Batten seam scantlings?

[Dan Pence]

Hello, I just joined this forum to ask for some help; I need recognized standard or formula for a specific type of hull scantling.

Details; We've almost accepted the donation of 4 old tour boats from Crater Lake National Park. They never went through a Coast Guard design review because they weren't on a "navigatable waterway". But we want to use them in our ferry service in downtown Portland OR, so the Coast Guard is asking us to prove they were built to approved standards. They are letting us find the standard. But they are insisting on a design review before these boats are put into service.

The boats are 60's era open Mahogony runabouts, hard chine, 39' LOA, 11'6" beam, with a single gas engine- we intend to replace with a 100 HP or so diesel. They weigh about 12,000 lbs empty.

Here's the nub; the carvel planked hulls have seam battens or ribbands at every seam, The frames are widely spaced- 38" on center. According to a few reference books(see below) batten -seam construction allows for widely spaced frames and thinner planking, but we need specific scantling rules that will satisfy the design review. Or guide us in modifying these boats to pass design review.

Please help us find a rule, formula or standard which specifies the minimum frame spacing for batten-seam constructions.

On the face of it this seems like an easy request, but we've been suprised to find this info. is quite obscure.

We've checked; Chapelle, Lloyds of London, Robert Stewart, Nevins, Dave Gerr's new book(excellent reference, apart from this narrow question), Skene's, Herreshoff, Pardy and a few other general boatbuilding/design books. We have a reputable N.A. working on this. We've asked a couple local yacht design firms for help. We've contacted the Century Owners Assoc. because they also were 100% batten-seam construction. So far we haven't anything we can take to the Coast Guard regarding batten seam construction guidelines.

I'm currently trying to dig up a copy of pertinent ABS rules(if they exist), any help with this would also be helpful.

Alternately, If anyone knows of a Coast Guard approved passenger vessel with similar hull construction, the owner would probably have documentation on how the vessel passed(or avoided) the design review.

Please don't send me on a wild goose chase. We have to decide within a week if we are going to accept the donation of these boats. This issue is critical to our decision.

Ideally some very generous, thoughtful person will e-mail me a table or formula. If not please cite chapter and verse of something that we can lay our hands on.

Thanks, Dan Pence, RiversWest

[Dan Pence]

This is me again with an update.

Turns out the plans for the Crater Lake Launches didn't come out of the boatbuilders head back in the 1960's. I was looking for a similar design in the Atkin and Co. website and recognized our boats as Billy's "Salimina" design minus the cabin.

This will probably make our case to the Coast Guard a whole lot easier.

I wonder what Atkins based his scantlings on? Assuming that Rudy Wilson, the guy who built these boats, followed the plans faithfully.

I still need help, obviously.

Dan Pence

[imported_Conrad]

Get a hold of Dave Gerr's book "Boat Strength", available at Amazon, etc. It came out about two years ago. He is a recognized engineer/navel architect (and I believe licensed) who has put together a system for calculating scantlings in all common materials using a few easily calculated criteria. Trust me, the math part is very simple and easily understood.

The key is to look for the footnotes, etc. that deal with specific modifications- different woods, speeds, etc., but it's all there- frame spacing (and exceptions/modifications) planking thickness, fastener size, etc. I'm sure the Coast Guard would accept proof that your hulls meet standardized criteria as expressed in his book.

I don't recall offhand a modifier for batten seam, but my guess is that the planking alone would prove sufficient, and the battens will just be frosting on the cake. Good luck! smile.gif

[TR]

Dan;

Batten-seam construction could be viewed as longitudinal frames on widely spaced transverse webs. This construction can be compared with any modern scantling rule. Your NA can certainly look at the structure using basic principals and wood properties to compare the boats with current rules.

You probably won't find any mention of Batten-seam in any published rule. It was used mostly by US builders, many of them intending use on inland waters. None had any need to use a published or international rule.

All the best, Tad

[RonW]

Suggestion- I think you have already answered your own question. You identified the boat as atkins -SALIMINA - when you scroll down to the drawing showing the side profile, it shows the frames,there are 12 spaces between the stem and the transom. When you multiply 39feet x 12 inches you get 468 inches, divide that by the 12 spaces and you get a answer of 39 inches.So appearantly the boats where built according to atkins drawings.Atkins was not only a marine architect, but a well respected marine architect. Copy the print form the website to show the coast guard, if you need to go further, then you could simply supply them with a set of the blueprints directly from the architect. Surely they could have no problem in accepting that. Plus you have the fact that the boats are already 40 years old, so the construction method obviously has with stood the most critical demand, THE TEST OF TIME.

[RGM]

Shame on you. You've gone and put the local Coast Guard inspectors in a very awkward and uncomfortable position. You are forcing them to inspect and hopefully approve your 60's era wood boats for the transportation of passengers. That makes them very nervous. Very few if any of them know what they are looking at when it comes to wood boat construction. They are not anxious to put their name on the line so-to-speak. So, they are taking the first fall back position by requiring you to prove that the vessels were built to an approved standard. They of course are hoping (with fingers crossed) that you can't satisfy this requirement. So, in advance of the next set of hoops and hurdles that they will place in front of you consider doing the following prior to inspection/review:
1. Have repair/maintemance records at the ready.
2. Renew any suspect hull penetrations and related fasteners. Including anything to do with your rudder and steering.
3. Have all the necessary PFD's passable and stored in easy access lockers or benches (labeled), with a certain percentage for children (I forget the ratio).
4. Have plenty of signage directing passengers in the event of an emergency.
5. Have a fire plan of sorts and plenty of current fire extinguishers. They may require you to have a fire suppression system installed in your engine compartment that can be actuated from more than one location.
6. Have a suitable means of retrieving a "man over board" and proof that you have practice drills.
7. Make sure that you have all the necessary venting of spaces and tanks. Probably Stainless Steel mesh over the bell fittings on your fuel tank vent(s). They may want to see some type of berm or coaming around your fuel fill(s).
The list goes on and perhaps you already have these items already working for you. Non-the- less, remember that they don't want to see your wooden boats carrying passengers on their waterway and they will most likely make it very difficult for you. Good luck.

[ 04-13-2004, 12:03 PM: Message edited by: RGM ]

[Roger Cumming]

If you intend to put these boats into public service, you must have a naval architect or marine engineer evaluate their construction as well as their condition. There will not be a formula that will give you the answer you seek. The professional will compare the boats's construction and structure with known standards applicable for similar service in similar waters, and judge its adequacy. It may be necessary to make alterations to strengthen or stiffen the structure, or provide other improvements such as watertight bulkheads. Repowering the boat with larger, heavier engines would alone require this. I believe the CG will take seriously a naval architect's report of how the boat measures up to the various standards and how it compares to other known designs in similar service. The public nature of this requires the services of a professional. Casting about for a formula is not adequate, even if you could find one that gave the answer you seek.

[Todd Bradshaw]

I'd also imagine that your insurance provider well might want to see current professional surveys and have the construction verified by a real N.A. before they'll let you transport anybody in them. If they don't, they're crazy!

[Dan Pence]

Wow, thanks to everyone who has responded to our request. I appreciate your time and effort in helping us through this maze.

I probably should have mentioned in my first post(it got awfully long) that the Coast Guard did certify these boats and related safety equipment to carry 48 passengers since 1998 on Crater Lake. But they didn't require a design review because the boats had such a long service history there already. So, these boats have official Coast Guard inspection stickers displayed, but only apply to service on Crater Lake.

I too hope the William Atkin name will help sway the inspectors, but they seem really adament about us getting these boats to match a bonified standard as to hull scantlings. I'm convinced that the batten seams are more than icing on the cake. These boats never would have kept the water outside minus the battens stitching all those seams together.

We're still hoping to find ABS standards that apply or an alternate standard. Or a passenger vessel with similar scantlings to magically appear.

Thanks again.

Dan Pence

[Dan Pence]

Well I managed to dig up something useful;

"Merchant Marine Safety Instruction no. 14-60.
Subject; Scantlings for Wooden Passenger Vessels."

Published by the Coast Guard in 1958, it contains the scantling data of 500 successful wooden passenger vessels under 65', otherwise known as "T Boats". "To provide guidence for vessel inspectors in determining the adequacy of small wooden vessels." It covers round bottom and V-bottom boats; a variety of planking types including carvel, diagonal, double planked, dia. double planked, clinker, etc. Even a couple of batten-seam boats; and the various types of traditional framing like bent, sawn, grown, etc. It specifies the type of service like ocean or protected waters, the nos. of passengers, lots of stuff that make for very interesting comparisons.

This is fantastic boat building data in many ways, and I found a couple boats that were similar to our Crater Lake Launches, so this should really help our case.

I got a photocopied version from our local CG Marine Safety Office in Portland.

Thanks again for the comments,

Dan Pence, RiversWest