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Underwing radiators

M

Morraine

Member
Have been slowly chipping away at my RV8 build and installed my wings complete with underwing radiators this past weekend. Really happy with the outcome so far and will now continue plumbing in the rest of the cooling system this weekend and begin ground running the system to see how it performs. Hopefully a late spring or early summer first flight date.
Follow link to pics.
http://s1277.photobucket.com/?postlogin=true
 
That's some pretty serious custom fabrication. Have you done any load analysis on the area of the lower wing skin that you slotted for the cowl flap actuator? I suppose it's pretty small compared to a gear door, but it just looks like a stress concentration.
 
PaigeHoffart said:
That's some pretty serious custom fabrication. Have you done any load analysis on the area of the lower wing skin that you slotted for the cowl flap actuator? I suppose it's pretty small compared to a gear door, but it just looks like a stress concentration.
Click to expand...

I have to agree with this. If you havn't done so already, I would suggest an .040 2024 T3 doubler, with a double row of staggered rivets. This should surround the entire slot.

Just my 2 cents. I'm excited to see your project fly! Did you get your radiator covers from supermarine, or did you fabricate them?
 
Safety concern

I'd be concerned with the susceptibility to ground fire with the under wing location. Just like the P51's under fuselage location.;)
 
Underwing rads

PaigeHoffart said:
That's some pretty serious custom fabrication. Have you done any load analysis on the area of the lower wing skin that you slotted for the cowl flap actuator? I suppose it's pretty small compared to a gear door, but it just looks like a stress concentration.
Click to expand...

All the area where the rads/cowl are mounted has been strengthened with the main load carrying ribs being doubled up. The rad itself is not actually attached to the wing structure but carried in the cowling....a very snug fit.
 
Underwing rads

flyboykelly said:
I have to agree with this. If you havn't done so already, I would suggest an .040 2024 T3 doubler, with a double row of staggered rivets. This should surround the entire slot.

Just my 2 cents. I'm excited to see your project fly! Did you get your radiator covers from supermarine, or did you fabricate them?
Click to expand...

Funny you should spot the similarity to the supermarine ones as I originally designed and fitted them to the kit spitfires when I worked there...good spotting. These ones however have been designed and built from scratch including building a dummy wing section to make the moulds on so the cowlings conform exactly to the wing shape. I then built all the cowl flap actuation mechanism and mounts etc in this dummy section so everthing fitted as it would on the wing structure. I made 2 sets of moulds and 8 sets of cowls before I was happy with the result!!!
I do like the suggestion of a doubler around the slot although the spitfire ones showed no signs of cracking in this area and the test aircraft was regularly flown in excess of 200 knots and dived to 240+as well. Might be 2cents worth but priceless advice if it saves grief further down the track!!!!!
Will try to keep updating as things progress...off to the airfield to keep building....all the little things now.
Cheers
 
Underwing rads

billnaz said:
I'd be concerned with the susceptibility to ground fire with the under wing location. Just like the P51's under fuselage location.;)
Click to expand...
I was initially concerned with this problem so did some research into bullet proof vests and found by incorporating Kevlar as the strengthening mat I was able to cover this problem quite elegantly...using one thing to do 2 jobs!!
Cheers
 
The fabrication looks nice.

I am curious as to why you would have 2, and mounted to the wings? As opposed to one on the belly.

Looks? Need that much rad surface area? less interference from something? Other?

I have a subie to be mounted on my -7 and I am considering a radiator scoop somewhere. Under the wings, I would be worried about disturbing the airflow around the wing. I was also thinking of radiator scoops along the side of the fuselage, like a P-38 Lightning, but this may disturb the airflow over the H. stabilizer/elevator.
Ultimately I may be following of the footsteps of: http://www.sdsefi.com/rv16.htm

Interested in your design criteria and reasoning.
 
jcaplins said:
The fabrication looks nice.

I am curious as to why you would have 2, and mounted to the wings? As opposed to one on the belly.

Looks? Need that much rad surface area? less interference from something? Other?

I have a subie to be mounted on my -7 and I am considering a radiator scoop somewhere. Under the wings, I would be worried about disturbing the airflow around the wing. I was also thinking of radiator scoops along the side of the fuselage, like a P-38 Lightning, but this may disturb the airflow over the H. stabilizer/elevator.
Ultimately I may be following of the footsteps of: http://www.sdsefi.com/rv16.htm

Interested in your design criteria and reasoning.
Click to expand...

In a previous life I had a lot to do with the Supermarine Spitfire 80% and 90% replicas and designed and fitted underwing rads to these aircraft. They were extremely successful and we had no issues what so ever with them so when it came time to build my own aircraft I went down this same path as I already had the experience to draw from.
We did extensive testing with these aircraft and the associated systems and had no problems either with the radiators and systems or any affect what so ever on the flight characteristics of the aircraft....and we had both in cowl type cooling systems and underwing systems to test back to back. All flight characteristics, speeds, stalling, spinning etc were almost identical...rather interesting from the point of view that the speeds were almost the same as we expected the underwing configuration to be slower...more drag...but not the case...the Meredith effect????? Maybe, maybe not.....
I agree that there may be some affect on the flight characteristics with this configuration on the RV8 but I suspect it will be minimal...time will tell.
If anything I have probably over estimated the size of the rads for my needs but would rather have a little too much rather than too little cooling. You will find that the actual cubic area of the system on Ross Farnhams aircraft with his P51 style scoop and my dual system is very similar...x amount of power output still requires the same amount of cooling capacity although efficiently designed ducts certainly enhance cooling efficiency. Incidentally the rads I am using are exactly the same dimensions as the ones I designed for the LS2 V8 powered Spitfire which was producing 430 hp!! My installation produces 305 hp but this is at 6500 rpm which I never use anyway so as I said earlier I will probably be over cooling.
The engine set up I am using has already been flown for 150 hrs in another aircraft I own so I am already aware of its cooling needs.
Hope this answers some questions. Will be doing ground testing this weekend if all goes to plan so will have a bit more to add then
Cheers
 
A friend of mine (who's near 90), did tests for the Air force in the Corsair. They found that a small bump on top of the wing had a greater effect than a shoebox mounted underneath.

Remember, the air over the top can be easily disturbed since it's low pressure air vs high pressure underneath.

Best,
 
Morraine said:
In a previous life I had a lot to do with the Supermarine Spitfire 80% and 90% replicas and designed and fitted underwing rads to these aircraft. They were extremely successful and we had no issues what so ever with them so when it came time to build my own aircraft I went down this same path as I already had the experience to draw from.
We did extensive testing with these aircraft and the associated systems and had no problems either with the radiators and systems or any affect what so ever on the flight characteristics of the aircraft....and we had both in cowl type cooling systems and underwing systems to test back to back. All flight characteristics, speeds, stalling, spinning etc were almost identical...rather interesting from the point of view that the speeds were almost the same as we expected the underwing configuration to be slower...more drag...but not the case...the Meredith effect????? Maybe, maybe not.....
I agree that there may be some affect on the flight characteristics with this configuration on the RV8 but I suspect it will be minimal...time will tell.
If anything I have probably over estimated the size of the rads for my needs but would rather have a little too much rather than too little cooling. You will find that the actual cubic area of the system on Ross Farnhams aircraft with his P51 style scoop and my dual system is very similar...x amount of power output still requires the same amount of cooling capacity although efficiently designed ducts certainly enhance cooling efficiency. Incidentally the rads I am using are exactly the same dimensions as the ones I designed for the LS2 V8 powered Spitfire which was producing 430 hp!! My installation produces 305 hp but this is at 6500 rpm which I never use anyway so as I said earlier I will probably be over cooling.
The engine set up I am using has already been flown for 150 hrs in another aircraft I own so I am already aware of its cooling needs.
Hope this answers some questions. Will be doing ground testing this weekend if all goes to plan so will have a bit more to add then
Cheers
Click to expand...


thanks, I look forward to the results.
 
Morraine said:
In a previous life I had a lot to do with the Supermarine Spitfire 80% and 90% replicas and designed and fitted underwing rads to these aircraft. They were extremely successful and we had no issues what so ever with them so when it came time to build my own aircraft I went down this same path as I already had the experience to draw from.
We did extensive testing with these aircraft and the associated systems and had no problems either with the radiators and systems or any affect what so ever on the flight characteristics of the aircraft....and we had both in cowl type cooling systems and underwing systems to test back to back. All flight characteristics, speeds, stalling, spinning etc were almost identical...rather interesting from the point of view that the speeds were almost the same as we expected the underwing configuration to be slower...more drag...but not the case...the Meredith effect????? Maybe, maybe not.....
I agree that there may be some affect on the flight characteristics with this configuration on the RV8 but I suspect it will be minimal...time will tell.
If anything I have probably over estimated the size of the rads for my needs but would rather have a little too much rather than too little cooling. You will find that the actual cubic area of the system on Ross Farnhams aircraft with his P51 style scoop and my dual system is very similar...x amount of power output still requires the same amount of cooling capacity although efficiently designed ducts certainly enhance cooling efficiency. Incidentally the rads I am using are exactly the same dimensions as the ones I designed for the LS2 V8 powered Spitfire which was producing 430 hp!! My installation produces 305 hp but this is at 6500 rpm which I never use anyway so as I said earlier I will probably be over cooling.
The engine set up I am using has already been flown for 150 hrs in another aircraft I own so I am already aware of its cooling needs.
Hope this answers some questions. Will be doing ground testing this weekend if all goes to plan so will have a bit more to add then
Cheers
Click to expand...

I got a chance to fly the 90% scale Spit, and you must have done a great job - no issues on cooling whatsoever, and I was flying it in Texas!
 
Underwing rads

Ironflight said:
I got a chance to fly the 90% scale Spit, and you must have done a great job - no issues on cooling whatsoever, and I was flying it in Texas!
Click to expand...

Hi Paul,
Thanks for the compliment...it was a huge task and many hours spent testing. Its great to hear that Supermarine is still operating in the States. I have not heard anything about how they are going so good news.
Sadly due to the economic downturn in 2008 I had to make a gut wrenching decision to leave Supermarine here in Australia as things were not looking too promising.
What was your impression of the V8 powered 90% aircraft and which aircraft did you actually fly, the original V8 prototype in the brown and blue camo which is the one I designed and built the engine installation and cooling system for or High Lady.
Cheers
Geoff
 
Underwing rads

pierre smith said:
A friend of mine (who's near 90), did tests for the Air force in the Corsair. They found that a small bump on top of the wing had a greater effect than a shoebox mounted underneath.

Remember, the air over the top can be easily disturbed since it's low pressure air vs high pressure underneath.

Best,
Click to expand...

Hi Pierre,
As always thankyou for your informative comments and particularly the history behind how some of these systems were evaluated.
Cheers
Geoff
 
Underwing rads

Spent all weekend plumbing in my water cooled oil cooler, mocal sandwich plate oil filter adapter and underwing radiators. Filled the cooling system, added about 500 mls of oil to the engine to account for the added capacity of the cooler and -10 oil lines and then checked and rechecked everthing.
Started and ran the motor. Temps came up and stabilised: water 82 deg Celcius and oil 60 degrees celcius. Ran motor to 4000 rpm, cycled rad coolant flaps and still no change in temps. Cycled prop to load engine and got boost up to 35 inches and coolant temp dropped to 78 deg Celcius.
I would have to say the underwing rad set-up seems to work!! Absolutely no leaks and absolutely no cooling issues ground running.
Now to finish the build and get flying. Hopefully by Christmas.
Cheers
 
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