> >(At least for some applications) I recall Brian Alley (composite
> guru,
> >pro Lancair builder) says that anodizing provides adequate galvanic
> >protection for certain applications.. Is the aluminum anodized?
> >Probably not.. I'd add one layup of thin fiberglass to the side of
> >the spinner backing plate that contacts the prop's drive side. It
> >doesn't take much to keep the carbon fibers from making direct
> contact
> >with the aluminum.
>
> >Get some of the very light weight, fine weave fiberglass cloth from
> >the hobby store. It's relatively easy to work with. And some slow
> >cure resin/hardner. Have you worked with fiberglass much?
>
> >I imagine that your setup uses drive lugs in the output flange? I
> >think the dependence friction to transmit the torque loads is lower
> >than when just mating the prop to a flat flange. The diameter of
the
> >drive lugs can be much larger than the bolts, and so can handle the
> >shear loads much better.
>
> >RTV would not be my choice. I suspect it would eventually cause you
> >headaches with prop tracking - especially after being removed and
> >installed a few times - the RTV will wad-up. It's not structural
> >(soft).
>
>
> >Regards,
>
> >Matt-
>
> Hi Brian,
> Something didn't sound right about sandwiching ANYTHING between the
> prop flange and the drive flange, so I went out to my workshop and
> looked at my Hartzel props. Sure enough the spinner bulkhead is
attached
> to the OD (outside diameter) of the prop flange. Its an elaborate setup
> but, the bottom line is there is DIRECT CONTACT of the prop flange and
> the drive flange, no bulkhead, no RTV, no aluminum disks, no carbon
> fiber or fiberglass. I have 2 props --a 2 blade & a 3 blade-- both are
> done the same. Hope this helps. Dave M
>
>
> Dave,
>
> Would it be possible to send a photo?
>
>
>
> Thanks,
>
> Brian Trubee
>
>
> Your prop backing plate may already be anodized, but if not it is easy
> enough to do. Google "anodize" and follow the simple instructions.
Karibian
>
My understanding was that the prop had an aluminum plate embedded into
its structure. It would have been easy to anodize it before building
the prop, but not it's monolithic with the wood and composite..
Matt-
The main problem is the six 3/8 bolts will put far more compressive
load on the epoxy than it can take. The best thing is mount the aft carbon
fiber
spinner bulkhead as Dave M suggest.
Paul Lamar
Paul,
The prop bolts can't be tightened any more than the compressive
strength of the wood can withstand - spinner or no. Normal stuff for
wood props... A composite spacer shouldn't be a problem (is normal).
Dave's solution must be designed into the hub of the propeller or the
drive flange on the extension/reduction unit. Or an aluminum spacer
could be added which has ears for mounting the backing plate.
Matt-
Good point Matt. I suspect hard wood is better than epoxy.
I think one would be asking for problems to sandwich composites in there.
I have seen wood props with carbon coverings fail due to insufficient
torque on the bolts. The prop face against the flange turns black
indicating a constant slippage back and fourth burning or charing the surface.
And this is despite having hollow dowel pins in there.
Now this is for a four cylinder Lyc so perhaps a rotary might be OK.
Paul Lamar ...No rotor no motor.
The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site.
http://www.rotaryeng.net
Youtube key word UTUBPLEASE
Copyright 1998-2008 All world wide rights reserved.