Glassing over removed thru hull. What glass to use?

[lostsoul]

I have removed a 2 inch diameter thru hull fitting in my fiberglass sailboat. The hole is underwater and the hull is ½ inch thick at that point.

My main question is regarding the type of glass I should use in making this patch. I will be using West System epoxy.

I have seen much info about doing such a repair, but what fabric exactly I should use remains a question. I would like to make the repair as strong as possible.

Some say use 1708. Some say 1708 with mat, some say 1708 without the mat. Some say 12 oz cloth would work.

My guess is that most any fabric would work, but I have to choose one. I do have confusion over chopped strand mat. I know there is the stitched type that would be compatible with epoxy. But is the CSM necessary?

If I had to do it right now, I would use 1708 with no mat….

I feel confident in my ability to lay up the glass from both the inside and the outside. The inside does not have as much room for tapering the patch, but I can still do some lay up.

So what fabric should I use?? Please, thank you!!

[Cthoops]

We were in a similar situation in the fall of '15, except we were glassing over four unused below the waterline thruhulls. We used West System epoxy and 10 oz cloth - that was our best choice out of what Defender had available).

Since we didn't have any experience working with fiberglass we followed the West instructions in their Fiberglass Boat Repair and Maintenance Manual (available as a pdf online) very closely. I even called them several times with questions, and they were extremely helpful.

We held our breath when we splashed last spring but all was well.

Good luck.

[rwidman]

West Systems sells a DVD on how to do this repair. They also publish books.

I suggest getting both and following their instructions.

[lostsoul]

Thanks guys,
Yep I have the west info and have watched their videos. They dont say what glass to use. That is my only question........

[guyrj33]

I would use bi-axial with a mat backing.

[Scot McPherson]

I used to love 12 oz glass for thick layups, unfortunately defender ran out of it this past spring and has no plans on restocking it. I guess it doesn't sell as quickly as 10 oz.

[KadeyKrogen38]

Mat has little strength, woven cloth or roving has long fibers which create strength. Mat is a filler between cloth or roving to hold resin and make layers of cloth adhere more securely to each other.

Bottom line is a layer of mat, then cloth, then mat, so on and so forth. Polyester or epoxy will both work.

[KimSails]

I think that there are a number of weights and options you can successfully use. Lighter weights will require more layers. It is important to ensure that the glass properly wetted with expoy (no dry spots), but also has no more epoxy than necessary.

That all said, you should follow CThoops suggestion and call West System tech support. I thought that they were very helpful a few years ago when I called them about a project to glass in new bulkheads.

[Scaramanga F25]

In normal mat/roving buildup the mat needs to be wetted out with polyester resin as it requires styrene to dissolve the binder in the mat.
However they now have produced a special mat that can be used with epoxy.

Epoxy and 10 cloth was my choice in rebuilding a 36 footer race boat hull bottom just aft of the keel. Held for all the years I kept it.

[Scot McPherson]

Originally Posted by KimSails

I think that there are a number of weights and options you can successfully use. Lighter weights will require more layers. It is important to ensure that the glass properly wetted with expoy (no dry spots), but also has no more epoxy than necessary.

That all said, you should follow CThoops suggestion and call West System tech support. I thought that they were very helpful a few years ago when I called them about a project to glass in new bulkheads.

It's ok to use more epoxy than needed when laying up so long as the viscosity of the epoxy is enough to hold the next layup of cloth. I personally usually lay up only 2 or 3 layers at a time, and then let them get a bit green before laying up more. Otherwise you get potentially undesirable movement in the layers beneath the one you are working.

Great thing about it is, if you screw up, let it cure a bit and sand some of it out so you can fix what you messed up. I use my angle grinder with a flap wheel for any rough sanding. It's the best tool I every used for sanding down fiberglass and epoxy.

[UNCIVILIZED]

- 1708 IS mat, paired with an axial. The 17 denotes the weight of the axials in oz/sqyd, & the 08 is the weight of the mat in oz/sqft. Note the different units of measurement there.

- Axials; biaxial, triaxial, & quadraxial tend to be the strongest reinforcements, since they're made from layers of unidirectional (tows) which are stitched, or otherwise mechanically held together. Though a few axials are layers of uni held together by chemical bonding.

- Yes, Exotic fibers are stronger than E-glass axials. Meaning Kevlar, Carbon Fiber, S-glass, Basaltic fiber, etc. And they too come in configurations similar to E-glass. Wovens, knitted (axials), uni's, etc. Though typically only Kevlar comes in mat, & it's for rather specialized applications.

- Use mat that's compatible with your resin. Since, as stated, most mat is made with built in binders that are designed to be dissolved by the Styrene in Polyester resins. But there are other "flavors" of mat which work with Epoxy, etc.

- Mat is fairly low strength, & generally is a "tie in" material, between layers of heavy woven roving, & sometimes axials. However, it's strength is omnidirectional, unlike; cloth, roving, uni's, or axials.

- If you use peel ply on the surface of a layup, you won't need to sand before applying more laminated, even if things have cured up hard.

- Download ALL of the user guides, & books from www.WESTSystem.com Then print out the user guides, & keep "disposable" copies in binders on your work bench/project site.

- For some Excellent visual + written examples of how to plan out, prep for, & apply multiple layers of reinforcements when doing repairs, read some of minaret's threads. Such as http://www.cruisersforum.com/forums/...ir-164093.html (by Hooked) in which the keel sump/stub on Hooked's boat is rebuilt with many, many layers of heavy (glass) reinforcements.
- It really does pay to plan out all of your work, as in the above noted thread. Including pre-staging all of your materials, tools, spreaders, etc.

[longjonsilver]

Originally Posted by lostsoul

I have removed a 2 inch diameter thru hull fitting in my fiberglass sailboat. The hole is underwater and the hull is ½ inch thick at that point.

Quick man the bilge pumps your boat is sinking!

[Deltasailor]

As usual lots of good advice from Uncivilized, Just one point, make sure the surrounding glass is roughed up so the new glass will adhere properly.
Cut the chop strand mat to size getting ever bigger with each lamination.
Prep it all before mixing the resin. Not rocket science.

[powsmias]

Originally Posted by lostsoul

I have removed a 2 inch diameter thru hull fitting in my fiberglass sailboat. The hole is underwater and the hull is ½ inch thick at that point.

My main question is regarding the type of glass I should use in making this patch. I will be using West System epoxy.

I have seen much info about doing such a repair, but what fabric exactly I should use remains a question. I would like to make the repair as strong as possible.

Some say use 1708. Some say 1708 with mat, some say 1708 without the mat. Some say 12 oz cloth would work.

My guess is that most any fabric would work, but I have to choose one. I do have confusion over chopped strand mat. I know there is the stitched type that would be compatible with epoxy. But is the CSM necessary?

If I had to do it right now, I would use 1708 with no mat….

I feel confident in my ability to lay up the glass from both the inside and the outside. The inside does not have as much room for tapering the patch, but I can still do some lay up.

So what fabric should I use?? Please, thank you!!

just a thought and looked on defender site but no one makes a dummy plug to seal the original? exact measurements with plate on exterior and bolt down the same way? seems a no brainer

[alansmith]

I was thinking the same thing. What sort of plug would you bang in there? I would want something that backs all of that mat and resin. Don't know if a rubber or plastic could be fit in there. I know I have seen straight epoxy poured in and allowed to cure...but never in a vertical hole like a through hull. Maybe it is overkill to plug it.