This is a question more pointed at the numerous repeat offenders out there. I am buiulding an RV8 and trying to decide whether to go the hinge or Skybolt route for cowling attachment. Has anyone tried both methods? Which do you prefer and why. I know the cost arguments but would we play with planes if cost was a huge object...
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Skybolt V. Hinge
- Thread starter Berchmans
- Start date
panhandler1956
Well Known Member
If you go with the stock piano hinge you'll cuss them at first, but you'll love them once they wear in. My only experience with camlocs are on other aircraft types.
My 2 cents.
My 2 cents.
jeffmoreau
Well Known Member
Skybolts
I was up in the air about using Skybolts. I finally decided to go with them.
I now consider it one of the best mods that I performed.
When you are flight testing you will be glad that you spent the money on them as it saves a lot of time and trouble during your test phase.
I was up in the air about using Skybolts. I finally decided to go with them.
I now consider it one of the best mods that I performed.
When you are flight testing you will be glad that you spent the money on them as it saves a lot of time and trouble during your test phase.
I have built my -8 with hinges, and the new -3 with Skybolts on the firewall. i honestly like the fit of the hinges better. I am satisfied with the Skybolts on the -3 firewall because of the changes in shape due to the cheek cowls. I really like th hinges on the sides (did both airplanes that way), and the fit on the firewall with hinges is great.
the Skybolts on the firewall are easier to install and remove of course!
Our older -6 has screws/nutplates for the sides, and that works fine - just a little extra time for removal and replacement.
All methods work!
Paul
the Skybolts on the firewall are easier to install and remove of course!
Our older -6 has screws/nutplates for the sides, and that works fine - just a little extra time for removal and replacement.
All methods work!
Paul
We haven't done as many as some, but quite a few (couldn't count 'em before or after my missing finger)! 
That being said, I'm open minded enough to try different things and we've built them with all hinges, all camlocks, combos of both and retrofits. Quantity of builds is great, but someone hasn't tried all the combinations, then....
Here's my take:
Bottom of firewall should have something other than hinges. You only have to fix a few broken hinges or get burned a few times to realize nutplates or camlocks are the way to go in that location.
Cowl sides between upper and lower are a nice spot for hinges and are plenty easy to both install and use. It was nicer in the past running the pins in from the rear through the center of carefully placed naca ducts (older kits) but front load pins can be fine if you're careful.
The firewall is nice to have camlocks and is my preference, especially on the upper.
There is no doubt that hinges can have tighter clearances and finish, but convenience is really worth a lot to me as someone who works on these things (and is lazy as well as like not to get burned & scratched)!
That's my 2 cents as usual and just my opinion based on what I like; not everyone will agree.
Cheers,
Stein
I forgot to mention things I really dislike for cowl fasteners - Dzus Fateners and screw with nutplates!
That being said, I'm open minded enough to try different things and we've built them with all hinges, all camlocks, combos of both and retrofits. Quantity of builds is great, but someone hasn't tried all the combinations, then....Here's my take:
Bottom of firewall should have something other than hinges. You only have to fix a few broken hinges or get burned a few times to realize nutplates or camlocks are the way to go in that location.
Cowl sides between upper and lower are a nice spot for hinges and are plenty easy to both install and use. It was nicer in the past running the pins in from the rear through the center of carefully placed naca ducts (older kits) but front load pins can be fine if you're careful.
The firewall is nice to have camlocks and is my preference, especially on the upper.
There is no doubt that hinges can have tighter clearances and finish, but convenience is really worth a lot to me as someone who works on these things (and is lazy as well as like not to get burned & scratched)!
That's my 2 cents as usual and just my opinion based on what I like; not everyone will agree.
Cheers,
Stein
I forgot to mention things I really dislike for cowl fasteners - Dzus Fateners and screw with nutplates!
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jay.pearlman
Well Known Member
to hinge or not to hinge
I went through the same agony and am just completing the cowl installation. Skybolt hardware is very well made (almost makes my engineering eyes water). Hinges produce a nice line, though tight to insert pin when new (used an electric drill to rotate the pins). I used the formed rather than rolled hinges - nicer quality, higher price. Hinges went on all but the upper firewall interface - sky bolts there. Might put sky bolts on the bottom also as hinges have been vulnerable there.
There are a lot of comments in the archives and photos also of various planes under construction
I went through the same agony and am just completing the cowl installation. Skybolt hardware is very well made (almost makes my engineering eyes water). Hinges produce a nice line, though tight to insert pin when new (used an electric drill to rotate the pins). I used the formed rather than rolled hinges - nicer quality, higher price. Hinges went on all but the upper firewall interface - sky bolts there. Might put sky bolts on the bottom also as hinges have been vulnerable there.
There are a lot of comments in the archives and photos also of various planes under construction
The hinge eyelets can fatigue and break off over time, concentrating load on the remaining eyelets, which accelerates the process. I think this problem has mostly occured on the firewall rather than on the side where the two halves meet. I think this is the reason many go with camlocks around the firewall, and hinges on the split. The eyelets on the hinges around my RV-3 firewall started breaking off after about 400 hrs, and I replaced them with Skybolts (same as camlocks), which worked great. Depends on the installation, though. I've seen others go a long time with hinges all around.
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And a word about fit....older 1/4 turn fastener kits seemed to specify a lot of floating receptacles at the firewall. The result was a cowl that could move around in its relationship to the fuselage.
I think I have either 2 or 4 floaters, total, at the "corners" of the upper cowl where it transitions from horizontal to vertical. More are not necessary, and with the majority being fixed receptacles (across the top, down the sides, under the bottom) you can hold clearances to a nice tolerance.
....and, BTW, no more hinges for me.
I think I have either 2 or 4 floaters, total, at the "corners" of the upper cowl where it transitions from horizontal to vertical. More are not necessary, and with the majority being fixed receptacles (across the top, down the sides, under the bottom) you can hold clearances to a nice tolerance.
....and, BTW, no more hinges for me.
I think the fewer changes you make to VANs plane, the faster you will get 'er done.
I went with the hinges all the way. I've looked at the fastener route, most look puckered.
I figured to 'play thru' and if the hinges present a problem down the road I'll deal with it then.
In life at work, I found that you don't need to look for solutions to problems that might come up, real problems present themselves soon enough.
If the hinges give me trouble, I can drill out the offending piece and replace or upgrade as required.
I went with the hinges all the way. I've looked at the fastener route, most look puckered.
I figured to 'play thru' and if the hinges present a problem down the road I'll deal with it then.
In life at work, I found that you don't need to look for solutions to problems that might come up, real problems present themselves soon enough.
If the hinges give me trouble, I can drill out the offending piece and replace or upgrade as required.
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jthocker
Well Known Member
Nothing against the Sky bolts, but after 9 cowls and all hinges, I still would only do hinges. If you do the hinges right( i.e. drilling them without any preload) they are the fastest to install and remove and the cleanest looking. That being said I do use screws now on the very bottom and I do appreciate the look of the Sky bolts!
Does that count the plane you got to almost build twice??
Joking aside and no sarcasm intended, but if you've never used 1/4 turn fastners how do you know hinges are faster to install (same question to other posters who've never used them)? We find the fastners to be quicker on the firewall than hinges now that we've figgured 'em out. Only one side to rivet and a simple hole to drill in the cowl. A first timer is gonna take awhile using either method.
The puckering can be eliminated rather easily if you're careful, and on the bottom it's so much quicker to remove the 1/4 turns than using a cordless or screwdriver and needing the extra screws to replace them when they get buggered.....at least that's my lazy view.
Warning - if you plan on using the rolled hinges on the bottoms....first an eye or two will break (no big deal), but if/when the pin breaks in half in the hinge on a taidragger 4/6/7/9 it's a real peach to fix.
Just my 2 cents as usual!
Cheers,
Stein
jthocker
Well Known Member
Does that count the plane you got to almost build twice??
Joking aside and no sarcasm intended, but if you've never used 1/4 turn fastners how do you know hinges are faster to install (same question to other posters who've never used them)? We find the fastners to be quicker on the firewall than hinges now that we've figgured 'em out. Only one side to rivet and a simple hole to drill in the cowl. A first timer is gonna take awhile using either method.
The puckering can be eliminated rather easily if you're careful, and on the bottom it's so much quicker to remove the 1/4 turns than using a cordless or screwdriver and needing the extra screws to replace them when they get buggered.....at least that's my lazy view.
Warning - if you plan on using the rolled hinges on the bottoms....first an eye or two will break (no big deal), but if/when the pin breaks in half in the hinge on a taidragger 4/6/7/9 it's a real peach to fix.
Just my 2 cents as usual!
Cheers,
Stein
OK Stein, you're right I haven't done Skybolts or 1/4 turns. I've only watched new guys take a long time to do their cowls (Scott Hersha notwithstanding). If I had some 1/4 turns laying around I'd probably use them on the bottom next time. Never thought about the hinge pin breaking in half, ouch!!
dedgemon
Well Known Member
OK Stein, you're right I haven't done Skybolts or 1/4 turns. I've only watched new guys take a long time to do their cowls (Scott Hersha notwithstanding). If I had some 1/4 turns laying around I'd probably use them on the bottom next time. Never thought about the hinge pin breaking in half, ouch!!
Heck Jon, I've watched new guys take a lomg time doing everything!!!
Camlocks all the way!
New Guy...sure, but I think I am on a pace to be flying next summer...that would be a construction time of 2 years, 8 months....is that good? Great comments all...and I had not even thought of what you would do if the hinge pin breaks......I like the mixture idea so far of skybolts on the firewall and hinge at the split seam...but I got a couple hundred other items to complete first...now the wife wants seat heat...but she likes the plane so far...Merry Christmas all...
I've done both. After about 1000 Hrs (RV-6A #1), the hinges began to break, especially over the top and along the bottoms and horizontal sides. The vertical sides seemed to hold up OK. At some point, the hinges over the top and bottom were replaced with screws, messing up the paint so that a flat strip could be installed.
On RV-6A #2 and the RV-7A I used all Skybolt fasteners. The units on the belly (I only had three per side) started breaking and had to be replaced (the "T" pin would break). Never had an issue with any of the other units.
So far, after 650 Hrs, I've not had any issues with the Skybolt fasteners on the RV-7A.....
On RV-6A #2 and the RV-7A I used all Skybolt fasteners. The units on the belly (I only had three per side) started breaking and had to be replaced (the "T" pin would break). Never had an issue with any of the other units.
So far, after 650 Hrs, I've not had any issues with the Skybolt fasteners on the RV-7A.....
More studying....
Camlocks seem the way to go around the firewall for me. Jury still out on the sides of the cowling.... The solid hinges instead of the rolled seem the way to go if using hinge. What about the stainless steel hinges for the sides?? Also like the sound of using a longer flange on the bottom hinge to offset the loops up from the seem between the upper and lower halves so that the 'teeth' don't smile at you if there is a 30/1000ths gap! All thoughts appreciated!!!
What is a good source of the camlocks??
Greg
Camlocks seem the way to go around the firewall for me. Jury still out on the sides of the cowling.... The solid hinges instead of the rolled seem the way to go if using hinge. What about the stainless steel hinges for the sides?? Also like the sound of using a longer flange on the bottom hinge to offset the loops up from the seem between the upper and lower halves so that the 'teeth' don't smile at you if there is a 30/1000ths gap! All thoughts appreciated!!!
What is a good source of the camlocks??
Greg
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Contact the folks at Milspec fasteners. They offer a firewall kit that has the Camloc tools included and all the fasteners you can use. (I had 2 left over) One of the advantage of the Camloc-style fasteners is they're adjustable for height. If there's a spot where you should have shimmed and didn't, you can adjust the Camlocs to bring both surfaces flush.
oops - forgot to add ....
... using one side of the hinge with a longer flange to get the teeth out of sight works wonderfully. That approach is recommended by the "James Gang" in the 'structions with their cowls; I used it on the horizontal side joints. It also seems to makes mounting the top and bottom cowls easier, because one sort of "nests" in the other.
... using one side of the hinge with a longer flange to get the teeth out of sight works wonderfully. That approach is recommended by the "James Gang" in the 'structions with their cowls; I used it on the horizontal side joints. It also seems to makes mounting the top and bottom cowls easier, because one sort of "nests" in the other.
It's all about the preparation
I have only built a cowl with Skybolt fasteners, but in my experience with this and other cowls, I think I have concluded the following:
1) Finished appearance of either fastening method depends largely on the time spent fitting the pieces during assembly. Either system can look awesome or crappy.
2) The same goes for ease of use
3) The same goes for durability and longevity
Some tips for a beautiful, bulge-free, long lasting Skybolt installation:
1) keep the spacing down to 4" or so (I added one or two fasteners to achieve this)
2) ensure you have sufficiently rigid flanges on the side joints. If the flanges are flimsy, reinforce them with a layer or two of glass. (don't go overboard and add unnecessary weight, of course.)
3) don't rely on the fastener adjustment to pull the cowl into alignment. Instead, work with the cowl halves to get the best alignment possible, and then use shims to achieve a perfect fit. After drilling the initial 1/8" cleco holes for each fastener, I used little dabs of thickened epoxy between flanges at each fastener location to achieve a perfect fit. Packaging tape made a great mold release during this step.
4) don't rely on scallops and flexing of the firewall flanges to achieve a perfect fit. Cut, bend, and shim the flange strips to achieve a good fit around the firewall. Use epoxy dabs again to create a perfect fit here.
5) I ignored the Skybolt recommendations on the position of the rigid vs. sliding fasteners. I spread both styles around, using good judgement on where the rigidity/flexibility could be used to good effect. In practice, a well-fit cowl doesn't seem to need the sliding fasteners at all.
I wouldn't consider the Skybolt installation particularly fast or easy, but it certainly wasn't at the top of the list of challenges I encountered on my RV4 firewall forward rebuild. I'm sure I could turn the hinge method into an equal challenge if it tried it.
I would use the Skybolt system again.
M
I have only built a cowl with Skybolt fasteners, but in my experience with this and other cowls, I think I have concluded the following:
1) Finished appearance of either fastening method depends largely on the time spent fitting the pieces during assembly. Either system can look awesome or crappy.
2) The same goes for ease of use
3) The same goes for durability and longevity
Some tips for a beautiful, bulge-free, long lasting Skybolt installation:
1) keep the spacing down to 4" or so (I added one or two fasteners to achieve this)
2) ensure you have sufficiently rigid flanges on the side joints. If the flanges are flimsy, reinforce them with a layer or two of glass. (don't go overboard and add unnecessary weight, of course.)
3) don't rely on the fastener adjustment to pull the cowl into alignment. Instead, work with the cowl halves to get the best alignment possible, and then use shims to achieve a perfect fit. After drilling the initial 1/8" cleco holes for each fastener, I used little dabs of thickened epoxy between flanges at each fastener location to achieve a perfect fit. Packaging tape made a great mold release during this step.
4) don't rely on scallops and flexing of the firewall flanges to achieve a perfect fit. Cut, bend, and shim the flange strips to achieve a good fit around the firewall. Use epoxy dabs again to create a perfect fit here.
5) I ignored the Skybolt recommendations on the position of the rigid vs. sliding fasteners. I spread both styles around, using good judgement on where the rigidity/flexibility could be used to good effect. In practice, a well-fit cowl doesn't seem to need the sliding fasteners at all.
I wouldn't consider the Skybolt installation particularly fast or easy, but it certainly wasn't at the top of the list of challenges I encountered on my RV4 firewall forward rebuild. I'm sure I could turn the hinge method into an equal challenge if it tried it.
I would use the Skybolt system again.
M
MilSpec Fasteners and Paint
I've installed these fasteners all around my cowls and have yet to install the snap rings or whatever they are called that hold the quarter turn fastners in the cowls. My though process was that it would be easier for a professional painter to remove them for painting. I'm going to fly before having it painted.
Is there a way to temporarily hold these in that would be easy for a painter to remove for painting and yet keep them attached to the cowls during the test flight phase?
I'm sure some of you have pondered this before and just wondered what the best way would be to accomplish this.
Thanks
I've installed these fasteners all around my cowls and have yet to install the snap rings or whatever they are called that hold the quarter turn fastners in the cowls. My though process was that it would be easier for a professional painter to remove them for painting. I'm going to fly before having it painted.
Is there a way to temporarily hold these in that would be easy for a painter to remove for painting and yet keep them attached to the cowls during the test flight phase?
I'm sure some of you have pondered this before and just wondered what the best way would be to accomplish this.
Thanks
FredMagare
Well Known Member
Small zip-tie where the snap-ring goes?
Mine aren't installed and I haven't looked at them to figure out if this would work but logically it seems that it might....
RV7Guy
Well Known Member
Skybolts!!!!
On the first 7 I used Skybolts except for the lower cowl sides where I used hinges. On the new 7 I'll be using all Skybolts.
Skybolt now has the mounting tabs pre made. This will take HOURS of work out of the equation and provide you with the proper spacing.
Ned Bowers at Skybolt is great to work with. The customer service is excellent.
The new instructions from Skybolt take the mystery out of the install as well.
On the first 7 I used Skybolts except for the lower cowl sides where I used hinges. On the new 7 I'll be using all Skybolts.
Skybolt now has the mounting tabs pre made. This will take HOURS of work out of the equation and provide you with the proper spacing.
Ned Bowers at Skybolt is great to work with. The customer service is excellent.
The new instructions from Skybolt take the mystery out of the install as well.
Skybolt/Milspec around the firewall, piano hinge on the split line.
Works really well.
Stick the wire in from the back, 90 degree bend and slip it under the bottom cowl - really neat.
Works really well.
Stick the wire in from the back, 90 degree bend and slip it under the bottom cowl - really neat.
Flying Scotsman
Well Known Member
One minor correction...the new tabs don't automatically set any spacing. You still have to figure it out and you position them appropriately (one tab per fastener, and they overlap...a very neat solution).
They DID save untold amounts of time, though. I started with firewall fasteners using the strips of Al, scalloped out, and it was a giant pain in the rear, although the hardest part was figuring out spacing given all the constraints involved. These new little tabs are *awesome*, and it took no time at all on the sides when I decided to switch from hinges to Skybolts there, too...
Internal pressure tries to blow the cowl into a round shape, just like a balloon. The bottom is a long flat section with no support across the span of the exhaust opening, so the inboard attach point on each side of the exit is heavily loaded. The load gets higher with increasing airspeed, improved conversion of dynamic pressure to static (good inlets), or reduced exit size.
Skybolt Learning Curve
Folks have mentioned how hinges become easier to operate over time - but I found exactly the same thing with Skybolts. Initially had 4 horixantal fasteners forward of the firewall that required some kind of magical perfect alignment to work. Over time (280 hours) that magical perfect alignment has become "very close alignment".
Folks have mentioned how hinges become easier to operate over time - but I found exactly the same thing with Skybolts. Initially had 4 horixantal fasteners forward of the firewall that required some kind of magical perfect alignment to work. Over time (280 hours) that magical perfect alignment has become "very close alignment".
