Re: epoxy and MDO
Keeping in mind that my boat isn't yet launched, here is what I have done:
1. I grind the ends of the sheets I am splicing as nearly as I can to
the thickness of the layers of tape I will be using and back from the
end 1/2 the width of the widest tape. I have been using 3 layers of 9
oz. bias tape split at 4", 3" and 2". I don't think it matters which
width you start with. Since the thickness of the tapes is feathered, I
try to feather the grinding a bit to match. I am building with 1/2 "
MDO. For thinner ply I would probably use 2 layers of tape each side. I
also butter the ends of the sheets with thickened epoxy before pushing
them together. I do the grinding NOT to remove the MDO overlay; but,
rather, to avoid a bulge. The cloth/epoxy actually adheres very well to
the MDO surface.
2. No, I use two sided MDO anywhere that it would show, whether inside
or out. As I said above. The cloth epoxy adheres very well. The resin
seems to penetrate into the MDO surface. As I spread on the first coat
of straight unthickened epoxy, I can see it soaking into the surface. By
all means; however, make up your own test pieces on some scrap. Leave
some extra cloth that you can grab hold of and try to tear your test
sheathing away from the surface after it cures. It is best to TEST ANY
IDEAS YOU GET FROM THHE LIST BEFORE USING. Conditions aren't always the
same. Don Hodges used a suggestion of mine that tileboard didn't adhere
to epoxy. It had worked well for me; but in his climate and with the
resin he had, he ended up having to grind tileboard off his boat.
3. Having ordered MDO in 3 batches, I have found that it is not all the
same in the outer layer under the paper. The first that I got was
Canadian and was fir in all the layers. The second batch wasn't
identified as to source and had a thin outer ply of what looked like
underlayment -- not as desirable in my opinion. Also, some nominal
1-sided MDO comes with paper both sides but the bad side has a few voids
under the paper. The voids are easy to spot, sand off and fill, but if
you have a choice, I would avoid this kind. Most 1-side doesn't have
this feature.
4. I left some scrap pieces of MDO weighted down over the Michigan
winter at the bottom of an open/ always wet drainage ditch that runs in
front my shop. The ends were not sealed. There was NO swelling or
delamination at all.
Vince
1. I grind the ends of the sheets I am splicing as nearly as I can to
the thickness of the layers of tape I will be using and back from the
end 1/2 the width of the widest tape. I have been using 3 layers of 9
oz. bias tape split at 4", 3" and 2". I don't think it matters which
width you start with. Since the thickness of the tapes is feathered, I
try to feather the grinding a bit to match. I am building with 1/2 "
MDO. For thinner ply I would probably use 2 layers of tape each side. I
also butter the ends of the sheets with thickened epoxy before pushing
them together. I do the grinding NOT to remove the MDO overlay; but,
rather, to avoid a bulge. The cloth/epoxy actually adheres very well to
the MDO surface.
2. No, I use two sided MDO anywhere that it would show, whether inside
or out. As I said above. The cloth epoxy adheres very well. The resin
seems to penetrate into the MDO surface. As I spread on the first coat
of straight unthickened epoxy, I can see it soaking into the surface. By
all means; however, make up your own test pieces on some scrap. Leave
some extra cloth that you can grab hold of and try to tear your test
sheathing away from the surface after it cures. It is best to TEST ANY
IDEAS YOU GET FROM THHE LIST BEFORE USING. Conditions aren't always the
same. Don Hodges used a suggestion of mine that tileboard didn't adhere
to epoxy. It had worked well for me; but in his climate and with the
resin he had, he ended up having to grind tileboard off his boat.
3. Having ordered MDO in 3 batches, I have found that it is not all the
same in the outer layer under the paper. The first that I got was
Canadian and was fir in all the layers. The second batch wasn't
identified as to source and had a thin outer ply of what looked like
underlayment -- not as desirable in my opinion. Also, some nominal
1-sided MDO comes with paper both sides but the bad side has a few voids
under the paper. The voids are easy to spot, sand off and fill, but if
you have a choice, I would avoid this kind. Most 1-side doesn't have
this feature.
4. I left some scrap pieces of MDO weighted down over the Michigan
winter at the bottom of an open/ always wet drainage ditch that runs in
front my shop. The ends were not sealed. There was NO swelling or
delamination at all.
Vince