Author Topic: I'm drowning, in bits of an Mu28  (Read 38779 times)

Happy Days

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I'm drowning, in bits of an Mu28
« Reply #30 on: November 29, 2011, 20:56:41 PM »
Quote from: "gerryb"
none of us IS perfect, french or otherwise


Wrong, my misses is perfect.

I used to own a complete Encyclopaedia Britannica but I threw it away,….My wife knows everything!

 :lol:
Try not to run out of airspeed, altitude and ideas....... all at the same time.

Brian

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« Reply #31 on: November 29, 2011, 23:10:04 PM »
Hi Keith,
Yes I would go for all moving ,if removable.
Just do a home made copy of something like the alpina.

Brian
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gerryb

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« Reply #32 on: November 29, 2011, 23:21:58 PM »
or just keep the same outline of the existing tailplane/ elevator

Brian

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« Reply #33 on: November 30, 2011, 00:20:09 AM »
Hi,
I assume the same tailplane.
I mean copy the mount, pivot and control mechanism .

Brian
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gerryb

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« Reply #34 on: November 30, 2011, 01:57:35 AM »
ok, i'm with you

Happy Days

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« Reply #35 on: November 30, 2011, 07:22:31 AM »
Yea’, fixed or all moving it will have to be removable for me to be able to get the fuse in my car. The fuse, as it is, just fits with a fraction to spare.  I’m hoping the rudder will have enough deflection to enable me to not have to drill a hole through the cars’ roof for the rudder to stick out of!  

I’m kinda hoping to have  a removable rudder.
This model has certainly caused crescendo of brain activity in my head. And I haven’t even started actually building it yet! :roll:

(I have to say, ..I feel more confident flying model aircraft than I do building them. Thank god for ARTF! :D )

K.
Try not to run out of airspeed, altitude and ideas....... all at the same time.

Brian

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« Reply #36 on: November 30, 2011, 09:56:05 AM »
Hi Keith,
I found a good article in 'that' hints thread on rcGroups on glassing a wing.
There he is using blue foam and with a vacuum and is applying 7psi.
; http://www.favonius.com/soaring/bagging/bagging.htm
We were using 1 to 2 psi on soft foam and soft balsa.
Your wing half is probably 500 in\2 maybe 550.
That is a lot of weight.
You should use as much weight as the foam can stand up to.
We will look at this on Thurs,, also.

When you are happy that you have a bench that is able it is a good idea to get/cut a piece of chip-board or mdf to place on top of the wing to carry this weight and spread the load evenly.
I have seen a 'stack' of concrete blocks on a wing.

Brian
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Happy Days

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« Reply #37 on: November 30, 2011, 11:20:14 AM »
Er, if I was going down the road of glassing the wing Brian, that would be a great idea………

My instinct is to go with a carbon  “ I ” section spar. I think that would be the lightest option & plenty of gliders fly with only such strengthening.

I’m not a ‘precision’ flyer like you F3A competition pilots. :wink:

K.
Try not to run out of airspeed, altitude and ideas....... all at the same time.

Brian

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« Reply #38 on: November 30, 2011, 11:39:28 AM »
Hi Keith,
I'm not suggesting you glass the wing.
I am trying to give you some guidance re gluing pressure for whatever skin is used.You have veneer which does not crush easily so use all the pressure the foam can stand up to.
Also you need to prepare the foam surface, sand with 320/400gt .
Make a 0.6 to 1m long sanding block.

Help I'm a nobody get me out of here !

Brian
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Happy Days

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« Reply #39 on: November 30, 2011, 19:54:37 PM »
Steady on Brian, don’t get your knickers twisted! :lol:

Just a simple question;
Assuming that the glue that I use to stick the obechi  does not expand as it cures, why would I need to apply one or two lbs (16 - 32 oz) pressure on each sq inch of surface while the glue cures?
In other words, what happens if less pressure is applied during the curing process?

Keith
Try not to run out of airspeed, altitude and ideas....... all at the same time.

gerryb

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« Reply #40 on: November 30, 2011, 23:36:39 PM »
a little clarification here keith, i think.

i think brian's advice refers to using epoxy as the adhesive to stick the veneer to the foam as this is a slow set glue.

copydex on the other hand is an impact glue (like the old evo-stick). you coat both surfaces thinly with copydex (which can be thinned slightly with water, helps the glue to spread easily), allow to dry for 10 to 15 min and then very carefully place thin pieces of balsa or such like across the foam, every 12" or so. you then place the veneer, glue side down onto cross pieces. don't worry, it won't stick to them. align the veneer over the foam and then one by one, carefully remove the cross pieces. gently press the veneer on to the foam as you go and watch your wing develop before your eyes. childs play!!

if you go this route, do be aware this method is a one shot only method, once copydex grabs, it stays grabbed. get it wrong and you bin the lot. i suggest a practise session before you go for real. great system but you have to get it right 1st time

Brian

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« Reply #41 on: December 01, 2011, 01:50:37 AM »
Hi Keith,
When using a slow glue ,that cures hard, the more pressure you use the less glue you need and the stiffer the bond and the stiffer the result/wing etc.
With high aspect wings stiffness is important especially if you want to fly it hard and in tough conditions
I think this is you.
You do not want a floppy wing !!!!

Brian
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Happy Days

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« Reply #42 on: December 01, 2011, 07:01:39 AM »
Thank you gentlemen. :clap:

 Considerable food for thought. :?:  :?:

Keith
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Happy Days

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« Reply #43 on: December 01, 2011, 19:14:45 PM »
So,......moving on & let’s move on the next problem…..

Each wing half is made up of three foam core sections, ( each section lines up beside each other)



The problem is very hard to show in a photo as it requires photographing something white next to something white.



Between my fingers, (okay Gerry, 'between my fingure and thumb') in the picture are the edges of two of the foam bases. My fingers are pushing the bases down onto a flat surface but there is a ridge. (Look carefully and give your eye time to ‘get in’ and you’ll see the ridge)That is to say, the edge of one of the bases is not at the same height as the other edge of the adjacent base.
If I place the wing core, and then the top of each section in place on all of the sections  the ridge is still apparent across the tops of the sections, i.e. each section has a different height.

In other words the base parts of each of the three sections is a different thickness. In addition, some of the base sections have different thicknesses from front to rear of the wing. So that although the front of two adjacent base section sections might be flush, the rear part of those same two sections might not be flush.

I’ve tried putting the sections up-side-down on the bench to see if that made the wing cores line up flush, but it doesn’t.

Clearly I can’t just gust glue the foam cores together as they are.

Anyone got any ideas?

Keith :cry:  :cry:
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Richard Boyd

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« Reply #44 on: December 01, 2011, 19:36:31 PM »
Hi Keith, I have not got my head around what you mean,
Maybe if the length of the each core was trimmed it would fit snuggly together, I am by no means an expert on wings or building gluing cores.
Richard Boyd
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