How to's with engine cooling, Firebolt bowl

Discussion in 'Steen Skybolt' started by taff, Sep 17, 2017.

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  1. Sep 17, 2017 #1

    taff

    taff

    taff

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    I am installing the cooling baffling kit from Vans Aircraft.
    Of course the front end is of a different design.

    I have trimmed a lot of aluminum off the parts to install under the Skybolt hood.
    At the air intake (the important entry point) and have a question to anyone that has installed the Firebolt nose bowl

    Looking at the photo's you will see my concern. What with the nose bowl close to the cylinders and the air space left after I install the air ramps. Will this be enough volume of air to sufficiently cool the engine?

    Also.
    Because the nose bowl is so close to the cylinders, the air ramp is no longer a ramp shape, but a wall, standing flat up against the oncoming air.
    All advice will be greatly appreciated.

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  2. Sep 17, 2017 #2

    FireboltEric

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    The openings on the face of the cowl are in original location. My left ramp slopes up to the midpoint of the cyl. The right one is very short and very steep, if you can see it in the photo. The metal dam on the right again only extends up to the cyl. midpoint. Because I sloped them up so much, I removed considerable horizontal material directly above the ramps, I think you can see it on the right one. My cyl head temps are normally just under 300.

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  3. Sep 17, 2017 #3

    FireboltEric

    FireboltEric

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    This shows the upper fiberglass removed. You'll have to zoom in.

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  4. Sep 17, 2017 #4

    taff

    taff

    taff

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    Thanks, this is great feedback.

    I cropped your photos and asked some questions.

    One other question, what engine do you have a 360 or 540?
    Reason for this is my prop spinner flange did not allow me to take the nose bowl any further from the cylinders. Or maybe it's because I have a constant speed prop that keeps the starter ring flange short.

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  5. Sep 17, 2017 #5

    FireboltEric

    FireboltEric

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    4 cyl angle valve. Yes, yes and yes. I think the right side is maybe 1/2 inch and the left a bit more, maybe 3/4. I think I did make a flat piece and then bond it in, then working in a radius after. I see what you are saying about the forward distance of the cowl. I was installing the fixed pitch. If I installed the prop directly on the ring gear the bowl was way to close to the cylinders. I wound up with a Saber 2 1/4 or 2 1/2 inch spacer. That makes up for the difference of a Hartzell constant speed which I believe is what McKenzie originally designed it for. I don't know how you could move yours forward, not familiar.

    It looks like it is in the right place.
     
    Last edited: Sep 17, 2017
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  6. Sep 17, 2017 #6

    PittsDriver68

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    With an angle valve engine you want the vertical baffle in front of the cylinders almost 2" high. Make them up to the level of the lower stud that holds the little coves for the rocker arms.

    Danny Adams at Aviat explained this to me. He has been doing this on factory airplanes and I did it on my S-2A. The higher front baffles even out the CHT's. Lower front baffles result is more spread in the CHT's. You want all cylinders running the same temps so they contribute the same HP. A cold cylinder delivers less HP.

    Looking at your nose bowl, you probably want to change the lower part of the nose bowl intakes to ramp up to the aluminum baffling. You need to prevent air from flowing under the cylinders from the intake and if you just use a flat aluminum plate at engine end of that pretty nose bowl intake, the bottom part of the nose bowl intake is just wasted.

    Best of luck,

    Wes
     
    Last edited: Sep 17, 2017
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  7. Sep 17, 2017 #7

    smizo

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    Not sure about your angle valve, but I have the vans kit on my parallel valve 360. I had that front plate full size as you show. Had to cut it down 1/4 inch below the lower side of the plate, straight across. All cylinders are around 375 now. I have about a 15-20 deg spread between all 4 cylinders. But who knows with your cowl. You can always cut them down.....
     
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  8. Sep 17, 2017 #8

    taff

    taff

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    Mine is a 360A1A parallel valve.
    Does this (one valve design over the other) have anything to do with the complexity of cooling methods/systems?

    A couple of photos to show how close the cylinder is to nose bowl.

    I am thinking to laminate in some fiberglass air ramps, as FireboltEric did.
    I know it's not much of a slope on the right ramp (photos), but what else can I do?

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  9. Sep 17, 2017 #9

    FireboltEric

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    I think that's all you can do, unless you could move farther forward or up. Ideally the openings should be much higher, but then they might be ugly. The right one is a very steep angle, and has some twist in it, as you have drawn in.
     
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  10. Sep 17, 2017 #10

    Cameron

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    I like the fiberglass ramp idea too.
     
  11. Sep 18, 2017 #11

    NDTOO

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    I will add some of my experiences since I have a Firebolt nose bowl as well. I have a fixed pitch propeller with a 1 inch saber extension on a parallel valve 540. All my baffles were copied from an old beat up set that came off a Piper Pawnee. The nose inlet area to the front cylinders are pretty tight and during the build I was wishing I would've gone with a 2" extension instead. Just would've given more room to work with. During initial flight testing I did deal with both oil temp and #5 CHT getting to the upper end of limits. I think part of this was due to engine break-in. I did opened up the exit area in the lower cowl a little more and sealed up the lower baffle area of the inlets which helped allot. Routine temps throughout last summer just cruising around down low at about 2400 rpm I would see oil temps around 190-205. Leaning out #5 would settle in at 380. #1 and 2 would run 280 and 3,4 and 6 would be about 300-320. This spring when I had the nose bowl off during condition inspection I removed more fiberglass from the top side of the left inlet as it was much closer to the #2 cylinder than it was on the #1 cylinder. This made a considerable difference in temps. This summer I have not seen the oil temp over 195. Cruising around sightseeing it settles in at 180. #5 CHT now runs 360 leaned. Opening up and balancing out that left side inlet area clearly made a noticeable difference. I am now considering adding some ramps like has been suggested here to try balance out the front two cylinders better.

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  12. Sep 18, 2017 #12

    NDTOO

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    One more. As you can see the front baffle does not come up very high on the number one cylinder, it is similar on the other side as well. Simply raising the baffles higher may balance the temps as well.

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  13. Sep 19, 2017 #13

    taff

    taff

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    A little progress today with some ideas from the forum.
    Still lots of thinking to do, At least I am working on it.

    Right now I am thinking a glass fiber ramp overlapping the aluminum, that has the rubber skirt.

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  14. Sep 19, 2017 #14

    airplanegeek

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    thanks for posting this, I am watching close, since i will have the exact same issue to deal with. My airplane will be Firebolt nose and a Catto prop with yet undecided baffling. I will probably go with the Vans kit because it is an affordable solution.
     
  15. Sep 19, 2017 #15

    NDTOO

    NDTOO

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    These are pics taken at Oshkosh in 2013. I'm sure some of you have seen this Firebolt. It is where I got the idea of doing this if needed.

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  16. Sep 19, 2017 #16

    taff

    taff

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    Brilliant!
    Thanks for posting.

    This could be worth the (it is worth) the donation money ;)
     
  17. Sep 23, 2017 #17

    taff

    taff

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    I am fudging around with the cooling baffling.

    I am leaving the air ramps for the time being (pain in the a$$) and progressing on another area.

    Some photos of the front panels.

    I am thinking, about 1 inch space between the aluminum and the top, for the rubber sealing strip?
    I'll see how flexible the rubber is and work from there.

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  18. Sep 23, 2017 #18

    Beej

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    I think mine were done with an 1/2 inch gap. Too big a gap and the seal could be forced to flip, thus leaking air....

    Looking at this RV baffle kit reminded me of how involved the baffle project was; it was a surprising pain in the butt, and took forever to do, neatly.
     
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  19. Sep 23, 2017 #19

    PittsDriver68

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    If you do a good job of sealing you will be surprised at how much upper deck air pressure there is. You want the baffle seal to fold over to lap on the top cowling by 1 1/2 to 2", and the less the gap between the to of the aluminum the better. Put a bend into the top of the aluminum baffles to get the rubber seal oriented to fold towards the center of the engine. This also helps with contact between the aluminum baffle and the top cowling when you do snaps and the front of the engine moves around.

    Best of luck,

    Wes
     
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  20. Sep 24, 2017 #20

    mjk51

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    I am currently fitting the baffles to my IO-540 with a Firbolt Nose-bowl. I have been able to use the original baffle that came with the engine for the most part. A bit of customizing but they will fit well. Those of you that are painting your baffles, could you recommend a paint that has a chance of lasting a couple hundred hours??? It's going to be tough to make these older aluminum pieces look good.
     

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