Cored Hulls

[FF]

On some work boats , police , fire and especially pilot boats the hull is reinforced to extreme levels by using a core with the same layup as a solid boat.

Lightning the hull is not considered, strength is primary.

 

[ksanders]

Exactly right Kevin. But one thing you need to remember is that Bayliner used ATC Core-Cell, an extremely tough closed-cell foam specifically designed for below-the-waterline applications. Other foams used for coring will still soak up some water and are known to deteriorate/delaminate over time due to hydro-shock.

Pacsoe reviewed Core-Cell here and compared it to other foams: www.yachtsurvey.com/ATC_Core-Cell.htm


Talking specifically about the Bayliner/Meridian motoryachts (only), it always seemed to me they had some of the best hull technology, this is one example. To my knowledge, Bayliner/Meridian is the only production builder that used ATC Core-Cell, and they did build thousands of them.

That said, I think Bayliner was an exception.

I would never buy any boat with a balsa cored hull bottom, and I would be very wary of any other foam-cored bottom unless I know what kind of foam was used and how much experience the manufacturer had with it.

Thanks for posting that link. Very good article.

 

[Rufus]

I just spoke with the technical director at ABYC. Turns out their guidelines regarding moving/handling/blocking boats (as it relates to the hull construction) is presently in their five year revision cycle. I pointed out that manufacturer's designate sling lift points for travel lifts, but they don't say a flippin' thing about the potential for punching holes in the bottom of hulls with these wrecking machine hydraulic trailers. (By the way, the boat next to us had a hole punched in the hull from one of these devices....cored hull 39' Sea Ray with optional (heavy) diesels.. Anyway, the ABYC gent recommended I also contact Boat U.S. technical staff. After that I called Carver Yachts...waiting on a return call.

The ABYC gent is sending me the current structural material that's in the revision cycle and suggested I add my thoughts. So, I will.....ban all pad lift hydraulic trailers.

 

[psneeld]

I just spoke with the technical director at ABYC. Turns out their guidelines regarding moving/handling/blocking boats (as it relates to the hull construction) is presently in their five year revision cycle. I pointed out that manufacturer's designate sling lift points for travel lifts, but they don't say a flippin' thing about the potential for punching holes in the bottom of hulls with these wrecking machine hydraulic trailers. (By the way, the boat next to us had a hole punched in the hull from one of these devices....cored hull 39' Sea Ray with optional (heavy) diesels.. Anyway, the ABYC gent recommended I also contact Boat U.S. technical staff. After that I called Carver Yachts...waiting on a return call.

The ABYC gent is sending me the current structural material that's in the revision cycle and suggested I add my thoughts. So, I will.....ban all pad lift hydraulic trailers.

Have worked in yards with hydraulic trailers and know a few hauling companies that haul long distance with them. Sure they can do damage like improper blocking or drop boats like improper use/maintenance of travel lifts. And yes...they aren't suitable for all hull designs.


One yard was a Sea Ray dealership and ALL their bigger winter storage boats (diesels included...up to 41 feet) got moved by hydraulic trailer 10 miles or so.



I would say you have had a bad experience with them (and a few more) but they aren't common to all or all those that operate them.


Also...not sure if I have seen any that didn't have some keel support for bigger boats and the cross member kept the trailer from spreading from the greater weights.



Banning them would kill a lot of operations I know of.

 

[TDunn]

The yard I store at hauls and launches 100% of the boats in the yard with a hydraulic trailer. Personally I prefer it to a travel lift. My boat is an 83 year old woody and a lot more fragile than any glass boat. I have never had a problem.

 

[Comodave]

Our yard has both a travel lift and a hydraulic trailer. They use the hydraulic trailer for boats up to around 32’ and the travel lift for the bigger boats. They are experts in moving boats around. They look for structural areas before lifting the boat with the hydraulic trailer. I think “banning” them is way to reactionary. Sure they can damage a boat if it is being used by a novice. But you can’t legislate stupidity. In the hands of a knowledgeable operator they are fine. They can put a boat in a place that a travel lift cannot fit. If they were banned our boatyard would probably loose 1/3 of their indoor storage revenue since a travel lift needs so much more room to get in and out. Personally I would not like to see that happen because our winter storage rate would go up due to the lower density of boats in the barn.

 

[smitty477]

I have seen damage done by all kinds of moving machinery - travel lift, crane, hydraulic trailer, rail line.
Does not really matter which machinery you have if you do not use it properly.

 

[Rufus]

I specifically said hydraulic pad lift trailers. Hydraulic trailers with keel supports are another animal. Most boat owners don't understand the differences and the risks with pad lift designs. I have no problem putting users of the pad lift devices out of business if they refuse to make a change to keel lift designs. I believe the manufacturers of larger boats will concur. But I'm going to find out.

And no I haven't had a personal bad experience with pad lift designs....because I refused to allow them to move my boat on one of them. In fact I'm relocating the boat to a yard with a keel lift design for winter storage. I've seen a 48' Viking motoryacht on a trailer designed for a nominal 35 foot length....spacing between the two pads on each side was about 20 feet....the hull bottom was bowed inward at the pad sites. No problem says the trailer operator...I went to the trailer manufacturer training course and it's designed to carry up to 60,000 pounds. I asked if they knew what sort of structure was behind the pads....nope....don't care....now please excuse me, sir.... I believe the technical understanding of most yard crews is of similar caliber.

The point is that there is no technical guidance from the boat manufacturers, ABYC, or anyone else as to how many pounds per square foot of pad is safe....where should the pads be placed...how many pads for a given hull....considerations for a cored hull, versus wooden hull, versus sold fiberglass....etc. Yard workers typically don't have the flick, nor should they be expected to be structural engineers. You can't tell equipment operators how to do the job if the information is not available. And even if it is....when yards on the Great Lakes start slamming boats into storage buildings...their objective is to squeeze them in as fast as possible and as close together as possible. Yes, they keep costs down for you...in the short run. They might also be wrecking your boat.

 

[psneeld]

What exactly are you calling a pad lift trailer?

 

[Comodave]

The reason there is no guide for how many pads or how many pounds per pad is that it will be different for every boat. There is no practical way to do that. There are literally thousands of different boats. Should ABYC do calculations for each boat? Not going to happen. That is why as a boat owner you should be picky about the yard you choose to store your boat. I have watched for many hours at our boatyard as they move boats in and out. They are not in a hurry and they are diligent in how they move and block the boats. Yes they are fast but that is because the owner and his primary worker have been together for over 10 years and they work as a team almost without talking. I watch in wonder as they work because it is a real pleasure to watch professionals work. If your yard isn’t like that then you are probably in the wrong yard.

 

[Rufus]

A pad lift trailer has hydraulically actuated arms with square pads on the end. The trailer is backed under the blocked boat and the arms/pads are extended against the hull. When they are snug against the sides/bottom of the hull, the operator hydraulically raises the entire articulated trailer frame along with the boat on the trailer's suspension (hydraulic rams). The boat weight rests solely on the pads....zero keel support. The other primary operation is transferring the boat from travel lift to trailer. The pad position is approximated. If the boat is dropped into the waiting pads/cradle in a caddy whompos fashion, or pads are not positioned correctly, the boat typically twists and groans until it finds equilibrium. If the boat owner is watching, he's groaning even more. Likewise if the trailer isn't perfectly straight under the travel lift, there's a longitudinal bending action on the hull. If pads are improperly prepositioned, some pads/hull areas bear the brunt of the load. Bottom paint scrapes are common as the pads are scraping along the hull. Then they haul the boat into the storage building where I've witness the 10,000 pound trailer actually lift off the floor because it's wedged/stuck to the bottom of the boat.

A keel lift trailer has removable lateral keel slats/beams (aluminum) that slide into slots in the longitudinal trailer stringers. The trailer is backed under the boat and the slats are inserted between the keel blocks. Then the stabilizing (only) hydraulic arms are brought against the hull to stabilize it laterally. At that point the articulated suspension on the trailer raises the entire frame plus the boat via the keel. When the boat is moved from the trailer to the travel lift it is simply picked straight up without twisting and bending of the hull as with the pad lift design. Same for the reverse....it's sitting on the keel....and then the arms/pads are brought up for side support and perhaps a bit of bottom support. This design is a little more work for the crew because the lateral keel slats have to be removed and replaced...but it's safe for your boat....no bending, twisting, scraping or bowing of the boat bottom. If a yard owner is using the keel lift design he understands boats and he gives a damn about your property.

Lifting heavy boats via pads is just nuts. Maybe with enough pads, judiciously positioned....but that's not happening in the real world. It's not like sling placards....there's nothing to guide the equipment operators.

 

[Ross Macdonald]

This topic has been beaten to death. No one mentions Westbay Sonships build in British Columbia. We own a 58 Westbay hull #60. Their hulls are cored and vacuum bagged with divinicell coring. All thru hulls are installed with glassed in teak pillow blocks. We have owned the boat 5 years and have completed 3 trips from San Diego Ca. to Mainland Mexico and back. Each trip lasting 6-7 months. We just finished this trip returning to San Diego on July 14. The weather outside the 800 mile run from Cabo to SD was especially bad this year. We waited for a number of shorter windows and still got our ass kicked during some segments. My wife and I run the boat ourselves. We have traveled about 6700 miles and this boat has taken way more than we can sometimes. We are at the moment hauled out for a bottom job. When the boat was in the travel lift we weighed 78,000 lbs. with 3/4 fuel and 3/4 water in the boat. With full water and fuel we are right about 80,000 lbs. Each time we haul we give the boat a close inspection and have yet to find a crack or water intrusion anywhere. So This discussion for us anyway doesn't compute because our experience does not come from hear say or some BS article by Pascoe. It comes from a lot of miles, many in adverse conditions and living on the boat for months at a time and not a 2 week vacation. Any of you on the west coast who have made the Baja Bash knows it is a test of patience, a sound vessel and some will power.

 

[hpogue123]

BTW, try to get any hauler to take responsibility for damage. It will cost you a fortune in survey, engineering, and legal expenses. It's very hard to prove they did the damage, the may have fine print exempting or limiting their liability. Lastly, they are usually buddies with the local people that don't want to loose referrals. If you do get something you'll be restrained from talking about it. Why do you think there's so little published about it.

 

[Ross Macdonald]

Not sure what if anything this last comment has to do with my post. We have hauled all of the boats we have had over 35 yrs. at Basin Marine Shipyard in Newport Beach Calif. and never had any issues with any of our boats in their travel lift or being blocked on the hard. A few times we have been on the hard for 2 weeks with no effect on the hull at all. All I was trying to convey was if a boat is constructed correctly with a cored hull then it will perform and be as safe as a solid glass hull. It involves proper materials, proper construction, proper layup and very good gelcoat work for the cosmetic part.