Baffle seals age slowly, and the effects of temperature and wear change CHT?s a little bit over a long time. Season after season passes, we go from winter to summer over and over again, and the overall rise in temperatures goes un-noticed until one day you realize that you?re compensating with increased climb speeds on every flight. Suddenly, you realize that the seals have been doing their duty for close to a decade and it is time for a re-do! Such was the case with the Valkyrie, my 1800+ hour RV-8?.so last weekend I decided it was time for new seals. As most builders remember, cutting and trimming baffle seals takes time and a lot of effort ? not something we remember fondly. But I?ve got good news ? replacing existing seals can be quick and easy! Here are a couple of notes from my project ? which really only took about five hours.
Crinkly! Yup ? these seals have taken a set and are heat checked ? ready to replace.
Use a center punch to pop the mandrels out of the pulled rivets ? a few clicks and they?ll come out with vigor!
After pulling off the old seal, use a sanding disk to grind off the shank ? sand it down flush to the baffle aluminum.
With the shank ground down, pull the tail off with a pair of dikes ? the holes will still be perfect!
Take each segment off one at a time. Lay them on the new material on top of a sacrificial wooden surface, then drill through the holes and cleco to the surface. Press down to flatten and cut with a new razor nice ? and the new piece will be perfect ? ready to remount.
All of the edge seals were done in about three hours ? only the center seals still to go!
Remember how complex those center seals were to figure out the first time around? The good news is that you don?t have to figure them out the second time ? just copy them!
Center section complete! If the cowl is hard to put back on, you?ve done it right ? the new seals need to compress and conform ? and that means you?ll get good results.
The results? Subjectively, duplicating a flight done the day before the replacement, with similar OAT?s (about 90 degrees F at 5,000?), I?d say that CHT?s ran about 20 degrees F cooler than with the old seals. The baffles themselves were in great shape, and although I went over the hole baffle, found very few things that needed additional caulking with RTV. Don?t be afraid to change seals if you seem to be running hotter than before ? it?s just not that hard.
(Look for a complete story on this in an upcoming issue of Kitplanes. I just figured this might help someone through the heat of summer!)
Paul
Crinkly! Yup ? these seals have taken a set and are heat checked ? ready to replace.
Use a center punch to pop the mandrels out of the pulled rivets ? a few clicks and they?ll come out with vigor!
After pulling off the old seal, use a sanding disk to grind off the shank ? sand it down flush to the baffle aluminum.
With the shank ground down, pull the tail off with a pair of dikes ? the holes will still be perfect!
Take each segment off one at a time. Lay them on the new material on top of a sacrificial wooden surface, then drill through the holes and cleco to the surface. Press down to flatten and cut with a new razor nice ? and the new piece will be perfect ? ready to remount.
All of the edge seals were done in about three hours ? only the center seals still to go!
Remember how complex those center seals were to figure out the first time around? The good news is that you don?t have to figure them out the second time ? just copy them!
Center section complete! If the cowl is hard to put back on, you?ve done it right ? the new seals need to compress and conform ? and that means you?ll get good results.
The results? Subjectively, duplicating a flight done the day before the replacement, with similar OAT?s (about 90 degrees F at 5,000?), I?d say that CHT?s ran about 20 degrees F cooler than with the old seals. The baffles themselves were in great shape, and although I went over the hole baffle, found very few things that needed additional caulking with RTV. Don?t be afraid to change seals if you seem to be running hotter than before ? it?s just not that hard.
(Look for a complete story on this in an upcoming issue of Kitplanes. I just figured this might help someone through the heat of summer!)
Paul