Glassing over removed thru hull. What glass to use?

[Dymaxion]

Would epoxying in a disc cut from 1/2" thick fibreglass board be advisable as a first step? Considering doing the same job.

[Scout 30]

I don't think glassing in a plug makes sense. Would the proper way to repair this be to grind the inside & outside into plate shapes & then patch from both sides or just grind out & patch the outside? I think I'd grind the outside but put a backing patch on the inside first. I'd use biaxial for it's strength.

[John_Trusty]

I've got a practical question on this esoteric discussion of the strength of weights of different mats vs. woven bi-axial etc. ... Does this really make much difference in filling a 2" through hull hole? I mean the mat is not running along a fillet for two feet, it only is securing to the sides of a hole that are on-average 1 inch away. I can see the weight, and ability to wet-out are critical, but is the linear strength of the material (chopped mat, woven, kevlar, etc.) relevant at all? Also, is there some concern with filling this all at once and having the exothermic reaction heat up the final product (3 cubic inches)? Perhaps this is the argument for doing it in layers and building up?

I'm not urgently in the same need for information, but some day I might be.

[Privilege]

Originally Posted by Scout 30

I don't think glassing in a plug makes sense. Would the proper way to repair this be to grind the inside & outside into plate shapes & then patch from both sides or just grind out & patch the outside? I think I'd grind the outside but put a backing patch on the inside first. I'd use biaxial for it's strength.

Do it the other way around. On the inside, feather the hole with a grinder so that the hole is plate-shaped. Make sure that you grind away any paint or coatings. A 2" hole should be ground at such an angle that the inside hole is now about 8-10" round. Then, on the outside hole, cover it with a piece of strong tape or if the hole is bigger, a piece of smooth laminate. Back on the inside, start with CSM just big enough to fill the 2" hole. Don't allow the polyester resin to puddle, there should be just enough to completely wet out the csm. You'll need ten or so small pieces of csm just to fill the first bit of the hole. They don't need to be neat as they will happily stick well to each other. Then gradually increase the size of the csm laying a slightly bigger one over the next in order to level the hole. The last three or four layers can be biaxial cloth to give it the final touch of added strength. The last piece will be about 10" square to cover everything. It will be level with the curve of the inside hull and certainly doesn't need to be anything more than a 1/4" higher than the original hull. Once it has cured, remove your tape, fill the outside imperfections with a bog or filler and paint over. The messy part is the grinding. Once this has been done, the filling of the hole only takes fifteen minutes.

[Pete7]

Close, but grind the inside to give a 1:12 ratio of depth to width of hole. Temporary bung hole and lay mat/cloth on the inside to completely fill the hole and ground down area.

Now turn to the outside and remove any bungs and grind to the same 1:12 ratio and fill in as before.

Its in the West System books somewhere but its been a while since I bought my last set.

Pete

[rwidman]

Or:

Reinstall the thruhull fitting and cap it off on the inside and go boating.

[Pete7]

Originally Posted by rwidman

Or:

Reinstall the thruhull fitting and cap it off on the inside and go boating.

Is that wot those wooden cone things are for? they are scattered all over the boat in really odd places

[rwidman]

Originally Posted by Pete7

Is that wot those wooden cone things are for? they are scattered all over the boat in really odd places

By "cap it off", I'm talking about a bronze or Marelon threaded cap that matches the thread of the thruhull. Sealed with the appropriate compound or tape.

[Hoosiersailor]

This may help WEST SYSTEM | Projects | Fiberglass Boat Repair & Restoration - Repairing machined holes in fiberglass

[mitiempo]

Originally Posted by Hoosiersailor

This may help WEST SYSTEM | Projects | Fiberglass Boat Repair & Restoration - Repairing machined holes in fiberglass

That is a good link. 12 to 1 bevel, always large pieces first working to the smaller ones. It can help if you wet out the biax on a sheet of cardboard first before applying. Epoxy works best.

[roygee]

Originally Posted by 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.

not true for the lack of preparation of surface of layup if using peel ply, you still have the amine blush to contend with if your layup gets cured!

[UNCIVILIZED]

Originally Posted by roygee

not true for the lack of preparation of surface of layup if using peel ply, you still have the amine blush to contend with if your layup gets cured!

Can you expound upon this please, with some supporting references. Or stated another way, what then is peel ply's purpose, if not to greatly simplyfy secondary bonding? Which by definition is bonding to cured laminates, non?

Nice boat BTW. Miss my old one!

[minaret]

Originally Posted by roygee

not true for the lack of preparation of surface of layup if using peel ply, you still have the amine blush to contend with if your layup gets cured!

Amine blush comes off with the peel ply. In theory, it also leaves sufficient tooth for bonding due to the weave imprint. In practice, I always always always sand for tooth. Blush, however, is not an issue with peel ply.