Modifications to the "Colorado River Dory"

Hello, I am in the very early phases of planning a "Colorado River Dory" build, This will be my first dory build however I have constructed a stitch and glue kayak. I had a couple of questions I thought I could pose to many of the builders here. I guess I should apologize in advance if these questions have already been addressed in other forums, but I have not been able to find them. My first question is on hull shape. I will be constructing this dory to be a large people/gear hauler for desert boating trips. Is there anyone who has had experience with extending the length/width of the Briggs design? Do commercial outfitters in locations like the grand canyon use boats larger then the traditional Briggs design?  What kinds of problems beyond slower turning and more weight could one expect with adding extra length/width? Is there even a need to extend this hull, or is it generally big enough?  

My second set of questions relates to the decking. I know that step is a ways off but I just get so excited. As I have looked through many of the photos posted here, and elsewhere I have seen that the decking on whitewater dories is largely attributed to personal preference. I would seem to me that building a flat decking in place of the slanted decking designed by Jerry Briggs would be advantageous to sleeping on the boat. Would this present an problems to a scupper system in the rowers foot well or otherwise. Continuing on this note, it would appear to me that a scupper system is more easily applied to the rower's position rather then for and aft guest seats. Is this untrue? does anyone have any ideas of how to integrate those compartments into the system?

Thanks for listening, I appreciate your help. Good day and happy boat building!

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Permalink Reply by lhedrick on October 3, 2011 at 2:24pm

The flat deck in the rower area can cause problems with oar hight.  If the deck is too high it's difficult to get the oar handles down low enough to keep the blades out of the chop.

 

My boat has a flat deck and the reason was I wanted to be able put a small tent on it.

 

The subject of bigger, wider Briggs boats is not a simple one, everyone has different views on the subject.  Since no one person is correct there isn't really any clear answer other then to find a way to row them.

 

As for bailing the front and rear areas are more difficult to self bail.  You will need to have raised floors but, smash the bottom below that raise floor and repairs are difficult.  I have been moving to battery powered pumps.  Keeps things simple and a small SLA battery is good for a long trip.

 

As for building a wider boat you can get modified Briggs type plans from Andy Hutchinson in CO.  Not cheap though.  17 foot is a big boat, how long were you thinking of?

 

http://web.mac.com/kthompson20/iWeb/High%20Desert%20Dories/Welcome....

Permalink Reply by Tom Martin on October 3, 2011 at 6:39pm
Hi Jacob, just curious as to why you might want to make such a large gear hauler? Please be sure the "Colorado River Dory" definition is a little more all inclusive then some may have it. A smaller decked constant rocker McKenzie hull design can haul two people and a lot of gear with comfort and be fully decked, and has been doing so in Grand Canyon since 1955. The larger flat-flat floor hull design trades maneuverability for gear hauling potential, but both decked boats are Colorado River Dory's. If you are going to row the San Juan, Grand Canyon and Yampa, you might wan to consider a smaller boat, 15 to 16 feet in length, 5ft at the chine, 6 ft at the gunwale.  As to decking, Larry has noted that if you raise the floor to allow self bailing, repairs can be problematic, and you are in essence raising the center of gravity. Scuppers work well but require tilting decks and side hatches out toward the side of the boat, making sleeping a bit of a challenge, if not impossible. Some folks have brought along boards that make tables, then after dinner, cover footwells to make sleeping platforms. Have Fun with your build! All the best, tom
Permalink Reply by Robb Grubb on October 4, 2011 at 11:28am

Jacob,

The concerns of the previous folks are quite valid for building a bigger, wider, taller boat. The below links will take you to my build of one such boat. I designed it for the same reasons you are thinking of. However, I have a 16 x 48 Mckenzie boat still in the fleet for all the smaller rivers I like to run as well.

http://www.woodenboatpeople.com/profile/RobbGrubb

http://www.woodenboatpeople.com/profiles/blogs/ta-dah-custom-18-x-5...

The hull is a modified Don Hill 18 foot flyfisherman, it turned out to be about an 18 1/2 foot gunnel, 54 inch wide bottom and about 3 inch higher sides and more flare than the DH model. The hull is a full rocker Mckenzie style and not a Briggs / Canyon style 'flat spot' design. All passenger / oarsman foot wells are completely self bailing (10 inches above the bottom of the boat) and they make me so happy I can't even stand it (I really dis-like being the self-bailer myself).

All the decks are flat with the exception of the front and rear compartments. They are great! The only draw back is the water stands on them a little longer and does not run off as quick (more water into the hatches) as an old school Briggs boat (probably the reason Jerry designed them that way, darn that common sense!) as well as like Larry says about having less room to bring oars out of the water.

The boat turns and moves like a dream even when loaded and I think that is due to the rocker and bottom width and flare...and...

Regarding Center of Gravity with higher false floors, I think my jury is still out. Haven't had any issues yet, however I do not run big volume, crashing, monster waves and holes like the big kids do in the Southwest. If I was concerned about CG for  a particular piece of water I would probably purchase 5 or 6 18 packs of my favorite tasty canned beverages (they probably weigh as much as your lower two legs...) and stuff them in under the false floor for ballast and hope that they were not empty when I arrived at the rapid of concern...

Cheers, Robb Grubb

www.RiverTraining.net

Permalink Reply by Jacob Anderson on October 4, 2011 at 5:15pm
Thanks so much for your input in the matter. This all has been very helpful. I am thinking of building something on the order of magnitude of 18ft or so. This estimation comes from my experiences running rivers in rafts. You guys have again peaked my interests. I can't wait to get started and hope that in the coming months I can make some progress or just chose a plan. Finally I would like to compliment you all on some beautiful boats. All of your suggestions are validated when one can see the works of art you have produced. All the best. Jake

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