Before I fiberglass ?

[barr5150]

http://i1000.photobucket.com/albums/af125/barr5150/th_76.jpg (http://s1000.photobucket.com/albums/af125/barr5150/?action=view&current=76.jpg)
http://i1000.photobucket.com/albums/af125/barr5150/th_81.jpg

I am about ready to fiberglass the hull of my boat. All boats I have seen have some type of strips on the bottom. I have no idea what they called and there is nothing showing them in the plans I have. Any ideas? I would do a search but I don't know what they are called! I assume they are there to keep the boat from walking around in the water? Thanks in advance.

[Brian Palmer]

A shallow strip along the bottom away from the centerline is usually called a rubbing strake and is meant to protect the bottom when pulling the boat up on a beach.

A deeper one in the middle (deepest part at the aft end of the boat) is called a skeg and provides directional stability and also helps protect the bottom. The forward end may also be part of the keel.

Both also add stiffness to the bottom of the boat.

From the pictures of your boat, you should probably glass the bottom before putting them on.

Hope that helps,

Brian

[Thorne]

You've referred to your boat as a dory in earlier posts, and dories usually have a skeg. If you are building to plans, follow them. If you are making up your own design, have fun!

[Corvus]

Sometimes the wedge shaped strips on power boats are called lifting strakes. I have doubts to whether they actually do any lifting, but they probably knock down a bit of spray and stiffen the hull.

[barr5150]

I am building a boat that Jeff Spira designed for me as kind of a takeoff from one of his other boats. The boat it somewhat takes after is called a dory but I'm not too sure what this one is. The plans don't show anything for the bottom of the hull but I would think some type of strips would be appropriate. Would it really be a good idea to put them on after the glass? I would think they would be better under.

[Thorne]

You will find that boatbuilding conversations go a lot easier if you use the specific terms -- just like computers and cars, boats have their own language of sorts.

So strips on the bottom of a skiff means 'abrasion strips' to most of us and they go on over the glass. Usually made from hardwoods like white oak, or somtimes slippery plastic materials. These do not provide directional stability, but keep the bottom from being chewed up by rocks or gravel, and are replaced when damaged.

If you mean 'skeg', please use that term. And since you are modifying the plans, safer to glass first before you add a skeg, as you may need to later remove it to make it larger, smaller, or just gone... Glass also helps protect against water intrusion and rot at the joint between skeg and bottom.

[Brian Palmer]

The strips will take more abuse than the rest of the hull, so you are likely to have a hole in the glass at some point if the glass goes over the strip. The water between the strip and the glass will promote rot, and the rot could go into the bottom plywood.

It will also be easier to glass the bottom when it is one smooth surface, rather than interrupted by the strips.

If you want to further protect the strips with glass, then put a second layer of glass over the strips after they are installed over the fiberglassed bottom.

Brian

[JimD]

Glass first, then add your rubby strippy things if you want to. They will protect the bottom when beaching, improve tracking, add wetted surface, so some pros and cons. But adding them after will make glassing the hull much easier and simpler.

[barr5150]

Thanks for the help. Sorry about the terminology. I have some poly stock that is used on asphalt rollers. They mount the strips lenght wise along the roller to scrape them as the roller comes around to remove any debri it picks up. Very wear resistant. It sounds from what I'm reading here they would be perfect. I have 3 so I assume 1 down the center and the other 2 off set to the sides. How would I mount them? Screw through the bottom into the ribs just using caution to use some sort of sealant on the threads?

[JimD]

I would make them out of wood and epoxy them on. Consider them somewhat sacraficial so when/if they get chewed up from wear and tear just sand/plane a bit and glue new strips on the old ones. That way there's no chance any water will ever get past a bedding compound and into the screw holes.

[Cuyahoga Chuck]

If you glass the bottom you have given it a perfectly watertight barrier. Well, almost. If you start driving screws into it you are creating entry points for water and whatever lifeforms the water contains.
Once the bottom is glassed you can epoxy any type of wood to it you
prefer. If you choose to epoxy strips of conventional lumber to it you can remove/replace them at any time with a well sharpened hand plane set for a coarse cut. The intergrety of the glass on the bottom will not be altered.
This will work for a plywood skeg too except the plywood will be harder to plane off.
So kiss screws and bedding compound (whatever that is) goodbye.
Repeat after me.
Epoxy is my friend.
Epoxy is my friend.
Epoxy.........

[kulas44]

This kinda looks like a fast boat. Strakes will help when you try to turn the boat at speed, Instead of just slipping sideways. the strakes help keep the bottom "hooked up". You could glass the hull and add them later, bedded in 5200, or add them now and glass them in, you decide. If you just glassed the hull flat and later decided it is to "slippery" you could add them later.

[the_gr8t_waldo]

before any fiberglassing takes place, i would round over the chine.(and probably the the transom>sides too) fiberglass will not lay flat on hard corners. like jimd said add the strakes afterwards. make it the easy way.

[ccx2]

What is the square cutout in the transom for?

[ccx2]

OOPS, I looked again and i think its a mold.