Ouch. I got careless and somehow over-wrote RAVC's original post rather than reply to it. He wanted to know about best choices for Au Sable Riverboat like drift boat combination, where you could negotiate shallow water but also stand up (which you cannot do in an Ausable style row boat). I've been running this forum since the late 1990s and this is the first time I obliterated someone else's post.

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My reply:

In order to negotiate shallow water you want width plus less rocker.
You could work with any drift boat plan and reduce its rocker.

Take a look at https://montana-riverboats.com/?robopage=Drift-boat-info/Reducing-Rocker

You could do this with any plan. Relatively flat bottomed boats are easy to slow down in a current and they do negotiate shallow water better. They are also harder and slower to turn. That's the price you pay for being able to drift in just a few inches of water.

I suspect a slight misinterpretation of my original message. That is, I'm not necessarily trying to reduce the draft of a given design. Rather, I am attempting to determine the draft of a given boat. So far, the boats I have looked into all state the same...4" empty and as much as 8" loaded. Is 8" an issue? I can only speculate because I do not have knowledge of all the rivers I am interested in fishing. I returned to fly fishing four years ago after a very long break from it in order to introduce my son the the sport and its conservationist lifestyle.

I referenced the Au Sable because it does have some shallow sections over rocks and we know rocks and wood hull drift boats do not go together well. For this reason I am looking into Plasticore and similar products for the bottom.

The main concern now is the 3-person capacity and a sufficient amount of symmetric floor space to walk around comfortably. It appears the 3-person desire reduces the list of potential candidates quickly. So far, the list includes the Beavertail, the DH 17FF, and the Recurve version of the Kingfisher. I have read the 48" wide floor of the Beavertail is not always admired by builders. However, it seems to be commonplace for builders to alter drift boat designs.

For negotiating shallow water, especially with 3 humans in the boat, wider is better. You also want a moderate rocker profile rather than white water radical. The Beavertail has a 49" bottom (sic) and moderate rocker. I designed it in the early 1980s. Flat bottomed floats in the shallowest water but flat bottomed is unresponsive and too hard to turn.

If I had time I'd redesign the Beavertail wider. Probably 56" inches wide, like the Honky Dory. I'm 73 and still recovering from Long Covid while ploddingly finishing a 17' foot Grand Canyon Dory. If I had time I'd make a wider Beavertail. Will I live long enough? We'll see.

It's not hard to do. The main obstacle to designing a new boat is fear and feeling intimidated. The solution is to plunge ahead. The MRB stitch and glue plans talk about using temporary trapezoid shaped rib like formers--made of of scraps or particle board.

You can make those formers as adjustable ribs instead of fixed dimenions. Then it's a snap. Make the boat (with adjustable ribs) approximately as per suggested dimensions (no bottom panel yet, just sides stem and transom, all fastened with dry wall screws and no glue yet).

No now use the adjustable ribs to make the boat wider, all the while keeping the same bottom profile. Now add a bottom panel. Now glass it up and paint it.



The Beavertail has a symmetrical bottom. It has as much flotation in the rear as the front. It was the first drift boat in existence (that I'm aware of) that trimmed properly with a rear-seated fisherman (behind the rower). Guys who actually guided out of it, for decades, like Victor Colvard, Randy Berry, Bobby Di Ambroso, Dan Delekta and others) still say it was the best rowing boat they ever had. 56" inches wide would make it even better.

I certainly have no interest in whitewater boating so we can safely exclude this. I'm intrigued by the idea of assisting with re-designing the Beavertail. The formers/adjustable ribs control the angle the sides make with the bottom. Your description here makes it sound more straightforward than I anticipated. Presumably, the length of the side panels remains as they are currently?

Are you open to the idea of a Plasticore, or similar, bottom? Would you place this over (i.e., below) a thinner plywood floor, such that the wood serves as the interior of the boat?

I'll review the plans. Stay healthy.

For stitch and glue Plascore makes the best bottom no matter what.
I built the first Honky Dory in 1986 using end grain balsa which made it easier to achieve a wide bottom. You can scarf plywood sideways to make a wider bottom but end grain balsa made it a snap. Unfortunately balsa soaks moisture like a sponge. I made several boats that way and found I really had to keep up with maintenance.

Jason Cajune was the first guy to work with Plascore. I recognized a good idea two or three seconds after I first saw it. I've used it ever since. I like plywood sides and Plascore bottom. For stitch and glue anyway.

I have a boat now 12 years old with a Plascore bottom. The chine was completely split 3 years ago, when it was 9 years old. It was a snap to fix. If it had been a plywood bottom that split chine would have allowed moisture to soak into the plywood for a foot or more, making repairs a giant pain in the butt. Plascore fixes that.

My white water buddy Larry Hedrick has built a decked all-Plascore white water boat (a Honky Dory with modifications). My little Dayak is an all Plascore boat. It's possible to build that way but it is a bit trickier to work with and grants no real benefit.

I like Plascore bottom (3/4" inch or better yet a full 1" inch thick) and plywood sides. My current boat uses 3/8" inch Meranti Hydrotech for the side panels. I like it a lot but it is expensive. I've mostly used 1/4" in the past.

One here-on-the-forum customer (Don Tyson) built a stitch and glue Buffalo Boat with cheap AC construction plywood several years ago. He uses it a lot. It's apparently a fine boat. That says something good about the stitch and glue process.

You can still buy AA and AB marine grade fir plywood, for a lot less than Meranti Hydrotech. The shipping on special plywood orders roughly equals the price of the plywood unless you aren't in a hurry. I sometimes go to my local lumber yard and order BB marine grade fir plywood (that I use for form making) but I tell them I want to wait, so they can have it thrown on top of the next semi-load they get in from Boise Cascade. Then there is no shipping charge at all. I can still buy that stuff for about 50 bucks a sheet.

Meranti Hydrotech is more like 135 bucks a sheet with 125 dollars shipping added on top.

Here is an adjustable rib in action, back when I was designing the Dayak. What you see here is a plywood plug which I covered with visqueen before covering with Plascore, to make an all Plascore boat.

But when making a plywood boat (or Plascore/plywood composite) the process is the same. Fiddle with adjustable ribs until it looks right. Then glass it up.

The only thing you have to decide in advance is the size and shape of the side panels. After that it's anything goes.

It's worth mentioning, about this on-the-fly full-size design process, after achieving what looks like your favored boat shape, the next step is to STRAIGHTEN up the form, before tracing out a bottom panel and attaching it.

There are lots of straighten the form tricks. There is a discussion about that in the MRBoats building manual.

I called one of the true 'local lumber yards' to ask about Hydrotek and Marine Fir. To my surprise they stock Hydrotek (3/8" x 4' x 8' = $97) and BB Fir ($77, same dimensions) as well as AC Fir ($85; same dim's). This same company was also known for being an Okoume dealer in the past but this is no longer true. Given this it seems the AC might be suitable if I choose to apply paint. I must admit the beauty of natural wood grain is appealing to me...

I am surprised to learn these boats are built by first glassing the side panels then forming them around the ribs.

Okay, Plascore bottom only. I thought this might be used in a sandwich configuration with a thin plywood sheet over the top of it, but if not then not. Yes, this makes the function of the adjustable ribs clear.

I have no space for this type of project currently. The 19' panels make this situation worse...maybe I can build a work surface featuring a surrounding catwalk over my ~14' Civic sedan?


Edit - I just found another local source that is much less expensive w/AB Fir and Hydrotek (6 mm/5 ply @ $52, 9 mm/7 ply @ $85). Worth the trip!

Adjustable ribs are a design tool that allow you to experiment with different boat shapes until you get what you want. Then you turn it into a boat.

For side panels and bottom panels both, whether plywood or Plascore, it works well to fiberglass ONE SIDE ONLY before attaching said panel to the form. If you pre-glass both sides you can no longer bend that panel. So then you are in big trouble. Pre-glass one side only, inside or out. It's harder to do good glass work on the inside of a boat so I always pre-glass the inside of any panel. But the other is possible.

The bottom panel should be Plascore only with no laminated plywood on top. Stiffness comes from adding enough glass top and bottom. Layups are variable, depending on who is talking.

When I need fiberglass I usually call RAKA in Florida and buy what ever is on sale. I bought a whole roll of 6 ounce 38" inch wide almost a decade ago, at a bargain price because they were discontinuing that brand. I still have some of it left.

How much glass do you need? White water boats need more stiffness and abrasion resistance than fishing boats. 3 layers 6oz outside and two inside
with added fiberglass tape over the chine works for me. Layups are set in resin but not in stone. You can vary things a lot and still get a good boat. You can always add more glass at a later date.

Okoume is lighter than hydrotech but not quite as strong.

Note too:

Meranti Aquatek is not the same as Meranti Hydrotek
Aquatek is good stuff but it is cheaper and less durable than Hydrotek.

The Aquatek is actually more costly than the Hydratek at this particular company. They also have Sapele and Okoume both of which are certified to BS1088 as they should be. Their prices on Sapele are not posted on the website but I now know who I will by my Okoume from for the saltwater microskiff I would like to build and I'll be able to drive to get it.

Would you suggest Kevlar over the external surface of the Plascore followed by low weight fiberglass to smooth out the finish? I would suspect this to be preferred but do not know what it is like to go back into a layup to repair it. RAKA currently has a 5 oz and 7 oz Kevlar/CarbonFiber on special because they want to get rid of it but these are 50' wide rolls and much more costly than any biaxial. Fiberglas cloth is always less than $10/yd. If any combination of fiber is used it seems a biaxial with normal cloth it the way to go. Their 6 oz glass cloth is the only 60" width role.

Width doesn't matter much. If it's wide fabric you can cut a whole panel out of it, although that does create waste. If it's narrow fabric you can piece the cloth together to cover what ever you need.

I have a buddy who is a professional fiberglass guy (he builds various ski sled contraptions for wheelchair people, so they can ski). He builds up fiberglass layups with semi-random shapes seldom more than 2' feet square, each piece overlapping the other 6" inches or so. By the end of the layup it's pretty smooth. Fairing putty or gel coat over top of that makes a baby smooth finish.

Kevlar under cheaper glass is the way to go, if you are going to use Kevlar at all. It is expensive. I've built a zillion boats without Kevlar and they're all still out there on the river.

Some biaxial fabrics are harder to wet out than others. For the heavy biaxial tapes some people use over the chine you will want to use a "fiberglass roller" which you can get at RAKA. It's like a stack of quarters with sharp edges mounted on a painter's roller frame. It helps squeeze out air bubbles when wetting out thicker fabrics. I have a roller from RAKA. I don't use it much but I'm always glad I've got it, when I do need it. They don't cost much.

The best layups are vacuum bagged, often using fancy fabrics like Kevlar or .... can't remember the other names. I bought a vacuum pump once and never used it. I still have it. The difference between vacuum bagged and a poorly done layup is large but the difference between vacuum bagged and an expertly done hand layup is not all that much.

Bob Pavlic--my buddy who makes the wheel chair ski sleds--convinced me of that. Bob has vacuum bagging equipment but seldom uses it. He claims it's a giant pain in the butt and the final product is only slightly lighter and tighter than what he does by hand. Although, Bob has been making layups for going on 50 years now. He's 70 something like me. He'll retire at the casket.

I checked on some materials for building a vacuum bagging system large enough for this purpose. I must admit it was more costly than I expected but I still regard it to be useful. I have only bagged considerably smaller parts.

using this simple boat on average twice a week for two year and a month. I still haven't bought proper oars and still love the boat. On larger lakes I now use the 30 lb Minnkota motor it get on site then I use whichever is necessary to re-possition. Since I use it allot on lakes and since the motor is on the side, where I can reach it) I might add a removable keel this winter. Or I may keep it original and build a small two man flat boat for lake fishing. Something with a lower transom for the motor.