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Tim's Skywriter Build

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Tim Ballinger13/03/2017 09:05:17
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540 forum posts
227 photos

Just not in stock in U.K. I have just emailed hi asking when?

Tim

Tim Ballinger15/03/2017 09:40:04
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540 forum posts
227 photos

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Must be my birthday...

Lucas Hofman15/03/2017 09:46:18
596 forum posts
316 photos

Congratulations my friend. Have you been given half an hour in the air in a Tiger Moth?

Lucas

Tim Ballinger15/03/2017 10:04:12
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540 forum posts
227 photos

No it was the sentiment that got that card chosen . I was indulged with an hour in a stampe a couple of years ago though. My full size flying days ended when I sold my open class cirrus and bought a horse to join the wife. I found Flying was too time consuming for a good family life. But my head is still in the clouds.

Tim

Tim Ballinger17/03/2017 17:49:57
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540 forum posts
227 photos

Top wing underway...

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Tim Ballinger18/03/2017 16:41:27
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540 forum posts
227 photos

bI quite like these 3mm self tapping brass inserts. All the cabane fixings seem to have ended up in the right places and bubbles in the middle as far as my eye can tell .

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john stones 118/03/2017 20:13:42
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10487 forum posts
1475 photos

Yep, looks all square n fit for purpose yes

Tim Ballinger19/03/2017 08:24:50
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540 forum posts
227 photos

Going to sort out the outer wing struts next while the structure is still open.

Lucas Hofman19/03/2017 09:23:51
596 forum posts
316 photos

This looks good Tim. Have you ever tried to pull out an insert? These bolts are on tension, and the upper wing can give about 140N (14 kgf) when stalling at speed, as in a flick roll.

Lucas

Lucas Hofman19/03/2017 11:28:01
596 forum posts
316 photos

Tim, these inserts are much more elegant than T-nuts, not in the least because one can insert them from the same side as the bolt will go in later. I looked at the model fixing site but they only have M4 and upper. OK for wing bolts but M3 is what one needs for struts, motor mounts etc.

Do you use M4 for the struts, or have you found a suppliers that has M3 inserts?

Lucas

Martin Dance 119/03/2017 12:25:39
194 forum posts
33 photos

Hi eventually found the details of the company I bought M3 inserts from. They're called Inserts Direct I Googled them, they still exist but prices on their site are for 1,000 off quantities. As I found their details on my phone! I guess I rang them and asked for some samples or a smaller quantity, which they supplied.

Tim Ballinger19/03/2017 12:50:22
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540 forum posts
227 photos

I used nexus modelling supplies which Martin found. I seem to remember they indicated being out of M3 when I bought mine and that they would back order. Then they seemed to arrive next day. Might be worth emailing them at

sales@nexusmodels.co.uk .

As for their pull out load ... I will do a test...

Tim

Tim Ballinger19/03/2017 14:13:02
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540 forum posts
227 photos

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Test results for 3mm insert....

Single insert good at 8kg

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Finally pulled out at 12kg

So assuming your load is spread over 4 bolts gives a safety factor of around 3.

Good enough ?

Tim

Lucas Hofman19/03/2017 15:19:43
596 forum posts
316 photos

More than enough! I will order some. How much did you pay? By the way, was it 2 times 4mm ply - not light ply - that you tested?

Lucas

Ps. Load on the upper will also be transferred to the lower wing through the outer struts. Probably not the same load on every attachment point, but better than a wing without outer struts.

Tim Ballinger19/03/2017 16:13:09
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540 forum posts
227 photos

Lucas, they were £1.11 for a pack of 4 so I bought 3 packs.

Actually yes it was lite ply and just 2x 3mm !

Tim

Tim Ballinger20/03/2017 13:05:35
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540 forum posts
227 photos

Having deviated from the original fixings had to adjust the strut length by 10mm to alllow room for the brackets and bolt/screw heads. I used the same thickness Ali for the brackets as the cabane strut which is probably overkill but it is what I had to hand. Angles are such that the brackets are 2 bespoke sets of three. Angle is set to match the cabane struts with a slight tweak for final ease of fit. No bolts at this stage just 2mm wire in the holes to ensure I have a fit which does not preload the wings.

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Tim Ballinger20/03/2017 15:50:57
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540 forum posts
227 photos

Definitely the fiddlesticks bit so far for me. Interplane heights measure the same both sides so content for now. Think I can get on with the top wing again now.

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Lucas Hofman22/03/2017 11:36:12
596 forum posts
316 photos

Nice that someone goes in front.... Would it be more elegant to have the lugs coming out of the wing going between the strut reinforcements.The strut is 2 mm ply isn't it. If one reinforced with 1.5 or 2mm each side at the ends and then "clamp" the lug between the reinforcment with a M3 (or M3) bolt.

What do you think?

Lucas

Tim Ballinger22/03/2017 13:49:57
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540 forum posts
227 photos

I did start thinking about sandwiching the Ali but as I was using 2mm thick it all started to feel too thick for a strut end but in principle you are absolutely right about it being the elegant solution. Of course if you stick with original lug fixed in the wing there isn't this problem ! It's the issue of leaving enough space for fiddling 2 screws into place that I think creates the problem. Having 'profiled' the lugs, from the outside I do not see the lugs as they are behind the strut .

Interesting to see what you come up with.

Tim

Tim Ballinger22/03/2017 22:14:23
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540 forum posts
227 photos

...but the sandwich might work if you are skilled enough smiley

Tim

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