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Re: Cracked Givi hard luggage

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  Re: Cracked Givi hard luggage bob prohaska <bp@www.zefox.net> - 2024-01-03 01:49 +0000
    Re: Cracked Givi hard luggage Spike <aero.spike@mail.com> - 2024-01-03 09:15 +0000
      Re: Cracked Givi hard luggage bob prohaska <bp@www.zefox.net> - 2024-01-03 17:08 +0000

#5140 — Re: Cracked Givi hard luggage

Spike <aero.spike@mail.com> wrote:
> 
> Find where the far ends of the cracks are, and drill small ?crack stopper?
> holes there. Then use fibreglass matting and a suitable adhesive inside the
> case  to reinforce the cracked area. 

I managed to get some 4" wide fiberglass ribbon and a small can of
cement for ABS pipe. The cement is basically ABS resin dissolved in
acetone. It seems to stick quite well to the case and soaks nicely
into the glass cloth, so that part of the project looks promising.

On close inspection the cracks are much longer than I realized,
extending from the bottom front of the case where the cleats screw
on forward and upward a couple inches toward the corners. 
That seems rather bad.

Does anybody have suggestions for a reasonable stop drill size?
My first guess would be no smaller than the case thickness, up 
to maybe five or ten times thickness, say somewhere between
one and six millimeters. Does anybody have a better-substantiated
approach to the sizing a stop drill hole?

Thanks to all for writing!

bob prohaska

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#5141

bob prohaska <bp@www.zefox.net> wrote:
> Spike <aero.spike@mail.com> wrote:
>> 
>> Find where the far ends of the cracks are, and drill small ?crack stopper?
>> holes there. Then use fibreglass matting and a suitable adhesive inside the
>> case  to reinforce the cracked area. 
> 
> I managed to get some 4" wide fiberglass ribbon and a small can of
> cement for ABS pipe. The cement is basically ABS resin dissolved in
> acetone. It seems to stick quite well to the case and soaks nicely
> into the glass cloth, so that part of the project looks promising.
> 
> On close inspection the cracks are much longer than I realized,
> extending from the bottom front of the case where the cleats screw
> on forward and upward a couple inches toward the corners. 
> That seems rather bad.
> 
> Does anybody have suggestions for a reasonable stop drill size?
> My first guess would be no smaller than the case thickness, up 
> to maybe five or ten times thickness, say somewhere between
> one and six millimeters. Does anybody have a better-substantiated
> approach to the sizing a stop drill hole?
> 
> Thanks to all for writing!

> bob prohaska

For a crack stopper, I’d suggest a 2mm drill, and a problem you might have
is that the through-thickness crack front might not be square across the
thickness. You’ll need to examine each crack to ascertain where the ends of
each crack is both inside and outside, and then drill along the crack
front, which might not be square to the local surfaces. This is to avoid 
drilling larger holes than needed.

Another thing you might consider is to epoxy short pieces of steel across
the ends of each crack, before applying the glass-fibre matting, whether or
not you drill crack-stopper holes. If doing this, clean the steel strip
with alcohol before applying the epoxy and avoid handling the bonding
surface. Apply pressure until the epoxy sets.

HTH

-- 
Spike

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#5142

In uk.rec.motorcycles Spike <aero.spike@mail.com> wrote:
> For a crack stopper, I?d suggest a 2mm drill, and a problem you might have
> is that the through-thickness crack front might not be square across the
> thickness. You?ll need to examine each crack to ascertain where the ends of
> each crack is both inside and outside, and then drill along the crack
> front, which might not be square to the local surfaces. This is to avoid 
> drilling larger holes than needed.
> 

There's enough material for 5-10 mm holes, but I'll look more carefully
to see if the crack inclination can be discerned.

> Another thing you might consider is to epoxy short pieces of steel across
> the ends of each crack, before applying the glass-fibre matting, whether or
> not you drill crack-stopper holes. If doing this, clean the steel strip
> with alcohol before applying the epoxy and avoid handling the bonding
> surface. Apply pressure until the epoxy sets.

I wonder if using a small screw, washers and nut clamping the ends of
the cracks flat might have a similar effect. That's easier to do,
looks aren't a huge issue. Flatness near the crack ends might be
as the cracks follow the curve from the bottom of the case to the
corners. The end area might not be entirely flat. 

Thanks for writing!

bob prohaska

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