IMAC Dalton Yak 54, 38% please submit suggestions here....
- Thread starter orthobird
- Start date
Vern.Smith
30cc
You have put together a very good system to cool the cylinders by forcing all the incoming air through the fins on the cylinders and then down the back of the engine to what should be a pretty large exit hole in the bottom rear of the cowl. Unfortunately, this system creates a dead air space under the engine where the induction system lives. I would suggest cutting a hole in the cowling under the spinner and making a duct to direct this air around the carburetors. If you go to your local airport you will see this arrangement on most of the light single engine airplanes sitting around the airport.
The hole in the bottom of the cowl where the hot air is exiting needs to be 1.5 times as large as the entry area and should have a lip "spoiler" along it's front edge to create a low pressure area behind the lip which will pull the hot air through the system.
The hole in the bottom of the cowl where the hot air is exiting needs to be 1.5 times as large as the entry area and should have a lip "spoiler" along it's front edge to create a low pressure area behind the lip which will pull the hot air through the system.
Hello Vern, thank you very much for your comments. However, I cannot take credit for it. This has been designed by others way before my time, and I have only copied them!! Also, yes, everything you have stated is true, the exit has to be at least 2 to 1, some say 3 to 1.
Well, I go overkill, and make it more so. DO not know if this hurts me.
May be increases my drag, do not know./
I also have a friend that has a sheet metal business, and he has cut for me some aluminum, which i use as lips under all my models, to help create an area of negative pressure, and thus, help extract the hot air out of the cowl/motor area.
In conclusion, as you have pointed out, to have a nice, healthy , happy motor, you need:
1. good oil
2. good needle settings
3. very good baffling
4. appropriate exit to inlet ratios, so that there is more area for air to escape than area where air goes in
5. create an area of negative pressure by using some form of "lip" (louvres) , that helps extract the hot air out.,
Here are some pictures for your enjoyment of how I overkill on this topic, but it shows in my telemetry. Most of my engines run well and have low temps, when the airplanes are set up like this.
Well, I go overkill, and make it more so. DO not know if this hurts me.
May be increases my drag, do not know./
I also have a friend that has a sheet metal business, and he has cut for me some aluminum, which i use as lips under all my models, to help create an area of negative pressure, and thus, help extract the hot air out of the cowl/motor area.
In conclusion, as you have pointed out, to have a nice, healthy , happy motor, you need:
1. good oil
2. good needle settings
3. very good baffling
4. appropriate exit to inlet ratios, so that there is more area for air to escape than area where air goes in
5. create an area of negative pressure by using some form of "lip" (louvres) , that helps extract the hot air out.,
Here are some pictures for your enjoyment of how I overkill on this topic, but it shows in my telemetry. Most of my engines run well and have low temps, when the airplanes are set up like this.
Vern.Smith
30cc
Yes, I can see you have taken the low pressure exit lip concept to heart in a big way 
Now if you can get some cool air to the induction system it will be even better. Can you put one of your on board sensors close to the carburetor intake to see what the temperature of the air the engine is breathing is?
Now if you can get some cool air to the induction system it will be even better. Can you put one of your on board sensors close to the carburetor intake to see what the temperature of the air the engine is breathing is?A year ago or so, I posted a question on what is the best technique to hold the header - coupler - coupler - pipe/canister connection. We basically got three answers, each with their own pros and cons. They are, drill thru teflon coupler and into header or pipe/can and use either a pop-rivet, or use a screw. or, 3rd option, only use the clamp with no other supporting fixation device. These all have their pros and cons. If you use a screw, the screw can back out, since you screw it into relatively thin metal. a pop-rivet = the cons is that the metal ball will eventiually come out, and now you will have a leak. The no fixation, maybe, the header and pipe will bang with each other, and produce sound (rattling) and wear of the junction.
Well, at Bobby Folsom 's IMAC contest few months back, I told Bobby, I think I have come up with the solution, and now, I present it to you all.
1st step, get your self a counter sink drill bit and a flat head machine 6-32 screw.
Now, drill a hole thru the coupler and the header or canister, and then remove the coupler, and then use the countersink drill bit, by hand, and remove enough teflon so that the screw is not proud.
here it is, another view....
here it is covered up. now the screw cannot back out, you do not have to worry of an air leak, and this prevents the pipe/header from sliding in the coupler!!
Well, at Bobby Folsom 's IMAC contest few months back, I told Bobby, I think I have come up with the solution, and now, I present it to you all.
1st step, get your self a counter sink drill bit and a flat head machine 6-32 screw.
Now, drill a hole thru the coupler and the header or canister, and then remove the coupler, and then use the countersink drill bit, by hand, and remove enough teflon so that the screw is not proud.
here it is, another view....
here it is covered up. now the screw cannot back out, you do not have to worry of an air leak, and this prevents the pipe/header from sliding in the coupler!!
I am getting ready to finish this bird off, need to do fine details now for the logistics of the mounting of the motor, radio, servos, etc....
I had to extend both headers, and Tony Russo sent me these header extensions. We were able to braze these on with the help, or I should say, my father in law did it for me:
I had to extend both headers, and Tony Russo sent me these header extensions. We were able to braze these on with the help, or I should say, my father in law did it for me:
Another challenge! Installing an arm onto the carb. in the current position, it would be very difficult to get a push-rod onto the throttle arm on the carb.
Tony Russo sent me this arm that i installed, and looked good!!
until i had to install the header, and then, Houston, we have a problem!!!
This was then trimmed, and now, it is perfect!!! ready to install throttle servo next!
this is now the clearance!
Tony Russo sent me this arm that i installed, and looked good!!
until i had to install the header, and then, Houston, we have a problem!!!
This was then trimmed, and now, it is perfect!!! ready to install throttle servo next!
this is now the clearance!
Got to do a little bit of work today on the Dalton Yak. Working on installing the mounts for the canisters!! this is not easy at all, quite complicated and labor intensive!.. Wish i had done this part before i sheeted the sides of the fuselage. anyways, on the next one. I made this aluminum brace, that spans the motor-box sides. On the outside of the motor-box, i will glue on some plywood as well to reinforce where the brace mounts on. As it is, it is an area for stress fracture if there external forces applied to it, being it is plywood coming to an "X". This will definitely have to be reinforced, but, the problem here is, i need to drill two small holes, and cannot do so. I need something like what the dentist have, that is a small drill bit at a 90 degree angle. I have a very limited area to work in. Anyone have any suggestions?
