PDA

View Full Version : Kevlacat construction? and front bulkhead crack



Flex
11-05-2014, 08:47 AM
Just a question for those in the know.
I have a newly acquired 1999 5.2 Kevlacat.
After crawling all over the hull and inside every crevice the construction seems very high standards, except for a few spots.

I noticed a crack inside the cab under the inspection hatches on the bulkheads. where it is glassed to the tunnel they are both cracked vertically along the bulkheads. This is the most forward one, directly under the steering wheel/entrance to the cab on both side of the hull. anyone elses like this?
This bulkhead also seems extremely thin. It had been repaired by previous owner but was an average job. so im looking at getting it professionally done. Just makes me wonder what the others look like. Im tossing up putting inspection ports all over for a look.

Also I noticed a small hole maybe 6mm in the bottom of all the bulk heads I have access to. I assumed each compartment was sealed, But its obviously not. anyone elses like this? how many bulkheads/compartments are inside each 5.2? does anyone know?

cheers all.

bannana
11-05-2014, 09:06 AM
Mate I had a 3000 kc and had the same holes in the bottom of each bulkhead. Over and above there was no centre bulkhead and water could run easily from one tunnel to the other. I sold the boat as I wasn't prepared to to be 100ks offshore in a boat that could sink in a couple of minutes if I was to hit something and penetrate the hull.
Only recently my thru hull transducer came loose and I took on water in my Noosacat. If I was in my Kevlacat I would have a good insurance claim and the boat would be at the bottom of the ocean.
My advice is buy a life raft for piece of mind.

stevemid
11-05-2014, 11:01 AM
Don't have Kevlacat specific knowledge but just built a cat and I've attached pictures of the bulkheads for you and provide this just as background knowledge. The purpose of the bulkheads is to maintain the structural integrity of the twin hulls. As you can see bulkheads are laminated into each hull and to the tunnel and they function to keep everything together. So I would be having those cracks checked by a professional who knows your design. If you can get access, repairing them wouldn't be so difficult: clean 'em up, rough 'em up, and incorporate (roller it down) a layer or two of 450 double bias to both sides, overlapping the crack on both sides by at least 100 mm. On mine, where cutouts for doorways potentially weaken the bulkhead, 10mm of the core material was routed out around the cutout and replaced with a sausage of wetted out strands of unidirectional fibreglass. You can see that the bulkhead doesn't have to be massive to do its job and it should give you confidence that the repair suggested would be sufficient. Regarding the holes at the bottom of each bulkhead? These seem too small to be limber holes which normally are about 25mm in diameter and allow water to escape to a place where it can be collected. My design doesn't have them and IMO 6mm would plug up too easily to be effective as a limber hole. Steve PS I have a main bulkhead every 2M and under-deck intermediates in each hull between the mains

Flex
11-05-2014, 05:24 PM
Hey Steve,
thanks for the info and pictures! Much appreciated
I don't think the repair will be very difficult at all. Easy access and not a huge crack., just a bit odd it's needed considering the reputation of KC.The bulkhead feels very very thin as we'll..Maybe 5-6mm and flexes back and forth very easily when pushed.So I'm wondering if it's just a divider and not a bulkhead at all?
are bulkheads usually capped by a thicker bit of timber/glass? Something to attach the floor to. This one seems to stop 20mm short of the floor and has a gap into the next chamber.
cheers

fromeo
11-05-2014, 08:20 PM
Hi Flex I have a 1990 5.2 , and it does not have any inspection hatches what so ever excepting at the transom bulk head which give access to the POD bolts . I am sure that all of the 5.2's non survey came out with sealed chambers and no inspection hatches . It may be possible that during its life inspection hatches were put in due to water ingress, as for the drain holes that's a misery to me . hope this helps . There are some members on this forum who have a great deal of knowledge on the 5.2 who actual knew the original owner Fred Temmick , They would be more than happy to help you.

Flex
11-05-2014, 08:29 PM
Thanks fromeo.

3 of the 5.2 KC I looked at in person all had square hatches under the cabin cushions. Like a little storage space under the deck up front. I assumed these where standard in all 5.2. So yours has no hatches in the floor under your cabin cushions either side of the hull?

Moray2004
12-05-2014, 06:58 PM
I have a 6.2m KC circa 1989. Not sure of the exact age but I believe it is the original model. I've owned it for about 12 years and personally knew the prior owner going back to about 1995. So the boat had about 6 to 7 years of service prior to this. I'm giving these details because it is relevant in the sense that I know that the boat has had a fairly easy life for most of its life. The previous owner hardly used her which is ultimately how I came to own it.

A couple of years after buying her I noticed that the floor had become soft and as an added bonus a fuel leak appeared. There are two inspections ports in the floor at the rear of the deck and in theory the fuel should have been contained within the bulkhead containing the fuel tanks, however, very small cracks/bug holes in the glass must have allowed the fuel to weep through and ultimate end up at the rear bulkhead. The engines needed replacement so I took the plunge and gave the boat a complete overhaul totally removing the floor from the transom all the way to the front of the hulls (including bunks). Had to cut out a section of the cabin wall to do this but it gave full access to all of the bulkheads and hull.

It revealed that the forward bulkheads from just inside the cabin to several back towards the stern had torn from the hull in places. The tears were not from the bottom of the hull across the tunnel. Rather there were evidently stress points which had caused the bulkhead to tear. The pics are at work but from memory the tears were where the tunnel curve kicks in. As you moved towards the stern the tears ceased. This makes sense since the impact and twisting would be worse towards the bow.
I was somewhat alarmed by this and ended up reglassing both sides of the bulkhead with several layers of glass mat and roving. I did the full extent of the bulkhead on the tunnel as well as the outer side of the hull. Went a bit overboard in hindsight and probably added god knows how much extra weight in the process.

After the full rebuild I installed two inspection hatches under the bunks beside the bulkhead that displayed the worst tearing. This enables me, with the aid of a torch, to peer in and check the integrity of my repairs. That was 8 years ago and it is in perfect condition.

Why was the floor rotten in the first place? It seems that the previous owner hardly ever used the boat and it sat under a very poorly arranged tarp on a slope facing the wrong way. Rainwater eventually filled up the deck and somehow got down into the hulls and the moisture killed the ply flooring.

The stainless steel tanks had suffered from corrosion and were pin holed something terrible. I was really surprised they were in such poor condition. As it turned out they were both completely stuffed and had been leaking for some time.

It was one hell of a job and not one I would ever like to do again. I seem to recall that the bulkheads were at about 400mm spacings. I even glassed the ones that were in perfect condition because I never wanted to rip off the floor again, ever.

So the long winded answer to your question is that yes, I have seen what I think you are referring to but in a 6.2m boat that has had a very easy life. Not being able to get in and see the condition of the bulkheads it is really anyone's guess as to how extensive the issue is. The only people who would really have a feel for it are those that have had the misfortune to have had to replace the floor or fuel tanks. Having said this I doubt you would find that it is confined to only one bulkhead.

I am a KC fan and at some point will upgrade to a newer KC. But the sealed bulkheads idea is poorly conceived in my view. The theory that you will never get water into your hull so you never have to get it out is fundamentally flawed. For example the fuel risers are glassed around but I would not consider them to be 100% waterproof. I also found water right up in the very front compartment because the previous owner must have screwed up putting it on the trailer and had hit her hard against the steel right beside the roller instead of resting hard on the roller. This resulted in a full depth cut through the glass (well above the water line) and presumably he used it so water go in there. So the water sat in there for years unbeknown to me until I gutted her. It would be far superior to have multiple sealed compartments, say 6 or 8 (3 or 4 per side) each connecting the bulkheads within each section (which would be say 3 or 4 bulkheads) and each with an inspection hatch. This way you would know with 100% certainty that there was no water anywhere in the hull and you could also get greater access along the length of the boat to check the bulkheads.

Hope this is of some use.

Moonlighter
12-05-2014, 08:16 PM
I know that Al Broughton up at Sea Trek Boats at Caloundra has done some pretty significant rebuilds/repairs on Kevlacats in the past few years, so i'd suggest a phone call to him might be worth your time. He will know what is under the floor and whether what you have found is if cosmetic or structural concern.

fromeo
12-05-2014, 10:07 PM
Thanks fromeo.

3 of the 5.2 KC I looked at in person all had square hatches under the cabin cushions. Like a little storage space under the deck up front. I assumed these where standard in all 5.2. So yours has no hatches in the floor under your cabin cushions either side of the hull?

Flex mine does have the both storage compartments port and starboard in the cabin where you mentioned , other than that no inspection hatches .

Flex
13-05-2014, 09:26 AM
Moray,
thankyou very much for the post. It's almost impossible to find information on kevlacat cracks in aussie built ones. I assumed they were all uncrackable!.I searched the net for months and never found a single issue aside 1 new model that had cracked.I wonder why yours and evidently mine have the issue.

im wondering if alot of them have cracking issues, but because they are all sealed no one really sees them? The ones with inspection ports are usually full of foam so it's hard to see as we'll.

thanks again. The crack on mine is only minor, it's a 99 model hull so it's not an ancient boat.
shouldnt be a hard fix, but annoying all the same.

Noelm
13-05-2014, 10:39 AM
I have seen a couple that needed repairs.

scottar
13-05-2014, 11:10 AM
Have seen plenty of cats with at least Gel Coat cracking where the tunnel meets the hulls at the transom. Have also drilled into a few to mount transducers over the years only to end up with puddles at my feet. One thing I can tell you about water and boats - It is a lot easier to let water out than keep water out. The individual compartments are a great idea and a safety feature but if I ever own one they will all have a bilge pump and waterproof inspection panel.

Moray2004
13-05-2014, 11:43 AM
Flex,

When something is fully concealed there is no way of knowing whether it is intact or not. Those who say that the build quality of KCs is awesome will never accept there could be cracking but they would be speaking on the basis of blind faith not fact. Those who have pulled up the floor are the only ones who would be able to give you factual advice. The saving grace is that I've never heard of a KC boat suffering a catastrophic failure, which would infer that even with some cracking of the bulkheads from the tunnel, it is still structurally ok. I don't believe that the cracking had just occurred prior to me replacing the floor. It would have been there for many years and presumably got a little worse over time. If left alone would it ever be an issue? Who knows, but I figured it was better to reinforce the hell out of it rather than take a gamble.

I've attached one pic which shows the cracking from the bottom of the bulkhead all the way up the tunnel and even partially across the top of the tunnel. Seems it was more extensive than I recalled last night. As I said in my earlier post it affected several bulkheads but I could not say exactly how many. What surprised me at the time was that the glass matting thickness seemed noticeably thinner at the tunnel interface compared to say 100mm away from the tunnel. You can see this in the pic where about 25mm or so is a different colour.

All this talk has dredged up some annoying memories of my attempted contact with KC at the time (2005 approx). Because the floor was soft I called them several times and emailed them simply seeking to find out how the floor was constructed so I could ascertain the complexity of the fix. I really did not want to start hacking out the floor with no idea of what lay beneath or how it would need to be reinstated. Unfortunately despite repeated attempts to speak with KC and just get some very basic information I got ignored by them. No idea why they refused to speak with me but if I had phoned to order a new boat I think they might have had a different response.

Over the years I have done a fair bit of glassing so I figured I could probably fix most things I wrecked removing the floor. Hence I took the plunge and removed the entire floor. I've also attached a pic of the stainless steel fuel tank removed and sitting in the top right of the photo. You can see the foam in the hull and it was full of fuel/oil mix. Both stainless steel tanks were full of pinholes.

103081103082

stevemid
13-05-2014, 05:59 PM
Moray2004 Its hard to tell from the picture, but it certainly doesn't look like much of a cove there to spread the load of the joint where the bulkhead attaches to the tunnel. Lack of a cove or something like flex noted at the bulkhead to deck join could certainly contribute to a join cracking. "are bulkheads usually capped by a thicker bit of timber/glass? Something to attach the floor to" Steve

overdraft
13-05-2014, 06:39 PM
Mate I had a 3000 kc and had the same holes in the bottom of each bulkhead. Over and above there was no centre bulkhead and water could run easily from one tunnel to the other. I sold the boat as I wasn't prepared to to be 100ks offshore in a boat that could sink in a couple of minutes if I was to hit something and penetrate the hull.
Only recently my thru hull transducer came loose and I took on water in my Noosacat. If I was in my Kevlacat I would have a good insurance claim and the boat would be at the bottom of the ocean.
My advice is buy a life raft for piece of mind.

Forget Bannanas advice, he knows nothing, buy a blow up doll it can be used as a life raft and a sex toy. Can't go wrong.

Flex
13-05-2014, 07:27 PM
Thanks for the pics Moray.

As steve mentioned how thick where the bulkheads throughout the boat? did they have a capping on them? The one I have access to doesn't. and seems very thin.
I'll try and get some decent photos up soon of the top of it.



I also have an inspection port in the floor of this compartment too. There is maybe a 50mm gap down to the actual bottom of the hull between the bottom of the compartment under the floor and the hull.(if that makes sense?)


Must have been a mammoth task to redo the floor and glass the bulk heads? be a task worth while if needed, but how long did it take you out of curiosity?

As for a blow up doll. if I had one on the boat I don't know how much fishing would get done....

Moray2004
13-05-2014, 09:44 PM
Flex,

The bulkheads have a glassed in piece of timber (seem to recall that it was about 10- 12mm thick by about 100mm wide approx. and the same as the flooring) at the top. So the bulkhead is an upside down "L" shape with a small downturned lip. The timber in the top was in perfect condition so I did not attempt to replace it. I imagine it was saved because it had been fully glassed in whereas the floor was glassed on top but only given a lick of resin underneath.

The bulkheads run full width of the boat giving about 100mm clearance over the top of the tunnel, possibly a little less towards the stern. They were in theory full sealed but in practice this was not the case as evidenced by the fuel making its way to the rear bulkhead. There is also an inverted glassed square "U" shape at the base of the hull running full length of the boat. It is hollow so would be the pathway for the fuel getting between the bulkheads.

As for how long it took - I seem to recall that it was out of action for 4 months. I worked on it most weekends and most nights after work. If I knew what I had to do before starting I think I would have taken it to a boat builder. The glass prep work was the worst. Getting out the entire floor without damaging the top of the bulkheads was a pain. Only the rear section of the floor was rotten but as I worked my way forward I discovered the cracks and so kept on removing. Grinding back the gel coat at the floor / wall interface below the side pockets was pure hell due to limited space. Then there was the issue of the fuel and oil that had been there for some time and was hell to clean out. I itched and scratched like a dog with fleas for the entire 4 months despite wearing lots of protective gear.

It was not just the floor that I replaced though - new fuel tanks, added two hatches to the cabin, completely removed the pods and repainted them, new motors, rewired the boat, new seating arrangement with removable esky and a host of other minor odds and ends. Figure it will be good for at least another 25 years.

What you are describing does not sound like a bulkhead or at least it is quite different to that in the 6.2. I would think that a bulkhead in the conventional sense would strengthen the hull by being attached to the hull (tunnel and outer wall) and the floor otherwise it would not have adequate stiffness.

There was a very small cove against the hull (guessing a radius of less than 7-10mm) which was a nuisance when I repaired the cracks as it was almost too tight when placing the glass matting.

cheers

rexaway123
14-05-2014, 09:12 PM
Just out of reference/interest this is the underfloor construction in my NC 2300 that I built in 2012...got step by step pics from first layup in mold to delivery the 'sealed" compartments...Where the bulk heads are, beams, noses are super thick and double skinned sealed off for most likely impact breach from before floor went down

Flex
15-05-2014, 07:25 AM
Thanks for the pics rexaway!

i have a few mates with noosa cats. I'd go as far saying as they are build a bit better than KC. We did some work on an my friends 5.2 and it was a solid boat. They are all built to commercial/survey standard from factory I believe. I just found their transom/deck layouts in the smaller 1850 to be awful setup for fishing. The KC is so more practical. I me think my next boat will be a 2300NC once I've gotten a few years out of my little KC..

I'm having mine looked at shortly. I'm thinking it's only a divider that's cracked. As it has no larger capping on it. It's got a 20-30mm gap at the top you can stick your fingers through.heres hoping eh

stevemid
16-05-2014, 12:35 PM
Just out of reference/interest this is the underfloor construction in my NC 2300 that I built in 2012...got step by step pics from first layup in mold to delivery the 'sealed" compartments...Where the bulk heads are, beams, noses are super thick and double skinned sealed off for most likely impact breach from before floor went down This really looks to be build like a brick shite house (strong as) to me.
Steve

rexaway123
16-05-2014, 01:46 PM
well yeah....thats why I towing 3Ton without full fuel ! they built same if for me or if ordered for marine resuce or coppers boats
glassing on side of back pods is 4 inch thick to cope with extra loading since coppers wanted to put twin 200hp on them, recreationally only rated to twin 150hp like mine

stevemid
16-05-2014, 03:54 PM
well yeah....thats why I towing 3Ton without full fuel ! they built same if for me or if ordered for marine resuce or coppers boats
glassing on side of back pods is 4 inch thick to cope with extra loading since coppers wanted to put twin 200hp on them, recreationally only rated to twin 150hp like mine
So you got a Kenworth to tow it with or what? Have you got an actual weight on the boat and trailer with all your gear aboard? I'm getting the sense that heaps of boats are heavier than the owner thinks.

Steve

rexaway123
16-05-2014, 04:20 PM
yes have had on weighbridge free standing un hitched with certificate with only 250L of fuel but gear and it hits 2920kg.

tows very easily with Ford ranger though and very stable on low set trailer with 13 inch wheels. Car brakes better with boat on than without too with the electronic setup

gofishin
19-05-2014, 12:48 PM
...I assumed each compartment was sealed, But its obviously not...

Hi Flex,
The topic of 'sealed compartments' in cats has come up a few times over the years. Many manufacturers claim to have such, but in my belief, in a man-made recreational ‘production’ cat that operates in‘the ocean, and is subject to much stress - there is probably no such thing as a 'sealed (for life) compartment'.

However, that NC construction looks pretty damn good (from what we can see anyway)! The difficult part, in my mind, is getting the floor down and 100% sealed to every bulkhead/member etc – and knowing that this has occurred – without being able to check from inside every compartment (unless of course they are completely foam filled).

Inspection ports are great where you can (safely) include them, especially if you need to keep an eye on structural issues, let alone checking for water were it isn’t supposed to be! Good ones cost a few bob, and the cheaper ones are crappy, and not suitable in high traffic/useareas such as the cockpit of cats etc.

Here is an excerpt from an old post of mine regarding so called water tight bulkheads/compartments. The thread started when a large cat sunk out of the GC. I posted about my experience with so called water tight compartments in a large-ish cat my father owned, and the significant quantity of water that I found (plus it was easier to search than to get the old memory bank in action and re-type etc J). Over the years I have seen and heard many stories about people finding water in all sorts of cats too. Here is an excerpt…


… As for water tightbulkheads in cats…

In the 80’s we imported a 328 ‘Power Cat’ (~33’ x 11’ beam) into PNG. These had a pretty good rep in those days for being one of the safest boatsbuilt in Oz, with 14 sealed ‘water tight’ bulkheads in total under a ‘fullysealed’ floor. This boat was claimed to be ‘built to’ survey standards, we even got the test samples presented at the time the hull was laid up, but it was not commissioned to be built to survey standards, hence required checks by a marine surveyor were not done. In ~two years of use and ~1150 hrs use we had not a hint of problems to come.

After shipping the boat back to Australia when we moved back, it was stored in the weather on a canal ramp (with proper covers etc). After a few years I noticed an increasing list to port over time, and eventually a small spongy part in thefloor caused me to get the power tools out.

From the port aft compartment forward there was ~400L of water in 4 of the 7 compartments, and in the stb aft there was ~80L. It got into the port aft compartment through a small area where the glass & flowcoat was insufficient in a concealed corner. The bulkheads had ~5mm gaps to the u/sidefloor in some places, and the longitudinal bulkhead b/w tunnel & floor had a ~10mm gap in many places. The sides & bottoms of the bulkheads were very well sealed & glassed, however with the sloshing around while the boat was at sea (i.e. in rough conditions) the water migrated up & across the hull…

Here is the full thread for those that might want a read…
http://www.ausfish.com.au/vforum/showthread.php?123438-Boat-Overturned-On-The-Seaway-Bar-!!!/page2 (http://www.ausfish.com.au/vforum/showthread.php?123438-Boat-Overturned-On-The-Seaway-Bar-!!!/page2)

stevemid
19-05-2014, 04:09 PM
The issue of sealing the under-floor compartments (or not) was the main issue I faced with building my cat. With either a main or an intermediate bulkhead every 1M, if you "attempt" to seal them, the problem becomes how do you glass the underside of the floor to the bulkheads? Sure you can glue the floor down but water displaces air pretty quickly if the air can escape and it doesnt take much of a hole for the air to escape. You can fill the compartments with foam, but how do you know what's happening under the foam and if you need to repair something the foam's a bitch to get out; plus the weight of it. The next question is how do you make sure there's no water ingress without inspection hatches? Carrying around a few hundred litres of water can get pretty expensive, even if the remaining compartments maintain floatation.

As they say, there is no perfect boat and every boat is filled with compromises. The older I get the more I realise just how true this is.
Steve

Steve

In the end, I decided to have rather big, friction fit inspection hatches in the floors over all the compartments. I can check the compartments regularly for water, and I can store stuff like portable bilge pumps in there. The exception is the forward floatation chambers made up of the front 3' of each sponson. In each of these I fitted two 6" round inspection hatches one in the anchor lockers and one in the bulkhead separating the berth/toilet areas from the floatation compartment. I was able to glass the inside joins through these ports so I know they are sealed but I've left them empty because I want to be able to see to the bottoms and make sure they're not leaking.

At the end of the day my decision to go this way was based on the fact that being balsa cored, the design itself has positive floatation, On the negative side, in if water gets in it has to pass through balsa, NOT something you'd be able to live with for very long. A solid glass boat on the other hand doesn't have positive floatation. In that case, in my opinion, the builder should cut access holes during construction, get the chopper gun in there and fully spray and seal the joins from the inside of each compartment, making each compartment a separate sealed area with no compartment-to-compartment water migration potential whatsoever. That done, the access holes can be sealed up and glassed over.