Slip wing Hurri. Hillson F.H. 40 Retrospective.

[TheLurker]

This is a build retrospective rather than a build in progress because I saw no point in boring everyone with something that stood a good chance of not even making it to the trimming stage.  You may have seen some of the pictures before.

To begin at the beginning...

I'd got well and truly stuck with both the Zanonia plan and a Peanut MKI Hurri so I thought I'd put them to one side and do something simple and quick to let the sub-conscious bit of my brain chew them over, especially the Zanonia.  That was in September last year.  Quick?  Oh well, never mind.

The Hawker Hurricane is one of my favourite aircraft and when I came across the FH40 experiment some years ago it was immediately added to the, "Really Must Build One" queue.  Being an idle sort I bought VMC's (waves at Arnie) MFM MK I Hurri kit three or so years ago with this is mind.  I'd previously used the kit as the basis for K5083 so knew my way around it and was confident it would make a sound basis for what I had in mind, that and it was only thirty odd quid for most of the bits I would need.  

If we accept the commonly available histories as accurate, there is some dissent, L1884 was a Block 1, Hawker Aircraft Ltd. machine built between 15th of Dec 37 and the 6th of Oct 1939. It was shipped to Canada and was in service with the RCAF as 321  by the 22nd of May 1939 at Sea Island BC. It returned to the UK with units of the RCAF in 1940 and it was struck off charge on the 20th of May 1940.

The available pictures aren't clear enough to be certain, but as an early L series airframe it would have orginally been fitted with fabric wings(1) and 5 spoke wheels (L & N serials) and it still had its fabric wings when Hills received it for his experiments in 1943.  What happened to it in the 2 years between being SoC & allocated to Hills is... unclear.

(1) Block 1 aircraft from L1976 onwards were factory fitted with metal skinned wings.  Many (most?) of those in RAF service were fitted with metal skinned wings when they underwent major repairs or refit.

So, what needed to be done?  Well first off a new upper main plane, so a bit of tracing of kit rib profiles and some tweaks like laminated tips. Then some mods. to the centre section.  The kit sets the outer panel dihedral on the outermost ribs of the CS.  This wouldn't work because I needed to have those ribs vertical so I could mount the interplane struts against them.  Cue two new CS main spars, one for the lower main plan, one for the upper and a dihedral gauge for the outer panel root ribs.

What else?  Well, I decided that I wanted, laminated outlines, elevators and a rudder so a little bit of scribbling gave me some new drawings for the tail assembly.

We're still not quite done with tweaks. I thought it would be interesting to make the radiator boat closer to scale than the kit sub-assembly, but I didn't want to vacuum form it, I'll tell you why if you're bored enough to ask. This meant puzzling out how I could do it in balsa *without* carving 'cos I can't carve my way out of soggy paper bag.   Fortunately I have a number of (more than 6, but fewer than 10, OK?) 1/72 MK I Hurri. kits to hand and while mulling this problem over I thought I'd see how the Airfix designer had solved the problem and with some minor adjustments I had a "two box" balsa variation of their solution that works surprisingly well.  I think the result is quite passable. It won't stand scrutiny by a Hurri obsessive, but passes the "Doesn't look off to the casual gaze." test.

Wheels.  I've gone with the 5 "spoke" pattern (the kit comes with a 4 spoke pattern hub) on the assumption that as L1884/321 still had its original fabric covered wings and had been "off the books" so wasn't being flown or subject to anything but the barest minimum of maintenance so could quite feasibly still be fitted with its factory issued wheels.

Thought I'd done with changes to the kit?  Hee hee, not a chance old cock. The last change was the introduction of a ballast space. You can only really do this if you're prepared to infill the nose, but it's worth the effort.  When I built my K5083 I extended the lower keel and left the front lowermost panels open so that I could slide in Pb after trimming. It worked, but it felt (still feels) like a bodge.  The other change was a couple of extra lengths of strip & some infill at the top of the dog kennel.  When I covered K5083 I could *not* get this area covered without dips & wrinkle, despite 2 or 4 goes at it.  It was better for 321, but there's still room for improvement.

Why is it grey & green rather than dark earth & green?  Interesting you should ask that, it's the result of a discussion I had with Andy Blackburn.  There are no colour photographs so it's balance of probabilities.  Although RCAF 321 was struck off charge in 1940 and would almost certainly have been dark earth / green when it was parked at the back of a hangar; spares, for the use of, RAF regs in 1943 (reference please AB) for flying airframes, when the F.H.40 was bolted together, mandated the grey/green scheme.  It is very difficult to be certain from the few photographs there are, but if you squint right you can just about convince yourself it's grey rather than dark earth.

The prototype yellow undersides are highly likely given that the fuselage carried the yellow prototype "P".  On which; the RAF's insistence on surrounding the yellow prototype "P" with a narrow yellow circle is a proper pest.  Don't they know how difficult it is to recreate this in tissue?

We'll start (as I did) with the mod sheets.

[TheLurker]

The tail assembly is completely new and uses basswood outlines because for this size of thing I find a single 1/16" x 1/16" or 1/16" x 1/32" strip of basswood far easier to work with than 1/32" laminations of balsa. 

The wing tips (upper & lower) were  also swapped to formed outlines and the upper spar extended & cracked as shown. 

Because the CS outer ribs have to sit vertically the inter-spar stiffener on the lower wing has to have the dihedral angle sanded into it. I didn't bother with it for the upper wing as it isn't subject to landing stress to the same extent.

[TheLurker]

The fuselage structure is largely unchanged.  The simplest changes are some extra bits of sheet & strip at the top of the dog kennel to make it easier to cover and a couple of supporting panels for the side bracing struts.

The only significant, and it's not that significant, change is the addition of the ballast space with a lid.

I couldn't resist making the aftermost former lighter though. Got to save that tail weight.

 

[TheLurker]

Think this is self explanatory.  Make two boxes bolt them together & sand to shape.

[TheLurker]

The undercarriage. Again no significant changes.  Five spoke wheels as mentioned in the opening post and I've used 3mm grass stem to represent the Oleo rather than the kit parts. Narrower stems would have been better, but I didn't have any to hand.  The tail wheel is reduced to a 24/26 SWG hook with a coloured / printed paper cover

The UC doors are covered with Al and yellow tissue.

I've gone for Gun Metal (Humbrol 53) for the painted parts because I think it gives a better effect at small sizes than, say, Al.  I find matt / satin colours usually give a less toy-like appearance than the correct shiny ones.

[TheLurker]

The struts.

The main thing to point out here is the use of a socket to receive the side braces at the fuselage with a matching plug on the braces.  It makes it infinitely easier to get the strut the correct size when fitting it.

The other wrinkle to note is the use of a couple of bits of thread glued to the main strut uprights. One at the top of the forward strut and one at the base of the after strut.  These set, with the joint to the side brace struts, the depth of insertion so you can be confident everything is at the right height when fitting the upper main plane.

[TheLurker]

This is the third* go at the canopy.  I couldn't get the moulding to sit right as a one piece so gave up and went for an open cockpit 'cos  I could make that look about right.

Of course that meant I needed a pilot. The problem with many of the stock images (and I think it was Andy Sephton who pointed this out in the BMFA mag.) is that they sit too upright.  So after a fruitless search for a decent image I bodged together a side view of a helmet on a mannequin & a separate image of an Irvin jacket likewise that I found on an memorabilia site making sure the pilot was leaning ever so slightly forward. There's no Mae West, but I choose to believe that the FH40 pilots wouldn't have bothered with one as all test flight operations would have been over land.


*I have spares.  I had fun with the canopy for K5083 so bought extras.  Just in case.

[TheLurker]

As is usual for my models it's a tissue only (ignoring bits like wheels & prop) finish.  There's nothing wrong with a painted or printed tissue covering, in fact they usually look far, far better, but I don't have an airbrush nor a printer capable of printing dope/water fast images so tissue it is.  It's also nice to show that you don't have to have expensive (ish) tools nor a dedicated workshop to build a reasonably convincing scale model.

Base cover is VMC's grey domestic water shrunk and with a single coat of 30% by volume of non-shrinking dope and the green is VMC's olive drab domestic pre-shrunk positioned by flooding with thinners and a single coat of 20% by vol. NS dope.  Needless to say this model is only for indoor use or for use out of doors in *dry* weather.

The prototype roundels didn't work as well as I'd hoped they would, the backing tissue was slightly too opaque and didn't become any less so when doped and the port side roundel needed to be touched up (very, very carefully) once in place to reinforce the colour.  I think the next time I do a prototype machine I'll (hand) paint with masks.

[TheLurker]

Well that's it.  Tomorrow (10th of Feb. '24) I find out whether or not it will fly.  Fingers crossed.

Although it was slow build there wasn't a great deal of rework.  Of course there was some, but no major, "Oh woe is me I shall have to start all over again." moments.  I find that drawing the mod. sheets / plan for a build and also writing my own "build guide" forces me to think hard about just how things are going to fit together.  It also helps that the base kit is so very suitable for tinkering.

And one final little tit-bit. Although members of the plastics brigade (see BritModeller.com) have a go at modelling the FH40 on a fairly regular basis this isn't the first go at a flying model.  Sears B. McCorrison did that, see https://plans.modelaircraft.org/product/hillson-fh40-slipwing-hurricane/

[Squirrelnet]

Great build Lurk

Some great ideas in there and the pilot with proper stance is great.

Fingers very firmly crossed for tomorrow

[martynk]

Brilliant. Two questions coz i am bored.

[AndyB]

Why is it grey & green rather than dark earth & green?  Interesting you should ask that, it's the result of a discussion I had with Andy Blackburn.  There are no colour photographs so it's balance of probabilities.  Although RCAF 321 was struck off charge in 1940 and would almost certainly have been dark earth / green when it was parked at the back of a hangar; spares, for the use of, RAF regs in 1943 (reference please AB)

The colour change appears to have been mandated on 15th August 1941 (implemented on production lines in late August or September).

The best I can do on references (because it seems that nobody is able to quote the official air ministry document) is:

"Camouflage & Markings, R.A.F. Fighter Command 1936-1945, James Goulding & Robert Jones, Ducimus Books Limited 1970-1971".

Page 68 has the colour change details, and pages 64/66 have details of colour scheme trials at the AFDU at Duxford. There are other reference works that have details (e.g. various Modellers Datafiles by SAM Publications) but I think C&M has the most detail.

A.

[martynk]

Brilliant. Two questions coz i am bored.

Not sure what happened to my questions, they must have been culled.

First question was where do you get strip basswood in the UK. I know Hobbycraft sell it by the sheet but I have never seen stripwood.
The other question was about 'Grass Stem' for the oleo legs.  What is it, or is it as the name suggests. Dried Grass?

Thanks

Martyn

[Slowmatch]

Nice write up Lurk. I look forward to the flying report.

Did you post photos of your K5083? I don't recall.


Jon

[Jez Wilkins]

First question was where do you get strip basswood in the UK.

Thanks

Martyn

Hi Martynk.

The Sun Lane Engineering Company [SLEC] certainly sell it - see the attached 'screenshot'.  For me, the issue with getting any wood delivered, is the carriage/postage.  If you only need a few strips, then the cost of carriage/postage can exceed the price that you have paid for the wood itself.  The wood order (1/16" square, 3/32" square and 1/8" square balsa strip, I think ) that I received from SLEC was very well packed though - a triangular cardboard outer and a tubular cardboard inner.

If you are lucky enough to live close to SLEC*, then you could always collect and save the carriage/postage.  Or wait until you see their stand at a show - depending upon just how urgent your need is.

The only other source(s) that I know of, are outlets that are involved with dolls houses - those that are into dolls houses seem to use basswood (in making the furniture?).  If you use your favourite internet search engine - you might find a seller close enough to your location, to be able to drive there and pick some up.

Cheers,

Jez Wilkins

* Just checked your profile - you're not, unfortunately.    

[billdennis747]

First question was where do you get strip basswood in the UK.

Well it used to be available down to tiny sizes (like 1/64") from SAMS models before they disappeared. I always thought it came from the model railways world. The smallest I've found now is 1/16" sq so you're better off with the 1/32" sheet from Hobbycraft, which strips well. Of course basswood responds well to the ammonia trick, which balsa does not

[TheLurker]

MartynK > ... grass stems...
As harvested from nearest fields.  Some years are better than others, but generally wander out late summer and get a handful in various diameters & lengths.

MartynK > ... strip basswood in the UK....
Like Bill, slice my own from sheets bought in Hobbycraft.  I don't use much so it wouldn't make sense to have fragile strip lying around waiting to break.  For short lengths (indoor models) of strip I use a couple of simple guides, see pic., to nick the sheet at the right width in 3 places and then use steel rule & scalpel, easy & quick.  For longer stuff, 2' plus, I've got a SLEC stripper.

Slowmatch> ...flying report...
It survived, but not unscathed.  Briefly; an 18" loop of 0.16" wasn't up to ROG but would give a circuit.  Four by 0.125" gave ROG, but was a bit too beefy and that flight wasn't 100% successful.   See the pics and Chris' newsreel when he's had time to edit it. I've had a good cry about it and declared Hung a false god, that's the last time he gets any of my sacred chickens, and have scheduled the repairs.  I've seen lots of broken balsa, but a cracked (like an eggshell m'dears) spinner is a first.

Will make up  a couple of 4 by "a bit less" motors for next month.  

[Squirrelnet]

Some pics.

Looking very promising, the last flight (wall aside) was very good

[martynk]

Thanks for the hints

That certainly looks very nice in the air, and on the ground..

--
Martyn

[piecost]

Good to see the lovely model flying and am glad that it is repairable