There's a hole in my boat!

[Project_Mayhem]

I'm removing a through hull on the bottom of my bow. I'm interested in advice on how to approach this. Here's some info on the current status:

• Hole size is 2 3/8"
• The glass was originally about 1/2" thick
• I've tapered it down to about 1/4"
  
• Tape is no less than 2" from edge of hole on all sides. I did not go past the centerline in an effort to preserve the shape of the hull
• We're seeing 50-70F weather right now

Here are the questions I have regarding this repair:

• Is this enough of a taper?
• I'm concerned about the fiberglass staying in place when its wet since this repair is essentially on the bottom side of the hull. Any advice on keeping it in place?
• Would you start this repair on the inside or outside of the hull?
• Any advice on avoiding air bubbles when mixing filler?

 

[dlochner]

The taper should be a 12:1. For a ½" thick hull the taper should be a circle about 6 inches in diameter, measured from the edge of the original hole.

See page 20 in this manual: https://www.westsystem.com/wp-content/uploads/Fiberglass-Manual-2015.pdf

Wet the area with unthickened epoxy, apply the first layer of glass. Wet out the glass with epoxy. Remove air bubble and excess epoxy with a fin roller, then repeat until the hole has been filled. Do the same on the inside.

Download and read the West System Manual. It is the Bible for working with epoxy.

 

[Charlie Jones s/v Tehani]

The taper should be a 12:1. For a ½" thick hull the taper should be a circle about 6 inches in diameter, measured from the edge of the original hole.

See page 20 in this manual: https://www.westsystem.com/wp-content/uploads/Fiberglass-Manual-2015.pdf

Wet the area with unthickened epoxy, apply the first layer of glass. Wet out the glass with epoxy. Remove air bubble and excess epoxy with a fin roller, then repeat until the hole has been filled. Do the same on the inside.

Download and read the West System Manual. It is the Bible for working with epoxy.

concur

 

[Hayden Watson]

For filling a hole like this it is easier to prewet the glass and put it up whole. On a work surface take the largest piece of glass and wet it out. then lay the next smaller down and wet and fin-roll. Continue until you have the full stack. then place the whole thing over the hole and fin-roll it down. Here is an example. glass work starts about 4 minutes in. fill portlight

 

[dlochner]

For filling a hole like this it is easier to prewet the glass and put it up whole. On a work surface take the largest piece of glass and wet it out. then lay the next smaller down and wet and fin-roll. Continue until you have the full stack. then place the whole thing over the hole and fin-roll it down. Here is an example. glass work starts about 4 minutes in. fill portlight

This works because Mads is working on a vertical surface. On an upside down horizontal surface gravity is not your friend. Mads also has a video on patching a hole in the hull. He uses a vacuum pump, because he has one, it is not required. Start by wetting out the surface and adding one layer of cloth at a time and rolling out the bubbles, repeat over and over again.

Hayden's method of wetting out all the glass first and then applying the whole patch works well when gravity is working with you. This is certainly a good method for repairing the inside of the hole.

 

[Richard19068]

The taper should be a 12:1. For a ½" thick hull the taper should be a circle about 6 inches in diameter, measured from the edge of the original hole.

See page 20 in this manual: https://www.westsystem.com/wp-content/uploads/Fiberglass-Manual-2015.pdf

Download and read the West System Manual. It is the Bible for working with epoxy.

Question: According to the West manual shouldn't the beveled circle have a radius of 6" (plus the radius of the hole), rather than a diameter of 6"? West says "A minimum 12-to-1 bevel is required..... For example, if you are left with a hole through a ¼" (6 mm)-thick laminate, the outer edge of the bevel will extend 3" (75 mm) from the inside edge of the hole."

So if you have a 1/2" thick hull the outer edge of the bevel should extend 6" from the inside edge of the hole. so 6" around the edges of the hole plus the 2-3/8 hole diameter would result in a total diameter of 14-3/8". Am I reading the manual wrong?

 

[Project_Mayhem]

Here is nearly the same scenario that I'm dealing with. Epoxyworks is published by West Systems

Repairing Machined Holes in Fiberglass

Example A seacock that is located below the waterline is being relocated. The hole is 2″ diameter through a solid laminate ½” thick. Access to the backside is good. The bottom is painted with antifouling paint.

The chart would place this repair in the upper right quadrant due to the hole’s location-a hole below the waterline certainly raises the consequences if it fails- yet, because this is a machined hole and not a puncture or impact hole, the repair should be easy to accomplish. The first step is to sand the inside of the hole to expose fresh laminate. Next, pour some mixed epoxy into a 2″ diameter cup to form a “puck” when cured that is about 1/8″ to 3/16″ thick. Sand the edge of the puck and both face surfaces, and then dry fit the puck in the hole so that it is centered with regard to the thickness of the laminate. You can then bond the puck in by brushing a thickened mixture of epoxy and 406 Colloidal Silica on the inside of the hole and the edges of the puck. If the puck fits loosely and doesn’t stay where placed, use duct tape to hold it in place until the epoxy cures.

Now grind back about 1/8″ to 3/16″ (depending on how thick the puck is) thickness from the laminate on both sides of the hole on a 12:1 bevel. This will give the beveled area about 5″ diameter. Fill the beveled area on both sides with a layered fiberglass patch and epoxy. Once the patches cure, sand them and an area larger than the patch to prep for fairing and finishing. It is especially important to remove all the antifouling paint anywhere epoxy will be applied because epoxy will not stick well to most bottom paints.

• I assume that the puck gives the wetted cloth more area to adhere to during layup?
• Regarding beveling - Should I go beyond the centerline just to achieve the 12:1 ratio? Seems like it might be difficult to get the shape back
• I'm also curious about @Richard19068's observation. If the thickness is 1/2" and ratio is 12 then .5*12=6". By this logic 3" bevel from the edge of the hole is sufficient
• A very thick fiberglass "backing plate" will be placed on the inside of the hull since waves will be bashing it
• Does anyone have any tips for avoiding air bubbles while mixing filler? I'm about ready to buy a baking pan to spread it out thin
• I currently have 404 filler. Would it be worth it to buy some 406?
• Also, diameter is D in the image below
• 
  
• 

 

[Richard19068]

• I'm also curious about @Richard19068's observation. If the thickness is 1/2" and ratio is 12 then .5*12=6". By this logic 3" bevel from the edge of the hole is sufficient

West's example is that for 1/4" laminate the outer edge of the bevel will extend 3" from the inside edge of the hole. That's their calculation. If you have a 1/2" laminate then the math results in a 6" bevel from the edge of the hole, not 3" as you are using in your example above.

In any case, the puck method you found sounds very good and reduces the area you need to grind/bevel..

 

[dlochner]

Question: According to the West manual shouldn't the beveled circle have a radius of 6" (plus the radius of the hole), rather than a diameter of 6"? West says "A minimum 12-to-1 bevel is required..... For example, if you are left with a hole through a ¼" (6 mm)-thick laminate, the outer edge of the bevel will extend 3" (75 mm) from the inside edge of the hole."

So if you have a 1/2" thick hull the outer edge of the bevel should extend 6" from the inside edge of the hole. so 6" around the edges of the hole plus the 2-3/8 hole diameter would result in a total diameter of 14-3/8". Am I reading the manual wrong?

No you're not reading the manual incorrectly. I used diameter when I should have said radius. What I meant to say was a circle that extends 6 inches beyond the edge of the existing hole. Sorry for the confusion.

 

[dlochner]

Here is nearly the same scenario that I'm dealing with. Epoxyworks is published by West Systems

Repairing Machined Holes in Fiberglass

• I assume that the puck gives the wetted cloth more area to adhere to during layup?
• Regarding beveling - Should I go beyond the centerline just to achieve the 12:1 ratio? Seems like it might be difficult to get the shape back
• I'm also curious about @Richard19068's observation. If the thickness is 1/2" and ratio is 12 then .5*12=6". By this logic 3" bevel from the edge of the hole is sufficient
• A very thick fiberglass "backing plate" will be placed on the inside of the hull since waves will be bashing it
• Does anyone have any tips for avoiding air bubbles while mixing filler? I'm about ready to buy a baking pan to spread it out thin
• I currently have 404 filler. Would it be worth it to buy some 406?
• Also, diameter is D in the image below
• 
  
• View attachment 179027

If the patch area is sanded and the surface is flat, I don't think thickened epoxy is necessary, neat epoxy should work fine. Of all the patches that Andy at Boatworks Today has done and Mads on Sail Life has done, I don't recall them using thickened epoxy. On the other hand, if the surface isn't flat, i.e, there are chips or voids, then thickened epoxy would provide a smoother surface for the cloth. Fiberglass cloth does not like sharp bends and voids, the cloth will tend to pull away from the void.

Absolutely go with the 12:1 bevel. Just ignore my math in an earlier post. The response was poorly written. It should have said go 6 inches beyond the outer edge of the existing hole. The edge of the existing hole should be paper thin when the bevel is ground.

The puck on the inside gives you something to push against as you work the air bubbles out of the glass. The reason it is waxed or covered in a release fabric is so it can be removed. BTW, for small areas, plastic packing tape works well. Its is the stuff that is USPS approved and comes in a 2" width.

Once the glass is laid up and cured it will need to be faired with an epoxy fairing compound. Microballoons (forget which West filler this is) work and are easy to said out, but also tends to leave pinholes where the balloons are opened up. Interlux and Total Boat both have better fairing compounds that leave a smoother finish.

 

[Hayden Watson]

You can also do the repair from both sides if the inside is accessible. with ½" total thickness, you would then grind a bevel on the inside to ¼" depth that is 12: (3") beyond the edge of the hole and fill that with cloth layups to fill. Then go to the outside and grind a bevel ¼: deep that extends 3" beyond the edge of the hole and then filling that. You only need 6" if the repair is only on one side. Of course, if you have a cored hull the repair will be one sided to the core but done on both skins as shown in the West System guide.

 

[Project_Mayhem]

Here's the email thread from West System's Tech Support

Me

I'm removing a through hull on the bottom of my bow. I'm interested in advice on how to approach this. Here's some info on the current status:

• Hole size is 2 3/8"
• The glass was originally about 1/2" thick
• I've tapered it down to about 1/4"
• I have access to the backside of the hole. Not fun but not horrible. Only outside is beveled at the moment
• Tape is no less than 2" from edge of hole on all sides. I did not go past the centerline in an effort to preserve the shape of the hull
• We're seeing 50-70F weather right now

Here are the questions I have regarding this repair:

• Is 3" from outside edge of the hole enough of a taper? This is about the max I can get on the side closest to the center line. I'm afraid if I go past it, it will be difficult to get the shape of the centerline back
• I'm concerned about the fiberglass staying in place when its wet since this repair is essentially on the bottom side of the hull. Any advice on keeping it in place?
• Would you start this repair on the inside or outside of the hull?
• Any advice on avoiding air bubbles when mixing filler?
• The epoxyworks article on repairing machined holes suggests using a "puck". Is the puck a temporary backing plate for the new cloth and resin or does it provide permanent structural support?

West

On a 1/4 inch deep repair, A 3inch taper works great. If it's a little shy by the keel, it will be fine.
The "puck" stays in place and fills any gap from the inside and outside repair.
Fiberglass on a small repair will hold it's self on the bottom as long as there is not an overload of epoxy.
I use a piece of wood with plastic coving as a workbench. I use this to wet my fiberglass out on, I'm able to squeegee off extra epoxy.
You can use plywood covered in plastic with a 2x2 to the ground to hold the fiberglass in place. If the bottom is not flat in that area you could add soft foam between the plastic and the plywood.
Mixing in filler without getting air bubbles. mix slow and add filler slowly is about all you can do help keep bubble to a minimum but mix fast enough not to use up all of your pot-life time.

Me

Thanks for the fast reply. To clarify, this part of the hull is 1/2" thick. The fiberglass at the edge of the hole is 1/4" because I ground it to a taper. If I taper on the backside that will of course be even thinner. Is 3" on all sides still adequate? Is it recommended to taper the backside as well? I do intend to create a very thick "backing plate" out of some heavy cloth on the inside of the hull. This will not be flush.

West

The 3" taper will be fine. The puck will fill the other 1/4 inch and then the backing of fiberglass over that.
sounds like a good plan

Me

Last two questions... Is there any significant benefit to tapering the backside? Should any cloth be used in the puck?

Waiting for reply

 

[Project_Mayhem]

West System's Reply

No cloth is needed in the puck. No need to taper the inside other than for cosmetics

Once the puck is epoxied in place, should I start with the largest or smallest cloth first? Would it be better to use heavy cloth or lighter? I'm guessing I would only be able to get two, maybe three, layers of thicker cloth in this taper

 

[Hayden Watson]

If you only get two or three layers in a 1/4" fill you are using very heavy cloth or very rich layup.
single ply thickness schedule

 

[dlochner]

What kind of cloth are you using? Do not use mat, it does not have much structural strength and unless it is designed for epoxy it does not take kindly to epoxy. It becomes very resin rich and heavy.

I like to use the big piece first. This ensures that glass fibers extend all the way across the hole. When finally laid up, the patch should be proud of the hull. Then sand and shape the patch to match the hull contours. If the big piece of fabric is on top, you will sand a good about of the glass away, leaving short pieces of glass providing the strength.

 

[Project_Mayhem]

These are the two types of cloth I have right now

 

[Hayden Watson]

Edit ( FYI, 1708 it notoriously hard to wet out with epoxy.)
I just learned something new. Mat is bad with epoxy due to the glue that holds it together will not dissolve. 1708 does not use glue because the mat is sewn and does not cause a problem with epoxy.

 

[dlochner]

These are the two types of cloth I have right now
View attachment 179096

View attachment 179097

So long as the biaxial cloth is stitched and absorbs epoxy and it is not too stiff to bend to the curves, then it should be OK.

Because your glass is in narrow strips each layer will require at least 2 strips. It will be important to avoid having the seams on top of each other. Thus, each layer of glass will need to be at about 45° to the underlying layer. I'd start with the 6" wide glass and lay up at least 2 or 3 layers of that, followed by a couple of layers of biaxial and finish with the woven cloth. The final layer is going to be sacrificial, so make sure it covers all of the biaxial.

 

[Project_Mayhem]

@Hayden Watson You're not wrong about the 1708 being hard to wet out. It has to be submerged in resin to get it saturated. I used it to repair my keel that suffered from a frozen water crack over the winter. It builds up pretty quick and is very strong

@dlochner When you say seems are you referring to the stitching or edges of the mat? I'm guessing overlaps should be avoided to ensure an even layer?

Should 404 or 406 be added to the resin to keep it in place? I've also had good luck pushing foam rubber wrapped in plastic up against fiberglass while it's curing

 

[dlochner]

If the diameter of the tapered hole is greater than the width of the cloth, then it will necessary to have 2 pieces of cloth laid side by side. That seam will be weak because there are no glass fibers crossing it. The strength of a laminate is in the glass not the resin. Changing the orientation of the fabric with each layer of fabric will bridge that seam and strengthen it.

I would not add any filler to the resin. It will make it more difficult to saturate the cloth. If the resin is dripping off the patch, there is too much resin. Peel ply or plastic wrap will speed curing as it holds some of the heat in and makes sanding later a little easier.