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Author Topic: Heath LNB-4 Parasol  (Read 881 times)
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Richard Hewitt
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« on: June 04, 2020, 01:18:35 AM »

Hello,

This will be my first attempt at a build thread so please make allowances...

After labouring mightily through the winter months to finish the Audax, I wanted a "light" project to do over the summer. I picked the Heath LNB-4 Parasol from the to-do pile of unbuilt plans. This will be 1/12 scale, wingspan approx 31", for the Redfin 020, a recent acquisition. (Mr Phin assures me it IS an 020, despite saying 030 on the casting). The drawings are based on Rob Lambert's 3-view in the Historic Aviation Archive (I think it's in the HPA plans gallery if anyone is interested). From Ron Moulton's rule-of-thumb tables in "Flying Scale Models", I should be aiming at a target weight of 7.5oz. This seems unrealistic to me (the components in the photo attached weigh 3oz already) so if I can get within 10oz for the finished model I will be happy.

So far, I have concentrated on fabricating parts for the fuselage, plus I have done the wing rib "sandwich".

More to follow, hopefully...and any advice from you experts out there will be welcome!
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Heath LNB-4 Parasol
Heath LNB-4 Parasol
Heath LNB-4 Parasol
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Squirrelnet
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« Reply #1 on: June 04, 2020, 07:26:01 AM »

Looks like an interesting build Richard, look forward to seeing it progress

Love the tiny instruments, very nicely done
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billdennis747
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« Reply #2 on: June 04, 2020, 08:23:36 AM »

Richard
This is a Super Parasol, which looks superficially similar. It is 36" with a wing area of 1.5sgft. The structure was built by a late friend who was not known for a light touch. I covered it with tissue and silk, and paint (!) and it weighs 8oz + 1.5oz engine (Dart). That's a loading of about 6oz/sq ft which is not bad.
So I would say 7.5oz is possible, although I suspect your engine may be heavy. There is a belief, wrong in my opinion, that power models need to be built much stronger (and heavier) than a rubber model. You could build this like a beefy rubber model with just local strengthening where handled.
It will be nose heavy so watch for that. I take it your 3 oz so far includes the engine?! If that is 1/8 ply in the pictures I would re-think. Elsewhere on this site, Squirrelnet is building a KK Cessna with no ply at all. Use medium- light balsa with local reinforcing with 1/64 ply. Can you replace wire in the cabane with carbon rod? Get in the mindset that every gram counts. I would be looking for 5oz/sq ft to preserve the slow flying character of this subject.
I'm sure someone else was doing this one - was it Mark Braunlich? It looks better than mine - it has dihedral and some sort of tailplane (mine is double scale size)
Bill
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Re: Heath LNB-4 Parasol
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Richard Hewitt
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« Reply #3 on: June 04, 2020, 09:15:45 AM »

Thanks for your comments Bill and Squirrel.

Yes Bill, the 3oz includes the engine/tank/prop. The "strong" formers are 2mm liteply, the others 1/8" balsa, very soft. I agree with trying to keep everything as light as possible to end up with the right flying charactestics for an ultra-light homebuilt.

The instruments are made from faces that were on a sheet given away as a cover-mount on one of the mags, maybe RCSA, back in the 90s. I glued a thin layer of celluloid on top, then cut bezels from alu tube - some careful work with the junior hacksaw. Then paint everything except the faces with gunmetal paint to make them look a bit more metal. (The alu is too bright IMHO). By using so-called "canopy" glue, the celluloid can be stuck down across the full width of the faces - the glue really DOES dry completely clear, as claimed.
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Mark Braunlich
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« Reply #4 on: June 04, 2020, 10:02:40 AM »

Yes Bill, I have one.  Mine is the first of all the Heath Parasols, 1/10 scale, 27.6" span, 4.3 oz and Cox .010 powered.  I can't say it's been a success as I've had major repairs following every flying session.

Just a mention of Heath Parasols in general.  There were FIVE major variants, not counting the multiples generated by individual home-builders adding their own personal touches.

     1.  Heath Parasol (late 1926-mid 1928) many factory-built with Thomas Morse S4C lower wings
     2.  Heath Super Parasol, new Clark Y wing (mid 1928-1930), many home-built, various engines
     3.  Heath V-Strut Parasol (intro. late 1930), featured in 6 part Popular Av. series starting 12/30.
     4.  Heath LNB-4 Parasol, (ATC 456 issued late 1931), Henderson-Heath B-4 powered
     5.  Heath LNA-40 Parasol, (ATC 487 issued 1932), Continental A-40 powered

Of these five, Ed Heath had involvement only with the first three.  Ed was killed in a crash in early 1931 and the certified Parasols were the products of a reincarnation of the Heath enterprise formed in Niles, Michigan.  The LNB-4 and LNA-40 were bigger and heavier airplanes.



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Re: Heath LNB-4 Parasol
Re: Heath LNB-4 Parasol
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« Reply #5 on: June 04, 2020, 11:14:20 AM »

You've already got all the pieces cut out, so this comment is a bit late -- I wouldn't use more than 1/16" wood on all of the balsa pieces.  I think I would take what you have there and either sand it down or drill a lightening hole in each one with a good sharp Forstner bit.  Or toss all of the formers, build a basic box, and then put stringers on the sides to get the right profile.

Something I learned in flying my own-design airplanes to learn RC on -- a nice stout fuselage just pulverizes the front end when you hit the ground.  It'll penetrate through the grass to find some dirt to smash itself on.  A super light stick & tissue fuselage will hit the ground and be repairable.  I was probably crashing more often and harder than I would have been if I'd been flying freeflight, so I think my observations count for something.
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Squirrelnet
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« Reply #6 on: June 04, 2020, 01:02:16 PM »

Hi Richard

 I agree with Bill on lightening the fuselage construction. The Cessna I'm building has opened my eyes to how light you can build the fuselage ( mind you I haven't flown it yet) but from my experience lighter is always better.

The Redfin is a bit heavier than a Dart, I just weighed my 030 TBR and its 1.75ozs with a 7x4 prop. The 020 is pretty much the same with a shorter stroke to reduce to 3cc, I guess there maybe some difference in weight in the Kompish casting and the straight TBR one too. Nice little engine, I've become a bit of a fan. I would expect your 020 to give comparable power to a Dart, the 030 gives a bit more than a Dart
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Richard Hewitt
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« Reply #7 on: June 05, 2020, 01:45:09 AM »

Thanks for the replies. Oh dear oh dear...looks like I have taken on a bigger challenge than I wanted in the weight department!

I have a Dart going spare but I chose the Redfin because I wanted LESS power, and thus less downthrust - I didn't expect it to produce more power than a Dart! I will do what I can to add lightness everywhere in the fuselage. I did the first stage of assembly yesterday so I wish I'd read your comments first - short of junking what I have done, it will be hard to mod the formers now.

Bill - I don't have any carbon rod, nor do I know where to get it - I have just started modelling again (last year) after a 20 - 25 year break and obviously a lot of things have changed! For that matter, where do I find small magnets? The smallest I can find are clunking great things intended for presentation boards etc.

Tim - your model looks very smart, I hope I can get close to your build standards!

More photos soon when I have something to show...
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Richard Hewitt
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« Reply #8 on: June 05, 2020, 01:55:34 AM »

Sorry Mark and Tim - I just realised I got your comments mixed up with each other. Thanks again for helping.
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billdennis747
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« Reply #9 on: June 05, 2020, 02:31:16 AM »

Bill - I don't have any carbon rod, nor do I know where to get it - I have just started modelling again (last year) after a 20 - 25 year break and obviously a lot of things have changed! For that matter, where do I find small magnets? The smallest I can find are clunking great things intended for presentation boards etc.
I get mine here. Don't go too big - you'll never get them off!

https://www.first4magnets.com/circular-disc-rod-c34

You don't need carbon rod but it's a useful material to have, especially on small models. It's the kind of thing to pick up when you see it but it can be got here

https://www.freeflightsupplies.co.uk/index.php/products/hi-tech-materials/pultruded-material



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kaintuck
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« Reply #10 on: June 05, 2020, 06:33:22 AM »

Or get cheap magnets from what not stores like wal-mart in the kitchen section. They are refrigerator magnets, sometimes a bunch of plain ones can be gotten cheap. Just cut off the plastic outsides!...and a Drexel cutting tool can be used to shape it any way you want....
Marc
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Richard Hewitt
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« Reply #11 on: June 05, 2020, 06:56:53 AM »

Thanks Marc - I did find some cheap ones locally, but they were about the size of a pound coin and rather heavy. I tried hacksawing them up but the "soft iron" defeated even my finest Eclipse hacksaw blade.

Also Bill - thanks for the links. I need to stock up on some of this stuff if I am going to keep up with you guys!
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Squirrelnet
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« Reply #12 on: June 05, 2020, 07:53:03 AM »

Hi Richard

  I really wouldn't bother chopping up magnets they are so cheap just buy the right size.

I have just used two pairs of these neodynium magnets 4mm x 2mm to hold down a removable hatch on the KK Cessna. 

https://www.ebay.co.uk/itm/small-large-NEODYMIUM-MAGNETS-1mm-2mm-3mm-thick-Round-Rings-Cylinder-Discs/132012556278?hash=item1ebc8fbff6:m:m6LGE2gVmrvLO2cZIUOy_Og
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Richard Hewitt
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« Reply #13 on: June 06, 2020, 06:35:11 AM »

Thanks squirrel - next time I am on-line shopping I will buy some of these bits.
I have an unstarted KK Cessna 170 in a pile of old kits in the loft. As a kid I thought it was the best-looking aircraft in the KK catalogue but couldn't afford it. Then in the early 90s, I was at a SAM35 event at Middle Wallop and saw a guy was selling one along with a lot of other stuff. Nostalgia struck and I bought it. One day...maybe...it might get built.
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Richard Hewitt
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« Reply #14 on: June 07, 2020, 02:25:21 AM »

OK, a few more pics as promised. I have done the lower fuselage assembly and made a start on the U/C and tail surfaces. The centre cores exactly fit on a 4" sheet - it's nice when things work out for once! The upper fuselage will wait until the cabane can be done, which in turn requires the wings to be available for test rigging.

I did some more thinking on the weight/wing loading issue. Bill's parasol model (see pic earlier) had 6oz/sq foot. My model has 137.5 sq inch area, so to achieve this wing loading, I would need an all-up weight of 5.75oz. I do not think this is feasible, at least not for a duffer like me. The weights so far are: engine/prop/tank 2.25oz, Fuselage as shown 0.75oz, U/C as shown 0.25oz. I would have to get everything else - wings, tail, struts, covering & paint - within 2.5oz.
Attached files Thumbnail(s):
Re: Heath LNB-4 Parasol
Re: Heath LNB-4 Parasol
Re: Heath LNB-4 Parasol
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billdennis747
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« Reply #15 on: June 07, 2020, 02:52:45 AM »

Richard
Two and a half oz is not impossible. You also have a nice thick wing section which will help. The problem is the heavy engine but at least you will have no ballast needed; not in the nose anyway. The fuselage does look very sturdy so keep that in mind for the next one. I would suggest you build as much of the model as you can and cover it and check the cg before building the tail, then build it accordingly. The sheet core method is very good but becomes less-so on a small model.
A tissue on mylar covering and light sprayed colour and you may be pleasantly surprised.
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Richard Hewitt
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« Reply #16 on: June 22, 2020, 03:04:39 PM »

I haven't updated this thread for a while...apologies, too busy outdoors managing things at Hewitt Acres, etc etc.

Anyhow, some progress HAS been made. Bill, thank you for your comments and encouragement on the topic of weight/wing loading. As I had begun the tail surfaces, I thought I would finish them - if I decide later to replace them with 1/8" ply plates, so be it! They weigh 7g as seen in the photo. There are struts to add later, so I can make any necessary tail ballast "useful" by making these from 10swg wire if I so choose...

The wings are done and as shown weigh a total of 22g including a 16swg joiner. The apparently random bits of balsa in places are to provide "hard points" for detail to be added after covering.

So, all my flying surfaces have used up 1oz of my "available" 2.5oz. My guess is I will end up closer to Mr. Moulton's 7.5oz than Mr. Dennis' 5.75oz  Undecided
Attached files Thumbnail(s):
Re: Heath LNB-4 Parasol
Re: Heath LNB-4 Parasol
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billdennis747
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« Reply #17 on: June 22, 2020, 03:10:25 PM »

Nice work Richard
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charlieman
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« Reply #18 on: June 24, 2020, 08:10:24 PM »

So, just how does one check for balance with a non-existant stab? Shocked
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Richard Hewitt
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« Reply #19 on: June 25, 2020, 12:50:26 AM »

Charlieman, I don't understand your question? The tailplane is on the right in the pictures above.
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Richard Hewitt
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« Reply #20 on: June 28, 2020, 03:04:55 PM »

OK, not many hours put in this week, but the project has progressed somewhat:

The cabane has been soldered up from 20swg (0.81mm) piano wire. Next, I wanted to do the wing struts, but without a centre section it proved infuriatingly difficult to support the wings in accurate alignment with the fuselage. So, I rummaged in the corner of the workshop and found some MDF left over from DIY projects (various). From this I fashioned a thick base and some supports to clamp everything in alignment as shown. The strut cores are 6mm by 0.5mm hardwood (Ramin I think). I have several lengths of this left over from a model sailing ship I built a while back, where it was used for the deck planking, glued over liteply. Normally I would use 1/64" ply for cores like these. I get a weird kick out of using up leftovers, from years ago, for something useful - am I alone in this?

Once everything is cut to size, the struts will be faired with balsa each side. The cabane struts get faired too.
Attached files Thumbnail(s):
Re: Heath LNB-4 Parasol
Re: Heath LNB-4 Parasol
Re: Heath LNB-4 Parasol
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charlieman
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« Reply #21 on: June 30, 2020, 11:12:23 AM »

Richard Hewrtt said  "Charlieman, I don't understand your question? The tailplane is on the right in the pictures above."

however

billdennis said: " I would suggest you build as much of the model as you can and cover it and check the cg before building the tail, then build it accordingly."

Sorry all. I was misunderstanding billdennis' statement and application/context,  entirely. Grin

Just noticed your cap strip added to wing ribs. I want to start doing more of that, as I feel taller spars, not to mention more scal like contruction, is key to solving weak wing structures, warping issues and un-scale spars marring  covering appearance etc.
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billdennis747
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« Reply #22 on: June 30, 2020, 11:59:19 AM »

Richard Hewrtt said  "Charlieman, I don't understand your question? The tailplane is on the right in the pictures above."

however

billdennis said: " I would suggest you build as much of the model as you can and cover it and check the cg before building the tail, then build it accordingly."
My fault. I meant find what weight tail is needed for balance and then build it accordingly.
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Richard Hewitt
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« Reply #23 on: July 01, 2020, 01:40:14 AM »

Re. cap strips, I got into the habit of using them on all my models back ca. 1992 or so. I built David Vaughan's Airspeed Courier design and saw the light! Cap strips strengthen up the ribs enormously, "automatically" recess spars, trailing edge cores, and all the other stuff we DON'T want to touch the covering, and make sanding the structure smooth prior to covering so much easier.
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Richard Hewitt
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« Reply #24 on: July 06, 2020, 01:28:33 PM »

A bit more progress has been made:

1. Once all the struts were done, the fuselage could be released from the jig, and the top deck added (photo 1).
2. A tailskid was made up from thin brass strip (photo 2). The £2 is not the tailwheel, it's for size comparison (although I might need it for tailweight  Cheesy). The tiny screws are from Mick Reeves Models.
3. A male plug for the cowling has been made from balsa, ply, and polyfilla (photo 3). I will mould the cowling over this using glass cloth and resin.
Attached files Thumbnail(s):
Re: Heath LNB-4 Parasol
Re: Heath LNB-4 Parasol
Re: Heath LNB-4 Parasol
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