On 10/01/2022 12:54, Leon Warrington wrote:
Hi all,
Hoping someone will have some experience / recommendations that they can help me with.
We have a perennial problem whereby on our 2001 empacher quad, the 'threaded insert' (not sure of correct terminology) in the rigger that the rigging bolt screws into has a tendency to come unbonded from the rigger. To this extent we rarely de-rig this boat as every time we remove the riggers there is a chance of this occurring again. We have used epoxy resiun the past, but this does not provide long-term solution.
Does anyone have some UK recommendations of the best kind of fixing substrate to ensure a long-lasting solution?
Is there also any recommendations for thread lubrication on this kind of rigger?
https://photos.app.goo.gl/F8Mcq5RoGQKU7fYb7
I have asked Empacher UK but had no response so far.
Leon
I'd thought, in error, that I'd posted this reply to the group as well
as to Leon. Here it is, in case it is useful to others:-
Leon -
Some of us don't mind helping, so let's explore this:
The tube is, apparently, a braided carbon laminate? One feature of
carbon is that it has a very low coefficient of thermal expansion
compared with most metals - about 15% of that for aluminium. If you
have an aluminium insert bonded into a carbon tube & later exposed to temperatures 30C colder than during its assembly, then a ~35mm diameter
insert will shrink by ~0.4mm more on diameter than the carbon tube. If
the bond was made at a higher temperature (to get a faster cure) then
the differential contraction will be correspondingly greater Now a
typical resin gap in such a bond would be ~0.2mm all round, or less. So
that 30C differential would already subject the bond line gap to a
potential doubling which could easily lead to failure.
Bonding between materials with resins depends heavily on surface
preparation, & if dealing with a fractured bond you have to remove all pre-existing bonding resin. We prepare all fresh composite and metal
surfaces for bonding by bead-blasting, which might not be easily
accessible to you. If not, then you should heavily abrade all surfaces
and not get sweat or natural grease from hands onto the bond surfaces.
Use either an acrylic (methyl methacrylate based) e.g. Plexus, or a
high-duty epoxy resin (never use rapid cure epoxy, & do check the words
on the packet).
When reassembling the failed joint, after full preparation of all
surfaces, it is essential to mix the resin thoroughly & then apply it
fully to both surfaces. Allow ample cure time, as recommended by the
maker. Cure rates are highly temperature dependent & the cure of some
resins can virtually cease if temperature drops below 10C. Also, the
bond strength continues to improve for several days.
If none of the other riggers have failed, the above should give you a
lasting result.
As for a lubricant - any decent grease should do well enough. If the
insert is aluminium, don't use a copper-based grease. Well-greased
threads hold far better than dry ones (which is why car wheel nuts
should always be greased).
HTH -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email:
carl@carldouglasrowing.com Tel: +44(0)1932-570946 Fax: -563682
URLs: carldouglasrowing.com & now on Facebook @ CarlDouglasRacingShells
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