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30CC SBACH 342


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Posted by john melia 1 on 20/01/2014 15:53:30:

thanks matt looking forward to seeing your photos . Thanks iqon , so are you saying I dont have to put any extra thickness onto the firewall yes

i would definitely add more ply, sorry if i misled you .. My point was you will probably have to add lead for your cg so adding thicker firewall is of no detriment.

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  • 2 weeks later...

Well, seemed to have hit a bit of a problem ..... engine bolted to firewall ........

Cowl sitting square and flush to airframe ...........

look at propshaft ........

and now with spinner backplate .......

any ideas on how to rectify this problem , the only solution i can see is to machine the back of the cowl which i have no means of doing

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First of all I would check which (or perhaps both) is incorrect. Level the fuselage so the datum is horizontal. Check the thrust-lines (Right and Down) are correct.

If they are OK, then you will need to trim the cowl. If not you will have to move the engine in relation to the firewall. I am not sure if you can use washers for spacers, but it doesn't look insurmountable

Good luck

Martyn

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Ok , as a rough guide get the plane dead level on the fus using a reference line,eg a stringer that goes from front to back. Then without moving anything and using the same level does the engine sit level putting the level on the prop thread?

If so then it is most likely the cowl will need trimming.

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I'm not sure this is an easy fix and I'll try to explain why:

1 - If you packed the top two aluminium mounts with washers to achieve the right downthrust you'll have two issues. a) the holes in the bulkhead won't line up properly with the mount or the engine won't be bolted square to the mount and b) the propshaft will have been displaced down so far the cowl won't fit.

2 - Looking at the way the cowl fits I would suggest that it's right. The paint line and the upper profile shows the fuselage transitioning nicely into the cowl. If you trim the cowl to fit the current position of the engine then it will suddenly deviate downwards in relation to the fuselage. It will look awful and once done is hard (but not impossible) to rectify.

If it was mine then there would be only one solution, it's a pain but the only way to do it properly. Working on the assumption that the cowl locates correctly (more photos would be helpful) then the engine must be adjusted to suit. I would build a new engine box and locate it higher up the firewall and build the downthrust angle in to the front face of the box.

Was the current box already attached when the kit arrived? Have you flagged this to HK yet to see what they're response is?

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