So this leaves me wondering; is the above drill-and-fill technique something that only knowledgeable boat owners do for themselves or is this the professional standard that could be expected when a boat is rigged and outfitted or additions purchased and installed at a quality boatyard?
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Cored Hulls
- Thread starter mjsiega
- Start date
The drill and fill is rarely done by riggers of boats, or the factory in production boats. That, or perhaps more frequently, some solid core material, is placed where thru hulls, cleats, life lines stanchions etc are placed when the boat is laminated, either in very high end boats or in custom boats.
I have done this on a number of boats--but not always, and not in all fittings. Several boats I have done it on every fitting (including the Cal 46 we rebuilt), and a couple of the C Dorys I have owned.
Should it be done? Absolutely. Why is it not done? Costs. Every production boat is done on a "Cost vs benefit" basis. The manufacturer figure most folks will now own a boat more than 5 to 10 years (max warrantee), and then it is someone else's problem. There are a lot of things done in boats on this principle. There are also reasons that the C Dory keeps it value far better than a Bayliner or Sea Ray.
The reality is that you don't see C Dory's being ground up and used for insulation or put into a land fill--where you do many other fiberglass boats. There have been some older (and a few newer) boats which have had core problems. 90+ % were boats left out in the open, water accumulated, freeze/thaw cycles, holes in the core, which allowed water intrusion. There have also been a very few boats which had factory defects--and for the most part there was restitution...But that is true of all boats.
Occasionally there is a catastrophic cored hull failure. I have seen photos of several. Not all were balsa. Some were caused by improper manufacture--and some by hitting a rock, and not repairing a core intrusion. But I have also cited in the past, where I was on a balsa cored boat which hit a container at 8 knots in 8 foot seas. The balsa absorbed most of the shock--3/8" outer glass (the thickness of many solid laminate hulls) was fractured--and an uncored boat would have sunk. In this case, there was delamination of the inner 1/4" glass over about 12 sq feet, but no hull breech. This happened in the middle of a dark night in 50 knot winds off the coast of Mexico. The difference between finishing the race (in first place), and spending some time in a life raft, until rescue elements arrived--and the potential loss of life, as well as loss of a very expensive boat.
I have done this on a number of boats--but not always, and not in all fittings. Several boats I have done it on every fitting (including the Cal 46 we rebuilt), and a couple of the C Dorys I have owned.
Should it be done? Absolutely. Why is it not done? Costs. Every production boat is done on a "Cost vs benefit" basis. The manufacturer figure most folks will now own a boat more than 5 to 10 years (max warrantee), and then it is someone else's problem. There are a lot of things done in boats on this principle. There are also reasons that the C Dory keeps it value far better than a Bayliner or Sea Ray.
The reality is that you don't see C Dory's being ground up and used for insulation or put into a land fill--where you do many other fiberglass boats. There have been some older (and a few newer) boats which have had core problems. 90+ % were boats left out in the open, water accumulated, freeze/thaw cycles, holes in the core, which allowed water intrusion. There have also been a very few boats which had factory defects--and for the most part there was restitution...But that is true of all boats.
Occasionally there is a catastrophic cored hull failure. I have seen photos of several. Not all were balsa. Some were caused by improper manufacture--and some by hitting a rock, and not repairing a core intrusion. But I have also cited in the past, where I was on a balsa cored boat which hit a container at 8 knots in 8 foot seas. The balsa absorbed most of the shock--3/8" outer glass (the thickness of many solid laminate hulls) was fractured--and an uncored boat would have sunk. In this case, there was delamination of the inner 1/4" glass over about 12 sq feet, but no hull breech. This happened in the middle of a dark night in 50 knot winds off the coast of Mexico. The difference between finishing the race (in first place), and spending some time in a life raft, until rescue elements arrived--and the potential loss of life, as well as loss of a very expensive boat.
My 28' Saber Offshore was balsa cored sandwiched between layers of bi-axial
knitted cloth (vs woven roving) with vinyl ester resin - all 100% hand layup.
I can tell you that boat took a pounding - much more than a C-Dory hull - and
I never gave a thought to "balsa below the waterline", blah blah, blah. Both the
Saber and C-Dorys are trailerable helping dissuade concern about water intrusion
into the balsa. More ammunition about balsa coring vs foam from the Mfg:
"End grain balsa core with a fiberglass skin on each side gives a stiff, strong, yet
light weight laminate, this I-beam principle gives it strength. Balsa core will not
rot because water cannot travel across the end grain. Balsa core is superior to
foams in impact strength, compression strength and shear strength."
The lesson here, IMO, is with FG wood sandwich construction, "wood below the
waterline" is a concern only IF your MFG cuts corners or is sloppy, uses sub-par
materials or you, the owner, abuse and neglect the hull; i.e., fail to inspect or
repair damage after grounding, etc.). ...
Aye.
knitted cloth (vs woven roving) with vinyl ester resin - all 100% hand layup.
I can tell you that boat took a pounding - much more than a C-Dory hull - and
I never gave a thought to "balsa below the waterline", blah blah, blah. Both the
Saber and C-Dorys are trailerable helping dissuade concern about water intrusion
into the balsa. More ammunition about balsa coring vs foam from the Mfg:
"End grain balsa core with a fiberglass skin on each side gives a stiff, strong, yet
light weight laminate, this I-beam principle gives it strength. Balsa core will not
rot because water cannot travel across the end grain. Balsa core is superior to
foams in impact strength, compression strength and shear strength."
The lesson here, IMO, is with FG wood sandwich construction, "wood below the
waterline" is a concern only IF your MFG cuts corners or is sloppy, uses sub-par
materials or you, the owner, abuse and neglect the hull; i.e., fail to inspect or
repair damage after grounding, etc.). ...
Aye.
BillE":26j8dpwe said:So this leaves me wondering; is the above drill-and-fill technique something that only knowledgeable boat owners do for themselves or is this the professional standard that could be expected when a boat is rigged and outfitted or additions purchased and installed at a quality boatyard?
I would say that very few production boat builders would do this during the build. Semi-custom builders would be more likely to.
As for boatyards doing refits? A good yard should and will close out the core in some way. But that's something to ask about on an individual basis. And of course it will cost more as it takes more time. Personally, if I were hiring and paying a yard to do work on my boat, I would specify it (and take my boat elsewhere if they acted like I was from Mars). I'm sure many yards would just use caulk or maybe a thin painted on layer of epoxy or other resin. I wouldn't be happy with that myself. So it's just something to ask about. I definitely wouldn't assume anything on that score without asking and getting a clear specification on how the work would be done.
A
Anonymous
Guest
Sunbeam,
My thoughts exactly. You set and articulate the specs, and if the installer looks at you askance, keep moving. The previous owner of my boat allowed a new engine to be installed with home-owner-grade silicone caulk to protect the balsa core. Anyone who's followed some of my re-do posts know the results of that fiasco. Do it right or pay lots of money to deal with the consequences...
T
My thoughts exactly. You set and articulate the specs, and if the installer looks at you askance, keep moving. The previous owner of my boat allowed a new engine to be installed with home-owner-grade silicone caulk to protect the balsa core. Anyone who's followed some of my re-do posts know the results of that fiasco. Do it right or pay lots of money to deal with the consequences...
T
I fully agree with the last post. When choosing a vendor to perform a boat repair or upgrade, and after I've done some research, I try to find a shop or tech who doesn't roll their eyes at my specifications, but either embraces them or explains to me a better approach (which I listen to if the credibility factor is there). If they don't get it I thank them for their time and move on. I also verbally make clear that I'm willing to pay the extra cost to have my spec's met, and that I don't want them to rush the job. This is whether it be genuine Honda motor oil, inline fuses in minor electronic installations, or anything else that's important to me. I just took myself, my spouse, and 5 dear friends across a nasty Rosario Strait this morning. In the middle of what seemed like a rolling car-wash, with life jackets donned and the kicker having been pre-warmed up, everyone took comfort in how "anal" I am with my boat maintenance.
flyinbob2001
New member
Im with the guy with the nuclear power plant analogy...a little leak turns into a big problem...In the best case scenario you have encased stuff model airplanes are built out of. Sealed in an airtight container? Ya right
Maybe c dory did this job the best but its the best out of sorry idea in the first place. Almost all boat builders have gotten away from the stuff and horror stories abound.Of course there are builders that messed up with composites too...bad layups voids etc..But at least its not ORGANIC.
Maybe c dory did this job the best but its the best out of sorry idea in the first place. Almost all boat builders have gotten away from the stuff and horror stories abound.Of course there are builders that messed up with composites too...bad layups voids etc..But at least its not ORGANIC.
flyinbob2001":1fdriac5 said:Im with the guy with the nuclear power plant analogy...a little leak turns into a big problem...In the best case scenario you have encased stuff model airplanes are built out of. Sealed in an airtight container? Ya right
Maybe c dory did this job the best but its the best out of sorry idea in the first place. Almost all boat builders have gotten away from the stuff and horror stories abound.Of course there are builders that messed up with composites too...bad layups voids etc..But at least its not ORGANIC.
So along with your opinion, why not answer Bob's questions.
Bob, I think you may be right.
Jay
Ditto. Especially since I'm pretty sure there weren't any 19' Anglers built in 1981. What say you flyinbob2001?thataway":tgvjfr4h said:Me thinks we have one of those rare "Troll" birds here.
Peter
Salmon Fisher
Member
I guess we should all just forget going out with our boats, heck, they could collapse and fall apart at any second :shock:
Nah, let's just forget about this guy, sounds like he is into finding fault where there really isn't any. We'll all go have fun on the water and he can sit on the beach
and b_ _ ch!!
Nah, let's just forget about this guy, sounds like he is into finding fault where there really isn't any. We'll all go have fun on the water and he can sit on the beach
and b_ _ ch!!
flyinbob2001
New member
Well heres the truth....When I joined the site asked for what your c dory was so I made it up...I have been trying to buy one for maybe 2 years now.I own a 96 proline 251 (FIST const) part owner of an alura 30 1988(Its a dreaded balsa cored hull below waterline no less)..and a G3 semi v 18ft john boat...Plus I have owned and built probaly 50 or so boats in my life.
Ive worked as a surveyor for a time also.I was around Ross yacht in clearwater florida in the 80s when there were some real horror stories in cored hulls mostly sailboats...I did not work at ross by the way
Several of the older cored boats I owned where there never was any water intrusion or moisture had core issues where it turned to dust after 20 plus years.
One of the reasons I think c dorys have had relative success with the bottom coring is because its a flat bottom boat and it pounds in a chop most of you guys poke around at slow speeds so the bottom is getting that hydraulic effect..It would be interesting to look or hear from the older hull owners that have been into the bottom for repair...Obviously there have been the usual transom issues.
Its a unique boat and I want one to add to my list ...But Im a bottom feeder in the boat world and Im not going over 15k for one.I know most of you take excellent care and are proud of your boats But its still a BOAT get real...and alot of the older ones for sale have old outboards on them and we all know what that entails...
Im currently working on a new acquisition a 96 25 seacat with the older honda 130s...It has had transoms redone,fuel tanks replace and Im having to refasten the hull to deck joint for starters.Its my first catamaran and Im interested in the better ride offshore...I like offshore fishing.
So to end this ....If you are close to me and interested in the lowball cash deal...Im partial to the twin setups..40s 50s 60s HP...Missed the one in ARK there is a guy in NJ with one ...guy sold his in VA with a single honda 50 for the 15k and he was going to deliver ...I would take the plunge..HA...winter is coming....Then I will have the opportunity to give the real analysis of the boat..Maybe it is that ideal boat...I can certainly appreciate the economy aspect of it....Thanks bob
Ive worked as a surveyor for a time also.I was around Ross yacht in clearwater florida in the 80s when there were some real horror stories in cored hulls mostly sailboats...I did not work at ross by the way
Several of the older cored boats I owned where there never was any water intrusion or moisture had core issues where it turned to dust after 20 plus years.
One of the reasons I think c dorys have had relative success with the bottom coring is because its a flat bottom boat and it pounds in a chop most of you guys poke around at slow speeds so the bottom is getting that hydraulic effect..It would be interesting to look or hear from the older hull owners that have been into the bottom for repair...Obviously there have been the usual transom issues.
Its a unique boat and I want one to add to my list ...But Im a bottom feeder in the boat world and Im not going over 15k for one.I know most of you take excellent care and are proud of your boats But its still a BOAT get real...and alot of the older ones for sale have old outboards on them and we all know what that entails...
Im currently working on a new acquisition a 96 25 seacat with the older honda 130s...It has had transoms redone,fuel tanks replace and Im having to refasten the hull to deck joint for starters.Its my first catamaran and Im interested in the better ride offshore...I like offshore fishing.
So to end this ....If you are close to me and interested in the lowball cash deal...Im partial to the twin setups..40s 50s 60s HP...Missed the one in ARK there is a guy in NJ with one ...guy sold his in VA with a single honda 50 for the 15k and he was going to deliver ...I would take the plunge..HA...winter is coming....Then I will have the opportunity to give the real analysis of the boat..Maybe it is that ideal boat...I can certainly appreciate the economy aspect of it....Thanks bob
flyinbob2001":14oc86rb said:..It would be interesting to look or hear from the older hull owners that have been into the bottom for repair...
Well I had to replace a 2' x 4' section of core in my 1990, thanks to a previous owner who installed a raw water wash down thru-hull fitting and sealed it with bathtub caulk. Nothing I saw was anything like what you describe..although the wet balsa was wet it was still very strong and difficult to remove, except for the wettest part in about a 6" radius of the penetration. I probably replaced more than was necessary but the 23 year old balsa (at the time, in 2013) that remained in the boat was every bit as good as the new balsa that went in.
-Mike
The reality with C Dory's in comparison to many other cored boats--and probably the secret to successful cored under water hulls, is that there is adequate glass on the bottom or outside of the hull. Many cored hulls do not have adequate glass outside the core. For example I have seen several Camano Trolls that have been slammed against pilings and the impact left quite a dent in the side of the hull. The core was crushed, and some damage to the in-adequate outer glass. Looking at a relatively new large sport fisher which had core delamination--there was both inadequate glass, and what appeared to be poor adhesion between layers of glass..
The only failures that I am aware in the C Dorys of have always been water intrusion. There were a couple exceptions which apparently were poor adhesion of layers at build. There were at least two boats replaced by the factory because of this many years ago. Water intrusion seems more common in ares with freeze thaw cycles--as one might expect. I have been consulted on a few boats which had problems where the owner did not want the issue disclosed on the list. Never saw or heard of balsa reduced to powder--if that happens, then there is zero core support--and it was poor construction.
As for running speeds--The boats are pretty much limited to less than 30 knots--both due to design and power plants. Many of us run the boats in chop up to 2 feet, with bow down, and may slow down--but our average cruising speed is about 20 mph. With the Tom Cat 255, our average cruising speed was closer to 25 mph, and we went up Perdido Bay from the ICW to our home at 35 mph in 2 to 2 1/2 foot chop many times--no problems with core.
I purchased a C Dory 25 which had been abused (left out in the weather in New Jersey for at least 2 winters.) We had to replace the raised cockpit floor due to balsa failure around the unsealed hatch openings, and then a 200+# crew member jumping on the floor. The owner admitted to the boat pounding. The tabbing of the forward bunk platform had come loose, as some of the tabbing of the console molding. But there was no evince of core delimitation, or water intrusion. (I did multiple core drill samplings--when I pulled all of the screws holding the "L" brackets which secured the wooden interior to the hull and replace them with fiberglass and epoxy tabbing.)
As for "Bargains"--they do exist--usually older boats, old power plants. The ones with 50 hp are going to barely plane--but kept light they will. Most folks who have bought those have repowered. The price is what a willing buyer is willing to pay what a willing seller is willing to accept. The reality is that the boats hold up far better than most, because they are well constructed, and are very simple. Plus there have been very few design changes thru the years...
I am sure that you will enjoy the Sea Cat 25 SL5--as you are aware there were changes to the hull thru the years. The mid 90's boats are great, except they have that terrible organic substance "wood" as part of the construction: frames/bulkheads/stringers/transom. The Honda 130's are really closer to the 115's than the 150's, but good engines--but you probably already know all that.
Come on down to Apalachicola, and meet some of the gang--you will be very welcome. Some of us stay in our boats or RV's at the site. We pass the hat to help Marc defray some of the costs of the great food and rental of the facility. But folks pay what they want..
The only failures that I am aware in the C Dorys of have always been water intrusion. There were a couple exceptions which apparently were poor adhesion of layers at build. There were at least two boats replaced by the factory because of this many years ago. Water intrusion seems more common in ares with freeze thaw cycles--as one might expect. I have been consulted on a few boats which had problems where the owner did not want the issue disclosed on the list. Never saw or heard of balsa reduced to powder--if that happens, then there is zero core support--and it was poor construction.
As for running speeds--The boats are pretty much limited to less than 30 knots--both due to design and power plants. Many of us run the boats in chop up to 2 feet, with bow down, and may slow down--but our average cruising speed is about 20 mph. With the Tom Cat 255, our average cruising speed was closer to 25 mph, and we went up Perdido Bay from the ICW to our home at 35 mph in 2 to 2 1/2 foot chop many times--no problems with core.
I purchased a C Dory 25 which had been abused (left out in the weather in New Jersey for at least 2 winters.) We had to replace the raised cockpit floor due to balsa failure around the unsealed hatch openings, and then a 200+# crew member jumping on the floor. The owner admitted to the boat pounding. The tabbing of the forward bunk platform had come loose, as some of the tabbing of the console molding. But there was no evince of core delimitation, or water intrusion. (I did multiple core drill samplings--when I pulled all of the screws holding the "L" brackets which secured the wooden interior to the hull and replace them with fiberglass and epoxy tabbing.)
As for "Bargains"--they do exist--usually older boats, old power plants. The ones with 50 hp are going to barely plane--but kept light they will. Most folks who have bought those have repowered. The price is what a willing buyer is willing to pay what a willing seller is willing to accept. The reality is that the boats hold up far better than most, because they are well constructed, and are very simple. Plus there have been very few design changes thru the years...
I am sure that you will enjoy the Sea Cat 25 SL5--as you are aware there were changes to the hull thru the years. The mid 90's boats are great, except they have that terrible organic substance "wood" as part of the construction: frames/bulkheads/stringers/transom. The Honda 130's are really closer to the 115's than the 150's, but good engines--but you probably already know all that.
Come on down to Apalachicola, and meet some of the gang--you will be very welcome. Some of us stay in our boats or RV's at the site. We pass the hat to help Marc defray some of the costs of the great food and rental of the facility. But folks pay what they want..