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Aug 18, 2019, 03:50 PM
Living on the Dark Side.
guitarcher's Avatar
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Thanks Tim and Paul.

The top skins were layed up yesterday and the centre was demolded. The centre turned out really well. It weighs 40g which is lighter than expected.

I'm thinking of making a wave spar for this build. I haven't tried it before so should be interesting.
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Aug 18, 2019, 09:49 PM
Themadartist
Quote:
Originally Posted by guitarcher
Thanks Tim and Paul.

The top skins were layed up yesterday and the centre was demolded. The centre turned out really well. It weighs 40g which is lighter than expected.

I'm thinking of making a wave spar for this build. I haven't tried it before so should be interesting.
Hey Greg, are they one-way valves in the vac lines on the second pic ???

If so, care to share where they came from ???
Aug 18, 2019, 09:53 PM
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Quote:
Originally Posted by Guy97
Hey Greg, are they one-way valves in the vac lines on the second pic ???

If so, care to share where they came from ???
Yes Steve, they are aquarium parts bought off my favorite supplier, ebay. I can't remember exactly how much they cost, something like 6 bucks for 10 of?
Aug 19, 2019, 09:40 PM
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After considering wave spars I was discouraged from this method by my trusted composites advisor so my standard foam cored carbon wrapped spars were made yesterday and both wing skins were joined. They were post cured in the hotbox overnight and guess what was on my mind all night long. At first light this morning the skins were demolded and I am very very happy with the results. Surface finish is really good, strength and stiffness seems more than adequate and both skins weigh 160g.

Joining the centre to the wing skins was contemplated this morning and after a few trial attempts a method was nutted out that worked well. The ends of the spar boxes were hollowed out and 10mm wide balsa shear webs with carbon glued to the sides were poked up the spar box and across the centre section with plenty of splooge. A foam cored wrapped drag spar was also glued in. Splooge was added to the centre section skins all round the edges and then clamped up to the wings.

While that's curing I'll start prepping the curved wing tips.
Aug 20, 2019, 12:41 AM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by guitarcher
After considering wave spars I was discouraged from this method by my trusted composites advisor .....................
I am relieved you decided against them Greg.
I was about to write up a comment to that end.

Wrapped, composite constructed spar is the best for this application.
I think I have described my latest development in wrapped spar construction elsewhere.

All good.
Getting close now to the festival!.................
Aug 22, 2019, 02:31 PM
Living on the Dark Side.
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Thanks for looking out for me Jim. Its good to see you're paying attention.

After a bit of filling and sanding the now blended centre was ready for some reinforcing with the addition of a couple layers of light uni across the spar area, biaxial aft of that and another layer of 165g glass on the nose and wrapped around the leading edges. This was all wet out and peel ply was used to help smooth everything out. Today I should be able to finish sanding the centre and give it a coat of resin.

I'm still working my way through the tips layup.
Aug 22, 2019, 10:21 PM
Themadartist
Quote:
Originally Posted by guitarcher
Thanks for looking out for me Jim. Its good to see you're paying attention.

After a bit of filling and sanding the now blended centre was ready for some reinforcing with the addition of a couple layers of light uni across the spar area, biaxial aft of that and another layer of 165g glass on the nose and wrapped around the leading edges. This was all wet out and peel ply was used to help smooth everything out. Today I should be able to finish sanding the centre and give it a coat of resin.

I'm still working my way through the tips layup.
Greg, I use a blue peel ply that's much finer than the red stripe stuff. If you want to be able to remove excess resin, and get a nice finish, you should definitley try the blue stuff. Cheers, Steve.
Aug 23, 2019, 03:53 PM
Living on the Dark Side.
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Quote:
Originally Posted by Guy97
Greg, I use a blue peel ply that's much finer than the red stripe stuff. If you want to be able to remove excess resin, and get a nice finish, you should definitley try the blue stuff. Cheers, Steve.
Thanks for sharing your ideas Steve, its always good to hear of other people's positive experiences. I have tried the blue peel ply and I found it annoying difficult to use. It tended to rip into shreds leaving lots of strands firmly adhered to the skin and trying to lift a glued down corner to start the peel back was sometimes near impossible. The peel ply with the red stripe has been a dream to use , That's something about composites, what works for some people may not be the same for others.

After a fair bit of stuffing around trying to make a reasonable foam cored shear web for the fins which is a complex compound curve I decided to have another go at using GP330 expanding foam. I've had good success in the past and also some horrible shrink back , but with the fins being such a complex shape I thought it would be worth having another go at the GP330 as it is such a good core when it works well. Its been so long since I used it that I had no idea how much too mix for each fin but in the end it worked out pretty good in the end. I think at least half as much again might make a more uniform density so I'll record the amount for future reference

Today's plan is to sand the centre again and layup both fins. I'll also continue repairing the Napalms that were damaged at Larrikan a couple days ago..
Aug 23, 2019, 04:06 PM
Entropy is happening!
Jim.Thompson's Avatar

Peel Ply.


Quote:
Originally Posted by guitarcher
................. I have tried the blue peel ply and I found it annoying difficult to use. It tended to rip into shreds leaving lots of strands firmly adhered to the skin and trying to lift a glued down corner to start the peel back was sometimes near impossible. The peel ply with the red stripe has been a dream to use ,.......................
That has been my experience too Greg. Maybe it comes down to batch difference? I don't know.
However, I now am cautious about using any peel ply due to excessive resin reduction. I use it less and less these days.

Quote:
................................. Larrikan a couple days ago....................
Where is this? (If it is not giving too much away!).
Aug 24, 2019, 03:27 PM
Living on the Dark Side.
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Control surfaces were cut yesterday and wiper prep was done but it was too late in the day to be mucking around with cold epoxy so I put it off. I also had another go at the GP330 fins using twice the amount of mix. The result didn't seem greatly different, maybe a little more uniform.
Aug 26, 2019, 03:14 PM
Living on the Dark Side.
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Ok, wipers have been completed and fin joiners made and glued in place. The fins turned out great and are really stiff. The completed bare airframe weighs 460g which I reckon is pretty good. I didn't have a specific target weight in mind, just to build it light and strong. Hopefully the servos and controls will go in today.
Aug 26, 2019, 06:14 PM
Entropy is happening!
Jim.Thompson's Avatar
I can visualise it flying off the mountain next month Greg!
I look forward to seeing it.
Aug 27, 2019, 03:33 PM
Living on the Dark Side.
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Hey thanks Jim. I'm really keen to get this one properly tuned so it can show its full potential.

Not long to go now.
Sep 16, 2019, 05:31 PM
Living on the Dark Side.
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Manilla Slope Fest Video.


https://www.rcgroups.com/forums/newr...eply&t=3033907

Well I am very happy to report that I have had a few opportunities to fly and tune Psycho Chicken in good lift and it now performs as well as I could possibly hoped for. It has a good speed envelope, turns hard, handles sink periods with a small amount of flap deflection to give extra lift and is a pleasure to fly.


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