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Thread: Cowling and spinner interference

  1. #1

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    Default Cowling and spinner interference

    I assume this is due to the new engine mount bushings. I don't recall where it was when I first bought the plane and I have had all the cowling off since then. Any ideas on a fix? I haven't run the motor yet since replacing the bushings so maybe it will "settle in" a little. Also, why do my pictures all come up sideways and how do I fix that? Thanks.
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    Mark Sprague
    914 Series 6 - flying

  2. #2
    Senior Member jiott's Avatar
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    Default Re: Cowling and spinner interference

    The simplest fix would be to install washers under the bolt heads where the engine mount attaches to the firewall. The shim washers under the top bolts would tip the whole engine assembly down and forward, which is what you want to line up with your cowl. The down side of this, of course, is that you will have changed the whole thrust line of the engine, which will affect the flight characteristics to some extent. How much I don't know. Maybe you will get lucky and it won't require enough shimming to matter much.

    The other fix is a more laborious rework of the cowl where it attaches to the firewall to pull it up and back.

    A longer prop spacer would get you clearance, but the lineup with the cowl would still be ugly.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  3. #3
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    Default Re: Cowling and spinner interference

    HI Mark,

    I am no expert but something doesn't seem right here to me! I mean the cowls would have fit ok originally when the engine was first fitted and the bushings were new would they not? Others more knowledgeable might be able to suggest possible reasons but the only thing I can think of is that the original bushing may have been different to ones you have used????? I guess I would just want to understand why the new bushings have raised the engine to the point of interfering with the cowl rather than restoring it an even distance all round? Does the old owner have some pics of the gap you can compare?

    I am sure you will get some good advice here but looks like you are making good progress with your overhaul - wont be long now!

    cheers

    ross
    Ross
    Mt Beauty, Vic
    OZ
    Sold to Richard and Scott Taubman in OZ, 2019. Kitfox SS7,Rotax 912is Sport, Airmaster CSP 75" blades.
    Landcruiser and Cub off road camper (doesn't get any kudos on this forum!)

  4. #4
    Senior Member jiott's Avatar
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    Default Re: Cowling and spinner interference

    Good call Ross. That is hard to explain. Some investigation is in order.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  5. #5

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    Default Re: Cowling and spinner interference

    The motor and mount came from another airplane originally and had around 100 hours before being installed on this plane. That is why I was thinking there may have been a bit of sag before the cowling was originally fitted for this airplane.
    Mark Sprague
    914 Series 6 - flying

  6. #6
    Senior Member Dave S's Avatar
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    Default Re: Cowling and spinner interference

    Mark,

    When you got the plane originally....was the cowl in place and correctly aligned?

    Reflecting off Ross's comments...if cowl/spinner was correct originally, a person would think it should be the same with new bushings.

    I see you have one photo of the ring mount, firewall mount and the bushings that were in place from your 7/12/2016 post.....in comparing that photo to the current asssembly of the mount - can you observe any differences in front/back offset between the top and bottom rubber bushings? The rubber bushings from the 7/12/2016 photo appear to centered correctly??

    I am sure you will figure this out...and it is an interesting predicament.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  7. #7

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    Default Re: Cowling and spinner interference

    I have definitely learned that you can't have too many photos. You would think I would know that already. Here is a shot from before the cowl ever came off the first day we saw it.

    It looks like it may have had some clearance issues from the beginning but it is hard to tell from this photo. You can see some of the darker blue from the spinner on the cowl. But that may suggest some separation and only an occasional contact. I wish I had a better shot.
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    Mark Sprague
    914 Series 6 - flying

  8. #8
    Senior Member Esser's Avatar
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    Default Re: Cowling and spinner interference

    I know it's a long shot Mark but do any of the videos your wife took show a side shot? Probably from too far away if it does....

    It will be MUCH easier to try to get this thing to settle down instead of reworking the cowl.

    In fact, I would shim before I messed with the cowl. Sure your thrust line may slllliightly change but it would be to where it was before you did the swap.
    ------------------
    Josh Esser
    Flying SS7
    Rotax 914iS
    AirMaster Prop

    Edmonton, AB, CWL3

  9. #9
    Senior Member Dave S's Avatar
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    Default Re: Cowling and spinner interference

    Mark,

    You know, with all the photos I took of our kitfox.......after the fact I found that I could have taken more...I think that is a common thread. I know what you mean.

    After looking at the photo in your last post, I think it is pretty clear that the original clearance between the cowl and the spinner is less than it should be...although that doesn't solve the original question. I'd guess that the paint transfer could have occurred from the simple act of removing and replacing the upper cowl. Some photos attached of the cowl fit on our plane - although it is an S7 and not the same exact cowl - but you get the idea.

    I wouldn't want to speculate too far out as to what the case may be; but, there are likely only a limited number of possibilities.

    1) The bolt up of the new bushings may have ended up differently between the old and new bushings - finding some way to make that comparison would be a good start.

    2) The order of assembly when building the firewall forward should be in your build manual - basically the engine and engine mount is assembled first, then the cowl is adjusted to match the prop hub, camlocks installed and spinner fit. I wouldn't rule out the possibility that there may be multiple things adding up affecting what you see - a little from the bushings, a little from the cowl fit, oversize camlock holes(?) etc....but I am speculating a lot - studying the build manual might help figure this out.

    3) If the engine mount came from a different aircraft....might be good to check for any damage/bending to the mount, unless it is known be correct. Wondering if this was the only/first engine mount fit to this aircraft; or, is it one that was install later when a different one was installed first?

    In any case, well worth taking your time to figure it out before drastically modifying anything.

    Hang in there - we all have our challenges.
    Attached Images Attached Images
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  10. #10

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    Default Re: Cowling and spinner interference

    Quote Originally Posted by Esser View Post
    I know it's a long shot Mark but do any of the videos your wife took show a side shot? Probably from too far away if it does....

    Unfortunately I never put the cowl back on after we took it off the first time we saw the aircraft. So all the videos are cowl off.

    Quote Originally Posted by Esser View Post
    It will be MUCH easier to try to get this thing to settle down instead of reworking the cowl.

    In fact, I would shim before I messed with the cowl. Sure your thrust line may slllliightly change but it would be to where it was before you did the swap.
    I am wondering if I overtightened the bushings or forgot some washer shims in between the firewall and the motor mount. I'll look into that first. Like you said it would only put the thrust line back where it was.

    The motor came off of one of Murle Williams airplanes and I have confirmed with John McBean that it is actually a series V round cowl firewall forward which was reworked for the series 6 smooth cowl so I am dealing with a bit of a custom job. I guess all kit airplanes are custom jobs.

    My build manual doesn't have the firewall forward part of it because, I'm assuming, that the builder didn't buy the firewall forward from Kitfox. I would love to have that part of it, although with it being so custom, I'm not sure how much it would help. I'm sure there is good info in there that I don't have however, like how much to torque the bushing part of the mount.

    And on that note, the bushings I got are exactly the same Lorde model number so unless they changed something, they should be the same.

    Thanks for the ideas and support. The community here is fantastic!
    Mark Sprague
    914 Series 6 - flying

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