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Macchi M.39 Speedbird: radiators


DMC

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Top left strut: thinking that I needed something a little stiffer for the struts than just a strip of styrene, I flattened a length of aluminium tube with a bit of wire in I.  This left an indentation down the length that needed filling, which I did with Milliput (that stuff sticks to anything) and filed it down a little to an airfoil shape.  This would work but is a bit of a faff shaping it to an airfoil and adjusting the length, which I would probably need to do, would be too difficult.  Top middle strut: staying with the tubing. I added a second bit of wire which almost eliminated the indentation and made  shaping it to an airfoil a little easier.   Top right strut:  this one is .010 styrene folded between two lengths of balsa and heated with a hair dryer to get a sharp crease. A length of wire was placed in the crease with a thread of Milliput and the trailing edge was clamped with a bulldog clamp and left to cure overnight.  Trimmed and cemented next day this method produces a pretty good airfoil shape and will only need a little thinning of the trailing edge and a minimum of sanding.  I went with this one and I've made four and two for the cross struts.

 

To attach the strut firmly to the float required something more than just the wire.  On the 1:1 there looks to be a fairing where the strut meets the float.  I did a quick balsa mould in a downsized version of the wing fairing/fillet mould and plunged a .015 square of styrene into a fairing shape for a trail run.  Looks okay for the first test but as the struts are at angles and the front ones slanted back I will need to work make moulds for each strut.  

 

The scoring on the Tabloid wing turned out (almost) okay but I didn't get enough camber in there and there is no dihedral to speak of, which the wing should have.  I messed up because I tried to get the camber and the dihedral done in one go and I had two curves working against each other.  Cleary , the camber has to be done separately and the dihedral perhaps achieved by using little hot water.  Perhaps!

 

Thanks for your interest

 

Dennis

 

 

 

 

 

 

 

 

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  • 2 weeks later...
On 9/21/2018 at 9:43 PM, DMC said:

Top right strut:  this one is .010 styrene folded between two lengths of balsa and heated with a hair dryer to get a sharp crease. A length of wire was placed in the crease with a thread of Milliput and the trailing edge was clamped with a bulldog clamp and left to cure overnight.  Trimmed and cemented next day this method produces a pretty good airfoil shape and will only need a little thinning of the trailing edge and a minimum of sanding.  I went with this one and I've made four and two for the cross struts.

 

Very nice exploration there Dennis, & I like the sound of this preferred method.  In particular the limited ‘finishing’ required appeals.  My method of squashing a brass tube gets a result  .. but with a LOT of laborious finishing!!

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On 9/17/2018 at 10:38 PM, DMC said:

I’m almost ready to start on the struts and would like a gander at how you set those jigs up.

 

I’ve made two jigs recently, each requiring a different approach, one simpler, the other more complicated.  The determining factor being the strut geometry when viewed in frontal elevation:

 

- if rear strut sits aligned in the same plane as (& therefore obscured by) the front strut, then the jig is more straight forward, with the two struts sharing a single inclined plane for support (this was the case with my Crusader);

 

- if the rear strut is not aligned in the same plane as the front, then you’re in for more geometric gymnastics work, as each strut will need its own independent support (this was the case with my Curtiss CR-3).

 

Might make more sense if you take at look at the two threads?  If you let me know which is relevant to the M39, then I can help more if needed.

 

g.

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Hi greggles,

 

Quick reply as I’m out in a minute.  I made a simple jig out of cardboard a few days ago.   Sturdy and portable it’ll also do for the .67 as the floats and their track are practically identical.  Pics as soon as I get better lighting.

 

Went way back and trawled through your thread again.  It is evident you enjoy solving problems as much as you enjoy assembling a kit.

 

More later.

 

Dennis

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1 hour ago, DMC said:

Went way back and trawled through your thread again.  It is evident you enjoy solving problems as much as you enjoy assembling a kit.

 

😆 such a gentleman! one might also submit that the evidence suggests I merely have a knack for making things hard for myself!!

 

You are right though.  This lets me enjoy solving the problems I choose, while working with inspiring designs .. without all the interference of clients, consultants, and approval authorities I find in my professional work (architect)!!

 

Mad keen to see you tackle that M67, but more than content to watch your progress on this one in the meantime.

 

g.

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Right, hoped to be a little further along with this but major house renovations have slowed things up a bit.  Anyway, floats and struts rigged up.  I don't mind admitting that this gave me fits.  Getting the correct height was the problem.  The vertical piece on the temporary brace on the floats served to establish the distance above the floats that the fuselage/wing should be.  I made each strut overlong and then had to keep trimming them until the flat rectangle rested on the vertical gauge.  The rectangle will be, after priming and painting, cemented to the bottom of the wing, after priming and painting.  The pictures of the 1:1 strut set-up on the museum .39 are not that much help but do give me a hint on how to go about rigging the model.  The wires in the struts are inserted into stretched tubing fixed at angles in the flat.   Pretty sure having this set-up will make painting the floats and fuselage a little easier.   

 

Not much more to do before painting.  

 

Thanks for your interest.

 

Dennis

 

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  • 7 months later...

(Village Photos back up)

 

While waiting for cement to cure on the Boeing, I spy the floats for the m39 gathering dust on the topmost shelf of a bookcase that is the collection point for all forlorn and forsaken projects and items displayed and set aside for newer, shiny items of interest.  

 

Close inspection revealed a number faults that had needed correcting before I could get on and finish the build.  Most obvious were the strut fairings.  They really needed redoing.  I made new male and female moulds and plunge moulded eight new ones.

This time I took a little more care in matching them up and fitting them to the floats.  Pleased with the results, not perfect but much better than my first efforts.  

 

Off to the races again?  Probably, as my Schneider Cup mojo has be rekindled a bit.  

 

Thanks for your interest 

 

Dennis

 

 

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2 hours ago, Marklo said:

Nice to see this back on the rails, as it's so close to finished also good to see another scratchbuild in progress

1 hour ago, Ex-FAAWAFU said:

Nice to see this back; good fairings, too.

Thanks, gents, will make a serious attempt to carry on with the build to the finish.  I do like a bit of scratchbuilding myself.

 

This photo of the underside of the M39 in the museum in Italy is the best (only one) I could find that shows how the struts connects to the fuselage.  They appear to be heavy metal rods with an airfoil covering.  The flat area could be part of the wing or an addition.   I could have fit the rectangular plate on top of the float struts into the wing but didn’t think of it at the time. 

 

A few few more shots of the float and strut assembly.  Very solid even in 1/48 scale.

 

I have three shades of Vallejo Model Air reds to choose from: Ferrari, scarlet and fire.  I will probably go with scarlet.  These reds are very translucent.  Interesting how the colour of the primer affects the top coat.

 

Thanks for your interest.

 

Dennis 

 

 

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No - no such plans at this point, but I’m interested in how DMC is dealing with all the struts and so forth. I’ve got a lot of that stuff coming up in my Avro 504 build and I need all the help and ideas I can get!

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2 hours ago, Courageous said:

think you need another little experiment

You think?  Hmmm, well, Stuart, you might be right.  I’ve sprayed  first coat on and, it being translucent, the yellow ochre primer gives it an orange cast.  I think that will be less obvious with another thin coat, or two.  Won’t be that screaming glossy bright red of the museum examples, however.   I’ll post a pic in a day or so. 

 

1 hour ago, Courageous said:

What...you're going to build a bigger one from woo

1 hour ago, Bandsaw Steve said:

need all the help and ideas I can get!

Why not, the originals were mostly wood.

 

Need help?  Steve, you could teach most of us a thing or two.

 

Cheers

 

Dennis

 

 

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Hallo Dennis,

 

Glad to see there are more scratbuilders here on this form.  I like the way you made those floats. Mostly I carve them out of solid wood. 

And I also learned a lot reading Harry Woodmans' book. 

 

Good luck with this beautiful model.

 

Greetings,

JohnHaa

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3 hours ago, JohnHaa said:

Good luck with this beautiful model.

Thank you, John, very much appreciated.  Pleased you got something out of the Woodman book. 

 

Keep on scratching.

 

Dennis 

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8 hours ago, Courageous said:

Ferrari type red, nice and bright,

I’ve given the floats two coats of Vallejo Model Air Ferrari red.  Not bright bright red but I like it well enough.  Thing is, Stuart, looking at contemporary photos, the Macchis look quite dark.  I realise that old black and white photos are no indication of actual colours but it’s what I have.   We’ll see.

 

Cheers

 

Dennis

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As I mentioned, it’s difficult to guess at a colour from a black and white  photo.  In this photo the Macchi looks much darker than the grey — pretty sure — of the uniforms.  Might be but without a paint chip to go by it is a guess.  

 

I used Vallejo Ferrari red on the 39’s floats and I think it must be pretty close.  Almost matches the Speedbirds book cover.  I painted the float bottoms first and then the tops.  Should have done it the other way around.  Would have been easier to mask and the results would have been neater.

 

Thanks for your interest.

 

Dennis 

 

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