FYI ... Fiberglass Strength.

[luckyinkentucky]

Just found out in dealing with the fiberglass for my bow eye that fiberglass cloth is can only withstand 750 lbs. per square foot where as fiberglass mat can withstand 1000 lbs. per square inch.

I guess I'm going to go back and get some more fiberglass mat before I do my bow eye. I hope to document the process for future reference on the board.

 

[KnottyBuoyz]

Re: FYI ... Fiberglass Strength.

That doesn't sound right. Who told you that? Fiberglass mat is used to add bulk to a layup as a core and to help prevent print through. The fiberglass fibers run in random patterns and are very short. Under extreme stress shorter stands of glass can be yanked loose from their binder (resin) and fail. The strongest layup you can get with fiberglass is from biaxial and triaxial fabrics with an approximate 50% glass & 50% resin ratio. Consult the fiberglass & resin mfgr for optomum mixes. A resin/fiberglass matrix is designed to work best in tension & compression. Right angle loads against the face of the layup is the weakest.

You should always back up your bow eye with a backing plate of ply or metal so that the extreme loads put on the eye cannot pull through the laminate.

 

[ondarvr]

Re: FYI ... Fiberglass Strength.

For what you're doing it won't make that much difference, but it's always good to use mat as the first layer to get a better bond. Not sure where you got your figures though, as matt has the least strength by weight.

 

[seven up]

Re: FYI ... Fiberglass Strength.

FYI ? Ok.
So...what did you use for a backer on this venerable bow eye of yours ?
FYI us.

 

[KnottyBuoyz]

Re: FYI ... Fiberglass Strength.

FYI ? Ok.
So...what did you use for a backer on this venerable bow eye of yours ?
FYI us.

Exploding bolts? Youch!

 

[luckyinkentucky]

Re: FYI ... Fiberglass Strength.

Didn't get to do it today since it started pouring rain the minute I got ready.

I got my information from the technician at Bondo.

As for the procedure I plan on using. I plan on taping off the existing holes with painter's tape, and filling the holes with a fiberglass / resin paste. Then I will add a small amount of resin to the backside of the bow, and put down 2 layers of mat with resin soaked into each layer. After 10 minutes I will start alternating layers of resin and cloth until I have 8 layers of cloth built up finishing off with a good outer coat of fiberglass / resin paste. I will then let that set up for around 2 days. Then I will re-drill my holes, fill all holes with 5200 Marine Sealant, and add a 1/4" steel plate that measures 4" X 6" for my backer to the bow eye I insert. Then I will fill the area liberally with the 5200 around the bolts, add 2 - 1 1/2" washers to the bolts, and tighten down with double lock nuts on each bolt. I talked to several people and this will be stronger than any wood I could replace in the bow eye.

Also, I will take the necessary safety precautions and be wearing a respirator, goggles, chemical safe gloves, and over alls.

 

[Marc III]

Re: FYI ... Fiberglass Strength.

Hey Seven Up, I think you'll need the big pack of Marine Tex, maybe two.

 

[KnottyBuoyz]

Re: FYI ... Fiberglass Strength.

Didn't get to do it today since it started pouring rain the minute I got ready.

I got my information from the technician at Bondo.

As for the procedure I plan on using. I plan on taping off the existing holes with painter's tape, and filling the holes with a fiberglass / resin paste. Then I will add a small amount of resin to the backside of the bow, and put down 2 layers of mat with resin soaked into each layer. After 10 minutes I will start alternating layers of resin and cloth until I have 8 layers of cloth built up finishing off with a good outer coat of fiberglass / resin paste. I will then let that set up for around 2 days. Then I will re-drill my holes, fill all holes with 5200 Marine Sealant, and add a 1/4" steel plate that measures 4" X 6" for my backer to the bow eye I insert. Then I will fill the area liberally with the 5200 around the bolts, add 2 - 1 1/2" washers to the bolts, and tighten down with double lock nuts on each bolt. I talked to several people and this will be stronger than any wood I could replace in the bow eye.

Also, I will take the necessary safety precautions and be wearing a respirator, goggles, chemical safe gloves, and over alls.

Bondo's fine for cars. It's polyester based. Better secondary bonds with epoxy.

Your plan sounds great. I'd be surprised if you couldn't pull the Titanic with that setup! I'm pretty sure you'd rip out the entire hull around your backing plate before the bow eye would fail! Post a pic if you can.

Baby powder on your forearms will help when you drill out the fiberglass. It's wickedly itchy if the tiny fibers get on your skin!

Good luck.

Rick

 

[57whitehouse]

Re: FYI ... Fiberglass Strength.

FYI ? Ok.
So...what did you use for a backer on this venerable bow eye of yours ?
FYI us.

I'd like to see the arm of the guy who cranked that boat up on the trailor.