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Old Aug 07, 2009, 02:39 AM
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hoffboy's Avatar
Olympia, WA
Joined Feb 2008
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Build Log
1/6 Scale Andreasson BA-4B (prototype)

Peter Rake likes the BA-4B so much, he designed two versions; a 1/5 scale (prototype build is ongoing here) and a simpler 3 channel (RET) 1/6 scale, which is being prototyped, well, right here.

I've found lots of great info about this biplane on the web, and also many nice color schemes and design modifications to ape, so I'll have some decisions to make down the road and welcome any and all input as I go along. I've attached a scheme that I'm particularly fond of....simple, sharp, and contrasty.

To start with, the nice folks at Manzano Laser Works sent me the cut parts and my local copy shop made quick work of Peter's plans. The smoked balsa smell had the usual effect on me this evening, and now I can't WAIT to get started with the build!

Tomorrow I'll see about stripping some balsa and gluing up some fuse sides.
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Old Aug 07, 2009, 02:53 AM
a.k.a Maltone
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Australia, NSW, Goulburn
Joined Jan 2005
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"Two sheets of plans and a nice pile of freshly laser cut balsa. What more could a man want?"

Three sheets of plans and an even bigger pile of freshly laser cut balsa

Looking forward to your build.

Pat
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Old Aug 07, 2009, 11:08 AM
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Olympia, WA
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Quote:
Originally Posted by maltone
"Two sheets of plans and a nice pile of freshly laser cut balsa. What more could a man want?"

Three sheets of plans and an even bigger pile of freshly laser cut balsa

Looking forward to your build.

Pat
And perhaps an extra hour of uninterrupted build time each day, so long as we're fantasizing.

I'm happy to have you aboard as you've set the "Rakian" build bar very high and thus I may need to lean on you a bit if things get tricky.

-Matt
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Old Aug 07, 2009, 02:00 PM
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Olympia, WA
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1/8 Balsa Fill?

The wise builder studies the plans VERY closely before cutting, gluing, etc.. I zoomed way in on the PDF of the fuse in an attempt to figure out what "1/8 Balsa Fill" might mean. Assuming the 1/8" longeron fits all the way forward into the notch at the bottom of the 1/8" forward fuse sheet (logical) I can't for the life of me sus out why a fill piece would be required here, forward of F4.
Going to have to mock it up and see what's what.
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Old Aug 07, 2009, 03:19 PM
North East England
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It's to give the hatch something to rest on, and also to give you something to iron the rear underside covering onto at the edge of the hatch. Just a piece of 1/8th across the fuselage.

Least that's what it looks like judging by Pete's other plans I have.

Steve
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Old Aug 07, 2009, 03:45 PM
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Olympia, WA
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Quote:
Originally Posted by Redbaron25
It's to give the hatch something to rest on, and also to give you something to iron the rear underside covering onto at the edge of the hatch. Just a piece of 1/8th across the fuselage.

Least that's what it looks like judging by Pete's other plans I have.

Steve
Yep, that's about all I could figure, since otherwise I'd just have the thickness of F4 to work with, which ain't much. I'll scab it in there, and it will also beef up F4 as a bonus. Thanks for the input!
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Old Aug 09, 2009, 02:40 AM
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Olympia, WA
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Fuselage Sides

1/8" balsa sticks cut, test fit, then glued up. Second side built over the top of the first. I use twice as much parchment paper as I need so, for the second side, I can just fold the parchment up and over between the two halves and pin everything back down.

There are two small infill sheets at the aft end that serve as control wire guides. Two questions have emerged:
  1. Should non-slotted pieces be manufactured and installed opposite the slotted pieces, for strength? There were none in the cut sheets, so I'm going to leave them out for the moment, but my gut says to add them and incur the weight penalty in exchange for beef.
  2. These aft sheets are thinner than the 1/8" sticks, which poses an interesting dilemma. Should they be flush with the outside (logical when you think about covering later) and if so, when you consider how the parts are pinned up, how do you hold the little sheet proud of the build surface and flush with the outside? (This is only a problem for the "near" half.) My solution was to do it incorrectly (pushed it all the way to the board thinking I'd sand down to it from the outside later as part of the aft thinning before joining the sides) then I realized that would probably require too much removal of material so I cut it out, flipped the whole works over, and glued it flush with the outside.
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Old Aug 09, 2009, 04:51 AM
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Right, since I'm feeling halfway human again, I'll get caught up with this thread.
On point one, the 1/8 fill is exactly as Steve describes it, simply a bit of 1/8 balsa to attach the covering and hatch to.
As regards points two and three, I DON'T DO 'BEEF'. Consequently, there are no un-slotted fill pieces at the tail, only the slotted ones provided with the cut parts. Although not as short nosed as many biplanes, I still can't see any reason to add weight at the tail.
When it comes to fitting the sheet parts that should be there, I would have fitted them after the basic fuselage was assembled and the longerons already curved in at the tail. Then they could be either pre-curved to match the longerons, or fitted proud and sanded to match. They're really only there to provide pushrod exits though the covering.
However, if Matt has already fitted the ones on his model, it may be neccessary to add those un-slotted bits simply to aid with even bending of the longerons as the tail is pulled in. It may well come down to a case of how hard the longerons are. If as hard as I'd make them, it may be that the longerons themselves will determine how the fuselage curves, rather than the softer sheet parts. Only Matt will be able to decide which way he needs to go on his model.

If, on this, or other models, I was fitting the exit pieces during the fuselage side bulid I'd do the reverse of what Matt did. I'd build one frame and fit the part flush with the top surface of that, rather than pushing it right against the board. Turn that side over, build the other side and fit the exit flush with the top surface. I do it that way simply because balsa thickness is something of a variable. Now, any variation is on the outside of the fuselage, where it can be resolved with sanding the finished fuselage.
Another reason is that I have yet to be able to fit this sort of part without glue getting under it and forming a nice, difficult to sand area around it. Not ideal when it comes to finish sanding.

As an aside, and by way of advance notice, I've changed the front of the cowl on both sizes of this model. For some reason, probably after looking at later versions, I left an open fronted cowl. On this version, it shouldn't be open. If Matt needs the new shape, just say so and I'll post an illustration. It is possible to create the new part from the old one, but the cut files for both models now show the correct cowl front. Needless to say, the cowl front will probably need to be removable for motor access/replacement.

Right, having turned a simple Q&A session into something of a lecture, I'll let Matt get on with his build.

Oh yes, I almost forgot. Thinking that Matt would be out of action after his sudden house purchase, I sorted out another builder for one of these. That has one big advantage for either of you, as long as one gets built exactly as per design, the other builder can intrduce slight mods to his model - like ailerons or a later variant. It's good because it demonstrates that either option is viable from the basic model. I leave you to fight it out over who does what. Isn't that kind of me?

Pete
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Old Aug 09, 2009, 05:04 AM
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Olympia, WA
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Quote:
Originally Posted by PETERRAKE
Right, since I'm feeling halfway human again, I'll get caught up with this thread.
On point one, the 1/8 fill is exactly as Steve describes it, simply a bit of 1/8 balsa to attach the covering and hatch to.
As regards points two and three, I DON'T DO 'BEEF'. Consequently, there are no un-slotted fill pieces at the tail, only the slotted ones provided with the cut parts. Although not as short nosed as many biplanes, I still can't see any reason to add weight at the tail.
When it comes to fitting the sheet parts that should be there, I would have fitted them after the basic fuselage was assembled and the longerons already curved in at the tail. Then they could be either pre-curved to match the longerons, or fitted proud and sanded to match. They're really only there to provide pushrod exits though the covering.
However, if Matt has already fitted the ones on his model, it may be neccessary to add those un-slotted bits simply to aid with even bending of the longerons as the tail is pulled in. It may well come down to a case of how hard the longerons are. If as hard as I'd make them, it may be that the longerons themselves will determine how the fuselage curves, rather than the softer sheet parts. Only Matt will be able to decide which way he needs to go on his model.

If, on this, or other models, I was fitting the exit pieces during the fuselage side bulid I'd do the reverse of what Matt did. I'd build one frame and fit the part flush with the top surface of that, rather than pushing it right against the board. Turn that side over, build the other side and fit the exit flush with the top surface. I do it that way simply because balsa thickness is something of a variable. Now, any variation is on the outside of the fuselage, where it can be resolved with sanding the finished fuselage.
Another reason is that I have yet to be able to fit this sort of part without glue getting under it and forming a nice, difficult to sand area around it. Not ideal when it comes to finish sanding.

As an aside, and by way of advance notice, I've changed the front of the cowl on both sizes of this model. For some reason, probably after looking at later versions, I left an open fronted cowl. On this version, it shouldn't be open. If Matt needs the new shape, just say so and I'll post an illustration. It is possible to create the new part from the old one, but the cut files for both models now show the correct cowl front. Needless to say, the cowl front will probably need to be removable for motor access/replacement.

Right, having turned a simple Q&A session into something of a lecture, I'll let Matt get on with his build.

Oh yes, I almost forgot. Thinking that Matt would be out of action after his sudden house purchase, I sorted out another builder for one of these. That has one big advantage for either of you, as long as one gets built exactly as per design, the other builder can intrduce slight mods to his model - like ailerons or a later variant. It's good because it demonstrates that either option is viable from the basic model. I leave you to fight it out over who does what. Isn't that kind of me?

Pete
All excellent points and duly noted for future reference.

I'll make the cowl mods if you post the illustration.

I hope this mysterious "other builder" gets cracking soon so we can have THREE BA-4B threads going simultaneously. That would have to be some sort of record.

Thanks Pete.

-Matt
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Old Aug 09, 2009, 06:03 AM
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'I hope this mysterious "other builder" gets cracking soon so we can have THREE BA-4B threads going simultaneously.'
..now there's a cue for someone......

Pat
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Old Aug 09, 2009, 06:45 AM
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One of your clubmates Pat. Any clues there? Giving disturbing reports of hovering Avros. No doubt Ian will chime in once he's ready. He's already pointed out that there aren't enough SS parts supplied and I've remedied that on the cut file.

Here's the cowl front shape, pasted into a Word doc. Just open it as is but I make no guarantee of the size being correct.

Pete
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Old Aug 09, 2009, 11:31 AM
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Olympia, WA
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Quote:
Originally Posted by PETERRAKE
One of your clubmates Pat. Any clues there? Giving disturbing reports of hovering Avros. No doubt Ian will chime in once he's ready. He's already pointed out that there aren't enough SS parts supplied and I've remedied that on the cut file.

Here's the cowl front shape, pasted into a Word doc. Just open it as is but I make no guarantee of the size being correct.

Pete
I show 3 SS parts on hand, so indeed, looks like I'm 5 short. Easy to fabricate.

I'll also need to make a new forward piece for the cowl as (thanks to Charlie's clever balsa maximizing) the original had F8 lasered out of the center void. Again, easy to whip up.
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Old Aug 09, 2009, 11:39 AM
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Former Time

With the sides dry, it's time to move from 2D to 3D. I don't currently possess self standing machinist's squares (hint hint Santa) so I fall back on whatever squares I can find to hold these bits in place while they cure. Not complicated, just fussy, and it's hard to overstate the value of laser cut pieces that fit perfectly the first time.
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Old Aug 09, 2009, 07:54 PM
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Queanbeyan, NSW,Australia
Joined Jul 2009
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Mysterious "Other Builder" here!

I have got cracking.....4 wings built last evening....centre section and sanding next.

Will post a couple of piccy's when the camera batteries have charged, flat as a road killed cane toad they were.

Couple of things to think about...a lost foam fibreglass cowl and slimmer profile centre section struts in line with full size builds from 80s.....Just a thought.

Ian
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Old Aug 09, 2009, 09:45 PM
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Olympia, WA
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Quote:
Originally Posted by ozybard
Mysterious "Other Builder" here!

I have got cracking.....4 wings built last evening....centre section and sanding next.

Will post a couple of piccy's when the camera batteries have charged, flat as a road killed cane toad they were.

Couple of things to think about...a lost foam fibreglass cowl and slimmer profile centre section struts in line with full size builds from 80s.....Just a thought.

Ian
Methinks, per Peter above and based on your cowl and strut thinking, that you may be just the man for the "later variant." I don't yet have those chops.

Please feel free to dog pile onto this thread with your build (could get messy, but the compare/contrast might also be conveniently informative) or if you start one of your own, I'll be your first subscriber!

Cheers from Olympia.

-Matt
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