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Updating a Protech Topic 400

Sort of an own design

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FilmBuff30/01/2018 15:09:19
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257 forum posts
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Found this lurking in the loft...

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1.5 M span with a Speed 400 - very under powered by today's standards. Got me thinking though. The wing is very good and quite light. All it needs is a new fuselage, motor and prop and ESC, radio gear, and lighter tail feathers.

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Here's my target design spreadsheet. Looking to save over 200 grammes in the process.

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Made a start, thanks to Hyperflight.

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And even dusted off some old drawing skills!

MattyB30/01/2018 16:10:39
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2014 forum posts
31 photos

Nice model, as I remember they float very nicely. The only issue you are likely to have is achieving the CG - with a modern brushless and lipo powertrain you are likely to need a fair bit of noseweight. That new fuse looks a smidge longer in the nose though, so perhaps you will be ok.

FilmBuff30/01/2018 16:31:15
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257 forum posts
28 photos
Posted by MattyB on 30/01/2018 16:10:39:

Nice model, as I remember they float very nicely. The only issue you are likely to have is achieving the CG - with a modern brushless and lipo powertrain you are likely to need a fair bit of noseweight. That new fuse looks a smidge longer in the nose though, so perhaps you will be ok.

Yes, you're right re CG. But a few factors work in my favour. The Pod and Carbon boom is very light - so the trick will be to build the stab and fin as light as possible and then adjust the boom length! The new fuselage will be nearly two ounces (54g) lighter - and much of that weight saved behind the CG. There is a trade off that with longer tail moment I can use a smaller tail. The SailplaneCalc design spreadsheet really helps here.

 

Edited By FilmBuff on 30/01/2018 16:57:39

FilmBuff04/02/2018 14:00:05
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257 forum posts
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tailplane.jpg

Simple, light but strong AMT that will fit on the Blaster V mount. Great wood selection from SLEC. In it's naked form (needs more shaping) it's just under 10g, and with covering and the mount will be smack on my 15g target. That's less than half the weight of the original.

FilmBuff07/02/2018 15:05:17
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257 forum posts
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In light of the demise of Solarfilm - I hastily ordered a few rolls of Solite! Only 20g/sq M...

FilmBuff19/02/2018 13:42:04
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257 forum posts
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Workshop heated a a relatively warm 16 degrees and kept company by The Cranberries.

Tailplane in Solarfilm So-Lite came in at only 12 grams, fin and rudder looking at around 6 grams.

FilmBuff07/06/2018 15:04:55
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257 forum posts
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Never thought magnets would play such a part in construction...

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FilmBuff07/06/2018 19:08:41
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257 forum posts
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Test flew in the calm between thunderstorms. Exceeded expectations. Launched on 20% power initially and then pulled it near vertical to around 150m. Stall and dive tests revealed CG needs moving forwards a smidgeon.

Hang time for a 1.5m glider is amazing. Weighs around 440 grams with a wing loading of around 6oz/sq ft. Funny how we mix units...

Little 2S 1300 battery gave me a 40 min dead air flight with 50% charge remaining.

First time with Spektrum. Liking the programming interface.

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Edited By FilmBuff on 07/06/2018 19:10:13

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