Repairing small drill holes in hull

Stephen,
Most dealers do not go to the trouble to use a Starboard block--they don't have to deal with the boat 10 years down the line. Dealers also do what is "quick and dirty"...(Builders often take short cuts also--unfortunately).
The foam filled transom will not rot, but you can still get some water intrusion, and even though the foam is "closed cell" it can get water into it, decrease the bond and eventually might cause some breakdown--not sure if it would be a problem. I probably would redrill the holes and put the screws back into solid epoxy.

Jay,
The reaason for the cross hatching, dovetail type of cut is to give some adherance to the Starboard--1" is more than thick enough. I usually make one peripheral cut--which tends to be sure that there is always plenty of 5200 along the edges and "catches" into the cut groove. I usually use 3/4".
 
Stephen Williams":3mtzhb7l said:
Thank you Bob for your response and advice. You and Sea Wolf are such a treasure!! Steve
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My thoughts exactly, thanks for sharing your insight and experience Bob.
I did take note of your cross hatching technique, this makes sense to help bond and hold the adhesive to the starboard.

Then Joe tosses out the Loctite 3030 Speedbonder Adhesive card. :?
 
The Loctite 3030 is a glue--and a good one--but it has relitatively poor filling qualities. ie; the parts need to fit very tight. If you had a good match between the HDPE and the glass hull, then it would work very well--but I would still use fasteners and drill out the screw holes to fill with epoxy. I don't see using it as a primer for 5200.
It mainly used for guling plastics to plastics.
 
thataway":3jedeb0q said:
The Loctite 3030 is a glue--and a good one--but it has relitatively poor filling qualities. ie; the parts need to fit very tight. If you had a good match between the HDPE and the glass hull, then it would work very well--but I would still use fasteners and drill out the screw holes to fill with epoxy. I don't see using it as a primer for 5200.
It mainly used for guling plastics to plastics.
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Good point, Bob!

I wasn't actually suggesting anyone use Loctite 3030 to glue the HDPE to the hull, just correcting the commonly held notion that there's no way to glue HDPE to itself or anything else because of it's "oily" nature.

Also good to know is that you can melt repairs over a crack or hole in HDPE, by buying a special torch that develops heat off of a propane/butane flame. (Yellow color flame, oxygen starved, and cooler than the typical blue flame.) They use these to repair RV water and holding tanks, etc. Out here on the left coast, Harbor Freight Tools sells one for about $35-$40, if I remember correctly.

As you and I both know, knowing what materials work together and how to join them with adhesives and/or mechanical bindings is half the battle of repair and maintaince sometimes!

Joe. :teeth :thup
 
Today was maintanence day for the HIGH TIDE. I needed to replace the transducer trying to clear up and intermittent HUMMINGBIRD from last fall.
In the process 5 or 6 old screw holes became uncovered. I took a previous suggestion and drilled them all out to reseal. To my pleasant surprise I found good solid new looking wood in the transom in all of the holes. As my boat is 25 yrs. old that has been working on my mind. No more. Some of those old holes only had RTV in them.
I resealed them with 5200. I then bolted the new transducer to my homemade up/down sliding lexan transducer mount, screwed it to the transom sealing those 4 screw with 5200 and popped a Mikes Hard Lemonade and admired my work.

Tomorrow I need to find out why my kicker water "pee hole" will not pee. The 90 HP Honda was just fine in that regard.

After the long winter, messing around in my boat is good fun.
 
I have successfully used the white opaque cutting boards found in Wallyworld in lieu of starboard. I think they are pretty much the same as HDPE. I drill a large number of 1/4" holes about 3/4 way through the back side to help the 5200/4200 adhere and have also doubled those boards to achieve greater thickness. No problems thus far. I hate drilling holes in the boat!!
 
This thread was great, since I found it searching for answers to pretty much the same questions.

However, I've seen a lot of reference to "undercutting" and cannot figure out what this means exactly. Can someone give me a definition?
 
"undercutting" means that after you drill the hole, you take something like a dremel tool or even a small allen wrench and, inserting it into the hole, you cut out some of the wood that is between the inside and outside "skins" of the hull, or deck or top, whatever you cut the hole in.

Then, you fill the hole with epoxy, let it harden and redrill the hole, usually smaller than the original hole. That way, there's no way for water to get into the core! :wink:

Charlie
 
There are several photo's in the "Thataway" album on under cutting:
fillets_and_filler_027.sized.jpg

This is a Dremel tool drum sander--the piece is of a boat I cut up for survey purposes and is balsa cored deck. I have cut the deck on the edge for demonistration purposes. You can use a smaller "tool" for the under cutting if there is a smaller hole. But if there is an area with wet core, you may want to remove this wet core.
 
Jack wrote"

"To my pleasant surprise I found good solid new looking wood in the transom in all of the holes. As my boat is 25 yrs. old that has been working on my mind. No more. Some of those old holes only had RTV in them."

That is great news to hear!!! GOOD DEAL! I hope you find the same 25 years from now!

Norm
 
Which epoxy are you using to fill the drilled out, undercut holes? The marine -tex I have is not suitable for use in a syringe and some epoxies have a warning in the small print,"Not for prolonged immersion in water" ie, loctite's extra time epoxy. I like the idea of filling with a syringe and needle and filling as you withdraw the needle.A name please.
Chica
 
Haven't read this entire thread so apologies if this has already been mentioned: Epoxy is great below the waterline or otherwise hidden from view where waterproofing/sealing trumps appearance. Higher up, especially in highly visible areas, you might have the following challenge: Chemicals in epoxy, even after curing, will "suck" the hardeners out of the gelcoat placed over the epoxy as a final finish, leaving the gelcoat patch uncured and gummy. The gummy spots can't be sanded and collect dirt, fingerprints, etc. I've run into this more than once. So what I'm saying is: If you will finish the repair with gelcoat it might be better to use fiberglass resin as your substrate repair material. I believe polyurethane paints, and certainly epoxy paints, are compatible with an epoxy substrate. Also, make sure you wear rubber gloves when working with epoxy and otherwise avoid touching it and minimize breathing its vapors or you could become sensitized and unable to be around it. Mike.
 
I certainly agree with Westward about skin protection--and what degree of respiratory safeguards are available. However this ""suck" the hardeners out of the gelcoat placed over the epoxy" is a bit of a misnomer--see below for explaination of the role of improperly cured epoxy and gel coat hardening.

The epoxy has far better adherence than polyester materials; they are also far more resistant to intrusion of water. At one point I was also pesimestic about use of gel coat over epoxy. Proset (West Systems professional products, has done a large amount of testing on this subject). I rebuilt an 18 foot Century CC which fell 30 + feet in a dry stack blow down, using epoxy for the structural repair, and Spectrum gelcoat for the finish. 3 years later you cannot tell where the repairs were made and where gelcoat was put over gel coat/polyester or over epoxy.

The adherance of gel coat to epoxy is at times a problem, but there are techniques which will minimize this.

West systems adresses these issues at: http://www.westsystem.com/ewmag/22/polyester.html

Another relitatively short answer I copied from West Systems is as follows:

There is a common misconception, fueled by some gelcoat manufacturers and by some expensive failures in the field, that gelcoat will not bond to epoxy. Polyester resin bonds poorly in a secondary (mechanical) bonding situation which consequently makes epoxy the resin of choice for repairs. How can one be squared with the other?

The answer is surprisingly simple - gelcoat does bond to a properly cured and prepared epoxy surface. There are a couple issues to be aware of to have success making this repair. There are three situations that cause gelcoat to not cure over epoxy... all related to the hardener chemistry. Epoxy hardeners are basically a blend of amines, which can terminate the chain reaction of the radical molecule that is the basis of polyester (and vinylester) cure chemistry. So by carefully mixing, curing, and preparing of the epoxy so that there are no unreacted amines to interfere with the gelcoat cure, gelcoat bonds quite well to epoxy.

The first situation is undercured epoxy. Gelcoat applied to undercured epoxy will be in contact with unreacted amines and the cure will be halted.

The second situation is if the epoxy is mixed off ratio so that it is hardener rich, again leaving unreacted amines free to interfere.

Third is the issue of amine blush, commonly called blush. Blush is a surface phenomena that is a reaction of the amine molecules at the surface with the carbon dioxide in the air. It forms easiest in the presence of moisture, so working in cool, humid environments will maximize the formation of blush. Any amine hardener has the potential to blush, but it can be minimized by careful choices of amines in the formulation. In fact, WEST SYSTEM 207 Special coating hardener is one of the lowest blushing hardeners on the market and still maintains structural properties on par with our other hardeners. Regardless of chemistry, blush is very easily dealt with because it is water soluble. A simple wash with clear water removes the blush. No soap, no solvents. Then sand that washed surface with 80 grit paper to provide the gelcoat with sufficient key so it won't run. Be sure to use non-air inhibited gelcoat that has a paraffin wax added. Gelcoat is applied over epoxy on a routine basis everyday in boatyards that are aware of these issues.

There are also gel coats which are specifically formulated to adhere with epoxies. Vinylester resins adhere better than polyester, and at times vinylester is used as a tie coat. Also tie coats for epoxy gel coat interface have been developed by :Neste, CCP, Duratec, intraplastic, Ferro, Scott Bader and others. There are any number of epoxy laminated boats which have a gel coated surface--however, I personally prefer 2 part LP painting of an epoxy composite.

As to applying epoxy to holes or under cut areas. You do not want to use un-thickened epoxy, such as in the two part tubes. You want to mix the epoxy with cabosil (fumed silica) as a thickener and a filler agent, such as medium density filler (depending on the application). I usually use a peanut butter thickness, and apply with a very thin spatchula, or a sliver of wood/tooth pick for application and packing down into the hole. The epoxy is left proud of the surface and then cleaned with water and sanded to make a surface for the gel coat. If you want to inject an epoxy, then buy the tubes which are available for caulking guns and then inject the thickened epoxy thru drilled holes....
 
If you are going to change your mind and use a piece of Starboard couldn't you just match the holes on the Starboard to the holes you already drilled in the boat? Then you wouldn't need to patch anything.
 
couldn't you just match the holes on the Starboard to the holes you already drilled in the boat?
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From the photos it's difficult to appreciate the size difference between the old Lowrance Bracket and the new Airmar Bracket. As I recall, I was uncomfortable with securing such a large plate (btw- it's polyethylene) using the tight hole pattern from the Lowrance Bracket. Leverage issues. As things turned out I could've (should've ?) gone that way. You see, I went back later and drilled out the capsules and epoxied in threaded inserts . I'd become concerned that a flotsam strike (on the transducer) might crack the epoxy. It's real strong but somewhat brittle. Molded_In_Insert.sized.jpg
 
If one uses mill fibers in the epoxy it is quite strong. I never advocate using plain epoxy resin for any filling application. There are boats which have deck fittings which are mounted with bolts into tapped, re-inforced epoxy.

The reason to use a polyethylene block is that allows one one drill holes to one's content and re-position/change out transducers. Often the bracket height has to be changed--and using the Starboard allows this to be done almost at will.
 
If one uses mill fibers in the epoxy it is quite strong. I never advocate using plain epoxy resin for any filling application. There are boats which have deck fittings which are mounted with bolts into tapped, re-inforced epoxy.

The reason to use a polyethylene block is that allows one one drill holes to one's content and re-position/change out transducers. Often the bracket height has to be changed--and using the Starboard allows this to be done almost at will.
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I agree 100%
If I was starting over new I'd install the biggest poly plate that would fit. Just in case I wanted to reposition/replace or install a second transducer. I'd secure it to stainless steel threaded inserts bedded in epoxy/milled fibers.
 
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