Van's Air Force
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Rivets in firewall
- Thread starter JanRV6UK
- Start date
Monel Rivets?
Hi Guys,
Bringing an old thread back to life again, I was speaking with an very experienced A&P yesterday (or Licenced Air Maintenance Engineer as we call them down here) and was bouncing a few questions off him regarding my RV-7's firewall installation. He mentioned that I should use monel rivets in the stainless firewall to limit the intermetallic corrosion risk. He says in the past that he has seen the factory heads of AN470 rivets pop off due to corrosion on stainless firewalls. To be fair, his maintenance facility is located half a mile from the ocean, as are many of his customer's aircraft, so one could say he is in a pretty extreme corrosion environment. That said, although I am based 60 miles in from the coast, most of the places I fly to are on the coast, so I am going all the way with corrosion protection. Today I spoke with a Glasair Glastar builder and he said that kit came delivered with monel firewall rivets from the factory, and strongly recommended the use of them if I have a stainless firewall. He said they were a little tougher to drive, but were manageable with a regular gun and bucking bar.
I have been unable to find any concrete documented use of monel rivets on VAF, however I have found things such as "On my Rocket the FW rivets appear to be stainless." indicating that perhaps there are builders out there using monel in this application.
Just sourcing the required countersunk rivets hasn't been easy, however I think I have found a supplier.
https://www.ecasinc.com/parts/number/MS20427M6-12
I know there are going to be people out there who will say "if it's worked for thousands of builders, then why change" however they probably don't live in the middle of an island and have to fly airfields that butt right up against the ocean. For everyone else, I guess the the question is before I pull the trigger on purchasing these monel rivets, are there any hurdles I have not foreseen, and is anyone who has installed monel rivets in this application able to chime in?
Regards,
Tom.
Hi Guys,
Bringing an old thread back to life again, I was speaking with an very experienced A&P yesterday (or Licenced Air Maintenance Engineer as we call them down here) and was bouncing a few questions off him regarding my RV-7's firewall installation. He mentioned that I should use monel rivets in the stainless firewall to limit the intermetallic corrosion risk. He says in the past that he has seen the factory heads of AN470 rivets pop off due to corrosion on stainless firewalls. To be fair, his maintenance facility is located half a mile from the ocean, as are many of his customer's aircraft, so one could say he is in a pretty extreme corrosion environment. That said, although I am based 60 miles in from the coast, most of the places I fly to are on the coast, so I am going all the way with corrosion protection. Today I spoke with a Glasair Glastar builder and he said that kit came delivered with monel firewall rivets from the factory, and strongly recommended the use of them if I have a stainless firewall. He said they were a little tougher to drive, but were manageable with a regular gun and bucking bar.
I have been unable to find any concrete documented use of monel rivets on VAF, however I have found things such as "On my Rocket the FW rivets appear to be stainless." indicating that perhaps there are builders out there using monel in this application.
Just sourcing the required countersunk rivets hasn't been easy, however I think I have found a supplier.
https://www.ecasinc.com/parts/number/MS20427M6-12
I know there are going to be people out there who will say "if it's worked for thousands of builders, then why change" however they probably don't live in the middle of an island and have to fly airfields that butt right up against the ocean. For everyone else, I guess the the question is before I pull the trigger on purchasing these monel rivets, are there any hurdles I have not foreseen, and is anyone who has installed monel rivets in this application able to chime in?
Regards,
Tom.
There are different grades of stainless. Perhaps Vans has chosen a type that minimizes the interaction with the rivets they specify. It may be worth a call to Van's and some additional research to determine if this is a different combination than what the A&P saw.
Bevan
Alternate data point.......
The original blue RV-6A prototype (N666RV) is still flown regularly.
It is now 28 years old.
It has 5100+ flight hours.
It has spent its entire life within 60 miles of the Pacific ocean
In that 28 years, it has made lots of trips to airports within a mile or two of the coastline.
It was built per plans with the rivets supplied in the kits.
It has no evidence of corrosion on the firewall.
The original blue RV-6A prototype (N666RV) is still flown regularly.
It is now 28 years old.
It has 5100+ flight hours.
It has spent its entire life within 60 miles of the Pacific ocean
In that 28 years, it has made lots of trips to airports within a mile or two of the coastline.
It was built per plans with the rivets supplied in the kits.
It has no evidence of corrosion on the firewall.
Thanks Scott. That's good to know. I think part of the problem here is that many of the aircraft this A&P is dealing with have spent their entire life sitting out in the elements as we have a severe lack of hangars. I guess the A&P's can't be blamed for projecting their experience onto you. I plan on keeping my aircraft hangared the majority of the time, so I think this will be significantly less of an issue. I think the other part of it is that these certified aircraft he has to maintain aren't really given the attention they need by their owners. It is a true testament to Cessna that many of the aircraft have lasted as long as they have given the abuse dished out to them.
On another point, tracking down monel rivets with countersunk heads is proving to be a dog of a task.
T.
On another point, tracking down monel rivets with countersunk heads is proving to be a dog of a task.
T.
Ok, so I took Bevan's advice to get another datapoint in addition to Scott's above, and called Van's support line (Joe).
I queried him about aircraft in places like Florida and he said that he had not had any reports of rivets corroding on firewalls. He was also concerned about driving the harder monel rivets and damage to the firewall or aluminium angle (which was a shared concern of mine). Thus I called my A&P back, and he said that if Van's wern't supportive of using monel rivets, then dipped rivets should be used. He said options for this included duralac, epoxy primer (not a self etch primer), proseal or a dissimilar metal paste that they use on squirrel helicopters that doesn't harden (unlike Duralac). So, I think I will go down the rout of dipping in proseal
as I have plenty left from the tanks.
On a slightly different subject, I also spoke with Joe at Van's about firewall protection (sound and heat) on the factory aircraft. He said they had nothing beyond the stock stainless firewall, and said that if you want noise protection, get an ANR headset. I guess that would be a whole lot lighter than 5 lbs of sound deadening material.
Cheers,
Tom.
I queried him about aircraft in places like Florida and he said that he had not had any reports of rivets corroding on firewalls. He was also concerned about driving the harder monel rivets and damage to the firewall or aluminium angle (which was a shared concern of mine). Thus I called my A&P back, and he said that if Van's wern't supportive of using monel rivets, then dipped rivets should be used. He said options for this included duralac, epoxy primer (not a self etch primer), proseal or a dissimilar metal paste that they use on squirrel helicopters that doesn't harden (unlike Duralac). So, I think I will go down the rout of dipping in proseal
as I have plenty left from the tanks.On a slightly different subject, I also spoke with Joe at Van's about firewall protection (sound and heat) on the factory aircraft. He said they had nothing beyond the stock stainless firewall, and said that if you want noise protection, get an ANR headset. I guess that would be a whole lot lighter than 5 lbs of sound deadening material.
Cheers,
Tom.
Ken Martin
Well Known Member
I would also be interested in hearing Van's Engineers thoughts on the opinions of some of the folks posted here that question the safety of the firewall installation as called out in the plans, based on "their" interpretation of the CFARs...
I would also be interested in hearing Van's Engineers thoughts on the opinions of some of the folks posted here that question the safety of the firewall installation as called out in the plans, based on "their" interpretation of the CFARs...
(Most) RV's say experimental on them, so very few of the CFAR's that regulate aircraft design apply (that doesn't mean that using them as a guideline isn't a good idea).
Because they are experimental, If anyone doesn't agree with a detail of the design they can change it to meet what ever they think it should be.... rolleyes:
Ken Martin
Well Known Member
I understand and agree with your point.
I'm just a little taken aback by folks that do not have aerospace engineering training that feel they can do a better job of engineering safety related structure than the folks that do have the training and many years of experience. Vans Engineers knew what they are doing and had to take more into consideration than just the CFARs that do not officially regulate the experimental side of aviation.
I'm just a little taken aback by folks that do not have aerospace engineering training that feel they can do a better job of engineering safety related structure than the folks that do have the training and many years of experience. Vans Engineers knew what they are doing and had to take more into consideration than just the CFARs that do not officially regulate the experimental side of aviation.
Hi Ken, for the record, I am a fully qualified aerospace engineer (RMIT 2002 grad) as are many other active members of this forum. Vans strives to to offer a simple, cost effective and easy to build solution that follows where practicle the FAA certified requirements, but they are not bound to these per the experimental category exemptions. If builders choose to take things a little closer to the certified standards, then that choice is theirs. I can tell you that being an aerospace engineer doesn't really matter in many of these situations, as a lot of them are just basic research of existing certified ideas combined with critical thinking skills, then the willingness to take solutions to peer review (aka this forum) prior to implementation. This has resulted in a number of modifications to later experimental aircraft, so without this crowd sourcing mentality, the experimental market would not be progressing at the rate it is.
My 2c.
Tom.
My 2c.
Tom.
Ken Martin
Well Known Member
Tom,
My apologies for the misunderstanding. I wasn't referring to your comments and should have clarified that. My comments were in reference to a previous thread that I will not resurrect, involving someone who is not an engineer. And in this case they were preaching their solution as gospel and everyone should follow suit or be subject to a tragic end.
On a side note, I understand and agree that people can do whatever they want to do what they feel improves their aircraft as long as they can get it through final inspection. Your previous question and comments about installing different rivets are valid and well thought out concerns based on the special operating environment found in your area.
Cheers!
Ken
My apologies for the misunderstanding. I wasn't referring to your comments and should have clarified that. My comments were in reference to a previous thread that I will not resurrect, involving someone who is not an engineer. And in this case they were preaching their solution as gospel and everyone should follow suit or be subject to a tragic end.
On a side note, I understand and agree that people can do whatever they want to do what they feel improves their aircraft as long as they can get it through final inspection. Your previous question and comments about installing different rivets are valid and well thought out concerns based on the special operating environment found in your area.
Cheers!
Ken
Tom, well said.
I'm that someone. My argument was that a builder should not add a flammable substance (specifically, paint) to the cabin side of a firewall assembly. Your argument was that the substance is advertised as meeting 25.853, so it's perfectly safe. We agreed to disagree.
