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  #1  
Old 05-31-2007, 12:33 PM
HiGeez HiGeez is offline
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Default MG Tab layup

Last night I started the MG tabs. All UNI and BID was pre-cut, 25 UNI and 20BID as per the layup schedule. BID being .013 thick and UNI being .009 should yield a .485 layup thickness. "No way hose saye". After the layup I had, maybe, a 3/8" thick tab. What gives? The layup was exact, no more- no less than 45 plys. The M drawing showed almost a 1/2 inch thick outer tap thickness. In the heat of the moment I added another 5 plys of BID, 25 total, for a tab thickness of 7/16".

I'm wetting out the 5 plys on 4 mil plastic and squeeging (sp) out excess resin (MGS 335 @ 95*). Am I pressing too hard? Why is the tab so thin? The extra 5 plys - good, not good? Will hold off on the other side 'till I get a response.

Jerry HiGeez Preiser
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  #2  
Old 05-31-2007, 12:43 PM
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John Slade John Slade is offline
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Default Re: MG Tab layup

My guess is the (good) technique you're using with low viscosity MGS and squeege through plastic is saving excess epoxy which would otherwise make up the thickness. In this case the thickness is important. I'd add extra plies to get the plans thickness. Your tab will just be a little stronger.
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  #3  
Old 05-31-2007, 01:49 PM
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crrobinson14 crrobinson14 is offline
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Default Re: MG Tab layup

Quote:
Originally Posted by HiGeez View Post
I'm wetting out the 5 plys on 4 mil plastic and squeeging (sp) out excess resin (MGS 335 @ 95*). Am I pressing too hard? Why is the tab so thin? The extra 5 plys - good, not good? Will hold off on the other side 'till I get a response.
I agree with John. You're just pressing too hard. The thickness number is just a guideline for an 'average' wet-out and squeegee technique. You can compress it quite a bit beyond that guideline.

Whenever the plans called for a specific thickness for a layup, I used a trick I've seen on others' Web sites. Put pieces of 1/4" (or whatever) foam or plywood on each side of the layup, and put a flat board or other surface and some weights on top. It will give you an exact thickness when you're done. For layups that you can't do on your table, you can clamp the spacers between boards on either side.
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Old 05-31-2007, 03:05 PM
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John Slade John Slade is offline
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Default Re: MG Tab layup

I wouldnt call it "pressing too hard" that infers that it might be short of epoxy. Using mgs, plastic and a hair drier its ez to get a perfectly good wetted out layup thats thinner .
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Old 05-31-2007, 03:33 PM
HiGeez HiGeez is offline
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Default Re: MG Tab layup

I did the block spacer technique. Blocks 1/2 thick were cut and ready. I did that with the landing gear bulkhead hard points and they were perfect, .250 + or - .0000000001. That's what led me to the "whatthehell", thus, this post. The remaining question John: Is 7/16" OK (50 plys)? It will come out to be only 1/8 inch shy of the M drawing overall width. Reason: I didn't peal ply the vertical face and I don't want to chance a delamanations at that point if I fatten up the fore and aft face to 1/2 inch.

No plan dimention is given other than by scaling the M drawing and/or layup schedule, hence 1/2 inch. My memory serves me correctly that someone else discovered this, I just don't remember the fix.

I try not to press too hard. There is always a small ridge in front of the squeegie.

Thanks guys.

I desided to forego my 40th high school reunion in N.Y. this fall to attend RR (my 3rd year). I'm at my 737 hour mark and have more questions than answers.

Jerry

Last edited by HiGeez : 05-31-2007 at 03:36 PM. Reason: additional material added
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  #6  
Old 05-31-2007, 04:30 PM
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John Slade John Slade is offline
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Default Re: MG Tab layup

My suggestion would be to sand it well, then add enough plies to make it the correct thinkness. You're talking about the main gear tab, right? You don't want any fore/aft slop in there.
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Old 06-01-2007, 12:18 AM
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crrobinson14 crrobinson14 is offline
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Default Re: MG Tab layup

Quote:
Originally Posted by John Slade View Post
I wouldnt call it "pressing too hard" that infers that it might be short of epoxy. Using mgs, plastic and a hair drier its ez to get a perfectly good wetted out layup thats thinner .
How about "pressing too hard to get a 1/4" thick layup with that many layers of BID"?

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  #8  
Old 06-02-2007, 09:58 AM
HiGeez HiGeez is offline
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Default Re: MG Tab layup

I use the 1/4" spacer blocks method as you described and as I remember, it was more than the requires 25 plys - two additional plys I think. I put a straight edge accross the blocks spanning the layup and added BID until the straight edge made contact with a slight depression.

John, (or anybody) what is the width of the tab? M-9 has it at 6 3/4". Mine is 6 5/8". Can washers be used to take up any slop. I mean, has anybody built their tab soooo acurate that it fits with NO slop? No washers? No sanding it down because it's tooooo tight?

I'm starting the layup on the other side in ten minutes so waiting for a replay is of no use. It's Saturday and the hanger is calling...........

Jerry HiGeez
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  #9  
Old 06-02-2007, 02:06 PM
HiGeez HiGeez is offline
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Default Re: MG Tab layup

Pilot side tab done. This time I didn't squeegie as hard and the results are the same. Finished thickness: 7/16". I'm going to let it cure and add more plys to both sides later if necessary. Now there are 50, 25 UNI and 25 BID.

Are spacer washer accebtable if it is too narrow?

Jerry Higeez
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  #10  
Old 06-07-2007, 01:37 PM
HiGeez HiGeez is offline
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Default Re: MG Tab layup question

OK, the on going MG saga. Looking at M9 and page 9.5, in question, the MG4 bushings, which way do they go into the bulkheads? Shoulders facing the MG tab or facing the MS20364-820 nuts. The M9 drawing shows something between the nut and MG1. Is this a washer (not called out) or the MG4 shoulder? Or just the way they drew the nut? Need to know by Saturday.

Jerry
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  #11  
Old 06-07-2007, 02:49 PM
Wayne Hicks Wayne Hicks is offline
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Default Re: MG Tab layup

Shoulders facing into the gear well. Later, you'll insert these same bushings into the tube that goes through the main gear tabs. The goal is to have these bushing shoulder-to-shoulder when all is installed and done.
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