Bertram 63 Sinks Off SC Coast

The Main Sand Box for bertram31.com

Moderators: CaptPatrick, mike ohlstein, Bruce

Tony Meola
Senior Member
Posts: 6906
Joined: Jun 29th, '06, 21:24
Location: Hillsdale, New Jersey
Contact:

Post by Tony Meola »

There is one thing we all forget, sometimes hitting a wall of water is like hitting a brick wall. We don't know what size wave he hit or how he hit it. I still say, boats don't come apart like that even ones that are not built well.

If this was the boat's first trip out after being built, then I would say that is some serious quality control. But the boat was several years old. If there was going to be hull failure, it would have started to show up before this incident. That hull would have been full of stress cracks long before this. Especially the way that thing came apart.

The shame is, there will always be speclation because no one but those on board really know what happened and it looks like they may not even know. Hard to beleive, but hey stranger things have happened.
Raybo Marine NY
Senior Member
Posts: 895
Joined: Jan 3rd, '07, 00:28
Location: Lindenhurst, NY
Contact:

Post by Raybo Marine NY »

Charlie- while the buoy might have a steel skeleton, the top of it IS a PVC pipe, with a alum. radar reflector on it.
User avatar
JP Dalik
Senior Member
Posts: 1317
Joined: Jun 30th, '06, 21:03
Location: Pt. Pleasant NJ
Contact:

Post by JP Dalik »

Wonder if Bertram is having any manufacturing issues today?

Wonder if you went to their yard if you'd see any boats that might be getting repaired for structural issues?

Wonder why the Bad Company boat didn't come apart when it hit a whale on the west coast.

Just wondering,,,,,,,,,,,,,,,,,,
KR


JP
1977 RLDT "CHIMERA"
captbone
Senior Member
Posts: 442
Joined: Feb 4th, '07, 15:50
Location: United States

Post by captbone »

I am in shock that the buoy is still in question.


The radar reflector is not even bent. Their is no real damage below the waterline on the hull. Not a chain rub, not a dent, nothing to the bottom.

The rudder post and strut damage looks exactly like damage sustained from impact with the bottom. The force of hitting bottom has to be great. The boat was also traveling on the bottom according to the divers.

The logic seems to indicate that the boat came part. That is much more logical then the magic buoy on the grassy nole.
jspiezio
Senior Member
Posts: 882
Joined: Nov 25th, '07, 07:21
Location: Long Island, NY

Post by jspiezio »

captbone wrote:I am in shock that the buoy is still in question.


The radar reflector is not even bent. Their is no real damage below the waterline on the hull. Not a chain rub, not a dent, nothing to the bottom.

The rudder post and strut damage looks exactly like damage sustained from impact with the bottom. The force of hitting bottom has to be great. The boat was also traveling on the bottom according to the divers.

The logic seems to indicate that the boat came part. That is much more logical then the magic buoy on the grassy nole.
Look at those photos more closely, there is no strut damage.
User avatar
Charlie
Senior Member
Posts: 357
Joined: Jun 29th, '06, 12:59

Post by Charlie »

No Raybo here read the buoy specs below. In the pics of the buoy you can plainly see what appear to be prop strikes. One strut is flattened in the leading edge. The height of just the ABS buoy part is 110 inches. According to the info the buoy floats with about 50% of that part out of the water. That means about 55" of hard plastic close cell foam cored (very hard). Sure looks to me that is what took the hull side out and the next wave did the rest, peeled back the bow deck and destroyed the forward hull.

Here are the buoy specs.
FIGURE 1, SCDNR, 200# with REFLECTOR
Height: 161.0”
Diameter: 24.0”
Visibility: 125.0”
Weight: 200 lbs.
Features:
• Durable ABS plastic outer shell
• Closed cell Polyurethane Foam filled
• Internal and external radar reflector
• color: yellow
• 24" x 24" aluminum radar reflector and day marker
• Heavy Duty steel internal frame with 1" steel yoke
• Internal radar reflector
Raybo Marine NY
Senior Member
Posts: 895
Joined: Jan 3rd, '07, 00:28
Location: Lindenhurst, NY
Contact:

Post by Raybo Marine NY »

I dont think anyone will ever agree on anything, I dont think I am going to comment any further either. Some will listen to one story, some another, thats understandable.

I would just steer way clear of these things, they put our steel buoys to shame.

Image

Image
jspiezio
Senior Member
Posts: 882
Joined: Nov 25th, '07, 07:21
Location: Long Island, NY

Post by jspiezio »

Here is a closer look at the photo of the struts. It almost looks like there is just paint gone from the leading edge and the result is an optical illusion that looks like damage from this angle. Did the divers report that the struts were damaged? IIRC the divers had reported that the visible (starboard) strut was in good condition. Does anyone know this?

Image

Charlie- I am definitely not a Bertram hater. My family has owned 6 Bertrams over the years, and I have always thought of them as top quality. I am in no way an expert, but the condition of this hull is frightening to me. Honestly, I would expect that if I hit that bouy at speed in a 31B the hull would not have failed like this B63 did. As I stated before, I know from experience that an old B25 can hit a steel can bouy in the Fire Island inlet at pretty good speed and float away with nothing but scratches on the gelcoat.
Is it plausible, as some on YF have posited, that the boat was damged through poor handling/docking or poor storage and that the hull sides had been compromised? Again I am just asking because as God is my witness I do not know, but I would like to find out.
User avatar
randall
Senior Member
Posts: 2623
Joined: Jun 29th, '06, 09:29
Contact:

Post by randall »

anchor drops unintentionally...big wave slams it into upper bow....water fire hoses into hull....just a thought.

couldnt happen to a 25 or a 31 but.......cored above the waterline.
User avatar
mike ohlstein
Site Admin
Posts: 2382
Joined: Jun 29th, '06, 11:39
Location: So many things seem like no-brainers until you run into someone with no brain.
Contact:

Post by mike ohlstein »

Looking at those pictures makes me wonder where the propane tanks were stored.......
Mike
Mean Team Leader
PREDATOR

Burn Oil
Eat Food
1973 FBC 1286 0273-315
User avatar
In Memory of Vicroy
Senior Member
Posts: 2340
Joined: Jun 29th, '06, 09:19
Location: Baton Rouge, LA

Post by In Memory of Vicroy »

It sure makes me feel a lot better to see how butt ugly the 63 really is. I'm not saying "good riddance", but my 37 year old B31 sho' looks a lot better and has run over some real nasty stuff at speed and remains above the surface.

No excuse for making butt ugly boats.

UV
User avatar
Charlie
Senior Member
Posts: 357
Joined: Jun 29th, '06, 12:59

Post by Charlie »

Got to agree I don't think my 35B would open up like that from a buoy strike. We had a guy drive his 33B into a steel channel marker a few years back. The boat was totaled; but did not sink. Calm waters. He hit it dead center and crushed the bow really bad. There may be something to be said for the boat's anchor chain maybe hooking the bottom after the buoy opened the anchor locker. I do believe this boat was surveyed as part of the sale and Bertram was to survey all 63B's after the delamination problem. you would think impending hull failure could have been detected.
User avatar
Carl
Senior Member
Posts: 5907
Joined: Jul 5th, '06, 06:45
Location: Staten Island NY

Post by Carl »

Look at that Rudder, Rudder Shaft and Rudder Log!!!....something sure ripped the hell outta that.

Something was hit or picked up that didn't want to go along for a ride.

Bertram says they Checked out he paint transfer...mmm..okay maybe... biased...


Anybody ever stop a boat real quickly when running fast, bow diggs in...at least on mine it does.

Stuff the nose at 25knts... in some seas...lots of force at work.
Now... if the the bow area did take a shot from a buoy... it may have been comprimised, (hit a 200lb deer with a car going 25knts, bound to leave a mark somewhere) do it with a 110,000lb plastic yacht...
now you have a comprimised Bow that gets stuffed, transom is comprimised...kinda starts to make some sence.
User avatar
Ironman
Senior Member
Posts: 527
Joined: Jun 30th, '06, 11:06

Post by Ironman »

Last I heard.. Bad Company.. a Viking..sent back to florida.. was totaled..
They barely made it in from 20miles out on a calm day,I got pics on my harddrive somewhere...
They removed the intake from the genny to remake a crash pump..

I wonder if a whale could jump high enough to land on the bow structure..
That happened here a few years ago with a 26ft boat near ventura.. messed up the boat & the skipper was ejected & the crew wasnt capable of turning around to fish him out..
(Give your crew a quick block of instruction on how to operate your boat in that event)
Wayne
captbone
Senior Member
Posts: 442
Joined: Feb 4th, '07, 15:50
Location: United States

Post by captbone »

If the anchor came loose and hooked bottom at speed, I would expect that the chain/rope would cut deep into the hull at the bow. I feel that the rode would have pull thru down to the waterline. You figure the force of a 63fter going 24kts is an amazing amount of energy. Plus the angle would have the chain going against the bottom and the bow below the waterline.

It would have to been an all chain rode of a couple hundred feet also.

Just my 2 cents
User avatar
coolair
Senior Member
Posts: 819
Joined: Apr 5th, '09, 10:10
Location: South Houston,tx
Contact:

Post by coolair »

This is where i am at with the whole deal, the 25+ pages on yachforums is filled with enough BS and speculation and letters from bertram presidents, and hate mail etc. The only ones that really know what happened are the ones on board, and davey jones... and if it really came apart instantly, well the ones on board may not even know. I am sure with all the "science"(accompanied with corporate PR) we will find out what they THINK happened. I just hope we can be better than all the folks on yachtforums and somehow get the real facts and and go from there. we all know that a brand new 63ft multimillion dollar BERTRAM shouldn't be on the bottom of the ocean. its easy to just start pointing fingers at Bertram, or the Capt. but in the great ocean, the reality is anything goes, anything can happen, rouge wave.. whale, container, glass did cure right(buddy has a brand new custom bay boat, damn stringers delaminated from hull, something happened that day with the glass lay up)... shit happens.
Thanks
Matt
Hull #315 - 854
jspiezio
Senior Member
Posts: 882
Joined: Nov 25th, '07, 07:21
Location: Long Island, NY

Post by jspiezio »

coolair wrote:This is where i am at with the whole deal, the 25+ pages on yachforums is filled with enough BS and speculation and letters from bertram presidents, and hate mail etc. The only ones that really know what happened are the ones on board, and davey jones... and if it really came apart instantly, well the ones on board may not even know. I am sure with all the "science"(accompanied with corporate PR) we will find out what they THINK happened. I just hope we can be better than all the folks on yachtforums and somehow get the real facts and and go from there. we all know that a brand new 63ft multimillion dollar BERTRAM shouldn't be on the bottom of the ocean. its easy to just start pointing fingers at Bertram, or the Capt. but in the great ocean, the reality is anything goes, anything can happen, rouge wave.. whale, container, glass did cure right(buddy has a brand new custom bay boat, damn stringers delaminated from hull, something happened that day with the glass lay up)... shit happens.
Coolair- I never looked at YF until this happened. What I see does not impress me so far, lots of blow hards. Something that this forum is thankfully in short supply of.
User avatar
In Memory Walter K
Senior Member
Posts: 2912
Joined: Jun 30th, '06, 21:25
Location: East Hampton LI, NY
Contact:

Post by In Memory Walter K »

It strikes me that there may be a length after which the stresses and strains of a flexing boat and the vibrations of running may be too much to ask of any coring lamination. I'm sure there are tests that were made to prove that theory (of mine) wrong, but as was just said, resins/curing/etc. are all variables that are not always perfect, and since everything is finally sealed up, there's no way of knowing until something goes wrong. Glue any two very long pieces of fiberglass together with something softer sandwiched in between and twist it from either end, and unless everything is perfect, I suspect there will be a separation, however small, somewhere. That separation never heals when the twisting stops. I guess I'll never be too comfortable with coring after a B-31.
IRGuy
Senior Member
Posts: 1767
Joined: Jun 29th, '06, 07:48
Location: Wilmington, NC

Post by IRGuy »

Lets face it.. when you venture out into the ocean in a small boat (and by "small" boat I mean anything smaller than maybe 100', maybe even larger) you are subjecting yourself and your crew and boat to a myraid of unforseen, invisible, and occasionally fatal dangers.

How many ships do you occasionally hear about which simply disappear at sea?

I have seen construction equipment tires 2' wide and probably 8' in diameter floating with maybe the top 10" barely visible above the water, 300 miles offshore. Imagine hitting that at almost any speed. We all have seen pieces of timber, trees, barrels, wooden boxes, refrigerators and other strange stuff floating. I have been on boats that ran over what we saw astern as a floating telephone pole. I know of one sailboat that had their prop caught in a tarpaulin floating just before the surface that almost pulled the prop shaft out of the boat.

The worst fear I have is hitting a container full of wooden furniture or sneakers or other buoyant material, so the container floats just breaking the surface, at night. I have a friend who hit something hard at night in the North Atlantic and spent over two months alone in a life raft. (He is said to hold the record for the longest time surviving alone in an inflatable craft.)

In the case of the Bertram, as Coolair says, we may never know what really happened, and in fact the crew who was aboard might not even know. All the comments I have read are interesting, but all are based of suspicion and none are based on facts. Some are based on what I suspect is CYA.

My take from all this is.. be careful out there, prepare as best you can for unexpected emergencies, keep a sharp lookout, and expect Mother Nature to creep up behind you one day and bite you in the ass.
Frank B
1983 Bertram 33 FBC "Phoenix"
--------------
Trump lied! Washington DC isn't a swamp.. it is a cesspool!
Tony Meola
Senior Member
Posts: 6906
Joined: Jun 29th, '06, 21:24
Location: Hillsdale, New Jersey
Contact:

Post by Tony Meola »

If you guys think Yacht Forum is bad, try the Hull Truth. Those guys are brutel. Raybo can attest to that. I think Charlie has felt that sting also.
User avatar
randall
Senior Member
Posts: 2623
Joined: Jun 29th, '06, 09:29
Contact:

Post by randall »

i got banned years ago(with a bunch of folks im still friends with, like the guy who started this thread) when they changed ownership.
User avatar
coolair
Senior Member
Posts: 819
Joined: Apr 5th, '09, 10:10
Location: South Houston,tx
Contact:

Post by coolair »

Didn't mean to rant too much, had a few beers and was on the soap box, but i to have never really read hull truth or yacht forms until this. really this is the only forum i read. Still haven't read hulltruth on this. nore do i think i will, and other than looking at pics i am pretty much done with yachtforms too, all the info i need is on here
matt
Thanks
Matt
Hull #315 - 854
BCBertie
Senior Member
Posts: 163
Joined: Nov 3rd, '06, 14:08
Location: California, British Columbia

Post by BCBertie »

IRGuy wrote:Lets face it.. when you venture out into the ocean in a small boat (and by "small" boat I mean anything smaller than maybe 100', maybe even larger) you are subjecting yourself and your crew and boat to a myraid of unforseen, invisible, and occasionally fatal dangers.
I come from a long line of ship captains, from barks through battleships. The most-repeated saying in my family has been:

"Oh Lord, thy ocean is so big...
and my ship is so small."

John
User avatar
Carl
Senior Member
Posts: 5907
Joined: Jul 5th, '06, 06:45
Location: Staten Island NY

Post by Carl »

BCBertie wrote: "Oh Lord, thy ocean is so big...
and my ship is so small."

John

So true
Raybo Marine NY
Senior Member
Posts: 895
Joined: Jan 3rd, '07, 00:28
Location: Lindenhurst, NY
Contact:

Post by Raybo Marine NY »

the ocean and mother nature are not a force to be reckoned with.

Seeing a 670 Bertram in a picture like this, everyone wants more speed, which means lighter weight.

To think people crossed the oceans hundreds of years ago is simply amazing, that took huge brass balls.





Image
User avatar
JohnCranston
Senior Member
Posts: 737
Joined: Jul 8th, '06, 17:50
Location: Spring, TX; Freeport TX

Post by JohnCranston »

Pretty scary stuff that I'm hearing on this thread...I think that I'll go back to wade fishing. After being rescued by the Coast Guard several years ago, a hundred miles offshore, this kind of verbage still gives me the creeps.
I'll never ruin a $50 buzz with a $4 sandwich
User avatar
coolair
Senior Member
Posts: 819
Joined: Apr 5th, '09, 10:10
Location: South Houston,tx
Contact:

Post by coolair »

Slow and steady wins the race.. i want solid structral construction with pretty good fuel burn, scew speed! if you want to go fast buy a center console and enjoy geting your teeth knocked out.
In that picture you posted, it reminds me of ones of race boats, and when they hit... smash boat comes apart.
Thanks
Matt
Hull #315 - 854
User avatar
coolair
Senior Member
Posts: 819
Joined: Apr 5th, '09, 10:10
Location: South Houston,tx
Contact:

Post by coolair »

<embed src="http://www.metacafe.com/fplayer/yt-2oBr ... at_sea.swf" width="400" height="345" wmode="transparent" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" allowFullScreen="true" allowScriptAccess="always" name="Metacafe_yt-2oBr8bHuZ1k"> </embed><br><font><a href="http://www.metacafe.com/watch/yt-2oBr8b ... _sea/">Top Ten Most Awesome Boat , Crashes, Collisions, Sinkings and Amazings Sights at Sea</a> - <a href="http://www.metacafe.com/">Click here for another funny movie. </a></font>

about 1 min. in check out what happed to the front of this race boat.
Thanks
Matt
Hull #315 - 854
User avatar
Dug
Senior Member
Posts: 2256
Joined: Jun 29th, '06, 11:04
Location: Worcester, MA

Post by Dug »

Here is all I can say.

First of all, EVERYTHING that Raybo has said so far, has proven to be true. When he described the extent of the damage, the pictures proved it out. I personally think he has no incentive to argue or lie about anything on this topic at this point. I ain't arguing with him. He appears to have been correct in his statements. Kudos, and thanks Raybo.

Second, thank the lord that the people on board that boat were ok. I just finished looking at the pictures, and holy hell, that must have been incredible, whatever it was.

Time will tell, as it has been stated. Then again it might not. But holy shit. That boat disintigrated. Wow. What the hell happened to such a beautiful ride...

Dug
jspiezio
Senior Member
Posts: 882
Joined: Nov 25th, '07, 07:21
Location: Long Island, NY

Post by jspiezio »

At 1:16 that close up shot looks a lot like photos of a 63 bertram that we've all been looking at.
User avatar
Rocky
Senior Member
Posts: 690
Joined: Nov 23rd, '08, 10:36
Location: Northern California

Post by Rocky »

I completely agree with you Dug, and time will tell, or not.You can speculate till your blue in the face but that won't get you the true answer.
BC Berti John, I had that phrase "Lord the ocean is so large and my boat is so small" on my Skipjack for years, so true. I do very much dislike any kind of structural coring I would think Bertram would never build though, as I destroyed a Whaler's hull on a "normal day" on the ocean, and witnessed another Whaler's hull come apart as well when we were commercial fishing.
Raybo Marine NY
Senior Member
Posts: 895
Joined: Jan 3rd, '07, 00:28
Location: Lindenhurst, NY
Contact:

Post by Raybo Marine NY »

Image


Image

Image
User avatar
randall
Senior Member
Posts: 2623
Joined: Jun 29th, '06, 09:29
Contact:

Post by randall »

what exactly am i looking at there?....it can't be what i think it is.
User avatar
CaptPatrick
Founder/Admin
Posts: 4161
Joined: Jun 7th, '06, 14:25
Location: 834 Scott Dr., LLANO, TX 78643 - 325.248.0809 bertram31@bertram31.com

Post by CaptPatrick »

randall wrote:what exactly am i looking at there?....it can't be what i think it is.
That my friend is what delaminated core looks like under water... Close up of a configuration called "scored". Scored foam are cubes of core held together by a scrim backing, making it easier to mold into curved surfaces.

Does look a bit like stacked square groupers... The translucent green in the 2nd image is the fiberglass that once apon a time was adhered to the foam.

Bertram is really learning the hard way about cored hulls...
User avatar
In Memory Walter K
Senior Member
Posts: 2912
Joined: Jun 30th, '06, 21:25
Location: East Hampton LI, NY
Contact:

Post by In Memory Walter K »

Am I correct in assuming that even under a severe hit/impact, they should have stayed together? What little basic physics knowledge I have tells me that once separated, structural integrity goes bye-bye.
User avatar
CaptPatrick
Founder/Admin
Posts: 4161
Joined: Jun 7th, '06, 14:25
Location: 834 Scott Dr., LLANO, TX 78643 - 325.248.0809 bertram31@bertram31.com

Post by CaptPatrick »

Am I correct in assuming that even under a severe hit/impact, they should have stayed together?
The cellular structure of the various types of "structural" foam has very little actual strength.

Applying a skin of fiberglass, or other laminate, whether using polyester, vinylester, or epoxy only creates a surface bond between the two materials. As the cells of the foam seperate internally, through impact, flexing, or other stress, the bond between the fiberglass and foam is effectively lost. Once delamination starts, the two materials act independantly from one another which can rapidly lead to more delamination. The only foam still in contact with the fiberglass skin was the surface of the foam.

As I've said many time before, foam coring of hulls, especially on larger vessels, isn't a good thing. And there are very few boat builders who build structurally sound cored hulls over 40'. Garlington Landeweer is one of them...

Obviously, Bertram isn't one of them, sad to say.
User avatar
Carl
Senior Member
Posts: 5907
Joined: Jul 5th, '06, 06:45
Location: Staten Island NY

Post by Carl »

If a hull was constructed correctly would we expect to see this kind of delamination? Even in the case of a severly impact?

How does a cored boat will break apart when constructed properly?


Beat me to it...

So even if constructed "correctly" this type of build can fail if impacted hard enough to break the inner foam apart...doesn't sound like something I'd want to be out in the ocean with.
Last edited by Carl on Dec 29th, '09, 17:51, edited 1 time in total.
User avatar
randall
Senior Member
Posts: 2623
Joined: Jun 29th, '06, 09:29
Contact:

Post by randall »

i repaired a large deck piece for a friend . it covered a built in gas tank. it was two glass skins sandwiched around 12 inch squares of scrap plywood. once the water got in it ran down the avenues and the cross streets. i replaced it with a solid piece and reused the top skin. this construction method on a 63 foot boat makes NO sense to me.
User avatar
CaptPatrick
Founder/Admin
Posts: 4161
Joined: Jun 7th, '06, 14:25
Location: 834 Scott Dr., LLANO, TX 78643 - 325.248.0809 bertram31@bertram31.com

Post by CaptPatrick »

sim wrote:If a hull was constructed correctly would we expect to see this kind of delamination? Even in the case of a severly impact?

How does a cored boat will break apart when constructed properly?
Refering only to Garlington, who's work and craftsmanship I know first hand, I don't know of any hull failures to date. They use Airex foam, which is far more plasticised, (tougher & less brittle), than Divinycell, they uses solid sheets rather than scored sheets, their layups are done with a healthy addition of carbon fiber and Kevlar, they may be using vinylester, but I think they're using epoxy. Everything is vacuum bagged, resin infused, and kept to exacting tollerances. They employ strict quality control at every stage of the construction. They've been doing their boats like this for over 20 years, and up to 80'.

Built correctly, as Garlington does it, they don't break apart...

Quoting Garlington:

"The broad based experience of our yard is reflected in the level of excellence we maintain from conception to completion of each yacht. Design innovations, detail, scrutiny, and exacting craftsmanship are all necessary to deliver this level of finish and performance. It is our firm belief that pride in the manufacturing of our product will result in pride of ownership.

To sum it all up, we've set out to accomplish a modern ideal. Not to be visionaries but to maintain respectable stature as leaders in the industry. To constantly strive for the top notch. To complete every task with the pride it deserves. Every boat to be launched with the great sense of satisfaction. In a day when rapid innovation is a main ingredient to success we fancy ourselves as achievers. We don't get pleasure from saying "we build the best" besides...that's the customer's decision. We get personal satisfaction from knowing that our daily accomplishments add up to the construction of what we believe in."
Raybo Marine NY
Senior Member
Posts: 895
Joined: Jan 3rd, '07, 00:28
Location: Lindenhurst, NY
Contact:

Post by Raybo Marine NY »

they make it squares so that the solid piece does not warp, it is a common practice in deck hatches.

Single screw into that core over 10-20 years and its a goner.
But you can have another hatch, same exact construction method, with beveled core so that the screws holding the hatch down did not go into wood, and that hatch could very well last forever.

Even one piece of wood will act as a sponge over time.
User avatar
randall
Senior Member
Posts: 2623
Joined: Jun 29th, '06, 09:29
Contact:

Post by randall »

i can understand that.......63 foot hull....not so much.

not saying it cant be done...obviously it can. but considering the forces at work it dosent appeal to me.
Raybo Marine NY
Senior Member
Posts: 895
Joined: Jan 3rd, '07, 00:28
Location: Lindenhurst, NY
Contact:

Post by Raybo Marine NY »

i thought we were talking about squares of plywood in a hatch, was the hatch you did balsa core or squares of ply?
User avatar
Rocky
Senior Member
Posts: 690
Joined: Nov 23rd, '08, 10:36
Location: Northern California

Post by Rocky »

Oh my god, in that first picture if that is a hand holding one side of the laminate sandwhich it is VERY thin, compare it to the fingers holding it! This is for a 63 footer?
User avatar
CaptPatrick
Founder/Admin
Posts: 4161
Joined: Jun 7th, '06, 14:25
Location: 834 Scott Dr., LLANO, TX 78643 - 325.248.0809 bertram31@bertram31.com

Post by CaptPatrick »

Pure theory and practical application of theory can be worlds apart...

The Holy Grail of boat builders is to create a very light, but very strong hull. So in theory, light weight skins bonded to thick, but very light weight cores will yield a very strong hull that is as strong, or stronger, and less flexible as a heavy single skin.

The theory of composite laminates is that the sandwich, (core bonded to two outer skins), is far stronger as a whole than the combined strength of the individual parts.

The skins are described as a compression skin and a tension skin. When pressure is applied one side of the sandwich that skin becomes the compression skin and the opposite side becomes the tension skin.

The core thickness greatly determines the overall theoretical strength of the sandwich. The greater the thickness, the greater the strength. See: Basic Composite Structure and Benefits of Core Materials

When pressure is applied and the sandwich deforms, the force is transmitted through the sandwich creating a biased force through the core and a high resistance between the bonded skins creating the ultimate strength.

However, this biased, (diagonal), transmission of force also creates a shearing force at the bond lines between the three components. So, in practical application the strength of both the bond itself and the strength of the core by itself determine how much or how little force it takes to reach a failure point.

The engineering of this type of construction for a boat hull is quite involved and beyond the abilities of the average boat builder/designer. It's one thing to design a composite sandwich panel for a door, bulkhead, or hatch plate. Not much knowledge is required. But for a boat hull, the engineering and physics required for practical application to live up to theory borderlines on rocket science.

Size does matter... And the ocean isn't a flat smooth plane.

A smaller boat has less flex and smaller parameters within the flexural range, primarily due to the reduced surface area in contact with the water. The larger a boat becomes the more wetted surface area it has and the more forces from the water beneath it are transmitted throughout the hull. A cored hull that might be plenty strong for a 30' boat, becomes a dismally weak hull for a boat twice the length.

A boat hull must be strong enough to withstand the forces that it will be subjected to, but at the same time it needs to be flexable enough not to be broken apart by those same forces. The design balance between strength and flexibility of a hull is a complex matter....
User avatar
randall
Senior Member
Posts: 2623
Joined: Jun 29th, '06, 09:29
Contact:

Post by randall »

patrick....thanks...that is exactly what i was thinkin. i fish a bit on a sixty foot bertram. one night we head out in 6 to 8s and NOT too throttled back. bigger boat...bigger fulcrum. the forces being exerted on each "pound" as the bow drops out of the air and blasts the next wave must be pretty high. it was interesting to me that even though you could do things you couldnt in a smaller boat you still took the beating. so does the boat.
User avatar
In Memory Walter K
Senior Member
Posts: 2912
Joined: Jun 30th, '06, 21:25
Location: East Hampton LI, NY
Contact:

Post by In Memory Walter K »

That's what I meant in my first post. A 63' hull might be more succeptible to delamination than a 43 footer just by virtue of the additional length and the stresses and strains the sea would put on her. What's ok for one might not be the case for the other. The only cases we have heard of have been with the bigger boats.
User avatar
Rocky
Senior Member
Posts: 690
Joined: Nov 23rd, '08, 10:36
Location: Northern California

Post by Rocky »

Capt Pat, then given this theory about maintaining light and strength with enough flexability, it would make more sense to use this Airex you spoke of which is more plastisized then the easy shearing of the other foam? It seems the foam this bertram has did not have a core material that was strong enough within itself.
User avatar
Carl
Senior Member
Posts: 5907
Joined: Jul 5th, '06, 06:45
Location: Staten Island NY

Post by Carl »

[quote="CaptPatrickBuilt correctly, as Garlington does it, they don't break apart...[/quote]

Pretty much "Everything" can break apart..just have not found the right circumstances and hopefully they would be outside the range of the boats use.

I'm thinking in a testing lab or if a boat/yacht fell from a Ships lift onto a concrete pier...just wondering how a properly cored Hull structure would give way. Delaminate or fracture as a whole. I'd guess it should fracture as a whole...
User avatar
randall
Senior Member
Posts: 2623
Joined: Jun 29th, '06, 09:29
Contact:

Post by randall »

Raybo Marine NY wrote:i thought we were talking about squares of plywood in a hatch, was the hatch you did balsa core or squares of ply?

it was squares of what looked like scrap plywood. it was very rotten. i replaced it with a solid piece of "signboard" warping isnt a factor as it is screwed down around the perimeter......now through solid epoxy. it just seemed mickey mouse to me in its original state. about 3x4.
User avatar
Rawleigh
Senior Member
Posts: 3432
Joined: Jun 29th, '06, 08:30
Location: Irvington, VA

Post by Rawleigh »

I would think that the water pressure from the forward momentum would cause more delamination than a stationary accident would, but to what extent I have no clue.
Rawleigh
1966 FBC 31
Locked

Who is online

Users browsing this forum: Bing [Bot], Google [Bot] and 13 guests