Catalina 34

General Activities => Main Message Board => Topic started by: Michael on April 11, 2007, 03:37:14 AM

Title: Voids (?) found adjacent to handrail bolt holes
Post by: Michael on April 11, 2007, 03:37:14 AM
On pulling the stb handrail to solve a leaking problem in one bolt hole, I found 3 of 5 bolt holes (but not the one that leaked) gave onto adjacent voids (?) that are apparently quite extensive.  I have read other posts about voids (which of themselves don't concern me particularly as I had four of them filled on surveyor's recommendation on buying the boat last month) and about re-bedding leaking handrails, but don't know whether what I am seeing leading off these bolt holes is normal and needs nothing done or abnormal and about about which something should be done.  If the latter, does anyone have any suggestions? I could inject resin or smear "bear####" through the walls of the bolt holes but am not sure whether that is what is called for.  As the voids seem to be quite extensive, I am concerned that I could send a lot of filler who knows where.  Sorry if this newbie's posting covers territory already canvassed.  Regards. Michael MacLeod, 1997 C34 #1352. Boat in the process of being renamed from "New Horizons".
Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: RV61 on April 11, 2007, 10:12:05 AM
Micheal,
When I re bedded my handrails as well as ports, stanchions and chain plates I sealed all holes with epoxy. When the ports were remove I found a huge void on rear portside main cabin  and filled until full with epoxy. On the hand rails I drilled two drill sizes larger and filled with epoxy and redrilled to size once cured. Thus next time it leaks  the water will not be able to migrate into to cabin top and create more serious problems. I kept an eye out for epoxy coming out somewhere else as we filled  and did not find any. Did your surveyor find any wet areas?
 
Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Michael on April 11, 2007, 08:08:53 PM
Hello, Rick.

Thank you for the note about your experience.

In order to get a better idea of the size of these "voids", at the boat this afternoon I threaded a fishtape down one of the handrail boltholes and into the void that opened off it.  I could send the fishtape for several feet in an aft direction - apparently running along the coachhouse roof just above one of the windows - and for several feet in a forward and downward (outboard) direction.  This latter area (if I recall correctly) was between two windows.  (When you refer to ports are you referring to these windows that give onto the galley and salon?)  Based on this fishing expedition and tapping on the inside of the boat in the same area, it seems to me that a good deal of the inclined sides of the coachhouse, beside and above the windows, is actually hollow, although the hollowness ends when one gets further forward closer to abeam the mast.  Whether this "hollowness" is intentional, to save weight up high on the boat, or otherwise, I do not know. Whether I should fill with epoxy, as you did around the port, is not clear to me.  Perhaps I will go back to my surveyor and discuss this with him.  We did inject epoxy into a void outboard of the stb winch by the companionway but that was clearly important to do for structural strength reasons in that area.

To answer your question, my surveyor found no wet areas in the boat other than the evidence (water on mug rack and rusted Phillips head bolt) of the one leaking handrail bolthole.

I like your solution of filling the holes entirely with epoxy and then drilling them out again but unless I am prepared to fill and fill and fill until the entire void is filled - something that in my ignorance I am not yet brave enough to do - I am inclined simply to caulk all five holes with Sikaflex 291 or silicone or that Boatlife Lifecaulk (not sure if I have the name of the last-mentioned right) that people mention in these posts, while I continue to research.  At least that way, if it is necessary to fill the voids entirely I can go back and do it readily and if it is not necessary or desirable to fill the voids entirely I can go back and just press enough epoxy into the voids to seal around the boltholes.

Michael MacLeod #1352 Vancouver
Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Michael on April 12, 2007, 08:02:31 AM
May I leave the board with these questions:

1. Does Catalina intentionally leave the inclined walls beside and above the windows of the salon and galley largely hollow?

2. Should these areas be left largely hollow, with epoxy packed only around the voids immediately adjacent to the handrail bolt holes?  Or should the entire voids be filled with epoxy?

Sorry about beating a dead horse.  Many thanks for whatever you can offer.



Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: tonywright on April 12, 2007, 01:39:51 PM
Michael, as the new owner of a 2003 model, I find your question intiguing, but of course can offer no answer, only another question. My quaetion is how did you remove the handrail, ie is there access from the inside to the other end of the bolt? Since the headlining on the C34 is mostly smooth unbroken surface, how does one in fact access anything that needs removal and repair from inside the boat? (IE line stoppers, traveller rail etc.)

Tony

Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Michael on April 12, 2007, 03:12:29 PM
Tony, on my 1997 each of the port and starboard handrails on the cabin roof are attached by five Phillips head machine screws that pass through the roof from next to the galley-salon windows.  The screw heads are accessible between the curtains and the windows in the galley and salon.  I suppose your setup is the same but don't know.  All the best.

Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: George Bean on April 12, 2007, 06:55:12 PM
"Voids" can happen in two ways.  First, air bubbles in the resin are not completely worked out during the vacuum bagging process and second, gaps in the plywood's sandwiched layers.  You should fill these with epoxy as you do not water intrusion into the plywood (or balsa!) core.  It is good practice to "line" all through bolt holes that go through core to protect against water intrusion.  IMHO, caulk alone isn't sufficient.  What you may have found when you did your tape snaking was the gap between the headliner (or one of the interior mold "plugs") and the deck mold.  The deck mold has about 1" of wood coring.  Are you snaking in that region?  A gap between the molds isn't as critical to fill as the cored deck is still protected by Its laminated layers.  A leak will just flow down between the two molds.


I discovered a "void" of the second type while drilling for some pad eyes on my foredeck and I must have poured down a cup of wood-penetrating epoxy into one 3/8 inch hole.  If your void is bigger, I would suggest using something thicker.  The resin syringes sold at West are perfect for filing through-bolt holes.  Masking tape over the bottom of the hole is sufficient to keep the epoxy where you want it.


Catalina does a pretty good job in having solid resin in areas where leaking is most likely to occur (like the shroud chain plates).  However, "normal" bolt holes are not lined.  Nor is the feed-thru hole for the Edson pedestal guard.  I found out the hard way that I had a leak in the calking in the joint between the metal tube and the socket.  Make sure you have some calk there!
Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Michael on April 12, 2007, 11:56:22 PM
George, thank you for your very helpful post.

If I read your post correctly, you are actually positing three types of voids:

1. voids arising from air bubbles incompletely worked out during the vacuum bagging process;

2. gaps in the plywood's sandwich layers; and

3. gaps between the headliner (or one of the interior mold "plugs") and the deck mold.

Have I understood you correctly?

Based on your post and my examination of the boat, I believe the "voids" I have seen adjacent to 3 of the 5 stb handrail bolt holes on my 1997 are of the third type, namely, a gap between the headliner and the deck mold, because the "voids" lead away from the holes about 1" below the deck surface - in other words, below the 1" of wod coring of the deck proper that you mentioned.

Your statement that a "gap between the molds is not as critical to fill as the cored deck is still protected by its laminated layers" and "a leak will just flow down between the two molds" raises these questions for me:

1.  Where will the water go?  Are there weep holes or some other intentional/actual points of egress for water that gets between the headliner and the deck mold?

2. When you say that "the cored deck is still protected by its laminated layers" do you mean that water that gets under the deck mold is against a fiberglass surface (bottom or inside of the deck) that coats the underside (or inner side) of the deck plywood?

You mentioned that you discovered "a void of the second type" when doing your pad-eyes.  Am I right in thinking that you mean by this that you discovered a gap in the plywood's sandwiched layers (and not a gap between the headliner and the deck mold) and that for that type of gap (#2 of the 3 as I have re-stated them above) using wood-penetrating epoxy would make sense because you expect it to flow between the sandwiched layers of the plywood?

On the other hand, if I am right in thinking that my voids (the ones in the boat anyway - not the ones upstairs) are between the headliner and the deck mold, would I be right in thinking it would not be appropriate or necessary to use wood-penetrating epoxy because I would likely be filling between two fiberglass surfaces?

I infer from what I have found and what you have written that Catalina might not have considered it necessary (at least in 1997 - I don't k ow what they do now) to line the bolt holes of the handrails.  Nonetheless, I take from your post that it would be prudent for me to line these holes now - even if I don't try to fill the really extensive gaps that the bolt holes give onto between the headliner and the deck mold.  Do you agree?

At any rate, when you mention using a thicker epoxy, I infer that what you are thinking is that the area immediately adjacent to the bolt holes should be thoroughly filled to prevent any water that does leak down the holes from weeping into the gap between the headliner and the deck mold.  Again, have I got your meaning correctly?

I was intrigued with your mention of pad eyes on the foredeck.  Although this leads us to another topic, were they for jack lines and, if so, did that project work out satisfactorily?

Finally, yes, I wil watch for that gap you mention at the Edson pedestal guard and be sure to caulk it.

Again, thanks for a very helpful post.

Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Stu Jackson on April 13, 2007, 10:54:47 AM
Michael, here's a picture of a void at the forward V berth portlight on the port side.  It comes from here:  http://c34.org/bbs/index.php/topic,3241.msg17589.html#msg17589
(http://c34.org/bbs/index.php/topic,3241.msg17589.html#msg17589)
The inner liner is separated from the exterior fiberglass.  This occurred only on the aft section of the portlight, the two pieces (inner and outer) were completely connected on the forward side of the portlight.  I believe this is what George was describing.

If it was my boat, and the condition pictured below is what you are finding and what George described, I would follow his advice and over drill the holes, fill with epoxy and re-drill and rebed the handrails.

If, however, you are finding soaked plywood, then you'll need to ream out the holes as far as you can and fill the cavity with epoxy and then re-drill, and rebed with sealant.

Your remaining questions are reasonable; the good news is that you are reporting that the voids seem to be like the ones shown in this picture because you can get the snake way far inside.  There appears to be no reason to fill that void, your goal is to seal the holes where the screws and bolts for the handrails come through the deck to avoid any water penetration.

Where will the water go?  There are no weep holes, the idea is to keep the water from getting through the top of the deck.

Laminated layers?  The laminated layers mean the different sections of the deck assembly.  There's the gelcoat then the fiberglass, then maybe a wood core, then more fiberglass, then sometime the void, then the headliner.  Don Casey's "This Old Boat" and many other books have a much better description of how the assembly is actually built.   Your goal is to determine if the intrusion is into the core or the void.  I'll leave it to George to respond to what he found at his padeye.

"...the area immediately adjacent to the bolt holes should be thoroughly filled to prevent any water that does leak down the holes from weeping into the gap between the headliner and the deck mold." -- Yes, that's the idea behind "over-drilling" the holes and filling with epoxy and re-drilling for the right size bolts and screws, as described in reply #1.

On our boat, none of the holes for the handrails were "lined."  The factory drilled through whatever was there and put in the bolts and screws, and in many cases the sealant was less than would be expected or that would be installed by a boat owner who was concerned about future leaks.  We've re-bedded our handrails, the starboard side earlier this year, and the port side two years ago. Leaks that were detected, necessitating the re-bedding, we did not examine for core rot.  I did not remove the handrails, since I found it's harder to get them back in by a complete removal than it was to just lift them up enough to clear out the old sealant below and rebed them.  There has been back and forth discussion over the years about whether to remove or just to lift the handrails (the teak ones, that is) for re-bedding, and even for refinishing.  Some choose to remove, I chose not to.

The newer boats may have had a beefier support and lining for the chainplates, as George described, but on my boat they sure did not.  I've re-bedded my chainplates any number of times and found no "lining" there, just deck, core and liner.  In the picture, it appears that there was no wood core where the port light was installed.
Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: George Bean on April 13, 2007, 02:07:20 PM
Yes, I guess that I am talking about three types of "voids".  Although I would really consider the one between molds more of a "gap".  That "gap" is very common in the industry as the builder is mating the rough sides of two moldings together.  The gap you describe has no practical impact on the strength or integrity of the hull or deck.  Stu has a good point.  A leak down into a "gap" ideally will eventually find it's way down into the bilge.  However it could also pool up behind an obstruction.  So therefore all leaks should be considered "bad".  Most boat builders do not put in solid resin everywhere they expect to drill a through bolt hole nor do they always "line" their holes.  They rely on the calking process to keep water from intruding into the core.  Like you, we plan on keeping Freya for a long time and we want a more permanent line of defense against water intrusion so we fill those voids and "line" the bolt holes as we come across them.  I used wood penetrating epoxy in my void in the wood because I wanted good penetration.  This type of epoxy while being "spendy" is also very thin and will migrate a fair distance via capillary action, before setting up.  If you can put a fish through your void opening, you could easily put down a hundred dollars of wood penetrating epoxy and still not seal the gap.  That is why you want something more viscous.  On the opening you describe, you will be able to get the thicker stuff to penetrate far enough into the void and still make a good seal.


My two forepeak pad eyes serve multiple purposes.  They are attachment points for my jacklines and also are used for my A-kite's tack line and eventually, for a spinnaker foreguy.  They can also be used to lash down the dink if necessary.
Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: RV61 on April 14, 2007, 12:48:28 PM
Micheal,
I am glad to hear your surveyor found no wet spots. The picture that Stu posted looks exactly what I had found when I removed my ports for replacement.  I used some penetrating epoxy sealent from the Rot Doctor and injected in several areas when we removed  all Stanchions chain plates  and the  deck and cabin top hardware before I did the drill and fill routine with the west systems thicker epoxy. I did this for the same reasons George mentions and wanted to extra protection encapsulating  the  wood core in the deck .  On my boat a took the view of seal and fill anywhere I found a possibility that water could enter because it has been my experience if water can get there it will in time as the boat ages. This year the Interlude turns 21 and I  will give her all the protection I can as I too plan to sail her in her old age or should I say mine.
Rick :D   
Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Michael on April 15, 2007, 02:17:32 AM
Many thanks (Stu, George, Rick, Tony) for weighing in so helpfully on this issue.  Stu, your reference on this thread (to "This Old  Boat") and in other threads to other material seems like a really helpful and efficient way of lending a hand. I appreciate the time you all took to give detailed information. It alleviated uncertainty about how to proceed that would surely have taken much longer to resolve if I were left to my other resources.

With the rain having stopped in Vancouver, it is off to the boat tomorrow to try to effect a "fix" of the handrail leak.  I will take some pics and consider posting them with commentary if they look at all helpful.

Meanwhile here are some comments on the last two (Stu and George's posts).

Stu, your comment "[y]our goal is to determine if the intrusion is into the core or into the void" taken with your later comment when you are mentioning rebedding your handrails "we did not examine for core rot" seem telling.  Even if you had removed the handrails, I can understand why you might not have examined for core rot. It seems to me that unless you can see core rot right at the bolt hole itself, it is pretty hard to tell whether water that might have leaked into what we are calling the gap between the headliner and the deck mold might have migrated and caused rot elsewhere.  I think this is an ancillary issue to the one that George is picking up on when he says about a leak into this [headliner-deck mold] gap that "it could also pool up behind an obstruction.  So therefore all leaks should be considered bad."   

George, how did you know that I plan to keep the boat a long time?  Was my Scottish name a clue?

George, I agree with you that the voids on "Hali" (as she is now to be called) are so large in the area of the handrail through deck bolts that she could drink a very large amount of resin.  Your statement that the kind of headliner-deck mold gap that I am seeing has no practical impact on the strength or integrity of the hull or deck, makes me think I will not attempt to fill these voids but will use a thickened epoxy resin as you suggested to make a good seal in the vicinity of each bolt hole.

Which leads me back to Stu's decision not to remove the handrails on Aquavite.  On Hali, I did remove the stb handrail. I had read some of the posts on the "remove/don't remove" debate that seemed (at least in my recollection) to swirl mostly around the question as it had to do with the boats with wooden handrails.  As Hali has the stainless steel handrails, and removing one seemed very simple, I just pulled the Phillips-head machine screws down into the cabin while someone held the handrail.  I was so pleased that the machine screws came out easily that I wasn't paying much attention to the fact that I was removing them entirely and taking the handrail off.  Only afterward did I realize that the screws are of different lengths; I hadn't numbered them. Now I am also beginning to think about a problem that arises if, as planned, I fill the bolt holes and adjacent inter-mold gap with epoxy resin and then re-drill the bolt holes: how do I re-drill the holes in exactly the same place as they are currently so that the ascending machine screws and descending female threads on the handrail enjoy a perfect union?  Well, there may be no perfect unions in this world but at least a long, happy, and not too stressful union anyway.

Thanks again.  More results from the boatyard later if they seem worth printing.





Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Phil Spicer on April 15, 2007, 08:58:54 AM
Michael, Here is something to think about. If you have a void around each hole you may want to think about this. Could you use a "curved end" syringe to inject a thick epoxy into the the void area all around the hole about 1 inch or so? If so, cover the inside of the hole (inside the boat) with duct tape & mask off the top side. Fill the void from the top side with your thick epoxy. Now, spray the bolt with cooking oil like Pam, & insert the bolt into the hole from the top side. With a little work you should be able to feel the hole in the inner liner & let the bolt sit there until the epoxy sets. The Pam will act as a release agent & let the bolt unscrew from the epoxy after the epoxy sets. Now the void is sealed around the hole & the hole is still at the same angle so you can redrill a little larger hole & the bit will follow the pilot hole left by the bolt. This SHOULD give you a good fit. If you need to alter the angle a little, you are only working the epoxy so the new seal is still fine. Countersink the deck. Fit everything DRY to check your alignment & fit. When all is good, GOOP & bolt.
I did this last Summer. The bolts came right out, opened up the holes with a little larger bit to re-bed. Worked real good, no leaks. This may work for you.
   
Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Michael on April 15, 2007, 11:18:53 AM
Phil, thank you for that suggestion.  I think it answered the last part of this puzzle, and I am glad that I checked the board before heading to the boat.  My wife has released the Pam to its new calling.  All the best. Michael
Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Phil Spicer on April 16, 2007, 08:36:35 AM
Hope all went well as you filled the voids. Let us know how it is progressing.
Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Michael on April 17, 2007, 10:46:34 AM
Well, the first part of the project is complete.

Lionel (another co-owner) and I discussed at length the merits of drilling out the bolt holes but demurred.  Phil's suggestion on how to get the bolts reinstalled at the correct angle seemed less likely to work if we drilled the holes larger.  We feared that if we drilled out the bolt holes and filled them entirely with epoxy there would be considerable opportunity for us to reinsert the bolts askew so they didn't pick up the handrail correctly. Thinking about it now, I think we could have measured the bolt angles with a protractor and pencilled radial marks every 90 degrees around the holes to indicate centres for drilling out new holes...but that is an after thought.  There's probably some even simpler trick along the lines of the one Phil suggested but it wasn't obvious to us.

In any event, as there was no evidence of rotting of the plywood, we settled for cleaning the bolt holes with a dremel sanding wheel and then paying (to a very limited extent) the voids adjacent to the bolt holes with a fairly thick epoxy resin (West Marine resin, hardener, and 404 filler I think).  Our intention was not to fill the voids but only to seal the bolt holes off from the voids so that any water that did get into the bolt holes would not run into the voids.

As for the plywood deck core adjacent to the holes, since it seemed completely unrotten Catalina might be vindicated in its decision not to have "lined" handrail bolt holes, at least on Hali. We probably smeared a bit of epoxy resin onto the plywood core while paying the voids lower down in the holes but we really didn't make a conscious decision (although we probably should have) to "paint" the plywood core next to the bolt holes with epoxy.  Hopefully, the next 10 years will see no more rot develop there than in the first 10 years of this boat's life.

We did the epoxy work from the top of the holes.  Although the "voids" were nearer the bottom of the holes than the top, we found it was impossible to pay the voids from below without drooling epoxy into the cabin.  So we sealed the bottom of the holes with duct tape and filled from the top.  Likely, we will have to drill out the holes a bit.  None of this could be easily photographed or would be too interesting to see in photographs, so no pics.

On further thinking about the repair, I think we should have measured the bolt angles and marked the bolt centres (as mentioned above or in some other fashion) and then drilled out the holes two sizes bigger then filled the holes entirely and finished up by drilling the holes to size. Perhaps we can test that technique on the port handrail, with the stb handrail providing a control.

Unless something unusual materializes in the re-bolting process, I should think this will end my posting on this subject.  Many thanks to all of you who tried to set me straight.



Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Stu Jackson on April 17, 2007, 11:28:24 AM
Glad that worked for you.  I was thinking of you and how to line up the holes, seems that a little chalk line(s) would work on the surface to get the hole centerlines where you need them.  Just also came across this on another board:  http://www.boatus.com/boattech/casey/39.htm  Maybe helpful to others and for your "other side".
Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Michael on April 17, 2007, 07:04:35 PM
Stu, thank you for your follow up and the Don Casey article.

Your post and his article have caused me to second guess the wisdom of shirking the full drill-fill-and-drill routine with these handrail bolt holes.  I will probably go back and do the full job.  (My father used to say, If you don't have time to do it right the first time when will you have time to do it again?)

At first, I puzzled about your reference only to making centering marks and not to measuring the angle of the bolt as it emerges from the deck.  In other words, it seemed to me at first that you thought it was sufficient to make marks on the deck only to indicate the centre of the top of the hole and not necessary to determine the angle the bolt makes to the deck (eg. in the rather convoluted way I had suggested in an earlier post in this thread, by using a protractor).  However, it does work (and probably this is what you meant) if we make centering marks at both the top of the hole (on the deck) and at the bottom of the hole (on the headliner) before filling with epoxy.  Then, when we drill (probably a pilot hole to start with) from top dead centre to bottom dead centre (based on the marks), or vice versa of course, through the new epoxy filling it is inevitable that we will be reproducing the angle and location of the current hole: the machine screws will fit the female threads of the handrail perfectly.

So it shall be tried.

Regards and thanks again.


Title: Re: Voids (?) found adjacent to handrail bolt holes
Post by: Michael on May 23, 2007, 02:04:00 AM
Subject to correction by the more knowledgeable on this site who helped with advice along the way, here is how to re-bed a stainless steel handrail on a Mk II Catalina 34 and deal with voids that may be found adjacent to the handrail bolt holes.  This summary is based on experience with the starboard, trunk cabin roof mounted, five-bolt, stainless steel handrail on a 1997 C34.

The decision to re-bed the starboard handrail was made after water was discovered leaking into the galley from the head of one of the five machine screws ("bolts").  The bolt head was rusty.

1.   Remove all cushions and valuables from the galley-salon.  Tape newspapers over everything out for a few feet from the windows.  Something is sure to fall/drip: in my case, fiberglass dust, sawdust, and epoxy resin.  I found removing invisibly even a few drips of hardened epoxy resin from the cushions to be impossible...so it was cut-out and sew.

2.   Unscrew the bolts retaining the handrail.  You will need a Phillips head screw driver.  The bolt heads are located between the curtains and the windows in the salon and galley.

3.   Remove the handrail and place it inside the boat, lest it sink.

4.   Using a pencil or other eraseable marker, mark on the deck the top dead center of each of the bolt holes by drawing at each hole a cross with one axis running fore and aft and one axis running transversely.  The transverse axis is the more important: the handrail will not stretch or shrink longitudinally so when you come to re-drill the hole you want to do so as accurately as possible in a fore and aft direction, that is, on the transverse axis; but there is some lateral flexibility in the stainless steel handrail (at least at either end), so you may have a bit of leeway (at least on holes 1 and 5) in that direction, so the accuracy of your drawing of the fore and aft line is not quite as critical.  Make sure you extend the radial lines far enough -- say three inches on each side of the hole -- so that they will not be drilled out or disappear under the tape or be ground off in the steps to come.

5.   From on top, drill out each hole 2 sizes larger. The hole you drill should be somewhat smaller than the diameter of the base of the handrail so that the epoxy plug you will fashion below will not show when the handrail is re-installed.

6.   Check the sides of the holes you have drilled.  I assume you are finding voids off the sides but the plywood deck core you find is not soaked.  (Stu Jackson advises if you are finding soaked plywood, then you'll need to ream out the holes as far as you can.)

7.   Sandpaper the sides of the new holes (to give the epoxy resin with which you will fill the holes in a later step some roughness to adhere to).

8.   Wipe the holes clean with an appropriate cleaner – I don't know which one to use, perhaps Interlux 202?? – to get rid of the fiberglass and plywood core dust from drilling and sanding.   I missed this step.

9.   From below, tape over the bottom of each hole.  Duct tape works fine.

10.   Tape with masking tape all around the top of the hole to protect the deck from the coming messiness.

11.   Make a batch of epoxy resin and filler to peanut butter consistency.  I used West System epoxy resin and hardener and one of their fillers, 404 I think.  If this "goop" is too liquid, voids adjacent to the hole will drink more of it than necessary.

12.   Pour/spread the goop into each hole, pressing it some way – an inch or two will suffice, I think - into any voids adjacent to the hole.  Your goal in packing the goop somewhat into any adjacent voids is not to fill the voids but just to create an epoxy-filled area immediately adjacent to the hole so that no water can get into the voids from the bolt holes that you will re-drill.  Complete filling the hole until the goop sits somewhat proud of the deck. The goop will likely ooze a bit over your deck-protecting masking tape. That's okay.  The goop may also settle a bit as it oozes further into the voids.  As you don't want to have to repeat the process later, it is better to err on the side of leaving too much of a mound of goop proud than too little.

13.   A day or two later, grind the epoxy plug flush with the deck – a Dremel tool with a sanding wheel seems to work well - and remove the masking tape.

14.   From on top, with a small diameter bit, drill a pilot hole vertically -- using a drill with a bubble level helps with this - through the center of the old (now hardened epoxy-filled) hole. (It seems, at least on my boat, that Catalina drilled the original bolt holes vertically, so while I needed to center the drill bit accurately there was no need to worry about drilling the new hole anything other than straight down.)

15.   Re-drill each hole with a drill bit one size larger than the handrail bolts.

16.   Fill the top of each bolt hole with flexible bedding compound. I used Sikkaflex 291 but opinions about the merits of bedding compounds will vary on this site.  Following the advice of Don Casey in an article cited by Stu Jackson at this thread, don't put any bedding compound near the bottom of the bolt hole: if water leaks around the handrail bolt, you want it to flow down into the cabin, where you will see it as a sign that it is time again to re-bed the handrail.  You don't want the water to pool invisibly and remain where it can do damage to your deck - that is, above a plug of misplaced bedding compound at the base of the bolt hole.

17.   Insert the handrail bolts from below.  Add bedding compound as needed around the bolt/handrail junction. Tighten the handrail bolts completely into the handrail.  (This is not a case where there is a nut that can be left somewhat untightened until after the bedding compound sets.  In this case, if you leave the handrail bolts untightened and tighten them later, you will break the bedding compound seal.)

18.   Wipe off any excess bedding compound.

19.   Erase radial lines.

Thanks for the help of all posters who contributed along the way.  Corrections/improvements would be welcome.