Old Holes In GRP

[slimted]

I am replacing my old sounder with shiny new one. The old transducer was through hull, therefore I am left with about a 20mm hole. What is the best way to fill this in.
Any help would be great.....

 

[richardf]

Leave the old one in there.

 

[slimted]

Too late. It's already out. Hindsight is a..........

 

[MarkGrubb]

You could try some Epoxy thickened with Silica or thin strips of chopped strand mat. Cover the bottom of the hole and poor the mixture in from the top.

 

[richardf]

Can't you adapt the hole for the new transducer?

 

[michael_w]

I'd stick the new transducer through the old hole. If it's too big then fill with epoxy. If too small then bore it out. Then make sure it'll never come adrift with 3m's 5200 sealant.

In my experience, through-hull echo sounders are never very satisfactory.

 

[Spuddy]

20mm is only a weeny so not worth grinding chamfers and such like. Epoxy and chopped strand mat don't take to each other but all the cloths and tapes will be fine. Try duct taping over the outside of the hole: nip to chandlers for smallest epoxy repair kit plus metre or so of fine to medium glass tape. Read instructions then chop up some of tape into short strands, mix with resin and fill up hole. Could do with hairdryer or heat gun to warm up hole before and after filling. Wait til tacky then make a poultice of tape and resin over inside of hole to give reassuring reinforcement. Naturally you'll be cleaning off old sealant and roughing up round hole. Presumably hole is not visible so cosmetics irrelevant.
Oldsaltoz might have alternative suggestions - in which case do as he says

 

[boatmike]

Put it back then! /forums/images/graemlins/smile.gif

 

[Poignard]

[ QUOTE ]
....20mm is only a weeny so not worth grinding chamfers and such like...

[/ QUOTE ]

That's interesting advice.

I filled in a hole in 3/8" thick grp, where a 1" fitting had been and, if I had followed WEST's advice to grind an 8:1 chamfer, I would have ended up with a 3" chamfer around the hole, resulting in a 7" diameter depression. To grind away so much perfectly sound hull laminate seemed totally over-the-top to me so I settled for less [and she's still afloat].

I can see the necessity for a wide chamfer when filling in a large hole caused by an impact, so as to restore hull strength; but not for a small hole. If the hull wasn't weakened by the original fitting being there I don't see why it has to be strengthened when all you want to do is block up the hole. But I'd be interested to hear what other people think.

 

[Channel Ribs]

Hello and welcome,

You might want to pad out your biographical detail a bit, there may be someone near you that is keen to help.

In my experience popping a replacement transducer in the hole is the neatest solution, as mentioned you can enlarge it to suit the new device.

 

[Bajansailor]

I filled up a couple of 38 mm (1.5") diameter holes where our cockpit drain through hull fittings were located (ran the cockpit drains out the aft end of the cockpit, so they now exit above the WL, rather 2' below via seacocks).

I did not worry to chamfer the edges - just sanded the fibreglass thoroughly, cleaned it with acetone, filled the holes from the inside with thickened epoxy (put some gaffer tape across the outside as a mould surface), then for each hole I used a layer of stitchmat and epoxy on the inside with a generous (about 3") overlap all round, and applied a layer of fine cloth on the outside, again with an overlap (about 2") on to the hull laminate.
This was about 4 years ago, and it seems to be very strong, and has held up OK.

 

[Salty John]

I filled a couple of old transducer holes on Adriana in a similar manner to Spuddy and Banjansailor. I put duct tape across the inside and filled the holes from the outside with layers of epoxy soaked medium cloth. I cut pieces about the diameter of the hole, thoroughly wetted them out and tamped them into the hole. I slightly overfilled the hole and then sanded smooth once the epoxy had set.

 

[yogi]

The best advice anyone can give you is to not take any advice you get on this or any other forum without a great deal more information. While doing some of the methods mentioned will work, are easy, and are proper some will only lead to problems. So as not to belittle anyone I will not mention any method recommended.
Find someone local who does fiberglass repairs and ask them, you will find most forum advisers are only voicing their opinions and are not necessarily giving useful advice.

 

[Channel Ribs]

[ QUOTE ]
... to not take any advice you get on this or any other forum...

[/ QUOTE ]

Thats a bit harsh, there is alot of experience and know-how to be had herin. Of course a first hand view of the problem cannot be matched, hence my paragraph about the bio.

 

[Bajansailor]

Agreed that there are many ways to skin a proverbial bear, same as there are many ways of filling holes in a GRP hull.
If you are at all doubtful about the quality of your repair work, get a good big mallet, and give your repair a few severe wallops once the epoxy has properly set.
If it disintegrates, no worries, have another bash at it.
If it doesn't, odds are that it should be OK........

 

[yogi]

This is only my opinion but I just categorised the replies and they came out as follows.
Three were totally good. leave in or replace the old fitting.
Six may or may not work but were not good practice even if they did work
Two were downright dangerous.
Three in fact said to get some advice from someone who knows.
The problem here is the writer may pick the two dangerous ones because they look the easiest.

 

[bigwow]

I would always slightly chamfer both sides of the hole , so you have a cotton reel shape hole. That way when you do your repair, the plug you make cannot physically come out. Then fill the hole with thickened resin, laminate over the inside and gel coat the outer skin and fair.

 

[oldsaltoz]

G'day Slimted and welcome to the YBW forums.

I have been flat out the last couple of weeks and missed a few postings, but this one is interesting reading with some banter on the quality of advice and so on.

Filling a small diameter hole in a fibreglass hull is not rocket science by any stretch of anyone's imagination.

Holes in hulls should be avoided, particularly the ones below or close to the water line, having stated the bleeding obvious, have you purchased another through hull transducer? will the manufacturer exchange it for an internal mounting unit?

If the answer to the above is Yes I have another through hull transducer and No they can't supply an internal unit. First look into changing the hole size rather than repair one and drill another, unless the existing hole is in the wrong position or you have some other reason to locate it some place else.

If you must fill the hole then consider the following points.
1 / It must be 100% dry or very close to it.
2 / It must be warm enough for an Epoxy resin to fully cure within 24 hours or the
strength of the repair may be compromised to some degree.
3 / It must be spotlessly clean, the easy way to ensure this is to re drill the hole 4 or
5 mm oversize, then inspect the inside if the hole, you may have to drill more
out till it is clean.
4 / Never repair a hole below or near the waterline with a simple fill / plug. It MUST
be countersunk at both ends, this not ensures it will not fall out but also spreads
the stress over a larger area when the hull flexes (and they all flex). Imagine
what happens when you bend a flexible layer of glass that has a much stronger
and harder plug in the muddle of the stressed area!
For small holes, hold the grinder wheel at about 15 degrees and leave an area
about an inch wide around the hole.
5 / Never use chopped strand mat (CSM) with an epoxy resin, it will weaken the
repair as the CSM has too many voids and the binder will not dissolve in epoxy.
To fill the hole in question I would proceed as follows:
Clean the hole by re drilling, then grind at 15* to get the one inch chamfer; wash with acetone 15 minutes before placing any resin. Precut small round patches of stitched epoxy cloth not more than 250 gram, ranging from the hole size to the size of the chamfer; working from below I would wet out the patches and place the smallest patch first then add the others in order so the largest patch was last. Now roll out as much resin as you can; epoxy and cloth should be close to a one to one ratio by weight (unlike standard resin and CSM this comes in at 3 resin to one cloth by weight). make sure the last layer is just below the edge of the chamfer. Let this
cure move to the inside, as this is a small hole a simple mix or epoxy resin and Micro-Fibres (Gorilla Hair) will be ok and easy to avoid air pockets; now add the rest of the patches as we did on the underside, again leaving the last patch just below the edge of the chamfer, let this cure. When epoxy resin cures it can leave a residue on the surface, this must be cleaned off before any further work is carried out, including sanding as this will only spread the contaminant not remove it. All you need is a plastic kitchen scourer and some fresh water (no soap), just rub till the water no longer forms beads like you see on your car just after finish polishing it and the heavens open up. Now sand off and high spots inside and out, on the inside just add a few closed cell micro balloons or 'Q' cells mixed with epoxy resin to about toothpaste thick and spread to fill the low we left, this can be final sanded and coated later and no sign of any repair will be visible. On the outside we need to ensure no water ingress takes place, this means applying at least 4 coats of epoxy resin, now this can be done wet on tacky to save washing and sanding between coats, having got them on, you can now fill the what is left of the depression with more closed cell balloons, I use a flexible plastic ruler at an angle and held tight to the hull shape, this leaves a nice smooth finish that required little sanding. When all fared off just add another coat or two of resin to protect the balloons and coat with a primer prior to antifouling.
Your all done, see you should have got that see thru' hull transducer. a lot less work and no lift out required.

Avagoodweekend......

PS If have made any errors please feel free to correct them as it's now 0100 hrs and I was up to my elbows in resin around 0530 this morning, (or should I say yesterday morning)

AvagoodChrissie......

 

[slimted]

Wow, thanks Oldsaltoz. If I use the new transducer in the old hole, would you recoment some kind of protection for it. It is located just forward of the keel.

 

[oldsaltoz]

It should not need too much protection if installed properly. Have you a bit more than nomal protruding?

You could add a few micro-balloons ahead of and after it to smooth the flow over the head and provide some protection I suppose, but it should not be sticking out at all.

Avagoodweekend......