Legacy Engine Room

[Randy Ryan]

Well, the airframe is complete except for a few small details. I put off making an exhaust adaptor to the end to make sure I got the fit correct. it turned out OK. The muffler is a Stalker .60 short. I now have to put a tank bay floor in and a clamp arrangement for the end of the muffler, then I can close up the chin. Gettin close!!!

[Michael Roberts]

Very nice...

[proparc]

I am really enjoying what you are doing here Randy.

[Dan McEntee]

   Doing anything about heat build up near the muffler? The rear exhaust set ups are neat, but the  heat build up in the enclosed area has to be a consideration. A good coating of thinned epoxy on the wood parts, and then some insulating material loosely wrapped around the muffler and held in place with the cowling? Or is it even a problem with enough air gap and some good airflow over the muffler? I don't have any rear exhaust engines so have never had t address this.
   Type at you later,
   Dan McEntee

[Brett Buck]

   Doing anything about heat build up near the muffler? The rear exhaust set ups are neat, but the  heat build up in the enclosed area has to be a consideration. A good coating of thinned epoxy on the wood parts, and then some insulating material loosely wrapped around the muffler and held in place with the cowling? Or is it even a problem with enough air gap and some good airflow over the muffler? I don't have any rear exhaust engines so have never had t address this.
   Type at you later,
   Dan McEntee

   I don't know about this one in particular, but yes, it can occasionally be an issue. So far I haven't seen any issue as long as you have a balsa tank floor between the header and the tank. But I have seen problems with exactly this sort of setup (Rustler-Merco 40 Metamorph) which was solved by - a 1/16 balsa insulator

    Brett

[Steve Fitton]

isn't the heat going to be removed by the fuel?

I used to use balsa insulators or TF-30 engine bay insulation, but it seems to work the same (in a piped PA-61 rig) insulated or not.  I realize I am not in the Varsity as far as stunt skills but I'm pretty sure I see no quantifiable change in motor run from insulated/non insulated.  However, tiny changes to the tank plumbing(or as little as 1/64th shim) have made *huge* observed changes in motor run.

I have seen little sign of heat damage in the engine bay or cowling itself.  Maybe a little darkening of the epoxy finish near the header on the inside of the cowling over 100s of flights.

[John Stiles]

Suhweeeeet.

[Dan McEntee]

    This will sound dumb, but grab hold of a muffler on a running engine sometime. Heat radiating from a a muffler in a confined area can cause problems. Like as mentioned, if you don't have a tank floor, heat can cause the fuel in the tank to get hot and cause run problems. Scorching is the most likely problem. Oil in the exhaust carries the heat of combustion out of the engine, and into the muffler/pipe. Balsa has a lot of air in it's make up and can be an insulator. There is all sorts of thin insulation that is used in small emgine and automotive applications that could be re-purposed if necessary. I guess the best course of action is to have a good gap all around the muffler canister and the header pipe, and provide some sort of air flow around it.
  HAPPY ST. PAT"S DAY TO YA ALL!
    Dan McEntee

[Randy Ryan]

   This will sound dumb, but grab hold of a muffler on a running engine sometime. Heat radiating from a a muffler in a confined area can cause problems. Like as mentioned, if you don't have a tank floor, heat can cause the fuel in the tank to get hot and cause run problems. Scorching is the most likely problem. Oil in the exhaust carries the heat of combustion out of the engine, and into the muffler/pipe. Balsa has a lot of air in it's make up and can be an insulator. There is all sorts of thin insulation that is used in small engine and automotive applications that could be re-purposed if necessary. I guess the best course of action is to have a good gap all around the muffler canister and the header pipe, and provide some sort of air flow around it.
  HAPPY ST. PAT"S DAY TO YA ALL!
    Dan McEntee

All, this is very similar to the setup I used on my Gladiator, There is very substantial airflow yet as some mentioned, I had some fuel heating problems at first. I solved that by wrapping the tank (plastic clunk) in aluminum foil, shiny side out. There was no tank floor in that model because the fuse is so shallow. This airplane has plenty of depth and the floor should be a good insulator, if no I still have the foil solution. Not very concerned with this having been around this block several times. A couple of pics, the tank floor now in and the muffler clamp. The well will only be edged on the bottom to fill out the profile and some dress-up around the rear leaving it fully open.

[Brett Buck]

isn't the heat going to be removed by the fuel?

   Yes, that's exactly what happens (sometimes). The fuel heats up, gets thinner, and makes the engine go rich.

      Brett

[Randy Ryan]

   Yes, that's exactly what happens (sometimes). The fuel heats up, gets thinner, and makes the engine go rich.

      Brett

That's it!!! very frustrating until I sorted it out.

[Larry Fruits]

   Yes, that's exactly what happens (sometimes). The fuel heats up, gets thinner, and makes the engine go rich.

      Brett

 What Brett says, is what happened with one of my header muffler equipped planes. Not until I installed a balsa spacer and aluminum foil faced ply heat shield, between the tank and header muffler, did I get good runs with the engine.
 Prior to adding the balsa shim and heat shield the top nose section of the plane would be really warm, and the spinner "very" warm after a flight. At times after a flight, raw fuel would spit out the tank vent a few moments after landing.   
 After the addition of the balsa shim and heat shield, the top nose section of the plane is same temp as the rest of the plane, the spinner is cool to the touch, and no fuel is ejected from the vent tube.
 Flying the plane without the cowl things worked fine. Flying with the cowl presented heat problems. I opened the hot air exits on four separate occasions with little gain each time. The cure was adding the balsa shim and heat shield.
 Good luck;
    Larry

[John Stiles]

Go on with it, hail...if it gets too hot, you can cut a hole, put a scoop over it and have ram air conditioning.

[Randy Ryan]

Go on with it, hail...if it gets too hot, you can cut a hole, put a scoop over it and have ram air conditioning.

They don't scare me John, I've already been there and done that!!! HAHAHAHAHAH