The OEM rope clutches on my Catalina 27 were not through bolted to the cabin top. There is a flat area glassed off on which the base sits. I want to put in a new one, but the mounting holes don't line up and it turns out the originals were mounted with machine screws. I can only imagine that a SS plate was glassed in under the flat area. Would you suggest 1) drilling and tapping holes in the new locations, or 2) just mount it with backed through bolts? A PO replaced one on the starboard side and didn't use through bolts there either. I haven't removed that one to see what the hole spacing is/was.
Mounting deck hardware
- Thread starter T37 Phil
- Start date
- Status
I agree
I agree with higgs, and not assume anything. I would plug the holes that don't line up, and go ahead and through bolt them. Not sure but the is probably a cored hull, so be careful.
I agree with higgs, and not assume anything. I would plug the holes that don't line up, and go ahead and through bolt them. Not sure but the is probably a cored hull, so be careful.
Used Machine Screws
Just replaced the Halyard clutch on our h27 1984. After redrilling for the new holes determined the mounting plate to be aluminum. The holes didn't move much and if I had no leaks/failures of the deck for 20+ years I figured why mess up the interior. It isn't that difficult to install leak proof deck hardware. Just to be clear, Machine Screws are really bolts threaded into a tapped hole. A Machine Screw becomes a Bolt when you put a Nut on it. Just want to make sure everyone was on the same page.
Just replaced the Halyard clutch on our h27 1984. After redrilling for the new holes determined the mounting plate to be aluminum. The holes didn't move much and if I had no leaks/failures of the deck for 20+ years I figured why mess up the interior. It isn't that difficult to install leak proof deck hardware. Just to be clear, Machine Screws are really bolts threaded into a tapped hole. A Machine Screw becomes a Bolt when you put a Nut on it. Just want to make sure everyone was on the same page.
Cat 27 comment....
Phil, if there is a plate there.... you can check by probing the old hole with and awl... I would be in favor of tapping new holes for the upgrade. If not... definintely through bolt. The cabin is a sandwich or glass and plywood.
Phil, if there is a plate there.... you can check by probing the old hole with and awl... I would be in favor of tapping new holes for the upgrade. If not... definintely through bolt. The cabin is a sandwich or glass and plywood.
Phil obviously you know
what a machine screw is. After rereading your post I see you know. One other thing I thought about. Depending on how big the glassed in plate is, couldn't the mounting actually be stronger if you used a tapped hole? When you redrill you'll find out but if it is SS or AL as oppossed to just glass, when you through-drill the plate you won't be distributing the load to as big an area of the plate unless your incabin backing plate is equally as big and, there are no voids between cabin-top/core/cabin liner. Now I'm not a GRP boat design engineer and this may be a small difference if the glass work is good in this area, and, it likely is or there likely would have been failures. However, I know when the halyard pulls it is going to torque on the clutch and for anything to move, that whole plate in the cabin top will have to move. While this is an assumption, there is a machine screw mounted winch right behind the clutch, so I'm pretty sure that plate is a lot larger than anything I would be willing to put on the ceiling of my cabin. Not to mention making it fare to the liner. OK nuf said, IMHO. Cheers, Hugh
what a machine screw is. After rereading your post I see you know. One other thing I thought about. Depending on how big the glassed in plate is, couldn't the mounting actually be stronger if you used a tapped hole? When you redrill you'll find out but if it is SS or AL as oppossed to just glass, when you through-drill the plate you won't be distributing the load to as big an area of the plate unless your incabin backing plate is equally as big and, there are no voids between cabin-top/core/cabin liner. Now I'm not a GRP boat design engineer and this may be a small difference if the glass work is good in this area, and, it likely is or there likely would have been failures. However, I know when the halyard pulls it is going to torque on the clutch and for anything to move, that whole plate in the cabin top will have to move. While this is an assumption, there is a machine screw mounted winch right behind the clutch, so I'm pretty sure that plate is a lot larger than anything I would be willing to put on the ceiling of my cabin. Not to mention making it fare to the liner. OK nuf said, IMHO. Cheers, Hugh
Agree w/Joe FWIW
Don't think I was completely clear. I agree with Joe, if there is NOT a plate of metal in there, through-bolt.
Don't think I was completely clear. I agree with Joe, if there is NOT a plate of metal in there, through-bolt.
Just to beat the horse a little more
I believe that the head of the fastener determines whether it is a screw or a bolt, hence lag bolt versus round head screw. I used round head 3/8 machine screws on the mooring bits on Bietzpadlin with backing plates and lock washers washers and nuts.
I believe that the head of the fastener determines whether it is a screw or a bolt, hence lag bolt versus round head screw. I used round head 3/8 machine screws on the mooring bits on Bietzpadlin with backing plates and lock washers washers and nuts.
My two cents
Lots of good advice. Make sure there is no gap between the cabin liner and the underside of the coach roof before you through-bolt. If there is a gap, you do not want to have the nut and backing plate on the inside (visible side) of the cabin liner. You will have to cut out the cabin liner to expose the underside of the coach roof and put the backing plate and nut there. Hopefully, you will be able to find an inspection port the right size to cover up the hole in the liner, and provide easy access for maintenance. If you mount the plate and nut on the cabin liner and there is a gap, you WILL crack the liner, or worse.
Lots of good advice. Make sure there is no gap between the cabin liner and the underside of the coach roof before you through-bolt. If there is a gap, you do not want to have the nut and backing plate on the inside (visible side) of the cabin liner. You will have to cut out the cabin liner to expose the underside of the coach roof and put the backing plate and nut there. Hopefully, you will be able to find an inspection port the right size to cover up the hole in the liner, and provide easy access for maintenance. If you mount the plate and nut on the cabin liner and there is a gap, you WILL crack the liner, or worse.
Phil, If you are going to mount the new
clutches, chose the hole that you will reuse, connect the clutch, and then drill with a small bit through the other hole in the new clutch. Right after you get the hole started, remove the clutch and watch the shavings as you drill. If there is a plate, redrill for the proper tap size. If there is no plate, drill all the way through. Make sure you do a good repair on the old unused hole. hope that helped. r.w.landau
clutches, chose the hole that you will reuse, connect the clutch, and then drill with a small bit through the other hole in the new clutch. Right after you get the hole started, remove the clutch and watch the shavings as you drill. If there is a plate, redrill for the proper tap size. If there is no plate, drill all the way through. Make sure you do a good repair on the old unused hole. hope that helped. r.w.landau
Thanks all
I think what I have in mind is what r.w. described. I believe there must be a plate, but drilling the second hole should tell. I don't think anyone (particularly a boat designer) would tap fiberglass for a screw. Is it even possible? Both winches appear to be OEM and are through bolted. Hugh has a point. A clutch or even a cam cleat has forces mainly parallel to the deck. A winch on the other hand has forces applied away from the deck if the line around it isn't kept level. I'm replacing a double with a double, so if the plate is there and held, I think I'll be ok. Regarding names, I'm not sure. I think the emphasis is on 'machine' screw to distinguish it from wood screws and sheet metal screws. What would you call the fasteners that look like wood screws but can be screwed directly into pilot holes drilled in the fiberglass? A screw with a nut on it becomes a bolt? On the other hand, lag bolts don't have nuts. I'm with Ross, it's either a slotted screw, phillips screws, allen key screw, etc... and if none of the above, then it's a bolt. The machine screw in a tapped metal plate is still a screw, since it's head is slotted.
I think what I have in mind is what r.w. described. I believe there must be a plate, but drilling the second hole should tell. I don't think anyone (particularly a boat designer) would tap fiberglass for a screw. Is it even possible? Both winches appear to be OEM and are through bolted. Hugh has a point. A clutch or even a cam cleat has forces mainly parallel to the deck. A winch on the other hand has forces applied away from the deck if the line around it isn't kept level. I'm replacing a double with a double, so if the plate is there and held, I think I'll be ok. Regarding names, I'm not sure. I think the emphasis is on 'machine' screw to distinguish it from wood screws and sheet metal screws. What would you call the fasteners that look like wood screws but can be screwed directly into pilot holes drilled in the fiberglass? A screw with a nut on it becomes a bolt? On the other hand, lag bolts don't have nuts. I'm with Ross, it's either a slotted screw, phillips screws, allen key screw, etc... and if none of the above, then it's a bolt. The machine screw in a tapped metal plate is still a screw, since it's head is slotted.
Bolts & Screws
OK now I know many won't give a ratsA but I'm a stickler for such things probably stemming from my mother making sure I used picture and pitcher correctly. Plus it's late or early I'm not sure. I was pretty positive about adding a nut to a machine screw to get a bolt but valid alternatives have been made and I'm always one to consider new data and not 'stay-the-course' if we're heading for the rocks. There will likely be exceptions to this like to any rule but I couldn't just forget about it. A little searching and I think I have my backing. A bolt goes through material and compresses it (with the nut) and a screw bites into the material and is compressed by the material(strength of the two material aside) for the holding power. Many of the exceptions may just be common misuse-lagbolts are really lagscrews. Here's one anchorbolt--it has a nut but doesn't quite go through but does compress it, I guess it is OK. There has to be others but I'm blank. I'll forget about it now and get back to thinking about gelcoat sanding and fare line routing. Cheers all, HughR
OK now I know many won't give a ratsA but I'm a stickler for such things probably stemming from my mother making sure I used picture and pitcher correctly. Plus it's late or early I'm not sure. I was pretty positive about adding a nut to a machine screw to get a bolt but valid alternatives have been made and I'm always one to consider new data and not 'stay-the-course' if we're heading for the rocks. There will likely be exceptions to this like to any rule but I couldn't just forget about it. A little searching and I think I have my backing. A bolt goes through material and compresses it (with the nut) and a screw bites into the material and is compressed by the material(strength of the two material aside) for the holding power. Many of the exceptions may just be common misuse-lagbolts are really lagscrews. Here's one anchorbolt--it has a nut but doesn't quite go through but does compress it, I guess it is OK. There has to be others but I'm blank. I'll forget about it now and get back to thinking about gelcoat sanding and fare line routing. Cheers all, HughR
Galling as it were
I know galling is more likely when the materials are different. And I think SS has less natural lubricating properties making it more susceptible. The white power is some kind of oxidation or corrosion from things not being pure is my guess. I often reuse bolts probably when I shouldn't but I'm a penny pincher even though I know penny wise-pound foolish. You don't hear many folks on these threads talking about anit-seize compounds. Almost everything I install is coated with silicone, polysulfide, or polyurethane. Maybe these coatings provide some anit-seize properties--maybe not the latter two. Hugh
I know galling is more likely when the materials are different. And I think SS has less natural lubricating properties making it more susceptible. The white power is some kind of oxidation or corrosion from things not being pure is my guess. I often reuse bolts probably when I shouldn't but I'm a penny pincher even though I know penny wise-pound foolish. You don't hear many folks on these threads talking about anit-seize compounds. Almost everything I install is coated with silicone, polysulfide, or polyurethane. Maybe these coatings provide some anit-seize properties--maybe not the latter two. Hugh
- Status