Fiberglass recommendations

8122pbrainard wrote: David, Evidently I trust epoxy bonding more than you do. Airplanes are being made completely from epoxy and carbon fiber. Every failure of wood or fiberglass mechanically fastened I have seen has always been around a screw or rivet. This is caused by the stress caused by the fastener and the hole. I.E. Wood will split around a nail. Steel structures for high rise buildings are being welded together to eliminate the bolt or rivet stress. Semi trailer and delivery truck bodies are now being glued together eliminating the thousands of rivets in each. Greg's point that the stringers aren't mechanically fastened to the hull is a good example. The stringer will see a lot more stress than the ply floor will. You are misinformed regarding stainless steel. If wet, it's not much better than a non plated steel screw. Stainless needs to dry out to form the oxide that keeps it from rusting. (even if passivated) Stainless deck screws fail and the reason they developed the ceramic coated deck screw. You're correct that brass is a poor choice especially if you are building a wood boat. Over time the zinc will leach out causing the screw to become brittle and fail. Silicon-bronze is the way to go. I'll keep trusting the epoxy!

I am not sure you understand. I never said nor do I recommend screwing the stringers to the hull. I do recommend screwing a plywood floor to the stringers. Why rely on a glued joint when you don't have to. If you read ALL of my comments you will note I said composite floors (such as originally installed) will flex and thus glueing is fine (no mechanical fasteners) this is the same principle as the airplanes you talk about. The wings are fiberglass composits over a syrofoam core...everything flexes together.

I know plenty about steel structures since I am an engineer. Welded connections are used when you need a connection that cam withstand a moment load/force. Otherwise bolted connections are used to save cost and ease erection.

Sure, it might work, but why in world would you not just use a few screws to ensure it does not seperate.

Congrats Kevin!

David, Evidently I trust epoxy bonding more than you do.

Airplanes are being made completely from epoxy and carbon fiber.


Every failure of wood or fiberglass mechanically fastened I have seen has always been around a screw or rivet. This is caused by the stress caused by the fastener and the hole. I.E. Wood will split around a nail.

Steel structures for high rise buildings are being welded together to eliminate the bolt or rivet stress.

Semi trailer and delivery truck bodies are now being glued together eliminating the thousands of rivets in each.

Greg's point that the stringers aren't mechanically fastened to the hull is a good example. The stringer will see a lot more stress than the ply floor will.

You are misinformed regarding stainless steel. If wet, it's not much better than a non plated steel screw. Stainless needs to dry out to form the oxide that keeps it from rusting. (even if passivated) Stainless deck screws fail and the reason they developed the ceramic coated deck screw.

You're correct that brass is a poor choice especially if you are building a wood boat. Over time the zinc will leach out causing the screw to become brittle and fail. Silicon-bronze is the way to go.

I'll keep trusting the epoxy!

With the pounding and flexing of a boat hull, I would not want to rely on a glued joint alone. A composite floor (as installed by factory) is very flexible and can give as needed. Thus my suggestion to mechanically fasten the floor (plywood wont give much). Also, it will pull the floor down tight to the stringers and keep it there. SS screws are recommended just in case water gets to them so they will not rust. More of a good practices kind of thing in a boat. Brass screws are to weak and tend to pop off the heads when tightening down.

8122pbrainard wrote: <snip> If you use ply for the floor, I recommend bonding it with thickened epoxy. Screws can be used as a temporary means of clamping but then I suggest removing them and sealing the holes.

I still recommend glueing and screwing the floor in place. Use SS wood screws. The top layer of glass/resin will seal the screws and holes and keep out the water. To be doubly safe, you could pour a bit of epoxy resin down the pre-drilled hole before installing the screws. A rigid plywood floor really needs mechanical fasteners. I agree about glueing with thickened epoxy...just not as thick as you would mix for a fillet. A

Kevin, I did find the Everfix epoxy. Interesting that it's a 1:1 mix when everyone elses is a 3:1 or 2:1. With the 1:1 they sure made it user friendly but I'm wondering if they sacrificed the strength!!

Now we know to stay away from one brand! Stick with the CPES and then U.S. Composites, Mas or West!!

pbrainard I am pretty sure that it says epoxy resin on the plastic jug but I will double check tomorrow at work.I do remember purchasing it from some boat site on ebay. I do know that it did not stick at all! Also I was drilling the 4" hole in the removable floor section for a floor drain that this stuff was chipping off! When I removed the plywood I drilled the same 4" hole in a section that was the west system it drilled with no chipping and if you look at the cross section you can see the penetration.I do know that I paid around 70$ for a gallon of this stuff and its not worth a damn! I am glad that the pumpkin patch motivated me to pull up the plywood and foam because I definetely would have had problems.Thank god for the pumpkin patch.Kevin

Hey coltsphan we had a bad game last night Hey I was checking on my epoxy/glass at work and I can tell you what not to buy.When I started I bought a epoxy resin from some internet boat supply and it was really bad.It was called evercoat.I pulled up the plywood that I already installed because I decided to foam and the part that I used this stuff on came up by hand?? The other that I used west on was a big pain to get up! Maybe it was a bad batch or old.Just thought that I would let you know.Kevin

I also looked at US composites. I would buy a 10-15 gallon kit for the epoxy. I have read a lot of these stringer threads also and one common thing in all of them is that they never bought enough epoxy. Nothing worse that finding you are short and have to wait for materials during a project.

Even if you have 5 gallons left over you could sell it on here to the next stringer candidate.


Tim

Pete, I didn't mention the West epoxy system because I feel they have gotten "fat and happy" and way over priced. I haven't used them in several years. I do like the Mas. and good prices. Pumps are available from all the sources. Do get their pumps because mix ratios do vari.

E-mat is stitched together, regular mat is glued. The epoxy doesn't melt the glue if I remember right.

From the US composites web site "The individual fibers that make up chopped strand mat is held together by an adhesive binder that is designed to break down in polyester and vinyl ester resins."

I used 1.5 oz e-mat(the mat is different for epoxy), 6 oz cloth and tape, and #1708 biaxial from US Composites.

I'll elaborate when I have some time.

Pete, I just went though Greg's "weeding the pumpkin patch" looking for his list of materials. Couldn't find it. There is also Bill's (skibum) thread on his stringer job. I'll keep looking. I never keep a list on my jobs and of coarse don't remember the gals. or feet on the yard goods!.

Both Greg and Bill used U.S. Composites for there supplies. I can also recommend Mas epoxy. They have a web site with tons of info and "how to's" as well.