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Eagle DW.1 - biplane cropduster 1/48 Scratchbuild


ianwau

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Time for another project.  One of my themes is modelling cropdusters in 1/48 - I have completed about 30 most of them scratchbuilt.  This one caught my eye a little while back - it's a US designed cropdusting biplane,  the Eagle DW.1, which first flew in 1977. That's correct 1977, who'd have thought. A distinctive feature is the incredibly long wings (55ft,  16.8m) with a very narrow wing chord and almost glider like in appearance.  Some clever design trickery was used to improve the roll rate.

 

Initially engined with a radial, it is more commonly found with a 300hp Lycoming flat six which in my view makes for a prettier aircraft and will be the subject of my model.  Gross weight is 2450kg and a load of ~1250kg could be carried. 95 examples were built between 1979 and 1983 - including a couple that came to Australia (that will be the scheme I model). 

 

The picture of the a/c below is shared from user "G.Verver" on Flickr in a banner towing role. 

Eagle DW-1 s/n DW-1-0064-82, N8810T

 

So, onto the project. I actually started this in July 2021, and have taken a few photos along the way. The pace is going to pick up a bit from here as I have finished some recent projects.

 

First up I had to refine some pretty rudimentary plans (which I think were enlarged from a Janes of the era). I've drawn these up in CAD including deciphering of the all important cross sections.  The fuselage aft of the engine is basically box section to about halfway up - then a compound curved deck over that, with the canopy perched on top of all that.  The box section part of the fuse is straightforward enough - just some cut to size styrene (carefully!) and some bulkheads at strategic points. A little forward planning required to make sure I had room for the cockpit later on. 

 

The top deck was going to be vacuformed for which I need to make a master. This begins with creating a skeleton - styrene base, main spine, cross sections 'ribs' added (slightly undersized to allow for thickness of plastic to be moulded). The skeleton doesn't need to be pretty - little chunks of plastic offcuts here and there to support the ribs 

DSC03737

 

The wing(s) were next on the agenda. Wings are very long, constant section - apart from a tapering of the chord and thickness towards the wing tip. The upper skin, and lower skin are each cut to size from 0.75mm (30thou) styrene sheet. 

  • Cut skins about 1mm oversize at the leading edge. (allows room for a bit of skin curvature over the wing, [it's easier to sand back vs fill gaps...]}
  • Trailing edges sanded on INNER surfaces to a knife edge taper. Don't skimp on the knife edging...
  • Main spar from a strip of styrene (40thou in this case) and very lightly tacked into position (if I glue it 'properly' I'll get deformation in the wing curvature when top and bottom are joined).
  • Leading edge (not show here) from 20thou styrene strip. 
  •  I've elected to leave the entire trailing edge dead straight - and insert the wing tip tape later on by doing a 'cut and shut' - ie crank that part of the wing forward to preserve the trailing edge, and fill/sand etc)

 

Next steps will be:

  • Glue and clamp the trailing edge first (not too much glue, and not too heavy on the clamps. Leave 24 hours.
  • Then glue and clamp leading edge. NO glue on the main spar (again, to avoid skin deformation). A bit more heavy handed on the leading edge glue as there'll be a bit more stress to overcome.  Leave 24 hours. 
  • Clamps off.   And a wet sand with course wet and dry to get correct wing profile.
  • From there - shift to finer grade wet and dry, and a bit of Milliput if required). 

 

Also in this pic you can see the progress on the master for vacforming the turtle deck - early days just the one coat of car bog at this point...

DSC03739

 

Here we see the wings now joined up but pre-sanding down. Tips yet to be 'cranked'. And the master for vacforming the top deck visible in the foreground. It took about 3 coats of car bog to get to this stage from the earlier version above. 

IMG_3646

 

Here we see the vacformed and cut to size fuselage top. I will cut out the cockpit opening after gluing. Leaving it intact ensures I don't get unwanted warpage/distortion when I glue. On the box section of the fuse - I have glued thin 'alignment strips' which will apart from helping with alignment will also give a bit more meat for the glue to bite into (ie far preferable to a butt joint for this sort of application. The basics of the cockpit interior have been added - the floor and formers for the seat bulkhead and seat base. With a quick squirt of black while I'm there. Detail will be added later once the cockpit opening is opened out (quite large) - it's pretty spartan inside...

IMG_3726

 

and here we have the fuselage top and bottom joined and held with some builders tape. It doesn't look like much at this stage but confident it'll scrub up. Also the wings are now sanded. The tips have now been 'cranked' - a cut and shut by removing a thin wedge of plastic, inserting a short spar to provide a) alignment and b) strength then glueing. I've given it one coat of Milliput - but have now gone for the Mr.Surfacer 500 to get rid of any remnants of the join. Note the wings are built slightly overlength - which will be remedied when I insert the dihedral and/or the fuselage in the middle! The black cutting matt underneath if 30cm wide (an A4 sheet) which give you an idea of the wingspan

IMG_3727

 

Next steps will be clean up fuse, make the fin and tailplane, make masters for the engine cowl and canopy etc etc....

 

 

Edited by ianwau
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A little more progress on the weekend.  Cleaned up the fuse - and decided to put a few hours into cutting the wings to size and setting the wing dihedral. Bottom wing looks to be 3 degrees dihedral and top wing 1 degree - so it was out with the high school calculator and a bit of trigonometry.  The bigger challenge was working out how to do the upper wing join and the lower wing to fuse join. Obviously a butt join wasn't going to cut it - and I wanted something that would basically maintain correct dihedral without relying on the 'other' wing. 

- The upper wing I've relied on brass tube spars, super glue and some revell contacta. Should be OK as this isn't going to get much handling before it's joined to the lower wing.

- the lower wing I've gone for a bit of a tongue and groove approach AND brass tube spars. This'll get blended into a cut-out in the bottom of the fuse. 

 

DSC03840

 

So here's the wings prepped, brass spars and evidence of my trigonometry calcs! The lower wing will have some knobbly bits where I've done the tongue and groove but figuring I will have some real strength in the join from take this approach, Brass spars have been bent to the required dihedral with a little fettling and a set of pliers.  

 

DSC03841

 

And here we are in Lego land with the dihedral set - and the lego giving me alignment in all 3 dimensions.  The Lego LAME actually serve a purpose in applying a bit of pressure while the glue dries - and their feet are just the right size to apply pressure to the leading edge of the wing. Lego obviously comes in pre-determined engineered dimensions - so I've used a couple of styrene layered 'chocks' at the wingtips in the wing at bottom of pic. This applies a bit of pressure to the join(s) at the centre of the wing while it all dries.  

DSC03842

 

Next steps - do the things I was going to do in previous post - empennage, masters for engine and canopy.  Oh and I might join the lower wing to fuse as that'll be a bit of a milestone ..

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Great work, loving the lego jig and master engineer overseeing the project. I think I might be off to Toyland to buy a lego set after seeing this. 

That wing joint will be nice and secure, especially with the brass spar. 

 

Richie

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46 minutes ago, RichieW said:

might be off to Toyland to buy a lego set after seeing this.

Thanks Richie,

I luckily have inherited Lego from the (grown up) children. It's been used umpteen times for this purpose, + fuse/wing alignment etc. The key item is the very large base plate - the rest of it you'll easily pick up at garage/yard sales or the charity shops.

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A little more progress - doing the things I said I would....

 

Cobbled together the masters for the canopy, and the engine cowl. Styrene skeletons for the moment - will fill them with car bog tomorrow once the glue drys. They look a bit rough at the moment but will clean up nicely with a bit of sanding - as we'll see....

DSC03845

 

And the empennage.  The 1:1 version is sufficiently slender to use a single piece of 1.5mm (60 thou) styrene - and taper the trailing edge and leading edge with some judicious sanding. Here they are post sanding with the rudder and elevator pencilled in ready for scribing...

DSC03844

 

And moving right along - scribing completed.  The fuselage has been 'slotted' ready for the horizontal tailplane. The fin has a tab - ready to pass thru a prepared hole in the fuse and thru the hole in the horizontal tailplane. Makes sense?  It makes sure the whole thing can be true, with strong joints.

 

DSC03846

 

So here's what it looks like just dry fitted.  Still a bit of fettling required to make it sit square - but you  get the idea...

 

DSC03847

 

And couldn't resist a rough setting out to get a sense of how it might come together? Pretty impressed with the slender wings and wingspan on this one. AND it's a biplane!

 

DSC03848

 

Next steps - fit the empennage, fit the lower wing, prep the canopy/cowl moulds for vacforming.....

 

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A little more progress. The major components were sent back to Legoland for assembly. This gives a good idea of how versatile Lego can be.  The lower wings have slotted back into their jig - maintaining dihedral and horizontal alignment. The fuselage is sandwiched between lego blocks - assured that it's perpendicular to the wings. Fin is in the prepared slot - and assured vertical by the lego towers sitting behind etc. Plenty of observers - some fulfilling a useful function.   Glued with Revell Contacta and left to sit for ~3 days (just because I had real work to do)

 

DSC03851

 

So onto a bit of vacforming (the masters for cowl and canopy are done). Here's one half of the cowl - straight after forming (with the home vacuum cleaner) after heating (in the home oven/grill) - and using a high-tech vacformer (a plastic container borrowed from the plastic container drawer - and drilled with umpteen hole - including a big hole for the vacuum cleaner hose).

DSC03859

 

And here's the canopy...

DSC03861

 

And here's what it looks like having been roughly cut out of the vacform sheet. Obviously lots of wastage here - but the styrene sheet is pretty cheap when put in bulk sheets.  White styrene is 0.75mm (30 thou) and ditto the clear (which is K&S Butyrate).

DSC03860

 

The upper and lower cowls have been trimmed to size and glued.  And have commenced trimming the canopy. The latter requires a little care and a lot of fettling.  Measure twice and cut once I think someone said?  Certainly holds true for this (not real keen on having to mould a new one if I muck up). Here's a quick dry fit showing progress.

 

DSC03872

 

Next steps - largely fitting out the cockpit. Open up the cockpit, fit instrument panel, seat, controls etc. Trim the canopy to fit.  From there - need to create some semblance of an engine (won't be able to see anything - but needs a lump in there vs empty space.

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Terrific work, I am really enjoying following your processes. The wing span is huge on this aircraft but it still looks very elegant.Legoland looks the place to be for scratch builders!

 

Richie

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  • 2 weeks later...

A bit of progress - but just the one picture to show for it....

  • front cowl has been cleaned up - still scratching my head about how to represent the 'grill' at the front - it's either a photo-etch solution or decalled representation.  Mr. D.W. must have had a passion for 1932 Fords?
  • Canopy has been fettled - not quite finished with it yet - but getting vewy vewy close.
  • Interior has been cut out and fitted out with instrument panel, rather groovy headrest/rollover fairing - and all ready for a seat (experimenting with something from the spares)
  • There's actually a semblance of an engine under the cowl - but just scraps of sprue etc.  If nothing else - gives me something solid to attach the prop to! Can't see any detail from outside - so my own view is what's the point of going to town on a flat 6 Lycoming IO-540 replica.

 

DSC03888

 

Next steps?

  • More general clean up - then start marking out for the struts etc for the upper wing, and prepping for the undercarriage (will need that on before I start painting)
  • Complete detailing on the wings 
  • Finish off cockpit and stick the canopy on (want to make sure I've finished drilling holes in the fuse before I do that - else there'll be swarf all over the inside of the canopy)
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Loving the build. I must try to track down some of that Butyrate sheet as I’m currently using petg and getting very varied results.

 

Interesting and semi related fact: there are apparently more Lego mini figures on the planet than there are people !

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How did I miss this until now? At least I'm here now :popcorn:

 

Would you mind describing the canopy master? My attempts to make my own master weren't successful. My first attempt showed every surface defect. When I tried to smooth the master, residue was infused into the molded canopy. :shrug:

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9 hours ago, Marklo said:

track down some of that Butyrate sheet as I’m currently using Petg and getting very varied results.

The butyrate I have been using for vacforming is from "K&S" - although the latest batch I bought was forming micro-bubbles early in the heating process (before it had even properly melted) - so I've actually ordered some PETG to give that a go!  PETG is apparently popular with the R/C crowd for canopy vacforming (and it seems to work well for drink bottles)

 

7 hours ago, dnl42 said:

Would you mind describing the canopy master?

The master is initially formed up from a skeleton of cross sections - top, front and sides. This is then filled in with 'car bog' - ie putty used by panel beaters on car repairs - and readily available from any of the automotive supplies stores. This is a two pack polyester putty ('golf ball' of putty + 'pea' of hardener). It is very similar in hardness to styrene which is a good thing when sanding back to the skeleton.  It takes about 3-4 coats to get built up and then finished off with increasingly fine grade wet and dry (1200 should be fine enough). Sounds tedious - but the putty goes off in ~15mins and sandable within 30mins.   You get a sense of how smooth the master is from some of the photos.  

 

There's some pictures early in the thread of the 'turtleback' master being formed up - which is identical process to that being used for canopy (less photos, later on in the thread). I never coat it with anything before moulding - eg a coat of primer is likely to react (badly) to the heat during vacforming. 

 

One important thing is to make the master undersize by the thickness of your final formed plastic. 

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Thanks for that. My biggest problem with petg is that it goes white if you overheat it. I find it’s very difficult to get it soft enough to vac form without overheating. I’ve found it’s ok for plunge molding.


ac47fe00-9ad1-4aa0-880c-0e2cd66ad303.jpeThis was my last attempt. the canopy is for my 1/48!scale AHRLAC and is fairly large. I wasted two sheets of PETG trying to vac form it, but ended up plunge molding the canopy. 
 

My master is just carved from a block of basswood btw.

 

Edited by Marklo
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On 9/27/2021 at 6:02 PM, Marklo said:

My biggest problem with petg is that it goes white if you overheat it. I find it’s very difficult to get it soft enough to vac form without overheating.

Thanks for the insights re PETG. Interested to see how I go with it.  I've been using butyrate for 20+ years without any issues till this latest batch. Your sample there looks pretty good - but I'm guessing by your description there's a few issues with it....

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1 hour ago, ianwau said:

but I'm guessing by your description there's a few issues with it....

Mm yes it’s a bit blurry so to speak. When it works PETG is great.

 

resized_70769251-2ef0-46de-8d13-85e21b74For example on my 1/48 Stuka. I just find  it to be very temperamental. I have some acrylic on order so I’ll probably have another go at the AHRLAC when that arrives.

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