Gulf Coast - Tolman Seabright Skiff 22' Inboard Diesel prototype

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kengrome
12-31-2007, 07:36 AM
Last year I contacted Renn Tolman, the designer of the three outboard powered Tolman Alaskan Skiffs for which he sells plans via his book:

http://www.alaska.net/~tolmanskiffs/img/book_front_cover.jpg

Here's a link to his web site for anyone interested:

http://www.alaska.net/~tolmanskiffs/index.html

These are easy-to-build plywood/epoxy/fiberglass composite boats that Renn designed and used himself for years to go offshore fishing in Alaska. The reason I contacted him is because a year or so ago he designed a fourth skiff -- a shallow water fuel-saving model powered by a small 20-25 HP inboard diesel which he calls his Tolman Seabright Skiff.

This new boat has an unusual bottom design that gives it shallow draft and makes it very fuel efficient at speeds of 15-20 mph, and in fact this is probably the fastest the boat will go with the specified HP. I saw the increasing fuel prices and thought to myself:

"Here's a boat that people are going to want more
and more as fuel prices continue to rise."

... so I asked Renn if I could build the prototype since he hadn't gotten much done on his at that time, and he said yes. I started several months ago and here's one of the most recent images I posted on my web site:


http://www.bagacayboatworks.com/images/seabright03/thumb/600p7280071.jpg


The rest of the images are here for anyone interested:

http://www.bagacayboatworks.com/images/seabright01/
http://www.bagacayboatworks.com/images/seabright02/
http://www.bagacayboatworks.com/images/seabright03/

I was going to build this boat with the intention of shipping it to the Gulf Coast and selling it there, hopefully for a profit, but now I plan to keep it myself. Nevertheless, there is a chance that I may build more of these boats, and that's the reason for this post -- so I can figure out if there is any interest in slower but far more fuel efficient boats like this one?

For more background on this boat I will post the introduction Renn Tolman wrote in his plans since I think this will help you to understand more about the design:

Building the Tolman/Seabright skiff

Introduction

What the world needs is a truly economical planing-hull power boat. Sure, Tolman skiffs are economical compared to other boats in their class due to their relative light weight, but the sad fact is an 18-wheeler running down the highway fully loaded gets better milage than I can get in my Jumbo skiff. A diesel engine would doubtless make it more efficient, but diesels are not commonly made as outboards, and the usual ways to install them are as outdrives (inboard/outboards), which are very expensive to buy and to maintain, or with conventional straight shaft-and-rudders, which result in boats that are deep draft and difficult to trailer because of a keel or other appendages. Neither drive system appeals to me.

Enter the Seabright skiff. This type was developed by many different builders for fishermen along the New Jersey shore that had to launch over beach due to the scarcity of harbors in the early 1900s. These skiffs used conventional inboard engines (gas in those days) with straight shafts and rudders, but what made them special was that the prop, running in a tunnel, which along with the rudder was placed entirely above the bottom of the hull. Thus these skiffs drew no more water than the hull itself, which because of its flat bottom, was often only inches. The peculiar shape of the stern, with its pod-shaped underbody and cut-away transom, gave these boats a good turn of speed, several times that of displacement-type boats (think sailboats), yet they were more efficient, at least at lower speeds, than conventional planing hulls (like Tolman skiffs, for example).

Perhaps the most famous modern version of a Seabright skiff was made by Robb White of Thomasville, Georgia, for use in the shallow waters of the Florida Panhandle about five years ago (see WoodenBoat Magazine, March/April 2006). His so-called Rescue Minor (the name refers to a Seabright skiff designed by naval architect William Atkin in 1943) draws only 6 inches and powered with a 20 hp Kubota diesel achieves more than 20 mph and 20 mpg. (It should be pointed out each of these numbers drops to less than 20 when the skiff is loaded with more than just the operator.) A large part of his skiff’s super efficiency was doubtless a result of its extremely light weight. Robb built his skiff like a strip-built canoe out of poplar wood cut on his own land. Furthermore, his skiff, while adequate for his needs and apparently a good sea boat, had very low sides, saving more weight, but the freeboard is too low in for most of us to feel comfortable in. His engine installation employed a belt-drive system which he built himself derived from a garden tiller that eliminated the conventional clutch and reverse gear, a further weight saving. You would have to judge Robb’s effort an extremely successful boat, but his act is a hard one to follow for most of us. Still, it gave me an idea.

What I have done is to take the traditional Seabright skiff underbody and graft it on, so to speak, to a Standard Tolman skiff topsides to give it more seaworthiness and interior volume. In the process I lengthened the Standard skiff from 20 to 22 feet but diminished the beam from 7 to 6 - 6 to reflect the proportions of traditional Seabright skiffs, which were relatively long and slender. In the process I think I have improved the bow by eliminating the hard knuckle of the original skiffs, which tends to make such boats yaw (bow steer) in a following sea. In other words, the bow looks much like that of a typical Tolman skiff, and we know these handle well. The bottom is flat, not veed, and although I have railed against flat bottoms in the past, the Seabright skiff has a feature which is said to mitigate pounding. The aft end of the tunnel has a slight downward curve, which deflects the water coming from the prop with the effect of forcing the bow down. Thus the hull punches through the seas, rather than rising over them and slamming down. (Robb White verified that this principle works.) This bow-down aspect can generate spray, but I have included the usual double sets of spray rails that are so effective on the Standard Tolman skiff.

Twenty to 25 hp engines are appropriate for this skiff. I intend to power my prototype with a 20 hp Yanmar diesel with a conventional clutch and reversing gear. I bought a used engine and gear, but I had to buy a new gear which has a 1:1 ratio rather than using the stock 2:1 reduction gear, which is designed to push displacement hulls. The Seabright tunnel permits only a small diameter prop, which must be run fast to get planing performance. This is an off-the-shelf item, however, and not too expensive. I expect to cruise at 17 mph. Economy will be outstanding as this engine burns 5/8 gph at about 1,900 rpms.

A diesel setup like mine new if new is about double the cost of an outboard of comparable power and thus has a long payback given the amount of hours the average boater drives per year. There may be other choices. Diesels made in China are significantly cheaper. To my knowledge these are not yet marinized, but it’s perfectly possible to do this, as Robb White did with his Kubota, or have it done. (Basically, the exhaust manifold must be liquid cooled.) Air-cooled gas engines are cheap although noisy. Diesel or gas automotive engines are a possibility. Making a belt drive system like Robb’s would also save money—and weight.

It might even be possible to run a Seabright with an outboard in a well, although there is a problem with this. When the skiff is at rest, the water pickup ports on the engine are above the waterline. My solution would be to mount the engine on what is known as a jack plate. This fits between the engine and the transom and operates electric/hydraulically to raise and lower the engine. (This is a wonderful feature on any shallow water skiff, by the way.) You would lower the engine 4 inches or so starting off, then raise the engine as you get under way. In the running position the lower unit of the outboard (and here I’m thinking of a 25 hp Honda) is completely shielded by the hull, and since in this position the ventilation plate on the outboard would be snug against the roof of the tunnel, you would steer with a separate rudder, the same as with an inboard installation.

I think fuel savings alone aren’t necessarily the Seabright/Tolman’s biggest advantage. There’s a lot of thin water in Alaska—tide flats and rivers, and a skiff that draws only 6 or 7 inches with full protection for the prop has a tremendous attraction for a hunter and fisherman like me. And as a lot of boaters know, there’s a lot of other places on earth with shallow water, as well. So maybe a Seabright skiff’s time has come—again.


I guess my questions are:

How many of you are concerned enough about fuel economy that you would buy a boat like this, which will certainly "go slower" than the fast planing speeds of your existing boats, in order to save a reasonable amount of money on fuel?

Would you ever buy a boat like this because of its upright beachability, its protected propeller and rudder, its shallow draft of only 7-8 inches, or its reported seakeeping performance in rough conditions?

Basically I'm just trying to figure out what people along the Gulf Coast are looking for these days. After joining this forum I'm not so sure that there are many guys here who care as much about fuel economy as I thought they might.

Will fuel prices have to double or triple again before people will "shift gears" and start considering economical boats like these? Or are boats like these simply not desirable except to the folks who want to build their own boats?

I thought that aside from fuel economy, a boat like this might be attractive to Gulf Coast fishermen because it offers very shallow draft while at the same time being extremely seaworthy -- and these two features are not that easy to get in the same boat, or so I'm told.

Any opinions you folks are willing to post about this issue would certainly help me to understand what kind of boats are "in demand" along the Gulf Coast these days.

Thanks and Happy New Years!


boat.12
01-01-2008, 06:11 PM
Pretty neat looking boat have you had a chance to use it yet it looks a bit narrow sure would like to see how it handkes a good chop with that bottom

tarponrunner
10-21-2013, 11:47 AM
I am very interested in the Seabright/Tolman skiff. I know that many designs only work well within their design parameters, length/beam, specifically, but what is your opinion on the possibility of re-producing this design in a larger version, suitable for a center console fishing-type configuration?


tarponrunner
10-21-2013, 11:48 AM
Last year I contacted Renn Tolman, the designer of the three outboard powered Tolman Alaskan Skiffs for which he sells plans via his book:

http://www.alaska.net/~tolmanskiffs/img/book_front_cover.jpg

Here's a link to his web site for anyone interested:

http://www.alaska.net/~tolmanskiffs/index.html

These are easy-to-build plywood/epoxy/fiberglass composite boats that Renn designed and used himself for years to go offshore fishing in Alaska. The reason I contacted him is because a year or so ago he designed a fourth skiff -- a shallow water fuel-saving model powered by a small 20-25 HP inboard diesel which he calls his Tolman Seabright Skiff.

This new boat has an unusual bottom design that gives it shallow draft and makes it very fuel efficient at speeds of 15-20 mph, and in fact this is probably the fastest the boat will go with the specified HP. I saw the increasing fuel prices and thought to myself:

"Here's a boat that people are going to want more
and more as fuel prices continue to rise."

... so I asked Renn if I could build the prototype since he hadn't gotten much done on his at that time, and he said yes. I started several months ago and here's one of the most recent images I posted on my web site:


http://www.bagacayboatworks.com/images/seabright03/thumb/600p7280071.jpg


The rest of the images are here for anyone interested:

http://www.bagacayboatworks.com/images/seabright01/
http://www.bagacayboatworks.com/images/seabright02/
http://www.bagacayboatworks.com/images/seabright03/

I was going to build this boat with the intention of shipping it to the Gulf Coast and selling it there, hopefully for a profit, but now I plan to keep it myself. Nevertheless, there is a chance that I may build more of these boats, and that's the reason for this post -- so I can figure out if there is any interest in slower but far more fuel efficient boats like this one?

For more background on this boat I will post the introduction Renn Tolman wrote in his plans since I think this will help you to understand more about the design:




I guess my questions are:

How many of you are concerned enough about fuel economy that you would buy a boat like this, which will certainly "go slower" than the fast planing speeds of your existing boats, in order to save a reasonable amount of money on fuel?

Would you ever buy a boat like this because of its upright beachability, its protected propeller and rudder, its shallow draft of only 7-8 inches, or its reported seakeeping performance in rough conditions?

Basically I'm just trying to figure out what people along the Gulf Coast are looking for these days. After joining this forum I'm not so sure that there are many guys here who care as much about fuel economy as I thought they might.

Will fuel prices have to double or triple again before people will "shift gears" and start considering economical boats like these? Or are boats like these simply not desirable except to the folks who want to build their own boats?

I thought that aside from fuel economy, a boat like this might be attractive to Gulf Coast fishermen because it offers very shallow draft while at the same time being extremely seaworthy -- and these two features are not that easy to get in the same boat, or so I'm told.

Any opinions you folks are willing to post about this issue would certainly help me to understand what kind of boats are "in demand" along the Gulf Coast these days.

Thanks and Happy New Years!
Just wanted to quote the thread to which I am responding



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