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Old Jun 28, 2012, 03:30 AM
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Liverpool, England
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Build Log
Henschel HS129 B-3

Hi Everyone,

I have decided for my next scratch build project I will model the Henschel HS129 B-3 'Panzerknacker'. This model was fitted with a very significant 75mm cannon which protrudes quite some way forward of the fuselage. I have been fascinated with the plane since building the Airfix kit as a boy.

Build is straight forward balsa, fully sheeted, with some GRP mouldings. I have learnt a lot from my P61 Black Widow build so am designing lightness into the structure.

Specs -
Wing Span - 2.4m (94.5in)
Dihedral - 5.5'
Incidence - 1.5'
Wing Area - 84.48 sq.dm
Target weight - 6kg
Wing loading - 71 g/sq.dm (24oz)
Motors - Turnigy G60 (400Kv)
Props - 17" 3 Blade
Batteries - 2 x 6S - 3300Mah

The plane has a large wing area and lots of dihedral, I am imagining it was designed to act as a slow flying and stable gun platform so I am imagining with the wing loading it will be a real floater.

I am using the same power train I have for my 2m Black Widow which is working very well at nearly 8kg in weight so there should be ample power.

Issues -
CG - The plane has a real snub nose (reminds me of a duck bill platypus) so getting the CG correct will be hard but there is the opportunity of using weight at the end of the cannon.
Battery placement - Engine nacelles are small but I may be able to get a 6S 3300 Mah battery sloping vertically behind the motor.
Cannon Fixing - Our field is not great so ground loops will be almost inevitable, should I build the cannon very strong to resist this or hinged to allow some movement?

This will be a long build, about a month to complete the design and 11 months to build

Any thoughts?
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Old Jun 28, 2012, 05:08 AM
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Australia, WA, Kalgoorlie
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Ha, another model on my "bucket list"

Nice work so far- well done!

I'll be following with interest.

Odd
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Old Jun 28, 2012, 09:21 AM
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Canada, ON, Mississauga
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You will probably finish this one before mine . I am eagerly on board for this one.
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Old Jun 28, 2012, 03:25 PM
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Have you seen this thread? http://www.rcgroups.com/forums/showt...t=henschel+129
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Old Jun 28, 2012, 04:25 PM
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Canada
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Here you go :-)
A 129b plan Old and small ...but as it's a .pdf one could enlarge/print it to "makes a debri field on unexpected arrival" size :-)
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Old Jun 29, 2012, 02:43 AM
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Liverpool, England
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Hi, Yes I had seen that thread made a fantastic job of it, there arent any reports of it flying yet.

Thanks for the plan it is helping me verify the cross sections, the fuse is a very strange triangular shape and the sides appear to slope in the same plane with a constant radius on the lower and upper corners but following the vertical and horizontal silhouettes of the plane makes this very difficult to draw.

Just establishing the correct postion and outline for the B-3 cannon housing and barrel length from this interesting line drawing of the magazine system, must have been very heavy.

One of the problems of using 3 views off the web is the innaccuracies between them, this drawing which looks really accurate shows the leading edge of the wing in a completely different place, this is probably correct but I will leave the wing where it is as any further forward will cause real CG problems I think.

It occurs to me that the cannon housing is a good place for electronics.

One more thing I saw recently a link to an actual firing gun (not real bullets of course) for RC use, probably beyond my budget but would be cool for this instance anybody remember the link?
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Old Jul 02, 2012, 01:19 PM
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Liverpool, England
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Took delivery of a 1:48 Hasegawa model today. The model is far more square on the top than I thought and the nose is completely different to how I viewed it so I need to make some changes. I think I will assume the model is correct as its difficult to find any really clear photographs.
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Old Jul 02, 2012, 04:39 PM
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Canada
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Have that Hasegawa Model too. Wierd (wrong!) fuse .. at least :-)
Frankly, I've learned, to my chagrin, that Many plastic models are Non scale. Despite claims to the contrary... of 'reputed' brands .
Have to remember that it's just some factory worker making molds from whatever, if any info, was supplied /made available to him.
Sometimes these are strikingly 'off' scale..
Trust Only to ancient photographs,
Like the ones found in here:
Silly Site won't accept a 7mb Zip file although It claims able to take 10mmb. Grr.
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Last edited by Bare; Jul 02, 2012 at 05:26 PM.
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Old Jul 03, 2012, 01:03 PM
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Will be following along for a couple reasons. I'm doing some preliminary design of an 87" span twin and will probably make it my first electric model. So I'll be watching your methods of designing light. Also I built an Hs129-b2 for controlline FAI scale competition. It flies very well. Did a lot of comparison of 3-views to photos and actually built my model to the same drawings wizard of odd posted. In my opinion the most acurrate drawings are those by Albert Bentley. I had not found them prior to building my model.
Chuck
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Old Jul 03, 2012, 06:14 PM
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Australia, WA, Kalgoorlie
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Here is a plan for an 86" model- may be worth a look.

http://shop.traplet.com/product.aspx?c=617

Odd
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Old Jul 04, 2012, 02:29 AM
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Liverpool, England
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Thanks all, Bare did you manage to upload the photos in the end, be appreciated if you could.

Lightness - I am certainly no expert and failed miserably in my last project but what I am trying to do is combine elements together so the wing spar is also a fuselage former etc.

Cant seem to find any drawings by Albert Bentley do you have any links?
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Old Jul 04, 2012, 07:42 AM
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Southington, Connecticut, United States
Joined Jun 2000
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Builder of the 86" plans that Odd posted is over at www.rcscalebuilder.com I also believe there was a build thread on this plane there.
stefanP
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Last edited by KOMET 44; Jul 04, 2012 at 07:44 AM. Reason: link issue
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Old Jul 04, 2012, 11:36 AM
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Canada
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Arthur Bentley drawings: 129 B-3
http://www.albentley-drawings.com/hs129.htm
(no luck with uploading.. yet.)
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Old Jul 20, 2012, 01:17 PM
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Liverpool, England
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Thanks for the help.

Made lots of progress on the design, had to redraw the nacelles over and over so its taken me longer than I thought, wont be ready to start building for another couple of weeks.

I have most components sited, air tank, elevator and rudder servos, motor mounts, battery mount, retracts etc. Tail group and wings left to do but these will be a breeze compared to the nacelles.

Managed to position a 4.5A, 6S upright behind the motor mount, the nacelles protrude forward quite a bit so I think I will be ok with CG placement

Ken
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Old Jul 27, 2012, 01:12 PM
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