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A little more done, in fact almost there now. All the controls are covered and last night I made a start...

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...on teasing the film around that chap. Look at all that stuff wrinkled up over the edges. Slowly does it...

...and a bit further on...

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...two surfaces done, two to go.

Soon time to take a break for the Christmas activities.

Edited By Nigel R on 07/12/2018 09:31:58

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Thank you gents. I'm not sure about infinite patience!

Well with these last two bits on the cowl that just about wraps up the base of white film all over.

Don't look too closely at the front. Starting to show a few wrinkles on some of those awkward corners...

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Next job is to assemble the surfaces and glue hinges before getting some decoration stuck on.

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  • 2 weeks later...

Thank you David.

 

No maiden yet. I have completely reassembled things, only to discover, despite planning, that my CG is rearward. Coming out about 3/8 behind the 1/3 chord position. This is with the lipo stuck forward as far as possible on its tray. sad

I therefore have to do something. Ideally that big heavy lipo needs to go forward about an inch. The small problem being that there is a firewall in the way. Worse yet, the two lower motor standoffs are also in the way.

Options, I think:

1) swerve the surgery, nail some lead to the firewall, go fly

2) build a ply motor box, cut a big hole in firewall, move lipo

or

3) make a ply mount to replace (or extend) the existing aluminium cross mount, allowing me to move the two lower standoffs out of the way of the lipo

#3 looks like less work than #2, which sounds good

Haven't decided yet. Maybe there is also a better mousetrap that I haven't thought of.

Obvious lesson for next time around is, make sure the standoffs (or motor box) don't prevent the lipo from being snuck up against the back of the motor.

Edited By Nigel R on 02/01/2019 13:15:27

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Actually, one better mousetrap, careful measurement required first, if and only if the firewall is deep enough (top to bottom that is), I might be able to move the lipo down and then forward, which maybe just maybe could mean it sneaks past the existing blind nuts.

More soon.

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Tack on some lead and see how it flies. You may find it's a bit conservative on the balance point and that you want to balance it further back so you just remove lead, at this point you would have been really peeved had you already chopped the nose about. If you find that it does need the lead then you can look into ways of moving the battery forward.

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I think through you two the voice of sanity hath spoken clearly. You're both right. Minimal effort, nail on the lead, get it flying right, then look at the harder options. It's sitting at 3-1/4lb right now (2oz over my initial guesswork). I reckon I'm looking at about 3oz - 4oz to move the CG to 33%. At 3-1/2lb it will still fly nicely enough to maiden.

This is what I love about this place, chuck some ideas around and one of you chaps will come up trumps with something good to throw back.

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As it stands, it needs a little more 1/4" tri reinforcement around the glue joints with the firewall.

Anyway.

The lipo will snug right up against the motor now. That's as much as I can easily do to fix the CG without lead.

The ESC will be relocated above the front of the lipo, inside the motor box.

Theory is:

- Some sort of lipo tray extension will go inside the box.

- I'll add a couple of baffles to make sure air goes over the ESC to manage the heat. Or, I'll box in the front of the lipo, which would have the same effect. Not sure yet, I'm kind of making this up as I go along.

Of course at this point I realise I've made the box too shallow, but only by the thickness of the firewall (5mm). Never mind - perhaps I will need the offcut of firewall after all - I can make a few ply washers to go between motor box and motor itself.

Mental note for the future:

- this fuselage had a reasonable amount of wood at the back, in the deck and the crossgrain sheeting

- servos were located close to the rear of the wing saddle

I could and probably should have put the servos forward in the wing opening. Live and learn. Maybe the thing to do would be to provide a couple of possible locations in the servo tray, and move things to suit when it starts getting close to time to balance the thing.

It wouldn't be impossible to move the servos now, but it's more surgery (knocking out the back end of the lipo tray, putting in a new tray for servos, sorting new control runs). I've seen snakes "extended" with an inch or two of outer stuck in place, so never say never, but I'll see where things lie with the new lipo location first.

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Using closed loop on the rudder instead of snakes might save some weight at the tail end, especially if you put the adjustable clevis at the front and just loop through the rudder horn. Saves moving the servo perhaps.

For major surgery on the ply firewall ( next time! ) consider using one of those vibrating saws from Bosch etc instead of chain drilling and hacking. Handy for specialist jobs but not worth buying specially but the sort of thing best borrowed when you need it for just 5 minutes...........

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