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windscreen base fairing layup

Bill Boyd

Well Known Member
I've been studying the plans, and watching the video for the -14 canopy fairing on YouTube.

Is there a good reason for not using dry micro as a substrate or as a filler sandwich for maybe three glass plies vs the ten plies called out in the plans?

Same question for high density expanding foam, allowed to fully expand first...

I can't see the mechanical or aesthetic need for a heavy chunk of glass and resin 10 plies thick up there. What am I missing?
 
I didn't think that thick micro was very strong. On my 6, I faired out the intersection to a nice curve with epoxy/cabosil, then maybe 4 layers of glass. Made a nice smooth curve.

That said, I would want something stronger than micro below it. Epoxy doesn't grab to alum or plexi very well, so also want my best chances. Not sure if the micro impacts adhesion.

Larry
 
DIY metal

I used this all aluminum fairing instead of of the glass. It turned out great and was easily completed in a few hours...

http://www.mlblueskunk.com/Fairing_Photo_s.html

That was a purchased one. Some DIY instructions are here from the 27 years of the RVator book.

Page 146. https://books.google.com/books?id=4dHwzsR8keEC&printsec=frontcover#v=onepage&q&f=false

I did this on my -6A and was pleased with the results. I did it in two halves - the first half took a couple of hours and in normal building fashion, the second half took about 45 minutes. :)

I intend to do the same on my -10
 
Windscreen layup

Has anyone experienced de-lamination across the top of the windscreen after several years? I bought my RV10 last Oct (2017) with Total time of 189hrs no issues observed at that time as part of the pre-buy inspection. Since then around Jun of this year I started to see some cracking above the pilot door right at the windscreen cabin interface. I generally know how i will need to repair it but wanted to know if anyone else has seen any de-lamination or cracking.
 
I've been studying the plans, and watching the video for the -14 canopy fairing on YouTube.

Is there a good reason for not using dry micro as a substrate or as a filler sandwich for maybe three glass plies vs the ten plies called out in the plans?

Same question for high density expanding foam, allowed to fully expand first...

I can't see the mechanical or aesthetic need for a heavy chunk of glass and resin 10 plies thick up there. What am I missing?

Some thoughts:
- Never get anything like expanding foam near your airplane.
- You can use mico to make a nice “bed” for the glass. Do that first to get everything fixed. Do not have so much that you have it coming out the bottom on the inside of the plane. Recommend you add epoxy color so that you see black instead of white on the inside: https://www.aircraftspruce.com/catalog/cmpages/epoxyPigments.php?clickkey=455661
- After the micro is set, sand to the profile you want. The micro should not extend up the glass, or more that a an inch or so on the aluminum.
- I did not like the “10 ply” thing either. I used carbon instead of glass for this as I find it much easier to work with - and it does not need the color add. I did a two bid layup about 1” wide, then a four bid layup about 2” wide over that.
- YOU MUST AGGRESSIVLY sand the windshield for good adhesion. Get the 30 grit paper out. The scratches get filled with resin so no worries about them.

For all window to fiberglass joints I filled the junction with micro, sanded smooth than overlaid two bids of regular fiberglass. If you don’t do this, the micro will crack at the glass to fiberglass joint and you get the “window frame” effect in your very expensive paint job.

Carl
 
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Consider how big the windshield is.....

The attachment of the base to the fuselage should be considered somewhat structural in the context of the windshield. I.E., this is more than a simple aerodynamic fairing you will be making.

For that reason, a bunch of non-structural filler (foam, micro mixture, etc., are all non structural fillers) and just a couple of layers of glass (or carbon fiber) cloth will not meet the structural strength intend for this area.
 
thanks, everyone.

I have bedded my windows in SilPruf silicone so they are free-floating inside the joggle space, no fiberglass overlap and cracking paint to worry about. I would suggest the factory consider officially endorsing this method of window installation as an alternative to the fiberglass on top of plexi method. The latter sounds like a science project on differential coefficients of expansion, and the troubles it has caused some builders are well-documented here. :eek:

Already on top of that resin tinting thing, have the black pigment in hand.

Will do the fairing as specified, then, for the reasons Scott listed.

Expanding foam of the high-density LocTite type already used in closing out my control surface ends with zero issues with creep/continued "bloom" under the fiberglass caps. Understand abundance of caution, but I certainly got away with it.
 
I have bedded my windows in SilPruf silicone so they are free-floating inside the joggle space, no fiberglass overlap and cracking paint to worry about. I would suggest the factory consider officially endorsing this method of window installation as an alternative to the fiberglass on top of plexi method. The latter sounds like a science project on differential coefficients of expansion, and the troubles it has caused some builders are well-documented here. :eek:
SNIP

We are of very different schools of thought on how to finish a window - but we all get do build as we wish.

Carl
 
I have bedded my windows in SilPruf silicone so they are free-floating inside the joggle space, no fiberglass overlap and cracking paint to worry about.

Bill, I imagine that the silicone should be OK. However, I know that auto manufacturers have moved to urethane adhesive on the windshields, because the designers now utilize the windshield as part of the structural rigidity of the frame. I would be a little concerned that Van's did something similar. If they did, I am sure that a structural adhesive would be required over a sealant.

Larry
 
Bill, I imagine that the silicone should be OK. However, I know that auto manufacturers have moved to urethane adhesive on the windshields, because the designers now utilize the windshield as part of the structural rigidity of the frame. I would be a little concerned that Van's did something similar. If they did, I am sure that a structural adhesive would be required over a sealant.

Larry

There was static load testing done of the cabin top to evaluate rollover protection design.
The test article had the windscreen and side windows bonded in using the method prescribed in the build manual.
It is experimental after all, but any change from that recommendation has the potential to have an impact on overall rollover protection.
What influence any given change would have is anybody's guess because testing wasn't done to evaluate alternatives. This is also why you wont likely see Van's officially endorse other window installation methods, and it is also why Van's has officially recommended against drilling holes in the door frames for sun shades, etc.
 
I know it's T.L.A.R. engineering, but

I did add composite cable chases to the A-pillars that should enhance the rollover strength of the cabin top - visor holes or no visor holes.


And the knowledgable guy that did the GlasStar SilPruf installation videos says his sample coupons ripped the gel coat from the composite without sealant failure after full cure. I'm not worried much about bond strength as it relates to plexiglass's structural contribution to cabin top load-bearing. And I'm also not worried about my fiberglass work ever cracking underneath the paint. Whoopie for me, right? :cool:

Sincere question: how many RV-10 rollover accidents do we know about?
 
Which technique?

It's time to do the fairing layup. Curious whether the method in the manual is still preferred or if the factory's method shown in the RV-14 video should supplant.

I recognize the need to have tinted resin against the windshield either way, but there is a reversal of order of laying out the ply widths between the two methods, as well as some templates addressing the shape transitions onto the lower corners/sides in the -14 video that are not featured in the -10 plans.

What are y'all's thoughts?
 
...I used carbon instead of glass for this as I find it much easier to work with - and it does not need the color add...

I strongly recommend that if you want to use carbon, you put down at least one ply of fiberglass to separate the carbon from the aluminum. Epoxy can absorb and retain a tiny bit of water, and the combination of carbon and aluminum with water as an electrolyte makes a dandy battery to drive galvanic corrosion of the aluminum.

--Bob K.
 
Not planning to use carbon, though it would be a good chance to gain educational familiarity with the material. More wondering if I'd get better results cutting the wider pieces in curves a la RV-14, or if they bend around the corners well enough not to pucker, considering they are not supposed to be bias-cut. Also thinking the -14 sequence of putting down the widest strip first would make it easiest to get uniform tinting of the resin that will show through the back side of the windshield, since pot life won't allow doing all the strips from the same batch of tinted resin (I think).

Maybe I'm overthinking this?
 
Lay up

I did my layup per vans plans with the narrow strip first. It does not take much tint so I don't think you will have much color differences, I only used 2 batches. I had plenty of time with the pot life. Be sure to have everthing at hand and even do a practice layup( without epoxy) so you know what will be entailed. I'm a novice fiberglass guy and I didn't have any issues. Just have to dig in and get at it.

Oh, and I didn't have any problems at the curves as the strips will conform while they are wet out.
 
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Not planning to use carbon, though it would be a good chance to gain educational familiarity with the material.

Gain it somewhere else. Consider the difference in thermal expansion rates. The CTE's are roughly...

units in/in per degree F

carbon/epoxy 0.000001
glass/epoxy 0.000007
aluminum 0.000013
plexiglass 0.000041

Doesn't make much sense to glue a material with almost no CTE to materials with CTEs 13x and 41x higher. The joint gets stressed just moving from sun to shade.
 
Thanks to DanH and Electrogunner for weighing in

Good to know that the 10 plans method works well enough. I was just lured in by the extra pains taken by the -14 manual to get it "just right." I suppose since it's composite, one can just throw it on and grind it down at the ends/corners where it would otherwise make sense to taper and shape the layups before wet-out.

After closing up the ends of all my RV-10 control surfaces, and doing the front fairing and targa strip on my -6A tip-up 20 years ago, I'm probably up to speed on making this work cosmetically. Just trying to make it easy for myself.
 
sanding block form ???

Okay, fellas. How did you go about making a sanding block to radius-sand the windshield fairing layup to a radius of 7"? A drywall mud bucket has a 6" radius, and might work with a scooping diagonal sanding motion. I'm not sure the preferred technique is to use a sanding block with the full desired final radius, but rather something a bit smaller?

If necessary, I can bandsaw a stack of wooden triangles with that radius and glue them into a block, but I was wondering if I was overlooking a household item that might already suffice to back the sandpaper.
 
Okay, fellas. How did you go about making a sanding block to radius-sand the windshield fairing layup to a radius of 7"? A drywall mud bucket has a 6" radius, and might work with a scooping diagonal sanding motion. I'm not sure the preferred technique is to use a sanding block with the full desired final radius, but rather something a bit smaller?

If necessary, I can bandsaw a stack of wooden triangles with that radius and glue them into a block, but I was wondering if I was overlooking a household item that might already suffice to back the sandpaper.

Take a chunk of stiff urethane foam and sand it to the shape you need.

Flower arrangers green foam should be easy to get (wally mart) and is stiff enough for the job.
 
Block

Okay, fellas. How did you go about making a sanding block to radius-sand the windshield fairing layup to a radius of 7"? A drywall mud bucket has a 6" radius, and might work with a scooping diagonal sanding motion. I'm not sure the preferred technique is to use a sanding block with the full desired final radius, but rather something a bit smaller?

If necessary, I can bandsaw a stack of wooden triangles with that radius and glue them into a block, but I was wondering if I was overlooking a household item that might already suffice to back the sandpaper.

Bill.
I just used a teardrop shape dura block sanding block. Work the curve of the fairing at angles with the rounded section of the block and alternate the angle as you go, so you don?t sand a flat spot in. Worked very well and I didn?t need much additional filler. I got a thumbs up from my painter.
 
I have an idea. A bit of inspiration that hit me last night as I pillowed my head at 2am following a marathon layup session. I've made a procurement run to the hardware store (custom foam sanding blocks are not available in retail stores here in Appalachia) and I will give it a shot, take pictures, and report back.

Stay tuned.

Oh, and BTW, I am a bit disappointed that the plans suggest you can bend straight-cut fiberglass cloth around a sweeping curve without it distorting. You cannot. Curved patterns, such as the -14 instructions apparently provide, are the way to go. Having a few wet layups in place is not the time to spot a problem and mess with making your own paper cutting patterns. I ended up making three butt joints per ply vs the one called for, just to relieve stress in the fabric and get it to lie flat. Sandpaper will "fix" this, as it does all things composite, but the frustration was avoidable if I'd have had some cutting patterns.
 
I've made a procurement run to the hardware store (custom foam sanding blocks are not available in retail stores here in Appalachia) and I will give it a shot, take pictures, and report back.

....

Some of the urethane home insulation works well too.... but not the stuff that looks like plastic/foam cups...
 
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