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  #391  
Old 02-25-2016, 05:59 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
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Wow, Andy, it almost looks like it would be easier to make it in clay and make a mold. But - I see molds everywhere.

Great progress!
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  #392  
Old 02-26-2016, 08:44 AM
crabandy crabandy is offline
 
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Quote:
Originally Posted by BillL View Post
Wow, Andy, it almost looks like it would be easier to make it in clay and make a mold. But - I see molds everywhere.

Great progress!
Yeah, Dunno. I've thought about it but the inlets are in the right spot and the back half of the cowling is correct it's just the bits in the middle. I probably should've built a mold around the existing cowling while I was still flying with the old cowling. Sometimes I find my direction by wandering around.
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  #393  
Old 02-29-2016, 11:07 PM
crabandy crabandy is offline
 
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I've spent mornings drinking coffee and evenings drinking beer, just sipping and staring at my cowling. I couldn't pass the garage without stealing a glance at my cowling peering at different angles, more filler here and sand more filler off there. After thinking several times there was no way to blend things together I think I about have it. My youngest helpers getting dirty with me.





Top of the inlet showing the fatter lips, the template helped a lot to keep things uniform and determine filler addition/sanding.





I think my next step is to layup the inside of the cowling, the new shape is just 2 plys of 8.9 oz glass sanded thin in spots and too weak to do the finish sanding on. Thanks to BillL's lead I ordered some lantor soric from Fiberglast, it's kinda like a cross between honeycomb and cloth (thinner and cheaper than honeycomb). It is like a dense thin mattress topper or dense quilting batting. It is made for vacuum bagging applications but the sales rep agreed it should work fine having epoxy brushed on and squeegeed out between a couple pieces of plastic. I made 2 test pieces, 1 with a layer of glass on each side of the soric and 1 with just the soric.



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  #394  
Old 03-01-2016, 05:58 AM
BillL BillL is offline
 
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Good process of experimentation, Andy. I was just joking about a mold, you are very close. Meaning, lots of tweaking and sanding, but close.

I, too, tested the Soric for layup with some test strips. Making several test strips (2" X 8") with different resin application methods showed that if both cloth and Soric are wet, then the shear bond is very good. One strip got the edges removed to reveal the core and rely on just the shear strength. It was very strong and stiff with a 1-core-1 test piece. I was concerned about debond or shear failure in the core, but it held nicely. No quantified test results though .

Use a roller and a final layer of peel ply to get an even resin content. Your body working skills will make short work of the final plenum piece. You will be in the plenum business in no time.

Spring is on the way!
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  #395  
Old 03-01-2016, 09:33 PM
crabandy crabandy is offline
 
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Bill, I was sure hoping you were joking!!

I couldn't believe how stiff/strong the soric sandwiched between 2 layers of glass was, not sure how to quantify it.
My first full half day I've had to work on the airplane in over 3 months summed up in 1 photo. The existing cowl/honeycomb was cut/sanded at an angle, a fiberglass soric sandwich was placed in the newly shaped areas with an epoxy/flox butter evening out the seams and an extra layer of glass over the seams topped with peel ply.

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  #396  
Old 03-03-2016, 08:33 AM
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jdeas jdeas is offline
 
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Default soric (aeromat)

Great stuff. I made my plenum out of it as well. Nothing else I tried worked as well on compound curves like this. It may be a bit heavier than traditional honeycomb but the ease of working with it and the strength of the finished part is worth it.
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  #397  
Old 03-03-2016, 03:23 PM
crabandy crabandy is offline
 
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The ol' yard stick straight line sawing jig and flush trim saw did another decent job making the split.





The top of the lip seems to be fine, fat enough and blends in with the rest of the cowl.



The outboard side of he cowling on the other hand has the fat lip than quick transition to a "pitot" tube.



I think inlet is placed fine vertically but needs to be moved inboard 3/8-1/2 inch, moving the inlet inboard would give me the geometry to work more curve on the outboard side like this:



As it sits now I think it's too flat to easily insert the horizontal hinge pin holding the cowling halts together. It's also a little heavier due to some extra glass and filler. I'm going to sit on it and ponder.

BillL or DanH do you happen to have a dimension between the center of your round inlets?
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  #398  
Old 03-04-2016, 09:43 AM
BillL BillL is offline
 
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SJ long cowl, RV7, 23 15/16" or 1/32" less center to center distance for inlets. The design dimension could have been a 24.000, but my glassing of the inlet rings is off that much.
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  #399  
Old 03-04-2016, 02:07 PM
crabandy crabandy is offline
 
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Thanks Bill, mine are pretty close at 23 5/8. Hmmmm, more coffee sipping staring and thinking.

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Last edited by crabandy : 03-04-2016 at 10:50 PM.
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  #400  
Old 03-15-2016, 07:44 PM
crabandy crabandy is offline
 
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If I had it to do over again I probably would move each inlet about 3/8" inch inboard for more outside curve, but I'm moving on with the existing inlets. I carved out a spot to nestle in the forward section of the new hinge, it helped with the angle for inserting the hinge from the front. I followed the Van's instructions on drilling extra holes and aggressively sanding the hinge flange and epoxying it to the cowl, the old hinges were not letting go virtually welded to the cowl. I used the hinge pin and an extra piece of hinge to position the new hinge with the existing hinge. After the epoxy dried I riveted the new sections.





I really should've waited to make my plenum until after re-shaping the cowl, oh well it's just fiberglass. The new cowling shape allowed for a slightly larger rounded opening up front, I thought about laying up a new plenum in the cowl but would be left with the flanges fitting the baffling problem again. I decided to shape some pour foam on the top to sand to shape. I laid the existing plenum in the cowl and measured a rough arc prior to pouring the foam.



Sanded to shape laying in the top cowling, about 1/8 shy for extra wiggle room.



I laid 2 plys of glass over the newly shaped foam. I poured more foam over the top of the plenum as reinforcement to hold the shape as I cut out the old fiberglass and foam.



Inside of the plenum sanded and ready for more glass, I cut the soric and glass but I'm waiting on more epoxy to finish it.





I also spent some more time sanding things to shape on the outside of the cowling at the juncture of old vs new cowling, a little more filler here and sand more off there....I think my main problem was trying to shape the curve with my larger 12" sanding block, it was sanding all of the curve out and I needed a smaller 4-6" block to shape the curve.
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Last edited by crabandy : 03-15-2016 at 07:54 PM.
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