Through Hull Fittings

[Don Guillette]

Normally, I leave sailboat maintenance issues to other sites at sailboatowners.com but this is a safety issue which mates might come up against if winter ever stops and they can get their boats ready for launch.

There is a marine sales office near me and they mainly sell power boats but there are a couple of trailer sailboats in the lot. I like to poke around and check out the sailboats. The other day I noticed there was a hole in one of the sailboats which looked like they were replacing a seacockl. While I was standing there the technician comes by and starts to install the through hull. He just screws both parts to the hull without a backing plate!!

Over time I've become friends with the boat yard owner - he always asks me when I might buy something instead of just wondering around the yard. I told him the technician was installing the through hull without a backing plate. He then told the technician to go find some scrap of wood to use as a backing plate. I told him that's not the way you do it and the following was my lesson to him for the day.

The function of the backing plate is to spread the load of the seacock so it doesn't create a hard spot in the hull and crack the hull. Any old piece of wood doesn't cut it and the shape of the block is also important. A round shape is best and the edge should be tapered.

The block can be plywood or a solid wood such as white oak, or mahogany. If plywood is selected is should be marine grade, have no voids and be finished with several coats of epoxy. If oak or mahagony is used it also should be have several coats of epoxy applied.

A seacock can last a long time so it is worth it to spend a little time preparing the backing block. If you do, the block and the seacock will probably outlast the boat and its owner.

If any of you guys are planning on replacing seacocks this season be very specific with the yard doing the work as to exactly what you want. Remember that the guy doing the boat work will probably never sail on your boat and he definately will not be next to when your in the middle of nowhere and the installation lets go.

 

[Johnb]

Correct me if I am wrong but is'nt an additional function of the backing block to swell if it gets wet and tighten the fit.

 

[Ed Schenck]

Glad you saved some poor soul a lot of grief. I use just plain old plywood because I soak it in epoxy. I don't think it will get wet, nor swell, nor delaminate. I try to install in flat areas of the hull so that I don't have to shape the block. Picture is where I installed two new Nexus transducers next to the originals(1979). Probably can't tell but the holes have a coat of expoxy as well.

 

[Ed A]

no the wood swelling just tells you that it wasnt properly coated. the block disperses the loads when you open and close the thru hull too. If the wood swells, its wet and it can rot.

 

[kpgraci]

This just reminds me of the advantages (and joys) of being boat poor and having to do any work myself - you know the old saying, if you want it done right.... I work on my own cars too - I will always do a better job than an overworked, underinterested mechanic.

 

[Don Guillette]

JohnB: Sorry, but I have to correct you. The swelling of the backing block is not an additional function and in fact it is the worse thing that can happen to the backing block/seacock installation. It also is the worse thing that happen to the MAST BLOCK that the mast sits on. Just ask any sailor who has to go through the problem of replacing the mast block when it rots away. Water rots wood if it is not properly prepared. Fresh water is bad enough but salt water is really great at rotting wood and does it much faster than fresh water.

Ed Schenck, Ed A and Kpgrace are spot on. Again, the main and ONLY purpose of the backing block is to spread the load of the seacock when you open and close the handle.

Kpgrace brings up an interesting point. It would be nice if we could do all the work on our boats (or cars) but for many reasons that sometimes is not possible. Unfortunately. a large percentage of yard workers arn't the most highly skilled or paid workers. Just because his shirt has a patch that says "A1 Boatyard" doesn't mean anything. Addditionally, your boat is just one more boat in a long line of boats he has to deal with on any given day and he's really like to be somewhere else or at least get home for dinner around 6PM and most importantly he'll never sail on your boat.

Sooo, "trust but verify (the work)" and here's the best one - "workers will do what you INSPECT, not what you EXPECT". When you order work to be done by the boat yard do a little homework first so you can explain to the yard owner exactly WHAT you want done and HOW you want it done. The advantage is HE knows YOU know what is going on.

 

[monkeybars]

this is why alot of shops be it marine or automotive don't want owners in the back where the work is being done. their afraid you'll see the low quality of work thats being inflicked upon your machine.

 

[Don Guillette]

I wrote in the last message that a mate should do his homework before ordering a job and to be careful with who does the work. My wife just read it and said why don't you tell the sail trim forum listers the dumb ass stunt you pulled with our motor home. I wish she wouldn't read my stuff!!

I have a 32' land yacht and I wanted to add a 30 amp shore power plug at my house to charge the house batts and I know nothing electrical. I bought the setup at Camping World and then hired a local electrician - I use that trade term losely!! - to save few bucks. He hooks up the shore power box and leaves and I can't wait to bring the motor home to try it, which I prompty do. When I plugged it in I heard noises coming from the motor home that I never heard before so I unplugged it and went inside to check. Everything looked good so I went outside and plugged it in again. This time all hell broke loose and the motor home filled up with smoke. When I went inside the plug outlets had melted and it really stunk of burning electrical wires.

I then called a good friend of mine who owned one of the largest electrical contracting co in Wisc to come over and check out my problem. He took one look at the installation and told me the handy man had hooked up the 30 amp plug to 220!!

A $50 job turned to $3000.00 damage, which the handy man paid. I've noticed he is no longer doing electrical work in our community of Saddlebrooke in Tucson plus he no longer talks to me - as if it was my fault. Actually, he tried to blame the problem on me until I showed him the plug clearly said 30 amp/120.

 

[Alan]

It's the old story, ya gets what ya pay for.
I have to disagree about the 'mechanic' however. The quality of the work done is a direct result of the yard owners control over quality control. If the yard workers are properly qualified and paid this kind of thing just would not happen. Years ago many guys used to do work on their own cars and trucks. Today that is just not possible (and get it done right). Automobiles are so technically complex that it requires a trained tech to work on them. I see butchered jobs all the time that come to my shop after some half wit has tried to do his own work only to make things worse. Boats on the other hand are still in the 50's and 60's era of cars where a good DIYer can still do a great job of repairs and maintenance on his boat. Of course, half wits are also working in some yards and I would steer well clear of these yards where the owner is 'willing' to hire people like this.

 

[Don Guillette]

Alan: What do you do at your shop? Give yourself a plug as there are a lot of sailors on this list that live in your area. For all you have contributed to the sail trim forum, you deserve a commercial.