werner_molder

HELP !!

Yesterday I ve managed to fly the third flight of my BF-109 powered with the RCV 90SP, this third one was with the aluminium spinner setted , so the model is completly now.

For my surprise , after 5 minutes in the airborne, I noted that the engine sounded like it going to stop, so I inmediatly took it to landing.
When I checked the model on the runaway , it was smoke comming out and smelling burning.

please can someone help me , what I did wrong ?

the only TWO differents things that I did yesterday was :

1) setting up the scale aluminium spinner.
2) I used fuel from another fly camrate , he was usig 20/20 sinthetic

Could the spinner blocking the air flowing trought the open prop axel ?

you can see this video taked one year ago, when it flown without the spinner
[youtube]http://www.youtube.com/watch?v=97u30r1mx9c[/youtube]

andi3142001

Hi Werner,

guess your suggestion is perfect right- the spinner takes away the cooling air.

regards
Andi

acefly34

My Feedback: (3)

Hi Werner,
After looking at the pictures of your BF109, the addition of the large spinner has blocked almost all of the air flow. If the engine still turns free, and it has compression, you might try running it with the spinner off again to see if everything is okay. Make sure the needle valve is set slightly on the rich side. to prove the spinner is the problem, you could use a laser temp. meter to check the engine temp both with the spinner off and on.

Mit best grussen,
Denny

Juice

werner,

I had the EXACT same problem when I didn't properly cool my RCV 90SP on my H9 Corsair... It ran great for a couple minutes, then the power dropped considerably, then on the ground there was smoke coming from the muffler and the smell of burnt castor. It obviously overheated. After properly redoing the air ducting the overheating problems went away.

So there's your problem. What's your solution?

BTW... Nice model.

Juice

werner_molder

Hi Denny, Andi and Juice, well, I figured out that scale spinner was the problem...., but how do I for at make more holes to the tiny cowling? I mean, where I have to do these ? I ve ready did some of these if you can see on the top , these original scale air intakes, and below you can see the big hole open for the muffler and air flow.

Do I have to "sacrify" the scale cowling making more holes ?

snif...

/Werner

acefly34

My Feedback: (3)

Werner,
I noticed not only is the spinner blocking the airflow but the ring behind the spinner just about cuts it off completely. Just an idea, but you might try flying it with the ring removed and the spinner on. If this allows enough air flow and keeps the engine cool enough, you could then try drilling a series of holes around the ring using a drill press and drilling them in line with the airflow. Just a thought...

Denny
PS: It is a good-looking airplane

werner_molder

Denny,

hmmm...this is very strange,because if you take a look to the others scale planes in the www.rcvengines.com site, in the gallery section under RCV90SP, you will see P-51, Spits and another more that you even cant see any hole AT ALL !!! in their cowlings...

but ... may be I have to get off the spinner...

Juice

Werner,

Those scale intake holes may be enough. What kind of baffling (ducting, directing air) do you have inside the cowl? Got any pics?

You have to make sure that whatever cool air goes in those holes, goes straight to the cooling fins of the engine, and then out the hole near the exhaust. The air should have NO WHERE to go except through the cooling fins.

Josh

werner_molder

Hi josh

That is exactly that I though, according to the other scale warbirds like the p-51 and spitfire in the www.rcvengines.com gallery, these intakes hole above of the cowling, should be enough, BUT like you say, it doesnt have any strips for redirecting the air flowing...

Tomorrow, I will put me into the work to make these "strips" of balsa or plywood.....and IF this dont work....well... I will hang the model to the ceiling again... and wait the next season.

Josh... I just wondering HOW many holes could be enough to get cooled the engine ?

now... I feel tired and depress...

Juice

I would try to make the holes a little more round as you look at them from the front. This frontal area is what the air sees and it's that cross section that will determine how much cool air gets in.

Try to avoid sharp 90 degree turns the air has to travel. This may create a pocket of high pressure that air will not want to travel through. Round the corners some how. You want to create the highest positive pressure (A) at the intake holes and the lowest negative pressure (B) at the exhaust hole. The air will naturally want to go from A to B taking the path of least resistance. You want the cooling fins to be in that path.

Let us know how you work it out.

Josh

Katman

Werner,

if i understand, you haven't constructed a baffle to direct the airflow over the head yet!!?? I'm not understanding how you're expecting it to cool properly. You must also ensure the exit is preferably 3x the intake air area. This is per the instructions.
I have a 60SP, in a H9 Mustang PTS. Cooling-wise w/cowl on, it was a total success(though on the ground just like a real P-51 it will start getting hot lol). You can get creative for inlet/exit air yet keep scale. I actually used the backward facing exhaust stacks(which act as suction) for more exit, using the stacks as a template and removing the cowl behind this where not visible. The baffle i simply built out of a clear(hard)plastic pomegraine juice bottle, which had the perfect contour to force most air coming in the small P-51 inlet up into the head. It was mounted into the cowl w/angled balsa blocks. I also opened up the cowl opening behind the spinner much as possible without being too obvious. And the inlet slightly, without affecting its scale appearance. The aluminum spinner/backplate is very important in my opinion for cooling, and acts like a heat sink. When i shut mine down it gets hot enough to burn you. I'd work around going without.
Now, having said all this my 60SP has failed under warranty and had to be sent off about a wk ago to UK. Please see next post for detail.
You did a very nice job on your plane, I hope my suggestions are of help. Please post how it works out for you!
Katman

werner_molder

Hi Josh and Katman !! again

well, I would like to see your cowlings please for at get ideas and "put hands on work" this winter. I think ther is not more good wheater att all this flight season. (Here in Sweden).

Katman or Josh, I understand perfectly the idea of these "baffles", but I really will aprecciate from you guys if you could post some pics about your cowlings inlets, specially the dimensions of the holes intakes.
These pics will help me soooo much !!

Katman, did you see the scales holes intakes on the top (in the front), of the 109 cowling ? do you think that I have to make more holes ? in the back of the prop ? or make these MORE biggest ? may be ?

and on the bottom of the cowling you can see clearly the hole exhaust of the muffler, this hole is 3X more biggest of these two of at the top.

werner_molder

recently pics of the COWLING....

please take a look...into and out from it.

Meanwhile I found this considerations in the Wikipedia :

"High-nitro fuels produce more power than low-nitro fuels, but also produce more heat. The higher the nitro content, the colder the plug, also due to the lower methanol content".....

That guy fuel that I served has 20% nitro and this according the RCV instructions manual is extremly !!!

Should I modify my cowling or wait to get a right fuel according the specs to test again ?
Should I make a flight test to prove the fuel perfomance OR just make this just on the ground ?

Katman

Werner,
the fact you went against the manual and used 20% nitro could very well be your overheat problem(and no baffles!). You are lucky if you don't ruin your motor doing that. I advise against doing so again - bad enough you did it but i'd not voice such a thing on here you may not have a warranty!

I would try using 10% nitro first, but also do not think you've got near enough airflow though baffles will definitely help. Kind of like the real 109 you don't have much opening area. Like i said there are tricks without being unscale in appearance. Utilize the exhaust stacks like i said. I'd open up front of cowl behind spinner much as possible. And baffle baffle baffle...

I will try to scrounge up some cowl photos for you.

Katman

werner_molder

Katman
I learned the lesson...it was the "group press" to get the plane on the air , you know what I mean

I really will aprecciate your "baffles" ideas pictures.

Michael211

My Feedback: (1)

Also if you're not already, go with a full synthetic based fuel with no more than 10% nitro... I found that my 90SP runs cooler with full synthetic oil based fuel than with the same nitro level caster oil based fuel. Use Coolpower 10% plane fuel or an equivelant full synthetic fuel. Ever little bit of extra coolness helps!

Gorgeous model btw! Once you get this heat problem thing ironed out, you need to send pics to RCV for their picture gallery page!

- Michael

werner_molder

Hi Michael

please..please...could you tell me what is the oil porcent that are u running in your RCV 90SP ? what porcent of Nitro ?

best

Hugo.

andi3142001

Hi,

if you can obtain Graupner SX12 up there in Sweden, give it a try. Its 15% Titan Oil (very similar to Aerosynth 3) and 12% nitro. Works great.

regards
Andi

Joe Lott

Hello Werner,

Per Michael's advice I switched to CoolPower 10%. I believe Michael is running the same. It has 18% oil content. I love the stuff and my 120SP loves it as well. If you can get it, it's worth a try. It definitely runs cooler than the caster blend I was using. Also, per Keith Lawes, (inventor of the engine), you probably haven't damaged your engine. These engines are pretty rugged and if you can still turn it over and it has compression, you should be fine.

Good luck,
Joe

werner_molder

Hi Joe

Yes it has still good compresion.
All things is pointing to the problem was the fuel that I did borrow from that guy at the field. (He used a saito fuel 20%/20%) and may be little the new scale spinner played some roll.

Well, here in Sweden we dont have too many options about fuel´s issues like in the States or rest of Europe.
There are just ONE hobby store in the whole Sweden that import COOLPOWER , and these just come from 15% Nitro and above

andi3142001

Hej,

you could ask the local store wether he would order fuel especially for you. Usually they do that for quantities of 20 Litres or more.

regards
Andi