backing plates
 

Hi all,

I want to put on backing plates for all the stuff attached to the transom
(exhaust ports, swim platform, steering arms etc). Through continually
snugging them, the previous owner has burried a couple of nuts through the
glass! I am really new to all this but the first thing that comes to mind is
reaction between two metals. If I use stainless bolts, could I use aluminum
for backing plates or maybe I should use something else, or maybe I
shouldn't do this at all?

Still asking and not able to answer much yet.

Thanks, Steve

Use some stainless backing plates and Nyloc nuts.

"sel1" wrote in message
...
Hi all,

I want to put on backing plates for all the stuff attached to the transom
(exhaust ports, swim platform, steering arms etc). Through continually
snugging them, the previous owner has burried a couple of nuts through the
glass! I am really new to all this but the first thing that comes to mind
is
reaction between two metals. If I use stainless bolts, could I use
aluminum
for backing plates or maybe I should use something else, or maybe I
shouldn't do this at all?

Still asking and not able to answer much yet.

Thanks, Steve

sel1 wrote:
Hi all,

I want to put on backing plates for all the stuff attached to the transom
(exhaust ports, swim platform, steering arms etc). Through continually
snugging them, the previous owner has burried a couple of nuts through the
glass! I am really new to all this but the first thing that comes to mind is
reaction between two metals. If I use stainless bolts, could I use aluminum
for backing plates or maybe I should use something else, or maybe I
shouldn't do this at all?

Still asking and not able to answer much yet.

Thanks, Steve




To do it properly takes a little time but doesn't cost a single cent
more as in;

(i) Aluminium is OK say;
(a) 1/4"
(b) Size/shape of the backing is up to you, usually the available space
will dictate the shape size etc, the rule is; if it looks right it
probably is:-)
(b) it's not under water as such so dissimilar metals shouldn't be an
issue (even with stainless you'd still need to ensure the same stainless
as the bolts say 316 vs 3xx or it corrodes anyway:-)
(c) aluminium is much easier to work & you can even drill it in situ
from the outside if you have a tricky nook or cranny.

(ii) Chamfer just the outer perimeter of the plates away from where
they'll pull against the hull, if you leave a sharp edge it can cut into
the outer glass under load & leave a crack in the flow or gelcoat for
water to get in.

(iii) You should try to seal inside all the through hull holes:
(a) particularly if it's the cored transom
(b) Coat the holes right through with any of the good epoxy fillers, then
(c) push the bolts back in while it's wet, having given the bolt a good
coat of grease first (dipped in candle wax works too).
(d) Once epoxy has gelled you should be able to get your bolts back out
with a spanner, leaving a good protection for the transom core (usually
plywood) & a good fit for the bolt.

(iv) When ready to put it all together again;
(a) use plenty of any of the good sealants, sadly price is a good
indicator so any marine recommended 3M or marine sikaflex (German?? not
sure) is OK.
(b) Clean the hull, parts, holes, bolts etc with solvent so the sealant
can adhere.
(c) Put all the bolts in & tighten the nuts (don't turn the bolts if
you can avoid it, it messes up the sealant) just tight enough to get all
the parts mated & snug, don't over tighten at this stage,
(d) get rid of excess squeezed out sealant with whatever solvent.
(e) Let the whole thing set for a while at least a day but longer is
OK, so the sealant can fully cure.
(f) Now you can tighten it all up, but again make sure someone holds
the bolts so they can't turn & you just tighten the nuts.

It'll be ticketyboo:-)


K

I just saw a nice chart of similar and dissimilar metals last week on the
Jamestown Distributors web site. It's he
http://www.jamestowndistributors.com...compmetals.asp

JD has a lot of hardware and information for boatbuilders and
do-it-yourselfers.

"sel1" wrote in message
...
Hi all,

I want to put on backing plates for all the stuff attached to the transom
(exhaust ports, swim platform, steering arms etc). Through continually
snugging them, the previous owner has burried a couple of nuts through the
glass! I am really new to all this but the first thing that comes to mind
is
reaction between two metals. If I use stainless bolts, could I use
aluminum
for backing plates or maybe I should use something else, or maybe I
shouldn't do this at all?

Still asking and not able to answer much yet.

Thanks, Steve

Thanks so much for the detail K, pretty straight forward. You say aluminum
is OK. As in not the best material?

Most of the work will be above the water line but my swim platform brackets
go below the water line and they are steel angle iron (probably home made).
Any ideas on what kind of support system I could use so that the it doesn't
have to go below water line? Either that or I switch to aluminum angle
pieces and stainless bolts. Aluminum should be OK below water line? Previous
owner didn't even use stainless bolts so they were really tough to get off.

To do it properly takes a little time but doesn't cost a single cent
more as in;

(i) Aluminium is OK say;
(a) 1/4"
(b) Size/shape of the backing is up to you, usually the available space
will dictate the shape size etc, the rule is; if it looks right it
probably is:-)
(b) it's not under water as such so dissimilar metals shouldn't be an
issue (even with stainless you'd still need to ensure the same stainless
as the bolts say 316 vs 3xx or it corrodes anyway:-)
(c) aluminium is much easier to work & you can even drill it in situ
from the outside if you have a tricky nook or cranny.

(ii) Chamfer just the outer perimeter of the plates away from where
they'll pull against the hull, if you leave a sharp edge it can cut into
the outer glass under load & leave a crack in the flow or gelcoat for
water to get in.

(iii) You should try to seal inside all the through hull holes:
(a) particularly if it's the cored transom
(b) Coat the holes right through with any of the good epoxy fillers, then
(c) push the bolts back in while it's wet, having given the bolt a good
coat of grease first (dipped in candle wax works too).
(d) Once epoxy has gelled you should be able to get your bolts back out
with a spanner, leaving a good protection for the transom core (usually
plywood) & a good fit for the bolt.

(iv) When ready to put it all together again;
(a) use plenty of any of the good sealants, sadly price is a good
indicator so any marine recommended 3M or marine sikaflex (German?? not
sure) is OK.
(b) Clean the hull, parts, holes, bolts etc with solvent so the sealant
can adhere.
(c) Put all the bolts in & tighten the nuts (don't turn the bolts if
you can avoid it, it messes up the sealant) just tight enough to get all
the parts mated & snug, don't over tighten at this stage,
(d) get rid of excess squeezed out sealant with whatever solvent.
(e) Let the whole thing set for a while at least a day but longer is
OK, so the sealant can fully cure.
(f) Now you can tighten it all up, but again make sure someone holds
the bolts so they can't turn & you just tighten the nuts.

It'll be ticketyboo:-)

K

"sel1" wrote in message
...
Thanks so much for the detail K, pretty straight forward. You say aluminum
is OK. As in not the best material?

I tried both 1/8" ss plate and 1/4" aluminum plate this summer. Unless you
have a drill press forget the ss. damn hard to cut or drill. On sume of
the aluminum backing plates, wehere the ss bolts and washes came in touch, I
used cutout plastic washers made of ice cream containers and liquid
electrical tape.

I use those hard 1/2" thick cutting boards with ss fender washers and nylock
nuts. Also I put epoxy between the backing plate and fiberglass. The
cutting board material cuts and drills like wood. Obviously it will never
rot and will not react with the bolts. I put my wake tower on 4 years ago
using them and I sometimes pull 6 people on 2 super screamer tubes from the
tower with no problems.

"sel1" wrote in message
...
Hi all,

I want to put on backing plates for all the stuff attached to the transom
(exhaust ports, swim platform, steering arms etc). Through continually
snugging them, the previous owner has burried a couple of nuts through the
glass! I am really new to all this but the first thing that comes to mind
is
reaction between two metals. If I use stainless bolts, could I use
aluminum
for backing plates or maybe I should use something else, or maybe I
shouldn't do this at all?

Still asking and not able to answer much yet.

Thanks, Steve

I'm waiting to see if anyone suggests to look for the reason for the
loose bolts, like rotten plywood core. So far there is a lot of good
info on backing plates.

Out drive boats are usually built with a plywood core in the transom,
because of the loads the transom takes. I doubt you'll find foam.

If you have some rot, there's no choice on the fix. Backing plates
isn't it.
Jim

I like this idea of using a white plastic cutting board for a backing plate.
I'm going to file that one away for myself.

Thanks

"JamesgangNC" wrote in message
nk.net...
I use those hard 1/2" thick cutting boards with ss fender washers and
nylock
nuts. Also I put epoxy between the backing plate and fiberglass. The
cutting board material cuts and drills like wood. Obviously it will never
rot and will not react with the bolts. I put my wake tower on 4 years ago
using them and I sometimes pull 6 people on 2 super screamer tubes from
the
tower with no problems.

Use a cutting oil when drilling the SS.

"Don White" wrote in message
...

"sel1" wrote in message
...
Thanks so much for the detail K, pretty straight forward. You say
aluminum
is OK. As in not the best material?

I tried both 1/8" ss plate and 1/4" aluminum plate this summer. Unless
you
have a drill press forget the ss. damn hard to cut or drill. On sume
of
the aluminum backing plates, wehere the ss bolts and washes came in touch,
I
used cutout plastic washers made of ice cream containers and liquid
electrical tape.