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Ton van Munsteren03/02/2011 21:25:08
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1274 forum posts
3296 photos
Tim,
 
What else can I say than that your doing a great job, love the splitting of the longerons.
 
More photos please
 
Ton
Tim Hooper05/02/2011 11:15:44
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2847 forum posts
2358 photos
Posted by Ton van Munsteren on 03/02/2011 21:25:08:More photos please
Ton
 
I'll do my best - I promise!
 
Just as an exercise in pointlessness, I thought I'd dump all the bit on the scales and see where where we are at the moment. My apologies for working in imperial units!
 
4S 4000Mah cellpack 20.4oz
Motor/ESC/UBEC 15.9oz
Servos (6) 11.4oz
Balsa airframe 25.1oz


TOTAL TO DATE 72.9oz (4lb 9oz)

So given my target weight of 8lb AUW, that leaves around 3½lb left for covering, struttery, undercart+wheels, linkages, rx., etc.
 
 
tim
 

 
Tim Hooper05/02/2011 20:29:59
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2847 forum posts
2358 photos
So, here's the start of the metalwork!
 
The cabane struts are cut from 12swg piano wire, and I drew out patterns and and cut balsa templates to keep them as accurate as possible. After all there's nothing worse than a biplane with wonky wings, is there?
 

Then I set about a pice of brass sheet with some tin snips, hammer and vice to produce these little saddle clamps, which will secure the struts to the top of the fuselage.
 

I'm using brass so I can solder the clamps to the struts to aid alignment of the upper wing. More to follow......
 
tim
Tim Hooper08/02/2011 09:00:55
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2847 forum posts
2358 photos
With all the brass widgets soldered to the struts, I made some mounts out of 1/8 ply, which were then screwed and glued to the tops of F2 and F3.
This view shows the underside of the mounts, with the 3mm blindnuts in place.
 
F2 and F3 are gussetted with obechi block. Note the cutouts to allow for the blind nuts!
 
The struts are temporarily screwed in place to check for alignment. What has become apparent is that I mis-measured the rear strut and it's about 2mm too long, which would lead to negative incidence on the wing. No matter - I'll shim up the bottom of the front strut to compensate!
 
The tiny fitments near the bottom of the verticals will allow me to fit static rigging when the model is finally assembled.
 
tim
mal brewer08/02/2011 13:46:04
289 forum posts
Hi Tim, just looking at your latest build,I don't know how you find the time! Regarding the wire cabane struts,which I have been told are correctly called centre section struts,I have found it preferable to use 3mm gas welding rod.This can be obtained from car body garages,and is a mild steel wire with a copper coating.It bends and solders much easier than piano wire,and is amply strong.I have used it on many models,and I am in fact using it on my latest Krier Kraft,which is to 1/4 scale.However,it is not resilient enough to use as undercarriage wire.Try some on your next model,I think you'll find it satisfactory,............................cheers,Mal.
Tim Hooper09/02/2011 09:07:01
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2847 forum posts
2358 photos
Thanks for the tip, Mal!
 
I actually have several bundles of mild steel arc welding rods in my shed (a legacy from my kit-car days......), but never thought to use them for anything other than welding chassis members together!
 
tim
Tim Hooper11/02/2011 09:06:55
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2847 forum posts
2358 photos
Some more progress!
 
It didn't take a genius to see that I made the rear struts a tad too long, when I compared the model to my plan. Look at all that negative incidence! Never mind, it didn't take too long to remake the strut......sigh.........
 

A lot of careful measuring saw the holes bored in the fuselage sides for the aluminium tubes for the lower wing rods. It all fitted first time (which sort of made up for the boo-boo with the rear strut!)
 
Looking promising!
 
tim
Danny Fenton11/02/2011 09:16:14
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8981 forum posts
3869 photos
Doesn't that look sweet Tim, well done
 
I should bin that centre section jig
 
Cheers
Danny
Tim Hooper11/02/2011 10:33:44
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2847 forum posts
2358 photos
Dan,
 
My drawing was spot-on! Much better than my measuring prowess anyway...

tim
Ton van Munsteren13/02/2011 14:19:26
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1274 forum posts
3296 photos
Just to let you know Iam still following this build.
 
What can I say more than nice.
 
Ton
 
 
Tim Hooper13/02/2011 18:28:07
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2847 forum posts
2358 photos
Cheers Ton!
 
Awful weather today, so It seemed a good time to have a crack at the undercart!
 
The front and rear frames are bent from 12swg piano wire, and were jigged on a plank of wood. The joints were bound in copper wire, before soldering together with my nice new 80watt iron.


To allow the 8swg axle to move on its hair-band bungee, I added plates of brass sheet.

Those central holes were enlarged to form a slot, and the spurs were used as anchor points for the bungee.
 

Seems to work just fine! The wheels are 3¼" items (to replicate the wheelbarrow items of the original!)

 
Wolfie14/02/2011 08:47:10
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129 forum posts
218 photos
Posted by Tim Hooper on 13/02/2011 18:28:07:
.......hair-band bungee......
 
 
Now that's lateral thinking!
 
Although I would probably find myseld in deep do-do's if I was discovered borrowing said articles
Tim Hooper14/02/2011 16:06:38
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2847 forum posts
2358 photos
Borrow? Who said anything about borrowing!
 
You have to assert yourself and comandeer the articles required!
 
tim (yes dear, coming dear......)
Tim Hooper17/02/2011 20:20:53
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2847 forum posts
2358 photos
I thought it about time to start on the top decking (the front part will also double as the hatch), so some strips of Sellotape were applied to the upper longerons to prevent permanent adhesion, followed by a 1/8 sheet 'floor.
 
The formers came next, closely pursued by the start of the 1/8 strips of planking.
 

Now somehow I need a way to be able to open the hatch without interfering with the centre-section rigging - which criss crosses over the top of the decking. More though required methinks!
 
To give my brain a rest, I made up the motor mount from 1/4 ply, drilled to accept the blind nuts, and then added the 1/8 ply sides, together with some internal reinforcement from very hard balsa. The rear face was then sanded to yield 2° side and downthrust, before being epoxied to the front of F1.
 

This meant that I was now able to introduce the motor to its new address (albeit temporarily!
 
 

Right, I'm away for a few days, so there won't be any more progress over the weekend.
 
tim
Tim Hooper22/02/2011 13:13:21
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2847 forum posts
2358 photos
I managed to get all the nose planking glued down yesterday, so this morning I gave it a quick sand down. After that I made a cardboard template, and used that to mark out the cockpit openings.

Seemed a good idea to test fit our pilot too!
 

The bit I always dread is seperating the hatch from the rest of the fuselage, but the Sellotape I laid onto the upper longerons earlier made life easy, so a bit of minmal jiggling with a long blade saw the hatch come away cleanly.
 
I then took the final decision to cut the hatch in half. The rear half will cover the bolts that hold the cabane struts in place, and will be left on the model semi-permanently.
 

I had to make clearance holes in the underside of the hatch to clear the strut fixings.

Front hatch off...

....front hatch on!

Danny Fenton22/02/2011 13:29:24
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8981 forum posts
3869 photos
Lovely work as usual Tim, really nice
Myron Beaumont22/02/2011 13:44:34
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5797 forum posts
51 photos
Tim
Just to say what a brilliant job you're doing & that your presentation will probably inspire more peeps to follow your example that otherwise might not think it feasible to build from an idea in your head. Keep it up . Isn't it a shame to have to cover up all that beautiful construction ? Only problem I have is that you havn't got a burbling engine up front ,but I won't mention that
Best build blog ever--- IMHO
Myron
Tim Hooper23/02/2011 13:19:11
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2847 forum posts
2358 photos
Thank you, gents!
 
I've taken today off from the build, but all those stringers along the rear fuselage can't be far away now.
 
There's still loads to do before I get the iron out and attack that big roll of Solartex though...
 
tim
Tim Hooper25/02/2011 13:27:38
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2847 forum posts
2358 photos
So.....given that the cross section of the upper fuselage changes from a sort of ellipse at the rear cockpit to a rectangular at the LE of the tailplane, it made sense to plot this on a sheet of card.

The radiating lines are the stringers, so divided these into quarters...

....and joined up points thus. Then it was a small matter to make tracings of the sub-formers so created.

These tracings formed the basis of the intermediate sub-formers, although I have to stress that a bit of fiddling and faddling was needed to make sure that all those stringers were straight and true.

I then fitted little blocks between the stringers just behind the front decking. These will be shaped and sanded when the glue dries!

It's all go, eh?
 
tim
Tim Hooper27/02/2011 17:21:09
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2847 forum posts
2358 photos
So those little blocks have been roughly hacked into shape.

Now there's a single 3/16 stringer that runs along each side of the fuselage. Adding the stringer took minutes, but it has a knock-on effect in that the covering will not be flat against the fuselage side. No biggie except that little items such as the exit guides for the elevator wires now need to be raised slightly, so that they'll lie directly underneath the Solartex......

....similarly, the lower wing mount needs a raised 'land' around it for the covering to adhere to. Those little vertical slots above the wing are for the anchorages for the rigging wires,

With the motor bolted on the nose, I've set about making up the cowl. The sides are flat 1/4" sheet.

You can see the built-in side thrust when viewed from above.

The top and bottom of the cowl will be hacked out of scrap block - after the glue dries, of course!

Now, ideally I'd like to cover the cowl in thin aluminium (eg beer can material), but I've never used this material before. The flat sides won't be an issue, but the upper and lower panels of the cowl both feature compound curves, so we'll have to see how it goes!
 
tim
 

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