Windburner MKII Super Light - RC Groups
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May 05, 2017, 09:09 PM
Rock Breaker
gazasmith's Avatar
Yippee!

Windburner MKII Super Light


5/5/17 moulds arrived Windburner fun time.
Last edited by gazasmith; May 05, 2017 at 09:34 PM.
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May 05, 2017, 09:47 PM
Rock Breaker
gazasmith's Avatar
Why build a super light Windburner when the standard ones are so good?
A heavy plane won't get enough flight time on my slopes. Go light and you can fly most days.
So my target is under 500g AUW. To achieve this weight I'll use everything I've learnt building the Rock Breaker. The Balance of weight to strength to get a light plane that can take punishment or my lack of flying ability.
The pics you can see the comparison of my RB wing and the Windburner wing. The RB wing is 220g the burner wing is a little bigger so 250-300g is a target.
May 06, 2017, 01:48 AM
Rock Breaker
gazasmith's Avatar
I wish I had a 4axis wire cutter be so much easier just to cut cores and hand work the tips.
Just have to wait for XPS cores.
Meanwhile see how good a PU core I can make. So far I have 1 just useable core. If I can get the pour perfected the PU cores could work well as a foamie.
The other part is getting to know the moulds. My moulds were designed for cores and sand which construction. No vac bagging, just fill up the mould and clamp it shut. Hehehe that sounds to easy you need to get prep correct and other stuff. I'll work something out to get a light build.

Need a beer Gaza
May 06, 2017, 02:57 AM
Rock Breaker
gazasmith's Avatar
Getting better.
Need a slow hardener lol.
Wing is a 2 pot poor. Easier to get resin mixed and into mould. Next I might try a 3 pour with 2 people. Got to get this stuff mixed properly for a better result.
Nose cone was easy.
Tail is old RB design PU 9g XPS with out paint would be 6g Happy with weight here.

Now I've just filled the WB fuse mould without using my industrial strength mould realease or the don't stuff Kevi's mould protection level, also known as cling wrap. RB tail come out should be good.
May 06, 2017, 03:47 AM
608 km/h!
josh18's Avatar
Hey Gaz this is pretty cool.
My one crack at a PU wing, I did the very light skins first then when they were cured and trimmed, poured foaming PU into both mould halves so it foamed up above the flange. I was able to do it in multiple pours and fill in low spots later. After cure I used a saw to trim the foam off flush and joined the halves with PU glue. I'm pretty sure I didn't use any splooge around the edges. It turned out really strong for the light weight. I reckon this is a better way to go with PU foam than a moulded core as you get more than one chance to get it right. Also I think it could end up lighter as the bond with the skin will be perfect with no chance of voids or the need to use splooge to bond the core to the skin.
The only drawback I had was that the surfaces were pretty flexible as I didn't use any spars anywhere, but that would be the same with both ways.
Cheers
May 06, 2017, 06:58 AM
Remember... Fly for fun!
ALEX HEWSON's Avatar
Thanks for all the info, really cool to follow what you're doing
May 06, 2017, 07:21 AM
Rock Breaker
gazasmith's Avatar
Well got a little stick in fuse mould.
We don't know the condition of the wax so I have decided to stop and do 8-10coats before anymore resin sticks.
I did get fuse core out mainly intacked, good enough to see how sexy a Windburner is.

Josh
I had herd how sticky this foamis so first pours were with cling wrap covers. I had thought about light skins to keep foam of surface on mould. At the moment fuse and nose cone look good to stay PU cores.
The wing would maybe be better in XPS. Off the edge' s wire cutter is broken, I need some one to cut me cores, my wire cutter is only 2 or 3 axis need a 4axis cutter or some one good at hand cutting with templates.
I need to get wing build as close as possible to my FB wing to get the strength to wait ratio sweet.

Almost Wax on time Gaza
May 06, 2017, 07:59 AM
608 km/h!
josh18's Avatar
Looking great! What does the whole thing weigh in just foam BTW?
May 06, 2017, 06:01 PM
Registered User
Thanks for taking the time to post all of this up gaz watching with interest.
Cheers Adam
May 06, 2017, 07:04 PM
Rock Breaker
gazasmith's Avatar
Quote:
Originally Posted by josh18
Looking great! What does the whole thing weigh in just foam BTW?
Josh
Wing 130g fuse 60g add some lam film and a bit of fibre tape could be a short life foamie.

Adam
This is to much fun not to share.
May 06, 2017, 11:05 PM
Rock Breaker
gazasmith's Avatar
I tried PVA for a poor result, maybe need to spray lots of layers. The wet wax has worked the best so far but is a priiick to polish after it hardens. A separate core mould may be need, even make it 4 pieces for easiest removal of cores.
A CNC router would be the go to machine all cores.

So now is painting time, I have a set of cores just good enough.
May 07, 2017, 04:02 AM
Rock Breaker
gazasmith's Avatar
I'm buggered but have got full WB moulds.
Now 24hrs wait to find out if they are any good.
Fuse core is to big mould is open 1-2mm.
Wing looks closed but there could be voids.
Nose cone most likely to be good unless I trapped air .

These parts will be rough and heavier than I want but Prob still be the lightest Windburner ever made.
They would be perfect for me to do some destructive flying with. Check for weak spots I haven't engineered.

Did get some flight time until I Put my FB through a tree again lol. Stupid red tail I could find. Must not make any more red tails they hide in the green grass.

Rum is good Gaza
May 07, 2017, 06:13 AM
Auzzie built planks
timbuck's Avatar
Nice work gazza That should be lots fun.
If you go back in kev's thread somewhere. Before the windburner was moulded , I built a full carbon vac-bagged version RTF it was 550g. It was my best burner ever had because it was so light , fun and so strong , Strength V weight we have spoken about was really good almost impossible to break it. I'll have to find the video's bungy launching it over the rainforest.
It was just blue foam core and one layer of 200g twill , no main spar , just TE and control spars.....the fuze was all 200g twill carbon and some 200g UNI in the tail and saddle area.

A few tips I can give you after a million hours doing R&D this is heat is your friend. Product and moulds must be above 35 to 40 deg to get best results...mix very very fast with electric mixer and don't lift the mixer to induce air larger bubbles.
It would make it 10x easier to do a windburner mould in 4 pieces.

As it a simple straight wing you could cut normal blue foam core most of it and then just PU the tip section. Make it simple and repeatable.

Talk soon

Tim
Latest blog entry: More colours
May 07, 2017, 08:28 PM
Rock Breaker
gazasmith's Avatar
Tim
Good to hear of a super light WB already being a fun plane. I reckon it would be like a super light Gizmo.

PU foam yep need to mix very well very quick and I did get better results when everything was hotter.

I did a test cut this morning on XPS 7000rpm sweet no problems with chipping even using a dull carbide tip. Crank up to 12000rpm for faster cuttting.
I'm think of making a plug from fuse mould then use it to generate a program to machine fuse cores. Going to be fun hand measure and program 500 plus lines. Do this and I'll get consistent cores that are lighter. Could also do wing tips like this but still wire cut the main bit.

More thoughts when I get home
Gaza
May 08, 2017, 07:50 AM
Rock Breaker
gazasmith's Avatar
Finally got the boots off I feel much better now.

Bloody good to get the first parts out.
They are rough, heavy and full of info to get the weight savings I'm after.
PU cores are out for the moment safer to do the work and use XPS.

First is fuse core.
I'm making a plug from mould, cheap as possible will only be good to map the shape. Making and programming will takes ages I don't have any fancy software to help it will be all manual work 500 plus lines to type.
Then I can machine XPS cores in two halves.
Machining cores gives the ability to easily change the size so you can change the layup for light or heavy builds.

That will do today

Cheers Gaza


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