New Hangar 9 P-51 60cc
06-10-2015, 08:24 AM
#951
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[QUOTE=sjhanc;12052363
. I had some extensive aircraft mechanic training both in the US Army and later for Bell Helicopter. I am used to seeing air intake and exhaust handling solutions in full scale aircraft and helicopters. I try to keep the scale models as simple as possible but a certain minimum of design and construction effort is necessary in order to have a nice flying day. In my military job as a crew chief I had to pay attention to the details so that others would not pay for a mistake with their lives. And I was along for the ride with them. I didn't have anything to do with the design of the aircraft I flew in but I got to take them apart every day and just got used to the way it needs to be. I flew up to 14 hours each day and pulled maintenance inspections all night with my gunner. When I needed extra manpower they got line mechanics out of bed to help us do a week's work in one night. When that happened I had to inspect all the other's work too. I got to sleep every time the pilots shut it down to go to a meeting for their mission orders (usually 10-15 minutes unless we were in a hot LZ being shot at).[/QUOTE]
Good to have you around...
. I had some extensive aircraft mechanic training both in the US Army and later for Bell Helicopter. I am used to seeing air intake and exhaust handling solutions in full scale aircraft and helicopters. I try to keep the scale models as simple as possible but a certain minimum of design and construction effort is necessary in order to have a nice flying day. In my military job as a crew chief I had to pay attention to the details so that others would not pay for a mistake with their lives. And I was along for the ride with them. I didn't have anything to do with the design of the aircraft I flew in but I got to take them apart every day and just got used to the way it needs to be. I flew up to 14 hours each day and pulled maintenance inspections all night with my gunner. When I needed extra manpower they got line mechanics out of bed to help us do a week's work in one night. When that happened I had to inspect all the other's work too. I got to sleep every time the pilots shut it down to go to a meeting for their mission orders (usually 10-15 minutes unless we were in a hot LZ being shot at).[/QUOTE]
Good to have you around...
06-10-2015, 10:30 AM
#953
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I don't have a lot to say to that other than it all sounds very questionable. I'm familiar with pressure recovery shapes ('pumpkin seed') but that has little to do with cooling here, or fuselage drag on the Mustang. The B, C and D wings are all the same thickness by the way, I've built them.
My point is that the 1:3-4 cooling ratio is a myth. As Kenny says above, pressure differential drives the system, and the air passing through the system has to go through the fins to be effective, not just near them or around them. If the air is not going where it's needed it doesn't matter how large or small the exit is. The pressure differential can be generated a number of ways, and the exit size is not generally considered to be a factor. Look at full-sized subjects and low pressure zones are created by doors, ramps, louvers, and external shaping. Inlet to outlet ratios are around 1:1-1.3.
Craig
My point is that the 1:3-4 cooling ratio is a myth. As Kenny says above, pressure differential drives the system, and the air passing through the system has to go through the fins to be effective, not just near them or around them. If the air is not going where it's needed it doesn't matter how large or small the exit is. The pressure differential can be generated a number of ways, and the exit size is not generally considered to be a factor. Look at full-sized subjects and low pressure zones are created by doors, ramps, louvers, and external shaping. Inlet to outlet ratios are around 1:1-1.3.
Craig
This is the nose exhaust of my TF GS P 51 B. You need to really look at a Mustang's shape. Because the air flow around the entire aircraft is spiral (due to the prop dragging air around with it), centrifugal force causes air to move out away from the skin creating a low pressure air mass that reattaches further back near the wing. Openings near the front (back to a few feet behind the nose of the full scale) are under pressure and openings behind the curve (where an opening can't see the spinner) are in low pressure. The area of this opening is approximately 2.5 times the chin scoop.
The main body of spiral airflow (spiral air flow is the reason the leading edge of the vertical fin is offset a few degrees to the left) is forced by the air that it compressed when the spinner charged through it to rebound, pushing the boundary layers against the fuselage and forcefully squeezing the rear of the aircraft and recovering a lot of the original energy that the nose expended when it pushed through. This is some times called the "Pumpkin seed effect", and is the point in the airframe's operating envelope that, having reached this speed (fast cruise), it takes less power to maintain this speed (best cruise speed for fuel economy), a feature the P 51 had that a lot of other planes could not duplicate. It took some pretty smart guys to design this plane and they didn't get it completely right until the B-C models were produced.
Changes made to the design for the D model (visibility(bubble canopy), thicker wing (6 upright machine guns), and the chin carb-air-scoop (Packard-Merlin)), made it a better gunfighter but actually slowed top speed under 10,000 feet.
The common P 51 model designs have a box fuselage and these airflow factors are minimal.
The H-9 P 51 design has an almost constant curve to the fuse from nose to tail (except the area around the sides of the cockpit, this area is also the flattest part of the full scale fuse) and should show better efficiency than its competitors.
The above picture shows the simple hot air exhaust I have been using for about ten years on 5 of the 6 TF GS Mustangs I have flown in the last 11 years. It is cut out of the lower firewall and is 1.5 inches deep and 3 inches wide. It has rounded edges inside except for the front edge on the back of the cowl. High velocity air flowing past the opening exerts a drag effect that pulls the slower air coming out of this vent. The same aerodynamic principle used for slotted and fowler flaps on wings. If you put a spoiler here you upset the air flow and create drag.
The engine cowling in the picture is for the large electric motor I'm flying now. I have used this same exhaust on a Fox 2.4, A ZDZ 80, And twice with my DA 50R. The other cowls for the gas engines had exhaust stack openings that were just large enough to avoid damage from hot mufflers and of course the top of the gas engine cylinder. I also filled in the area behind the chin scoop with block balsa and created an aerodynamic air passage to carry the cool air directly to the engine cylinder. No overheating. And it is not visible unless you look at it from this angle.
The main body of spiral airflow (spiral air flow is the reason the leading edge of the vertical fin is offset a few degrees to the left) is forced by the air that it compressed when the spinner charged through it to rebound, pushing the boundary layers against the fuselage and forcefully squeezing the rear of the aircraft and recovering a lot of the original energy that the nose expended when it pushed through. This is some times called the "Pumpkin seed effect", and is the point in the airframe's operating envelope that, having reached this speed (fast cruise), it takes less power to maintain this speed (best cruise speed for fuel economy), a feature the P 51 had that a lot of other planes could not duplicate. It took some pretty smart guys to design this plane and they didn't get it completely right until the B-C models were produced.
Changes made to the design for the D model (visibility(bubble canopy), thicker wing (6 upright machine guns), and the chin carb-air-scoop (Packard-Merlin)), made it a better gunfighter but actually slowed top speed under 10,000 feet.
The common P 51 model designs have a box fuselage and these airflow factors are minimal.
The H-9 P 51 design has an almost constant curve to the fuse from nose to tail (except the area around the sides of the cockpit, this area is also the flattest part of the full scale fuse) and should show better efficiency than its competitors.
The above picture shows the simple hot air exhaust I have been using for about ten years on 5 of the 6 TF GS Mustangs I have flown in the last 11 years. It is cut out of the lower firewall and is 1.5 inches deep and 3 inches wide. It has rounded edges inside except for the front edge on the back of the cowl. High velocity air flowing past the opening exerts a drag effect that pulls the slower air coming out of this vent. The same aerodynamic principle used for slotted and fowler flaps on wings. If you put a spoiler here you upset the air flow and create drag.
The engine cowling in the picture is for the large electric motor I'm flying now. I have used this same exhaust on a Fox 2.4, A ZDZ 80, And twice with my DA 50R. The other cowls for the gas engines had exhaust stack openings that were just large enough to avoid damage from hot mufflers and of course the top of the gas engine cylinder. I also filled in the area behind the chin scoop with block balsa and created an aerodynamic air passage to carry the cool air directly to the engine cylinder. No overheating. And it is not visible unless you look at it from this angle.
Last edited by CRG; 06-10-2015 at 10:32 AM.
06-10-2015, 02:43 PM
#954
There can many different ways to accomplish a task and it is possible most of them will work to some degree. My cooling method works for me and is neater and looks better than spoilers stuck on that are not scale in appearance. My understanding of the wing thickness change is based on what I have read in several different books. The reason NAA made the D model wing 1.5 inches thicker is the same reason the A/B/C model P 51 full scale aircraft had 4 wing guns laid over on an angle- they did not fit in the wing straight up and they had ammo feed problems if the pilot pulled Gs when firing-the guns jammed. To get (6) .50 caliber guns into this wing (upright) it had to be thicker. It is possible these authors were mistaken but I have never read anything on this subject that would refute it. It is also possible that the fuselage wing mounts will accept either wing. Since most of the early P 51 A/B/C aircraft were junked there may be no alternative for rebuilders. You build it from scratch or use the D model wing you can get.
Through experimentation with air cooling flow in several planes I came up with a simple solution that works-no overheating. When I build a new plane I include features from prior models that worked and look for other areas in which it may be possible to improve performance.
There is a reason that when modelers build a plane and fly it they frequently have overheating problems. 2 stroke gasoline engines are notoriously prone to overheating and the designers of the models don't know what engine will be put into their planes so they don't usually even make recommendations on how to do it.
Through experimentation with air cooling flow in several planes I came up with a simple solution that works-no overheating. When I build a new plane I include features from prior models that worked and look for other areas in which it may be possible to improve performance.
There is a reason that when modelers build a plane and fly it they frequently have overheating problems. 2 stroke gasoline engines are notoriously prone to overheating and the designers of the models don't know what engine will be put into their planes so they don't usually even make recommendations on how to do it.
06-10-2015, 04:18 PM
#956
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Yellow that will work if you take the template they have in the kit for a duct and re-make it from some .o625 G-10 and set the duct right above the front inlet upper lip. I glued a small block to the fire wall at the end of the mufler main tube for the right side and glued a block to the spark plug side of the chin cowl to attach that side. That will direct the inlet air through the fins around the cylender. You will need to open the back area behind the exhaust tubes. I made a oval hole about 3" x 2" and hysoled a 5/8 tall spoiler at an angle leaning to the wing. that will create the low pressure to draw the hot air out of the cowl. Like I said in phx it is hot now and I have had no heating issues.
06-10-2015, 06:03 PM
#957
YellowAircraft,
My first GS TF P 51 D ARF was equipped with a Fox 2.4 gas engine and had cowl openings almost identical to your picture with the exception of a carburetor air feed hole in the right side due to the Fox being a piston port engine design with a side mounted carb. I began flying it March 13, 04 and the weather here in Florida was still cool enough that we all had jackets on for the 50-60 degree f temps that day. The combination worked well until the ambient temps rose into the 85-95 degree f range and I began having what I thought were lean runs. I tried richening the carb mixture and the problem seemed to go away. Summer temps here are typically 100+ f and density altitude soars at ground level and I began having definite overheat problems that caused vapor lock before I could get it into the air. The symptom is a tendency to run perfectly until the motor warms up then it would gasp or choke on throttle-up and die. I began starting it at the end of the runway and doing an immediate take off and it seemed to work ok until I did a landing approach and then tried a touch and go, it would choke and die and I got my introduction to the wing landing gear mount problem.
Experimenting with cooling air flow which we are discussing here led me to try to speed up the cooling are flow past the engine, in other words-try to get the cool air directly to the hottest part and then out as quickly as possible. I believed that air coming off the cylinder met the muffler which was much hotter than the engine and caused a rapid heating-expansion of the air trying to get out. My brother has an infrared temp sensor and we pointed that at the various parts inside the cowl. In cool weather we got cylinder temps of 180-200 f and muffler temps of 230-250f. Much warmer summer temps gave us readings of cylinder temps of 250+f and muffler temps of 400 f and continuing to rise until the motor vapor locked and died.
Thinking that maybe the gas in the fuel lines was being boiled into vapor I rerouted the fuel lines well away from the motor and muffler and installed the split tubing that insulates spark plug wires on the fuel tubing. This prevented the gas bubbles I saw in the fuel going into the carb but I still had soaring engine temps when it was hot out.
My flying was limited to the early morning hours after day break when ambient temps were usually in the 60 f range.
I glued blocks of balsa to the front of the cowl closing off the chin scoop, then using drill bits in a slow turning electric drill motor I out lined an air passage that pointed at the upper cylinder area, then shaped it with a sanding drum on a Dremel. My reasoning for this is to take the air which was available, (chin scoop) and keep it moving undisturbed, then point it where it was needed most ( the upper half of the cylinder). The exposed head is already getting full blast from outside air so we can't do anything there.
This mod lowered cylinder temps below 200 f in hot weather but didn't do anything for the temps behind the cylinder so I figured the shape of the muffler was disrupting air flow, slowing it and allowing it to super-heat as it was bouncing off of everything around it, heat expanding(possible) and taking too long to exit the cowl.
Since there is not much you can do about the muffler's aerodynamics I decided to work on an airflow exit solution. My first attempt removed almost all of the cowl around the muffler area, was unsightly and still didn't do much for the overheat problem.
Getting a new cowl from Fiber Glass Specialties I did what you can see in the previous post (one page back), that the other guy does not like. All I can say is it works on any temp situation, is simple (minor surgery on the firewall) and the cowl is relieved only enough to clear the cylinder and muffler and prevent heat damage. The cowl clearance around the cylinder is actually pretty tight.
One strange thing I noticed at this point was a tendency for the motor to run rich (the mixture had been richened previously and I don't fool around with carb settings much). The plane was flying at 120+ mph out of a dive and would four stroke at the bottom. I slowly leaned the high needle until it smoothed out. That seemed to solve my over heat problems and I got 202 flights from it until the wing broke. That's another story.
Another thing I tried on the electric motor was to shim the motor forward until I had a measured 1/4 inch clearance between the cowl front and the spinner back-plate. I had noticed when running the electric with a spinner but no prop I had a jet of air leaking from this area. The back-plate clearance was 1/16 inch. I figured if I increased this clearance it might be beneficial. With the gap at 1/4 inch the motor temp dropped 40 degrees f. this was verified in flight with an onboard WIFI temp sensor and ground based receiver ($10 WalMart). Even at 160 amps current draw motor temp never got over 134 f. I am using everything possible to lower power-plant temps (intake and exhaust flow, scale exhaust pipes drilled out, and hot air getting out from behind the spinner). I have stopped checking temperatures as no longer necessary and my mods are barely visible. Check out my gallery photos.
My first GS TF P 51 D ARF was equipped with a Fox 2.4 gas engine and had cowl openings almost identical to your picture with the exception of a carburetor air feed hole in the right side due to the Fox being a piston port engine design with a side mounted carb. I began flying it March 13, 04 and the weather here in Florida was still cool enough that we all had jackets on for the 50-60 degree f temps that day. The combination worked well until the ambient temps rose into the 85-95 degree f range and I began having what I thought were lean runs. I tried richening the carb mixture and the problem seemed to go away. Summer temps here are typically 100+ f and density altitude soars at ground level and I began having definite overheat problems that caused vapor lock before I could get it into the air. The symptom is a tendency to run perfectly until the motor warms up then it would gasp or choke on throttle-up and die. I began starting it at the end of the runway and doing an immediate take off and it seemed to work ok until I did a landing approach and then tried a touch and go, it would choke and die and I got my introduction to the wing landing gear mount problem.
Experimenting with cooling air flow which we are discussing here led me to try to speed up the cooling are flow past the engine, in other words-try to get the cool air directly to the hottest part and then out as quickly as possible. I believed that air coming off the cylinder met the muffler which was much hotter than the engine and caused a rapid heating-expansion of the air trying to get out. My brother has an infrared temp sensor and we pointed that at the various parts inside the cowl. In cool weather we got cylinder temps of 180-200 f and muffler temps of 230-250f. Much warmer summer temps gave us readings of cylinder temps of 250+f and muffler temps of 400 f and continuing to rise until the motor vapor locked and died.
Thinking that maybe the gas in the fuel lines was being boiled into vapor I rerouted the fuel lines well away from the motor and muffler and installed the split tubing that insulates spark plug wires on the fuel tubing. This prevented the gas bubbles I saw in the fuel going into the carb but I still had soaring engine temps when it was hot out.
My flying was limited to the early morning hours after day break when ambient temps were usually in the 60 f range.
I glued blocks of balsa to the front of the cowl closing off the chin scoop, then using drill bits in a slow turning electric drill motor I out lined an air passage that pointed at the upper cylinder area, then shaped it with a sanding drum on a Dremel. My reasoning for this is to take the air which was available, (chin scoop) and keep it moving undisturbed, then point it where it was needed most ( the upper half of the cylinder). The exposed head is already getting full blast from outside air so we can't do anything there.
Since there is not much you can do about the muffler's aerodynamics I decided to work on an airflow exit solution. My first attempt removed almost all of the cowl around the muffler area, was unsightly and still didn't do much for the overheat problem.
Getting a new cowl from Fiber Glass Specialties I did what you can see in the previous post (one page back), that the other guy does not like. All I can say is it works on any temp situation, is simple (minor surgery on the firewall) and the cowl is relieved only enough to clear the cylinder and muffler and prevent heat damage. The cowl clearance around the cylinder is actually pretty tight.
One strange thing I noticed at this point was a tendency for the motor to run rich (the mixture had been richened previously and I don't fool around with carb settings much). The plane was flying at 120+ mph out of a dive and would four stroke at the bottom. I slowly leaned the high needle until it smoothed out. That seemed to solve my over heat problems and I got 202 flights from it until the wing broke. That's another story.
Another thing I tried on the electric motor was to shim the motor forward until I had a measured 1/4 inch clearance between the cowl front and the spinner back-plate. I had noticed when running the electric with a spinner but no prop I had a jet of air leaking from this area. The back-plate clearance was 1/16 inch. I figured if I increased this clearance it might be beneficial. With the gap at 1/4 inch the motor temp dropped 40 degrees f. this was verified in flight with an onboard WIFI temp sensor and ground based receiver ($10 WalMart). Even at 160 amps current draw motor temp never got over 134 f. I am using everything possible to lower power-plant temps (intake and exhaust flow, scale exhaust pipes drilled out, and hot air getting out from behind the spinner). I have stopped checking temperatures as no longer necessary and my mods are barely visible. Check out my gallery photos.
06-11-2015, 12:29 AM
#958
Ive built two fully cowled DLE 35RA's into a YA P-38 and the engine temps are good.
Heres a quick summary;
To cool the carb I put alloy velocity stacks on them. They draw cool air from the other side of the firewall.
To prevent vapor lock on the carb diaphram I soldered a brass fitting to the cover. Run a length of fuel tube to thru the firewall so the carb can have cool air to pump.
In the cowl I built a baffle at the centerline of the cilynder and the centerline of the crank case to direct air around the head.
Between the carb and the muffler I made a radiant heat barrier from tin sheet.
The exhaust goes straight down thru the cowl and there are no additional holes, its a tailored fit per tube.
There are three cowl exhausts on each engine and their area is greater than the intake or chin scoop.
With your hand you can feel the hot air exit the cowl very well.
So, on a P-51 you can do all of the above except you will have to sacrifice on the air exhaust appearance. A mesh screen could be used to make it look clean. Also, the dummy exhaust can be stood off and an air gap created to help remove hot air from above the crank case. You wont notice it and its effective at allowing air to escape.
Heres a quick summary;
To cool the carb I put alloy velocity stacks on them. They draw cool air from the other side of the firewall.
To prevent vapor lock on the carb diaphram I soldered a brass fitting to the cover. Run a length of fuel tube to thru the firewall so the carb can have cool air to pump.
In the cowl I built a baffle at the centerline of the cilynder and the centerline of the crank case to direct air around the head.
Between the carb and the muffler I made a radiant heat barrier from tin sheet.
The exhaust goes straight down thru the cowl and there are no additional holes, its a tailored fit per tube.
There are three cowl exhausts on each engine and their area is greater than the intake or chin scoop.
With your hand you can feel the hot air exit the cowl very well.
So, on a P-51 you can do all of the above except you will have to sacrifice on the air exhaust appearance. A mesh screen could be used to make it look clean. Also, the dummy exhaust can be stood off and an air gap created to help remove hot air from above the crank case. You wont notice it and its effective at allowing air to escape.
06-11-2015, 08:04 AM
#960
If I had it to do again, I would do the outflow ramp. One thing I'm wondering is won't the air blowing over the hole in the chin create enough venturi to suck out the hot air? If I'm using an improved baffle that takes the air from the chin scoop straight to the cylinder, could the air blowing over the hole be enough? Also, what's an acceptable temp for the head?
06-12-2015, 11:24 AM
#961
Hi,
I must have some sort of curse going cuz whenever I post a question in this thread, it stays the last comment for a LONG TIME. Here's another one: Anybody feel like posting pics of how/where you installed your gear controller and such?
I must have some sort of curse going cuz whenever I post a question in this thread, it stays the last comment for a LONG TIME. Here's another one: Anybody feel like posting pics of how/where you installed your gear controller and such?
06-12-2015, 12:33 PM
#962
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The airflow that I have is similar to yours. I had an issue of stalling out that was solved for me by changing the air fuel mix and opening up the front a bit more. The engine leaned out as it heated up. I am attaching pictures of my area under the cowl. I can get good flow over the cylinder head because it is outside the muffler and the small hole under the spinner is baffled to direct air right over it as well. I have another slot right behind the muffler in the cowl right near the battery compartment. To do some rudimentary airflow simulation I taped some yarn right behind the muffler and up in the cowl on the bottom. The test was to see if the yarn would blow up into the cowl or be forced out the holes. Of course this was on the ground. I ran the motor pretty hard on the ground to get it heated up as well for 5 min. I realize this is not in the air but it is something and the yarn blew down and out. In short, mine is not stalling now. Clearly there is not much air going over the crankcase for obvious reasons but as long at the air is being pulled out the bottom it should be fine. There is a ton of discussion behind this from guys who have thought this through much more than I. I am just interested in solving for "X" and flying
As far as temperature goes I can't answer that, I am sure there is a range (200 - 300) around this to a limit and depending where you measure it and when. Looking at the spark plug was a key indicator as to how the engine was running to for me.On the gear controller, you can see in the picture where mine is before I attached it via velcro to the horizontal wall right next to the receiver. I think you can put wherever your Receiver is as long as there is room. If you have a separate battery (I do not) for the controller that would of course require some thought on space. My goal was to not have to detach the center section at all once everything is working.
Hope this helps a bit.
06-12-2015, 01:04 PM
#963
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Hi,
If I had it to do again, I would do the outflow ramp. One thing I'm wondering is won't the air blowing over the hole in the chin create enough venturi to suck out the hot air? If I'm using an improved baffle that takes the air from the chin scoop straight to the cylinder, could the air blowing over the hole be enough? Also, what's an acceptable temp for the head?
If I had it to do again, I would do the outflow ramp. One thing I'm wondering is won't the air blowing over the hole in the chin create enough venturi to suck out the hot air? If I'm using an improved baffle that takes the air from the chin scoop straight to the cylinder, could the air blowing over the hole be enough? Also, what's an acceptable temp for the head?
06-13-2015, 08:20 AM
#964
It occurs to me that my solutions for engine cooling might not work on models that are performing non full-scale P 51 maneuvers like hovering etc. In a case where there is no relative wind effect it might be necessary to try to optimize the only option-use prop blast. The tiny opening available for cooling with the P 51 models (chin scoop) would offer little cooling air for these high alpha stunts.
here is an older picture of my plane taken by the Tricountyrcclub photographer when I had the DA 50 r installed. When I think about it, I have several possible cooling exhaust outlets on this plane, The scale exhaust pipes are drilled out on both sides, there is a large hole in the fire-wall for carb air, the engine cowling is not a tight fit on both sides and the engine is shimmed forward to 1/4 inch clearance behind the spinner in addition to the cooling exhaust duct at the bottom of the firewall. All of these could add up to quit a lot of suction helping remove heat from the engine area. Anyway. it works on the hottest days and my solutions are not obvious unless I point them out.
06-13-2015, 04:15 PM
#966
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I ran my DA-60 today and put the motor thru some more testing (on the ground), I don't like the way this DA-60 runs after just a few minutes with the cowl on. The engine runs so much better with the cowl off that I have decided to rethink my air flow setup. The crankcase is clearly getting to hot and I don't think there is enough air flowing to the carb either which is essentially in/behind the firewall. I will be using some of the techniques described in this thread. I don't know if I'll get it to run like it does with the cowl off but that is my goal. I want the aircraft to look good but it needs to run good too. I'll follow-up with some posts after I work this.
06-14-2015, 04:11 PM
#967
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Today I modified the cowl based on information on this thread. I took some scrap cowl fiberglass and did the following:
1. I created a baffle up front right under the small scoop. I made sure the baffle forced the air upwards towards the crankshaft.
2. I added a center strap across the cowl between the cylinder fins and the exhaust tips.
3. I made the hole behind the exhaust tips larger and made a flap/spoiler facing down in front of the hole.
I tested the motor on the ground in 90+ degree heat today. Tested it without the spinner and then with the spinner on.
Ran the motor pretty hard for 5-6 minutes.
The Motor ran great just as if the cowl were off. I'll test in the air soon an report back.
Here are pics of my mods.
1. I created a baffle up front right under the small scoop. I made sure the baffle forced the air upwards towards the crankshaft.
2. I added a center strap across the cowl between the cylinder fins and the exhaust tips.
3. I made the hole behind the exhaust tips larger and made a flap/spoiler facing down in front of the hole.
I tested the motor on the ground in 90+ degree heat today. Tested it without the spinner and then with the spinner on.
Ran the motor pretty hard for 5-6 minutes.
The Motor ran great just as if the cowl were off. I'll test in the air soon an report back.
Here are pics of my mods.
06-14-2015, 11:47 PM
#968
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Today I modified the cowl based on information on this thread. I took some scrap cowl fiberglass and did the following:
1. I created a baffle up front right under the small scoop. I made sure the baffle forced the air upwards towards the crankshaft.
2. I added a center strap across the cowl between the cylinder fins and the exhaust tips.
3. I made the hole behind the exhaust tips larger and made a flap/spoiler facing down in front of the hole.
I tested the motor on the ground in 90+ degree heat today. Tested it without the spinner and then with the spinner on.
Ran the motor pretty hard for 5-6 minutes.
The Motor ran great just as if the cowl were off. I'll test in the air soon an report back.
Here are pics of my mods.
1. I created a baffle up front right under the small scoop. I made sure the baffle forced the air upwards towards the crankshaft.
2. I added a center strap across the cowl between the cylinder fins and the exhaust tips.
3. I made the hole behind the exhaust tips larger and made a flap/spoiler facing down in front of the hole.
I tested the motor on the ground in 90+ degree heat today. Tested it without the spinner and then with the spinner on.
Ran the motor pretty hard for 5-6 minutes.
The Motor ran great just as if the cowl were off. I'll test in the air soon an report back.
Here are pics of my mods.
06-15-2015, 05:39 AM
#969
I run telemetry temp sensing on the cylinder at the base of the head on all my DLE 55s and 111. Normal running temps seen on my DLE 55s are between 230 and 270 degrees F. During breakins, I occasionally see 300s on long idles. If you get the air flowing correctly on the cylinder fins and head, the cylinder will heat sink the crankcase. But, you have to get the air flowing thru the fins not around them. I use baffles and small air dams in front of the exit, when necessary. I have seen 30-60 degree temp drops using the air dams alone. But, they do mess with scale detail. Everything has a price.
06-17-2015, 01:39 AM
#971
To the guy who says "All full-scale P 51 aircraft had the same wing, and, HE had built them all." I found this on google seach; Wikipedia- "North American Aviation P 51 D-K, The new model Mustang also had a redesigned wing; alterations to the undercarriage up-locks and inner-door retracting mechanisms meant that there was an additional fillet added forward of each of the wheel bays, increasing the wing area and creating a distinctive "kink" at the inner leading edges. MOST SIGNIFICANT was a deepening of the wing to the allow the guns to be mounted upright, resulting in a slightly reduced maximum speed compared to P-51B/C variants". Author- Bert Kinsey, P 51 In Detail & Scale, Parts 1&2 1996-1997.
06-17-2015, 02:20 AM
#972
06-17-2015, 04:33 AM
#973
To the guy who says "All full-scale P 51 aircraft had the same wing, and, HE had built them all." I found this on google seach; Wikipedia- "North American Aviation P 51 D-K, The new model Mustang also had a redesigned wing; alterations to the undercarriage up-locks and inner-door retracting mechanisms meant that there was an additional fillet added forward of each of the wheel bays, increasing the wing area and creating a distinctive "kink" at the inner leading edges. MOST SIGNIFICANT was a deepening of the wing to the allow the guns to be mounted upright, resulting in a slightly reduced maximum speed compared to P-51B/C variants". Author- Bert Kinsey, P 51 In Detail & Scale, Parts 1&2 1996-1997.
I thought he was referring to the Top Flite Mustangs.
06-17-2015, 06:54 AM
#974
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I said the same thickness, not the same wing. You are correct regarding the inboard changes to accommodate strengthening and gear door changes. Drop a ruler into the gun bays of B,C and D models and you'll see they're identical.
The D was a touch slower at the same power settings due to the bubble canopy, not the wing.
The D was a touch slower at the same power settings due to the bubble canopy, not the wing.
To the guy who says "All full-scale P 51 aircraft had the same wing, and, HE had built them all." I found this on google seach; Wikipedia- "North American Aviation P 51 D-K, The new model Mustang also had a redesigned wing; alterations to the undercarriage up-locks and inner-door retracting mechanisms meant that there was an additional fillet added forward of each of the wheel bays, increasing the wing area and creating a distinctive "kink" at the inner leading edges. MOST SIGNIFICANT was a deepening of the wing to the allow the guns to be mounted upright, resulting in a slightly reduced maximum speed compared to P-51B/C variants". Author- Bert Kinsey, P 51 In Detail & Scale, Parts 1&2 1996-1997.