[Rhodes22-list] A fix for the short furler

[Roger Pihlaja]

Bob,

Unfortunately, torque does not work that way.  Think about the drive shaft
on your car.  The entire torque of the engine goes in at the front of the
driveshaft & it comes out at the rear when it enters the differential.  I'm
concerned your design will not stand up to the load for very long.

Roger Pihlaja
S/V Dynamic Equilibrium

----- Original Message -----
From: "Robert Dilk" <Robert.Dilk at TRW.COM>
To: <cen09402 at centurytel.net>; <rhodes22-list at rhodes22.org>
Sent: Tuesday, September 28, 2004 8:32 AM
Subject: Re: [Rhodes22-list] A fix for the short furler


> Thank you for the great comments as always Roger.
>
> You are correct the center bushing will connect the top 16 inches to
> the main furler section. I have tapped and threaded for a # 10 screw in
> the top and bottom sections to transmit the torque to the upper
> section.
>
> It was my thought that since only the top 16 inches have to driven,
> this modest material will suffice. Please note the lower screw also
> secures the luff through a reinforcing patch.
>
> I do not want to epoxy the center section as this will not allow the
> Forestay to be removed.
>
> Bob
>
> >>> cen09402 at centurytel.net 09/28/04 08:16AM >>>
> Bob,
>
> I'm not quite certain what I'm looking at in those pictures.  I
> understand
> you had to make new plastic end bushings because the old ones were
> probably
> old & brittle & disintegrated when you tried to remove them.  But, what
> are
> you going to do with the center bushing?  Are you planning to join the
> two
> pieces of the furling tube with the center bushing vs. welding them
> together?  If so, how do you plan to immobilize the top & bottom pieces
> of
> the furling tube so they can't rotate relative to each other?
> Remember, the
> head of your genoa is bolted to the top of the furling tube.  During
> furling, the required torque to turn the furling tube is applied at
> the
> furling drum at deck level.  The tack of the genoa is tied to the
> furling
> drum, so it must rotate with the furling drum.  But, the furling tube
> design
> assumes the furling tube will also transmit the torque up to the head
> of the
> genoa & cause the entire headsail to wrap around the furling tube in
> sync.
> If your extension is not somehow locked to original lower part of the
> furling tube; then, the torque will have to be at least partially
> transmitted by the luff tube on the genoa.  This load will take the
> form of
> a distributed shear load all down the length of the luff tube.
> Sailcloth is
> intrinsically at its weakest against this sort of shear loading & this
> twisting action will shorten the life of the sail, although I can't say
> by
> how much.  In addition, I would think the sail shape will look pretty
> odd
> with the leading edge of the sail all twisted out of shape.
>
> Assuming I've analyzed your plan correctly; then, plastic is a poor
> choice
> for the material of construction of the center bushing.  Consider
> refashioning that center bushing out of Al 7075-T6 aluminum alloy &
> using at
> least three
> 10-32 UNF oval head stainless steel set screws on the top & bottom
> sections
> to immobilize them relative to each other.  I would also epoxy these
> set
> screws in place during assembly.  It won't be as strong as welding & it
> will
> be also be heavier; but, it should lock the upper & lower sections
> together
> and hold them in proper alignment for a long time.
>
> Roger Pihlaja
> S/V Dynamic Equilibrium
>
> ----- Original Message -----
> From: "Robert Dilk" <Robert.Dilk at TRW.COM>
> To: <rhodes22-list at rhodes22.org>
> Sent: Monday, September 27, 2004 9:28 AM
> Subject: [Rhodes22-list] A fix for the short furler
>
>
> > Here is my solution.
> > I was unable to remove the  original split bushings intact, so I
> > measured and designed these from scratch.
> >
> > Note the two end bushing and the center bushing . I will use the
> center
> > bushing to connect the of furling tube to the new extension.
> >
> > The new Forestay is due in Friday. I will tell you how it works out.
> >
> > Bob
> > S/V Knot Necessary
> >
>
>
> --------------------------------------------------------------------------
--
> ----
>
>
> > Name: RHODES 22 FURLING PLUGS.jpg Type: image/jpeg Size: 22059 bytes
> Desc:
> not available
> > Url:
>
http://www.rhodes22.org/pipermail/rhodes22-list/attch/200409/27/RHODES22FURL
>
> INGPLUGS.jpg
> >
>
>
> --------------------------------------------------------------------------
--
> ----
>
>
> > Name: RHODES 22 FURLING PLUGS 2.jpg Type: image/jpeg Size: 22914
> bytes
> Desc: not available
> > Url:
>
http://www.rhodes22.org/pipermail/rhodes22-list/attch/200409/27/RHODES22FURL
>
> INGPLUGS2.jpg
> >
>
>
> --------------------------------------------------------------------------
--
> ----
>
>
> > __________________________________________________
> > Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
>
>
> __________________________________________________
> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
> __________________________________________________
> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
>
>