I finished my lower gear leg intersection fairings a few months ago, I used the clay method as the plans describe but found it difficult to make smooth. The results turned out pretty good but there was a lot more filling and sanding than I would have liked. Now it is time for the upper fairings, is there something other than clay than can be used and easily shaped? I was thinking maybe plaster or something that can be sanded to its final shape. I also see that vans is offering these fairings now, any experience with these?, are they worth it?
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Gear leg fairings, is clay the best option
- Thread starter jibby212
- Start date
Kyle Boatright
Well Known Member
Van's fairings are pretty good as are some of the third party fairings.
But making your own guarantees a good fit. Remember, every 5 minute shortcut you take on making the form or mold will cost you 10x that much time on the back end. If you "roll your own", get your forms perfect before you even think about fiberglass...
But making your own guarantees a good fit. Remember, every 5 minute shortcut you take on making the form or mold will cost you 10x that much time on the back end. If you "roll your own", get your forms perfect before you even think about fiberglass...
N941WR
Legacy Member
I had to may the fairings for my -9 as Van's as no one provides them and the ones for the -7 don't work on the -9 due to different angles that the gear legs exit the cowl.
(This is for a -9, not a -9A.)
I did use clay and use a lot of water to smooth them down. If the clay is not smooth then the fiberglass won't be either.
It just takes time to smooth them out.
(This is for a -9, not a -9A.)
I did use clay and use a lot of water to smooth them down. If the clay is not smooth then the fiberglass won't be either.
It just takes time to smooth them out.
Carl Froehlich
Well Known Member
I assume you used non-hardening clay.
I found that a little Coleman Fuel on my fingers worked a lot better than water to smooth the clay. Once I figure this out it was fairly straight forward.
Don?t forget to use a couple of coats of hair spray as a release agent.
Carl
I found that a little Coleman Fuel on my fingers worked a lot better than water to smooth the clay. Once I figure this out it was fairly straight forward.
Don?t forget to use a couple of coats of hair spray as a release agent.
Carl
bkc3921
Well Known Member
3rd Party
I didn't care much for the Van's ones, so I bought the popular 3rd party choice and were pleased with them. I cannot deny that it is probably cheaper to build your own, and yes, this IS a home built....but there are simply some jobs on these planes that simply scream out for "just bite the bullet, buy them, and save yourself a month of grief"....This is one of them, in my opinion...YMMV.
I didn't care much for the Van's ones, so I bought the popular 3rd party choice and were pleased with them. I cannot deny that it is probably cheaper to build your own, and yes, this IS a home built....but there are simply some jobs on these planes that simply scream out for "just bite the bullet, buy them, and save yourself a month of grief"....This is one of them, in my opinion...YMMV.
David Paule
Well Known Member
Dan, can you give us the link to that?
Thanks,
Dave
Thanks,
Dave
N941WR
Legacy Member
It depends on what he is building, aftermarket fairings may not be available.
bkc3921
Well Known Member
Well, true..but
I looked at the OP's profile before I responded, and his RV of interest was a -7, so I concluded that was what he was building. However, who knows...
I looked at the OP's profile before I responded, and his RV of interest was a -7, so I concluded that was what he was building. However, who knows...
rightrudder
Well Known Member
Well said. I came to the same conclusion after doing the lower intersection fairings...I ended up buying the 3rd-party uppers. The sanding, filling, reapplication of 'glass here was one of the most time-consuming parts of the build.
Awful, don't bother.
http://www.shopmaninc.com/foam.html
2 lb density works fine for large forms, 4 lb is good all around, pick higher density for more accuracy or detail.
Naaa. A half dozen happy hours away from the cares of the world.
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cajunwings
Well Known Member
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Pittsartist
Well Known Member
I've always thought that some sort of moulded synthetic rubber / urethane / PVC universal fairing would be a GREAT aftermarket product for an RV
Maybe something that you trim a moulding to size and then secure with screws through an aluminium ring around its edges onto the cowls ?. A bit like the boot on a car handbrake lever perhaps ?. Flexible enough to fit all types - and cope with U/C flex.
Maybe something that you trim a moulding to size and then secure with screws through an aluminium ring around its edges onto the cowls ?. A bit like the boot on a car handbrake lever perhaps ?. Flexible enough to fit all types - and cope with U/C flex.
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Hmmm.......
David Paule
Well Known Member
Remember their purpose. No ripples or wrinkles desired.
Dave
Dave
Pittsartist
Well Known Member
Ah .... clearly not convinced then ?. Perhaps not the best description of the idea
I did a little more research. What I had envisaged was a PVC dip moulding (cheap tooling) in exactly the same shape as the top fiberglass intersection fairings
Roughly 2mm thick PVC and just flexible enough to trim and fit to any cowl / leg fairing variation. Smooth finished & secured in place with a 1/2" wide strip of anodized aluminium with screws into plate nuts in the cowl & leg fairings.
Very few of the RV's I see here in the UK have pristine leg & intersection fairings - even if they were perfect when new. I suppose the high proportion of grass strips we have here takes its toll.
The drawbacks would be (probably) "black only" and also difficulty in fitting unless they could be slit & re joined to get them over the U/C leg like the fiberglass ones are.
I hated making my fiberglass ones during my last build & sure enough, 300hrs later they are looking a little tatty.
Maybe I'll try putting the idea into action on my current 7 build when the time comes.
I did a little more research. What I had envisaged was a PVC dip moulding (cheap tooling) in exactly the same shape as the top fiberglass intersection fairings
Roughly 2mm thick PVC and just flexible enough to trim and fit to any cowl / leg fairing variation. Smooth finished & secured in place with a 1/2" wide strip of anodized aluminium with screws into plate nuts in the cowl & leg fairings.
Very few of the RV's I see here in the UK have pristine leg & intersection fairings - even if they were perfect when new. I suppose the high proportion of grass strips we have here takes its toll.
The drawbacks would be (probably) "black only" and also difficulty in fitting unless they could be slit & re joined to get them over the U/C leg like the fiberglass ones are.
I hated making my fiberglass ones during my last build & sure enough, 300hrs later they are looking a little tatty.
Maybe I'll try putting the idea into action on my current 7 build when the time comes.
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rightrudder
Well Known Member
Ah .... clearly not convinced then ?. Perhaps not the best description of the idea
I did a little more research. What I had envisaged was a PVC dip moulding (cheap tooling) in exactly the same shape as the top fiberglass intersection fairings
Roughly 2mm thick PVC and just flexible enough to trim and fit to any cowl / leg fairing variation. Smooth finished & secured in place with a 1/2" wide strip of anodized aluminium with screws into plate nuts in the cowl & leg fairings.
Very few of the RV's I see here in the UK have pristine leg & intersection fairings - even if they were perfect when new. I suppose the high proportion of grass strips we have here takes its toll.
The drawbacks would be (probably) "black only" and also difficulty in fitting unless they could be slit & re joined to get them over the U/C leg like the fiberglass ones are.
I hated making my fiberglass ones during my last build & sure enough, 300hrs later they are looking a little tatty.
Maybe I'll try putting the idea into action on my current 7 build when the time comes.
That's the spirit of Experimental aviation!
How do you apply for a fairing base - are any of the densities trowlable?
(I think i understand the foam is placed aproximately to shape, more or less sort of. And then shaped after it hardens? My question is, as a pourable, how easy or not is it to get it to stay in place until hard?)
Or do i completely misunderstand the app?
Pitts artist - "a long time ago"
i cast several sets of urethane rubber rolls for feedworks on woodworking equipment, e.g. for custom apps and a couple customers. After a pour one time, quite a bit was left over, so i saturated some fabric strips cut from polyester knit fabric, and draped it in layers over the side of a PVC pipe. My curiosity was whether it might be useful to cast odd-ball or obsolete MC intake or airbox parts. I never did, but the materials could probably be used for your flex fairing idea, so long as the parts were cast into a female mold (for surface smoothness). I was using Devcon products, which are expensive, but included options from a range of modifiers, accelerators, and primers for my then use. The unmodified durometer as cast & aged was 90A. Could be mixed proportionally with a modifier to yield hardness range as low as 70 (for feed roll stiction) or lower.smt
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I bought the foam and gave it one try and found it to be messy and hard to work with, I am now using 20 minute drywall mud, going back to my construction roots I guess. I put 3 coats on so far and it cuts good with a metal binding strap before it is totally cured, there is a large window of time to do this cutting and pre forming. I will sand to the final finish once it sets up fully. That's where I am at now, waiting for the final cure, so far so good. I wouldn't use the pre mixed dry wall mud, that stuff just dries, don't actually chemically "set up" , it would take a long time to dry when using as thick as needed for the fairings.
David Paule
Well Known Member
In those thicknesses, it would crack, too. You'd have to make several layers and let each dry before doing the next, using the pre-mixed compound.
Dave
Dave
The basic plan is to tape a piece of cardboard or typing paper into place to act as a dam, mix/pour the urethane, and stand back while it expands. Do not try to trowel it, shape it, or guide it in any way, because you'll make a change to local density. Just let it expand and harden, then hack off the excess. A hacksaw blade or a crosscut handsaw works real well, then it's shaped sanding blocks or tubes.
More elaborate parts are possible:
Sometimes a mixed approach (pour foam and block foam) is best.
Flying that idea about 900 hours now.
http://www.vansairforce.com/community/showthread.php?t=43391&highlight=rubber+ducts
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Dan -
Thanks for the very clear tutorial, pics, and link for supplies!
Re the "rubberized" fabric - my suggestion was that the 90A duro might be good for flexible fairings as mentioned by another poster, besides the manifold ideas i had and you implemented. Also on that subject, DOW Corning makes a 2 part castable red silicone that is good for over 300?C * (aprox 600?F).https://pilotshq.com/dow-corning-rtv-3120-red-base-silicone-sealant-453g-p-12944.html At that point the fabric matrix could be the limiting factor. I did not compare tear strengths directly with an specific urethane, which are often tougher.
smt
Thanks for the very clear tutorial, pics, and link for supplies!
Re the "rubberized" fabric - my suggestion was that the 90A duro might be good for flexible fairings as mentioned by another poster, besides the manifold ideas i had and you implemented. Also on that subject, DOW Corning makes a 2 part castable red silicone that is good for over 300?C * (aprox 600?F).https://pilotshq.com/dow-corning-rtv-3120-red-base-silicone-sealant-453g-p-12944.html At that point the fabric matrix could be the limiting factor. I did not compare tear strengths directly with an specific urethane, which are often tougher.
smt
BTW, do not try to use 2lb density pour foam as core in a finished part. I've not tried 4lb and higher as core, but I'd be real shy about it. Altitude pressure change made 2lb expand and contract in ways that left lumpy waves on the finished glass surface. So, use it for forms, but then remove it all.
