Stupid frakin flippin Heat shield!
05-23-2014, 04:30 PM
#1
Stupid frakin flippin Heat shield!
Well since i have yet to get a return phone call from BVM about this issue, i guess ill ask here.
What is the secret to getting Heat Shield (the brush on stuff) to stick to the inside of a bvm bypass!? Im on application #5 right now. Each time the bypass was scuffed with 40grit paper, then cleaned with acetone. 20 seconds after the turbine is started, the stuff starts bubbling and pulling away from the bypass.
This last application had the opportunity to cure for 8 weeks before being put into use.
Thanks,
thomas
What is the secret to getting Heat Shield (the brush on stuff) to stick to the inside of a bvm bypass!? Im on application #5 right now. Each time the bypass was scuffed with 40grit paper, then cleaned with acetone. 20 seconds after the turbine is started, the stuff starts bubbling and pulling away from the bypass.
This last application had the opportunity to cure for 8 weeks before being put into use.
Thanks,
thomas
05-23-2014, 05:46 PM
#3
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With my bandit the heat shield and external paint on the bypass will only bubble if I don't cool the bypass with a blower immediately after shutdown. The radiant heat is very high with the absence of airflow over the exhaust cone, vacuum created by exhaust gases within the pipe pulls air over the tail cone to keep the area cool while running. My bypass is just warm to the touch when running. I have three coats of heatshield and just about the same procedure used to apply as yourself. If this is happening while running there is a problem within the bypass, insufficient cooling air caused by too small gap around turbine case or turbine position in the bypass.
Mike
Mike
05-23-2014, 06:04 PM
#4
With my bandit the heat shield and external paint on the bypass will only bubble if I don't cool the bypass with a blower immediately after shutdown. The radiant heat is very high with the absence of airflow over the exhaust cone, vacuum created by exhaust gases within the pipe pulls air over the tail cone to keep the area cool while running. My bypass is just warm to the touch when running. I have three coats of heatshield and just about the same procedure used to apply as yourself. If this is happening while running there is a problem within the bypass, insufficient cooling air caused by too small gap around turbine case or turbine position in the bypass.
Mike
Mike
that was my thoughts as well. The bypass is a brand new large P80 bypass and the tailpipe is brand new. The dimension for mounting is exactly as stated on the plans for the classic Bandit.
The gap around the turbine (ram 1000) is 1/4-3/8" just by eyeballing it. I dont see any way of getting more space around it. I would like to get this issue fixed so i can repaint the bypass..
05-24-2014, 04:48 AM
#5
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I have never seen or heard of anyone who has painted the inside of a bypass with BVM heatshield - I don't think it's resistent enough to withstand the direct exhaust temperature in that area?
05-24-2014, 05:39 AM
#6
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I have, as per the instructions in the manual- only the rear of it, from the rear of the turbine case to the front of the pipe.
i don't know how big the ram1000 is but it might be worth checking if you've definitely got the p80 bypass. I was sent the wrong sized bypass to begin with.
for reference, I'm using the p100 and I'm fairly sure I've got more than 1/4 " around the engine.
i don't know how big the ram1000 is but it might be worth checking if you've definitely got the p80 bypass. I was sent the wrong sized bypass to begin with.
for reference, I'm using the p100 and I'm fairly sure I've got more than 1/4 " around the engine.
05-24-2014, 06:05 AM
#7
Painting the inner / aft section of the bypass is not unusual, Many of us that have built and flown turbines going back to the mid 90s used to do this. Engines back then took longer to start and would reach higher start temperatures for sustained periods. The bubbling is occurring on start up. You need to have a minimum 3/8 inch all around the engine - particularly between the aft edge of the canister and the wall of the bypass. Ensure that you also have enough of a gap around the front of the engine to allow for air flow. I have seen cases where a FOD screen increases bypass and tail cone temperatures remarkably. You may have to remove the FOD screen if using one..
05-24-2014, 07:50 AM
#8
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BVM does not recommend using a FOD screen inside a bypass tube.
Dean is correct (Helijet) the turbine needs top have adequate clearance to allow airflow , especially during startup, idle and shutdown. Sight up the tailpipe and make sure the turbine exhaust nozzle is centered in the bypass tube. The entire turbine should be centered as well. Do not allow the nozzle to point downward, as the aft edge of the bypass tube could get burned.
We usually paint the aft 3" of the tube and cover with three coats of BVM "Heat Shield".
A "hat section" made from strap material can be used on the mount straps to keep the engine from dropping down on hard landings. See attachments:
Dean is correct (Helijet) the turbine needs top have adequate clearance to allow airflow , especially during startup, idle and shutdown. Sight up the tailpipe and make sure the turbine exhaust nozzle is centered in the bypass tube. The entire turbine should be centered as well. Do not allow the nozzle to point downward, as the aft edge of the bypass tube could get burned.
We usually paint the aft 3" of the tube and cover with three coats of BVM "Heat Shield".
A "hat section" made from strap material can be used on the mount straps to keep the engine from dropping down on hard landings. See attachments:
05-24-2014, 07:51 AM
#9
I have, as per the instructions in the manual- only the rear of it, from the rear of the turbine case to the front of the pipe.
i don't know how big the ram1000 is but it might be worth checking if you've definitely got the p80 bypass. I was sent the wrong sized bypass to begin with.
for reference, I'm using the p100 and I'm fairly sure I've got more than 1/4 " around the engine.
i don't know how big the ram1000 is but it might be worth checking if you've definitely got the p80 bypass. I was sent the wrong sized bypass to begin with.
for reference, I'm using the p100 and I'm fairly sure I've got more than 1/4 " around the engine.
Its definitely the larger bypass as it is significantly larger than what came out of it and the part number engraved into the bypass matches what is listed as the large bypass on the bvm website.
05-24-2014, 07:54 AM
#10
Painting the inner / aft section of the bypass is not unusual, Many of us that have built and flown turbines going back to the mid 90s used to do this. Engines back then took longer to start and would reach higher start temperatures for sustained periods. The bubbling is occurring on start up. You need to have a minimum 3/8 inch all around the engine - particularly between the aft edge of the canister and the wall of the bypass. Ensure that you also have enough of a gap around the front of the engine to allow for air flow. I have seen cases where a FOD screen increases bypass and tail cone temperatures remarkably. You may have to remove the FOD screen if using one..
This is the 3rd bandit i have either built or flown (and the second with this exact motor) and i have never had this much problems from one model. Kinda makes me wish i would of never bought it.
05-24-2014, 09:39 AM
#11
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Heat Shield is a water based product.
If the second coat is applied before the first one has "completely" dried (one day at least), the water in the first coat gets trapped forever and will bubble when heated.
Thin multiple coats are preferable for this reason.
If properly applied still bubbles and separates, there is a temperature problem ..... Heat Shield is just shouting that
If the second coat is applied before the first one has "completely" dried (one day at least), the water in the first coat gets trapped forever and will bubble when heated.
Thin multiple coats are preferable for this reason.
If properly applied still bubbles and separates, there is a temperature problem ..... Heat Shield is just shouting that
Last edited by Jack Diaz; 05-24-2014 at 09:42 AM.
05-24-2014, 12:59 PM
#12
Heat Shield is a water based product.
If the second coat is applied before the first one has "completely" dried (one day at least), the water in the first coat gets trapped forever and will bubble when heated.
Thin multiple coats are preferable for this reason.
If properly applied still bubbles and separates, there is a temperature problem ..... Heat Shield is just shouting that
If the second coat is applied before the first one has "completely" dried (one day at least), the water in the first coat gets trapped forever and will bubble when heated.
Thin multiple coats are preferable for this reason.
If properly applied still bubbles and separates, there is a temperature problem ..... Heat Shield is just shouting that
I repositioned the turbine slightly and got an extra .050" of clearance around it. The smallest clearance area between the turbine and bypass is now at the end of the can with 3/8" and at the intake bell seam ive got nearly 1/2"
05-24-2014, 02:09 PM
#13
Dump the bypass?
When I fixed the crappy elevator setup on a 60 inch BVM Sabre there wasn't room
for the bypass so I mounted the engine & pipe conventionally & left the bypass out
so fitting a FOD screen wasn't an issue.
I left the intake as designed.
John.
When I fixed the crappy elevator setup on a 60 inch BVM Sabre there wasn't room
for the bypass so I mounted the engine & pipe conventionally & left the bypass out
so fitting a FOD screen wasn't an issue.
I left the intake as designed.
John.
05-24-2014, 06:31 PM
#15
Bandits need the bypass. It is after all a high performance (low drag) sport machine designed to be flown fast... I recall that BVM published a warning that flying with out the even the bypass cover could risk the whole aircraft as dynamic pressure could blow the engin hatch off..
I think Jack is right with his theory on the drying time of heat shield. I just checked my tins instructions, and it does say to wait until previous coat is fully dry, but doesn't give a an actual drying time.. My last application of this stuff did bubble a tiny bit when I first ran the engine..
Roger
I think Jack is right with his theory on the drying time of heat shield. I just checked my tins instructions, and it does say to wait until previous coat is fully dry, but doesn't give a an actual drying time.. My last application of this stuff did bubble a tiny bit when I first ran the engine..
Roger
05-24-2014, 07:15 PM
#16
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Sorry, I'm away from BVM at the moment. I did not know you called. That bypass and engine combo has worked for years. I would certainly use a blower on shut down. I agree with others about the dry time between coats. I get bubbles too when I rush it. The stuff must be dry for the next coat. Use a heat gun, carefully, if faster dry time is required.
05-24-2014, 07:56 PM
#17
Sorry, I'm away from BVM at the moment. I did not know you called. That bypass and engine combo has worked for years. I would certainly use a blower on shut down. I agree with others about the dry time between coats. I get bubbles too when I rush it. The stuff must be dry for the next coat. Use a heat gun, carefully, if faster dry time is required.
No worries. I spoke to Patty On Tuesday and she said she would forward the message to you guys since you were on the way to FiF. After 3 months of working on this thing and the wait for the tailpipe, im a bit anxious to get it flying.
When i left the stuff to cure, it was solid to the touch before i appied the next coat. But it looks like i get to reapply anyways.
Does anyone have a link to a blower for cool down?
05-25-2014, 01:59 AM
#20
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I have used BVM heat shield in BVM bypasses for almost 15 years now and never had a problem other than hot starts where it does bubble up. I use three layers and I dry the first two quickly using a fan heater before putting the next on. The only issues I have seen with BVM bypasses is where the outer wall of the tail pipe is the type that slides on the bypass (P-70 install for instance) instead of the inner tube sliding on. This setup seems to recirculate hot air during cool down.
Jason
Jason
05-25-2014, 04:34 AM
#21
Regarding blowers, I was thinking about buying a Makita until I recently saw somebody using a 12V marine blower for that purpose.
http://www.attwoodmarine.com/store/p.../turbo-4000-ii
The guy was using one of these blowers together with a Lipo and just attach it to thereat of the plane after he shut down the turbine. The amount of air moved was amazing and the cooling cycle was really short. The airplane he was flying was a bandit.
Walmart have them for a good price and not to say that you would save a lot of money with this solution.
http://www.attwoodmarine.com/store/p.../turbo-4000-ii
The guy was using one of these blowers together with a Lipo and just attach it to thereat of the plane after he shut down the turbine. The amount of air moved was amazing and the cooling cycle was really short. The airplane he was flying was a bandit.
Walmart have them for a good price and not to say that you would save a lot of money with this solution.
05-25-2014, 05:01 AM
#22
Regarding blowers, I was thinking about buying a Makita until I recently saw somebody using a 12V marine blower for that purpose.
http://www.attwoodmarine.com/store/p.../turbo-4000-ii
The guy was using one of these blowers together with a Lipo and just attach it to thereat of the plane after he shut down the turbine. The amount of air moved was amazing and the cooling cycle was really short. The airplane he was flying was a bandit.
Walmart have them for a good price and not to say that you would save a lot of money with this solution.
http://www.attwoodmarine.com/store/p.../turbo-4000-ii
The guy was using one of these blowers together with a Lipo and just attach it to thereat of the plane after he shut down the turbine. The amount of air moved was amazing and the cooling cycle was really short. The airplane he was flying was a bandit.
Walmart have them for a good price and not to say that you would save a lot of money with this solution.
05-25-2014, 10:03 AM
#23
Thomas,
I think they've pegged this as a drying-time problem. Did the same thing with my Starfire. I always paint the aft half of the bypass with heat-shield and I got the bubbles the first couple of times. I believe it was Mr. 411 (Harley) who pointed out years ago that I needed to let it dry completely between coats. I sit the bypass in direct sunlight all day. 3 coats over 3 days. Now, my heat shield might get browned, but it doesn't bubble or flake away anymore.
I think they've pegged this as a drying-time problem. Did the same thing with my Starfire. I always paint the aft half of the bypass with heat-shield and I got the bubbles the first couple of times. I believe it was Mr. 411 (Harley) who pointed out years ago that I needed to let it dry completely between coats. I sit the bypass in direct sunlight all day. 3 coats over 3 days. Now, my heat shield might get browned, but it doesn't bubble or flake away anymore.
05-25-2014, 12:35 PM
#24
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Regarding blowers, I was thinking about buying a Makita until I recently saw somebody using a 12V marine blower for that purpose.
http://www.attwoodmarine.com/store/p.../turbo-4000-ii
I have using this for years. I just updated it today with a 12 volt 7 amp Hangar 9 battery. The old RC car NiCad packs were finally giving up.
It has a length of 3" dryer hose clamped on the end, and sits on the ground behind the jet, I have used it with BobCats, KingCats, Bandits, Ultra Bandits, without a hitch.
I put some pictures on this site a few yerars ago, but must give the credit to either Rob Janiger or maybe Matt (I don't remember which).
It uses a Radio Shack 270-1807 project box and an Atwood Turbo 3000 12 volt bilge blower from the boat shop.
The guy was using one of these blowers together with a Lipo and just attach it to thereat of the plane after he shut down the turbine. The amount of air moved was amazing and the cooling cycle was really short. The airplane he was flying was a bandit.
Walmart have them for a good price and not to say that you would save a lot of money with this solution.
http://www.attwoodmarine.com/store/p.../turbo-4000-ii
It has a length of 3" dryer hose clamped on the end, and sits on the ground behind the jet, I have used it with BobCats, KingCats, Bandits, Ultra Bandits, without a hitch.
I put some pictures on this site a few yerars ago, but must give the credit to either Rob Janiger or maybe Matt (I don't remember which).
It uses a Radio Shack 270-1807 project box and an Atwood Turbo 3000 12 volt bilge blower from the boat shop.
The guy was using one of these blowers together with a Lipo and just attach it to thereat of the plane after he shut down the turbine. The amount of air moved was amazing and the cooling cycle was really short. The airplane he was flying was a bandit.
Walmart have them for a good price and not to say that you would save a lot of money with this solution.
I have using this for years. I just updated it today with a 12 volt 7 amp Hangar 9 battery. The old RC car NiCad packs were finally giving up.
It has a length of 3" dryer hose clamped on the end, and sits on the ground behind the jet, I have used it with BobCats, KingCats, Bandits, Ultra Bandits, without a hitch.
I put some pictures on this site a few yerars ago, but must give the credit to either Rob Janiger or maybe Matt (I don't remember which).
It uses a Radio Shack 270-1807 project box and an Atwood Turbo 3000 12 volt bilge blower from the boat shop.
05-25-2014, 05:43 PM
#25
Why do you need a blower? To prevent soakback damage all you need to do is run the starter motor. Does your turbine not have a cool down sequence?
Just 30 seconds worth of dry running the starter motor is enough to lower the temperature by 100-200C, if you can.
Just 30 seconds worth of dry running the starter motor is enough to lower the temperature by 100-200C, if you can.