..I started by nicking one of Mrs airscales mascaras as it was the right diameter to give me good forms to start making a mould to form the duct over - she put up a small fight, but with a promise to buy her a better one, it was soon cut to bits..

 

I made up a plastic card 'bath', put the sectioned mascara tubes in it and filled it with P38 filler - that gave me a good basis to make the mould which I later pulled a vacform over..

 

8UKdKC.jpg

 

..as the real one is natural metal, I needed to skin this part, so while it was still on the mould I started working some annealed litho..

 

..the main tools of the trade here are a tiny ball pein hammer and a coffee stick..

 

Eo0FcO.jpg

 

..after working it, sanding it and wire wooling it, the part was getting near to being finished..

 

xcmvwJ.jpg

 

..the three components - it took me way longer to make the mould bits than the part itself..

 

9GrQoe.jpg

 

..added the holes and rivets that hold this panel..

 

NVtZUp.jpg

 

 

..to actually integrate it into the airframe I had to section the keel and remove a section so I could fettle it and get it in position..

 

..also started on the bulkhead..

 

8JxeF4.jpg

 

..added a black plastic card backing to the bulkhead and cemented it all in place.. the radiators themselves and some of the fittings are in the monster PE set I have coming from PPD next week

 

Do76pt.jpg

 

 

6xYIwl.jpg

 

..it was quite a job to get all this to line up - especially the angles and sit of where the duct meets the rads..

 

PZMxDK.jpg

 

..next up, I am going to try filling the fuselage with this sculpting foam and then a skin of P38 before skinning the airframe in metal..

 

F3Cg6j.jpg

 

LneKAu.jpg

 

..should be interesting - hope it works out :)

 

TTFN

Peter

 

 

Great project , and as always first rate work !!! I think that you will like using the high density urethane foam, it so much better than balsa due to it not having grain, it sands great, I'm not sure what density you are going to purchase, I always like the 20 lb foam you can make patterns with it and vacuum form over it with great results. It crazy glues really good, you need to use thicker ca when you glue it because it tends to soak into the foam more so if the foam is lighter density. Looking foward to your progress, good luck with it !!!

Pat

 

Edited by patricksparks
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afternoon all :)

 

On 1/5/2022 at 7:45 PM, Antonio Argudo said:

very interesting material, expecting to see if indeed does the trick, cheers

 

 

Thanks Antonio - well this installment should have the answers :)

 

 

On 1/5/2022 at 9:10 PM, KUROK said:

Just joined for a ride along.  P-40 is a favorite of mine.  Jumpei's drawings are very good and I'm glad you have them.

Seems like he may have missed the shape of the intake diverter as he perhaps used a drawing reference that had an older prototype shape there.  Who knows but glad you caught it early!!!

 

Nice job so far.  That intake exit trunking is nicknamed the "nun's hat" for obvious reasons!

 

 

Thanks Kurok and yes, I am so glad I spotted it, and even more glad it was early enough to rip it out and start again. I trust Jumpei's drawings implicitly and have always used them, but no matter how God like the artist, I must learn to check with photo's!

 

 

On 1/5/2022 at 9:42 PM, patricksparks said:

Great project , and as always first rate work !!! I think that you will like using the high density urethane foam, it so much better than balsa due to it not having grain, it sands great, I'm not sure what density you are going to purchase, I always like the 20 lb foam you can make patterns with it and vacuum form over it with great results. It crazy glues really good, you need to use thicker ca when you glue it because it tends to soak into the foam more so if the foam is lighter density. Looking foward to your progress, good luck with it !!!

Pat

 

 

Indeed Pat - thanks for the tips - I would never have thought of vacforming onto it, so thats a real bonus

 

In fact, that is where I started trying out this new material - there is a keel assembly that is underneath the P40 made of 3 or 4 sections, so I got the drawings and scaled a floor and three cross sections. From here I filled the blanks with foam and sanded it down.

 

I found a saw works best for main cuts, then a rasp for major shaping and then a sanding stick for finessing. One thing is it makes a lot of gritty dust which gets everywhere - it is hard stuff a bit like the stuff flower arrangers use

 

GqsYIs.jpg

 

I used quite thick card in my dental vacformer to pull a couple of copies of keel parts - found they make for a great way to knock up moulds for these sorts of parts which previously I would have spent longer using P38 filler. It sands really easily and stuff like this can be made in minutes..

 

fJIGTp.jpg

 

..In thinking about using it on the airframe itself - I wanted to be happy I could skin metal onto it so made up a test piece of foam with compound curves

 

..the first try just using it raw failed - the contact adhesive largely absorbed into the foam and the surface area of all the structure between what are essentially foam bubbles is not enough to get any adhesion

 

I tried a skin of P38 filler & primer like I would anyway and this fixed the adhesion - but care is needed in forming the sheets as its quite easy to scar the foam even with hard wood coffee stirrers

 

when i riveted the skin once its in place (which has to be done for compound curved areas), the distortion of the metal is more pronounced and there is a danger of going straight through it and puncturing the skin

 

a tried a wash with thin CA and that helped a little with rigidity so I am sure with a combo of filler and CA I can make it work..

 

with the test done it was time to start doing the airframe.. the pro's in being able to get a 'body' in a couple of hours vs being careful with skinning is too strong - as opposed to days of trying to plank or fill all the areas with balsa & P38..

 

hBWbhj.jpg

 

..soon the airframe was done and the basic shaping complete - I will probably vacform the chin area and the area under the spinner will be P38 as there is a lot of scalloping and compound curves..

 

Gyt3Ql.jpg

 

h406vq.jpg

 

EMpXRE.jpg

 

dTcX4E.jpg

 

..the keel parts sit here..

 

5dY2Xe.jpg

 

Kgze8T.jpg

 

WJAObH.jpg

 

..so now I need to give it a skim of P38 and do A LOT of refinement before its in a fit state to be skinned in metal later..

 

TTFN

Peter

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41 minutes ago, Hans said:

hi, Peter, perhaps you can use very thin expoxy to harden the foam? I know boatbuilders use this method to get a hull quite quickly as opposed to the classic methods of hull construction.  

 

 

Hans  


Hans,

 I was just about to suggest something along those lines. Epoxy does work well as a hardening agent for foam surfaces. So does polyurethane varnish. It’s a bit easier to sand than epoxy and soaks deeper into the foam. I recall that the great Peter Cooke used polyester resin to harden the balsa cores of his models, but I wouldn’t use it on foams without testing, to make sure that it won’t melt down the surfaces and/or kill everyone with toxic fumes.
 

Cheers,

Adam

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1 hour ago, Hans said:

hi, Peter, perhaps you can use very thin expoxy to harden the foam? I know boatbuilders use this method to get a hull quite quickly as opposed to the classic methods of hull construction.  

 

 

Hans  

 

11 minutes ago, adameliclem said:


Hans,

 I was just about to suggest something along those lines. Epoxy does work well as a hardening agent for foam surfaces. So does polyurethane varnish. It’s a bit easier to sand than epoxy and soaks deeper into the foam. I recall that the great Peter Cooke used polyester resin to harden the balsa cores of his models, but I wouldn’t use it on foams without testing, to make sure that it won’t melt down the surfaces and/or kill everyone with toxic fumes.
 

Cheers,

Adam

 

 

Fascinating - what brilliant suggestions!

 

On looking a bit further at this, I found a boat builder that made a hull, put it in his wifes old tights (twice) and used resin..

 

B6rpgf.jpg

 

Seems a really simple solution so in the spirit of trying new things that is what I am going to experiment with :)

 

Thanks again - super helpful

 

Ptere

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Hi Peter,

 

Happy to help. The  Z-proxy looks promising. If you test it to see how it interacts with the foam, I suggest you also test it on the plastic you used for the formers, or laminate a bit of scrap foam and plastic to see how they behave together. I don’t think there’s much chance of another Great Banana Fuselage Crisis, but I remember it well.

 

As always, you’re doing terrific work.

 

Cheers,

Adam

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4 hours ago, airscale said:

afternoon all :)

 

 

 

Thanks Antonio - well this installment should have the answers :)

 

 

 

 

Thanks Kurok and yes, I am so glad I spotted it, and even more glad it was early enough to rip it out and start again. I trust Jumpei's drawings implicitly and have always used them, but no matter how God like the artist, I must learn to check with photo's!

 

 

 

Indeed Pat - thanks for the tips - I would never have thought of vacforming onto it, so thats a real bonus

 

In fact, that is where I started trying out this new material - there is a keel assembly that is underneath the P40 made of 3 or 4 sections, so I got the drawings and scaled a floor and three cross sections. From here I filled the blanks with foam and sanded it down.

 

I found a saw works best for main cuts, then a rasp for major shaping and then a sanding stick for finessing. One thing is it makes a lot of gritty dust which gets everywhere - it is hard stuff a bit like the stuff flower arrangers use

 

GqsYIs.jpg

 

I used quite thick card in my dental vacformer to pull a couple of copies of keel parts - found they make for a great way to knock up moulds for these sorts of parts which previously I would have spent longer using P38 filler. It sands really easily and stuff like this can be made in minutes..

 

fJIGTp.jpg

 

..In thinking about using it on the airframe itself - I wanted to be happy I could skin metal onto it so made up a test piece of foam with compound curves

 

..the first try just using it raw failed - the contact adhesive largely absorbed into the foam and the surface area of all the structure between what are essentially foam bubbles is not enough to get any adhesion

 

I tried a skin of P38 filler & primer like I would anyway and this fixed the adhesion - but care is needed in forming the sheets as its quite easy to scar the foam even with hard wood coffee stirrers

 

when i riveted the skin once its in place (which has to be done for compound curved areas), the distortion of the metal is more pronounced and there is a danger of going straight through it and puncturing the skin

 

a tried a wash with thin CA and that helped a little with rigidity so I am sure with a combo of filler and CA I can make it work..

 

with the test done it was time to start doing the airframe.. the pro's in being able to get a 'body' in a couple of hours vs being careful with skinning is too strong - as opposed to days of trying to plank or fill all the areas with balsa & P38..

 

hBWbhj.jpg

 

..soon the airframe was done and the basic shaping complete - I will probably vacform the chin area and the area under the spinner will be P38 as there is a lot of scalloping and compound curves..

 

Gyt3Ql.jpg

 

h406vq.jpg

 

EMpXRE.jpg

 

dTcX4E.jpg

 

..the keel parts sit here..

 

5dY2Xe.jpg

 

Kgze8T.jpg

 

WJAObH.jpg

 

..so now I need to give it a skim of P38 and do A LOT of refinement before its in a fit state to be skinned in metal later..

 

TTFN

Peter

Awesome progress !!! looks like the foam worked well so far. It looks like your foam is a lighter density than I've been using, the foam that you are using is much easier to sand though than the 20lb stuff, it requres some serious elbow grease, I use a small drum sander on my fordom flexible grinder and rasps to knock down large areas and get shapes close and then finess with 60-80 grit sanding blocks and files then go down to the finishing grits. The 20lb density is much more solid and stable for making patterns that can be vac-formed over, just an fyi if you want to use foam for forming it's definately a good alternative to hardwood and acrylic patterns, I have pulled pretty heavy thickness(.080-.125) shots over the heavy foam. I have also made some canopies over it, I made the pattern slightly under sized and pulled petg over it, left that shot on the pattern and pulled another petg shot over it with the polyethelene film left on the side that goes down onto the pattern.

Always a great treat to watch your projects, thank you !!!

Pat

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