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Tim's Skywriter Build

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Lucas Hofman31/03/2017 14:12:47
596 forum posts
316 photos

The CG on the plan is for sure a safe starting point. I would not be surprised if you end up with 5% further back after flying a while. But this is very dependent on how "neutral" you prefer planes to be - that is will they level out when sticks are released or do you want them to continue straigth on.

Lucas

Lucas Hofman31/03/2017 14:24:50
596 forum posts
316 photos

Your computation is correct but the starting points may not be:

- 30% MAC for each wing is quite far back. 23-25% is safer to start with

- the upper wing is in free air and is more effective. The second drawing on the rcgroup thread accounts for that.

I would stick to the 30% as on the plan for the first flights. If you have to use weights that you can easily remove to achieve that. The "leads" used to balance Aluminium car wheels are ideal for that.

Lucas

Tim Ballinger31/03/2017 15:34:55
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545 forum posts
229 photos

Without access to a wind tunnel to figure out where the CP actually is, erring on the safe side makes good sense. However if I come out at 35% without ballast I will be well satisfied.wink

Tim

Tim Ballinger25/04/2017 18:49:14
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545 forum posts
229 photos

Had a bit of a break and started off again by having a fiddle with the cockpit and windshield. Windshield not quite as symmetrical as I would like but I guess it will suffice.

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Tim Ballinger28/04/2017 14:04:56
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545 forum posts
229 photos

Fuselage covered except for trim lines which will be white just not decided where and how many.

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Lucas Hofman28/04/2017 14:07:31
596 forum posts
316 photos

At least one is still making progress!. Will your wings be black and red too?

Regards, Lucas

Edited By Lucas Hofman on 28/04/2017 14:07:49

Dwain Dibley.28/04/2017 16:26:53
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1268 forum posts
1265 photos

Very tidy job Tim ..Cockpit is nice too.

D.D.

Tim Ballinger28/04/2017 17:32:46
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545 forum posts
229 photos

Current plan is dark blue ( only looks black in the pic !) undersides and a sunburst red and blue on the top.

Tailplane the same. Not sure about the fin. Making it up as I go along really.

Fus has some white trim lines now as well. I'll take another pic when I have screwed the windshield back.

First time I've covered anything since the early 70's and I really don't remember it being as stressful as this was. Must be an age thing !

Tim

Tim Ballinger28/04/2017 20:53:41
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545 forum posts
229 photos

Went a bit mad with the photos.....

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Tim Ballinger01/05/2017 08:56:30
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545 forum posts
229 photos

Tail fixed on now and fus just about finished.

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Edited By Tim Ballinger on 01/05/2017 08:57:26

Tim Ballinger06/05/2017 08:10:11
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545 forum posts
229 photos

Bottom wing finished now.

Saw your post Lucas; will see how it compares to the last formula we used in due course.

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Lucas Hofman08/05/2017 07:47:01
596 forum posts
316 photos

This is a great scheme Tim! Maybe I should reconsider mine....

Lucas

Tim Ballinger08/05/2017 11:20:02
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545 forum posts
229 photos

Thanks Lucas. More sport than scale but it fits the bill for me. After the detail of measuring, cutting and fiddling the top of the wings in different colours it was great to use a single piece of film on the undersides.

Tim

Tim Ballinger08/05/2017 22:17:00
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545 forum posts
229 photos

Covering finished.

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Lucas Hofman09/05/2017 07:08:45
596 forum posts
316 photos

Looking really good! And strikingly different in appearance from Tim's orginal with this sunburst scheme Tim. Waiting for nice weather to maiden now Tim?

Lucas

Tim Ballinger09/05/2017 07:30:04
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545 forum posts
229 photos

Lucas,

I guess so but that's always the nervous bit. Might take me a few months to install the motor and find a spare Rx !!

Tim

Tim Ballinger15/05/2017 19:57:37
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545 forum posts
229 photos

Radio installation complete, motor installed and waiting for weather now.

Tried the cg formula that Lucas posted and I got 8cm from upper L.E.

Measured mine and it came out at 8 cm. 1cm further back than the plan original of 7cm but I am happy and will not be adding any lead.

Final numbers are:-

Weight: 2.35kg or 5 lb 4oz

I have set deflections to :

Elevator: 3.5 cm

Rudder: 3cm

Aileron: 1cm

Can up by 25% using dual rate if needed.

That's about it ,as I say waiting for weather now.

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Lucas Hofman16/05/2017 07:08:48
596 forum posts
316 photos

Tim,

Unless you are very glad in spins the elevator deflection seems very high to me. I remember about 1.5cm from the Ballerina (except for the flight mode I use for spins).

What does the drawing/article say?

Anyway, gratulation on having finished your Skywriter!

Lucas

Tim Ballinger16/05/2017 07:34:55
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545 forum posts
229 photos

Lucas, could not find any info on control deflections. Given no data I would rather have too much and reduce later. Equally happy to go with numbers that have been used on Skywriter before. Anyone ?

Tim

Lucas Hofman16/05/2017 07:43:48
596 forum posts
316 photos

The nasty thing about to much is that you may stall her when you do not want to, 2 m over the ground for example.

There is a picture on page 5 of the article which points towards big deflections, so you are maybe right here. Dial in a good amount of expo, so you can give small amounts of elevator too.

Have you tried sending Todd a message?

Good luck with the maiden, Lucas

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