by Pat Patteson

Power and Control for an AF4 Grande Cabin Boat

Editor's note: The following is edited from a series of posts that Mr. Patteson made to the Wooden Power Boat discussion group

I haven't read the posts here is a few days and have gotten a little behind but I am interested in the progress of what appears to be 3 AF4Grande's now. Steve, Eric and Pierre.

I've been corresponding with Eric and Pierre a little to try to help them through some parts of the plans they didn't completely understand. I have probably bored them Both to death with Too much detail and filled their hard drives with pictures of my PK construction pics. But, I think They are both making sawdust too.

I've been following Steve's ideas for the Grande Cabin Boat and I know Mikeeeee has been thinking about a Grande Cabin Boat for a long time.

"I am building an AF4 Grande, Jim Michalak’s 120% version. It will be 21'6" with a 6'6" beam. Powered by a long shaft 35 horse Mercury that I earned in a trade for a dory skiff." Oct 22, 2001

I've been thinking about adding some sort of hard top, raised cabin to my PK-20 for a while, and now that the Oregon rains have started in earnest, I'm thinking about it even more.

My PK-20 is basically a 20’, 10% scale up of the AF4 for those that don’t know. But I made So many changes that it is no longer an AF anything and I am taking full responsibility for the design.

The PK is the first boat I have built with a slot top. Actually the first I have built with a cabin that could Have a slot top. (If you don’t count the 10’ “Cabin Cruiser” I built when I was about 10. It was built from “Recycled” (stolen) materials from an abandoned house, and had the seams caulked with tar scraped up from a road. It floated and didn’t leak too bad, but was a little Too top heavy with the 3/4” lumber cabin. It floated best in a “Stable 2” position. It was only used one day.)

All the rest of my boats have been open skiffs or dories.

I Really Like the slot top on our PK. The big slot seems to make the boat Feel a Lot bigger than it really is and lets one walk the full length of the boat.

I currently have two slot covers. One is a blue tarp cover supported by a rather highly arched 1/2” CPVC pipe that gives nearly 5’ feet of headroom at the aft part of the cabin.

The second top is a one piece hard cover made of 1/4-“ Luanne. I use the hard top for trailering or for when I Know the weather is gong to be Not so Nice and I won’t have the slot open.

Pat's PK-20

I enjoy the boat the way it is now, for nice weather. But for Not so Nice weather, I am thinking about some sort of Removable, Standing headroom (over the cockpit) cover that would cover the entire cockpit and about half of the cabin.

My helm is mounted on the bulkhead just in front of the motor, and I sit on a compartment next to the motor to steer, so I need a top that will keep the rain off my bald head, way back there.

The top would probably be made with light “Sticks” and skinned with 3/16” Luanne, or even “Door skins” to keep the weight down. Just strong enough to support itself and not blow away.

I’m not sure how much of the sides would be covered, but at least the part over the existing cabin, but maybe just half the sides of the cockpit, to help keep blowing rain out, and sill allow some open, side access at the back for working around a dock.

I am thinking of building the forward windshield in 3 sections and have the center window hinged so it could fold to the side, or maybe Up over the top.

I had a side hinged cabin windshield like that on my old Reinell 21’ Hardtop cruiser. If stepped up on the head of the V berth I could pretty easily crawl though that window to get to the bow.

I would build another, shorter version of the hard cover I have now, but strong enough to climb on. Some line handling could be done by just reaching through that center window, or with the help of a little 2 step, folding ladder (that I already have for getting on and off the PK while it is on the trailer) I might be able to climb through that window to work from the forward, hard cabin top.

I plan to have the sides of this thing overhang the sides of the cabin top and cockpit sides, so water will just run down and not have to worry much about gasketing a joint.

The existing side cabin top slopes slightly to the sides, so a couple of pieces of wood attached to the top there would let the front of this new top rest in front of those and make a water “Resistant” joint at the front.

The center window would close at the bottom against another stick across the forward hard slot top, so water would run off the slot cover, down to the existing cabin top and over the sides.

(Might take a little work make the water go where I want it to, but doesn’t look too difficult. If I wanted to get more complicated I could hinge the new slot top and have it fold back as a hatch to give quick access to the bow and anchor well. I already have a little door in the forward bulkhead so that would be pretty easy to get through.

I’m following Steve plans and will see what his final design is and maybe I can incorporate much of his design into my Temporary top.

More in the next message.


It seems that none of us are happy with the Nice Lightweight, Low HP, Well performing boat that Jim has designed as the AF4Grande.

Build it just like Jim says and throw in a couple of air mattresses and an ice chest and head off with that little 25HP motor.


If you intend to change Jim’s, relatively low, lightweight boat be prepared to add a bunch more HP and more underwater directional control.

Read on if you want to hear my experiences and rationale for doing otherwise and my consequences.

You are warned. This is a Loooong one even for me.

Seeing that 22’ (“Only” 20’ in the case of my boat) Hull we think the AF4Grande Needs a Lot More Stuff to be a Real Cruiser.

I Need a Head, and a Gallery would be nice, but my PK is really too small for a galley, so I added an “almost galley”, flip up cockpit table that serve the purpose.

I didn’t like the simple transom and thought something “Better” could be done with that area so I cut up the simple transom and added storage compartments. A whole lot more work and some downsides.

My sitting tests of the AF4 specs cabin lead me to decide that Jim's cabin was not as high as I Wanted. (not needed)

So, I decided to add a few inches to the cabin height. And since I now have more cabin height I decided that some nice cabin seats with lots of storage under them would be nice too. With the side seats it was a natural to put in a bed board to span the opening between them and have a Raise Double Bunk so we don't have to sleep on the bottom of the boat.

When I originally launched my boat, other than a couple of changes I made, it was Still the lightweight, open 20’ boat that was able to plane with 2 adults using a 1956 Johnson 15 tiller motor. “Only” about 11-12 MPH, but very good performance for 15HP on a 20’ cabin boat. With no bodies aboard, the tops of the 1-1/2” high chines were almost out of the water.

The 15 pushed the boat well at slow speed and adding throttle just made the boat go faster until it was charging along at 11MPH, with no “Hump” getting on plane, the boat just seemed to levitate, and at no time was there much Wake left behind.

Very Nice. Just like Jim had intended.

But, we didn’t have All the Stuff we thought we Needed for comfortable cruising.

The start of the long, downhill slide began when we took a friend along for a ride. The boat floated a little lower on its lines and when I cranked up the 15 we gained some speed and started making a wake I hadn’t seen before, but with the added 200+ pounds of our friend (I’m being nice, there might have been a couple more +’s after that 200 pounds) the PK kept making a larger wake, but try as it would that poor old 15 just couldn’t get the boat up on plane. Maybe move everybody forward? No. The 15 old ponies were Not going to plane the PK at that weight.

So, a search began for a Bigger Motor. I was hoping to find a nearly new 25HP 4 stoke for under $500, but that didn’t happen.

With good luck and good friends, (maybe there is such a thing as “Karma”) John Kohnen said he had friend with a 33HP Evinrude and his friend needed money. A few days later the friend showed up in my driveway with a 1965 Evinrude 33HP motor and a bunch of controls and wires in the back of his Pick Up.

It had a few cosmetic problems, but the couple hundred dollars and change price was realistic for my budget and he said that it ran well and I had confirmation of that from another friend, so I had My “New 33” and he had my money. We were both happy. (My money’s probably gone, but I still have the motor.)

After looking at the motor it seemed to be in pretty good shape. It did have the electric start, something I knew nothing about, but thought would be nice. I can say I got electric start so my Wife, Kay could start it, but, electric start Is Very nice, and I have never even tried to pull start it to see if I can.

The motor did Not have the generator I Thought it was going to have, but the price was still very good and for another $100 I was able to get a used generator and all the stuff I needed to bolt it on.

It makes juice.

While I had the motor apart to examine it I decided to spend a few more dollars to put in new coils and points.

I now have a nice, inexpensive, electric start 33HP motor with a generator to keep the starting battery charged.

Staring battery. I thought I Needed Some 12Volts, to run nav lights, so the battery would have been Needed anyway. I have a big boat so the Big marine battery was not going to be too much extra weight. The 33HP motor only weighs about 100 pounds (or seems to) more that the 15, and it is too heavy for me to easily put on or even move around like the 15.

Of course, the extra weight of the motor is hanging off the stern and I wanted the starting battery close to the motor, so that extra weight is back there too. So, now I have added all most as much weight as our friend and the weight is in the worst place it can be. I found the 33 burns a lot more gas than the 15, so the 6-gallon gas tank (also in the stern) was marginal for a feeling of security.

At first I carried a couple of 2 gallon jugs for reserve and had to use them a couple of times, spilling gas in the process. Those compartments are nice, but make pouring gas from a jug to the fuel take a messy task. So, I traded the 2 jugs (4 gallons=24# for a new 6 gallon tank. Another 12# where I don’t need it, but the second tank does make it easy to snap off the hose from the empty tank and snap it on the full one. A few tools and some extra quarts of 2 cycle oil stored back there too, just so I will have it, If I need to buy even More gas.

Luckily I don’t have room for another “Security” gas OB but I carry a little Minn Kota that will get me a few miles if the 33 decides it is not going to run. I added a trolling plate to slow the boat enough for fishing.

The 33 did quit once, but that was not the motor’s fault and the little trolling motor saved my butt.

Note: A 20+ foot AF4 is Not a good Rowboat.

Now those chines that were just below the surface are no longer visible most of the time and the boat draws about 8” at the stern, not the 2-4 it did with the 15.

(I have a very rough estimate that 300 sinks the PK about 1 inch.)

The 33 HP motor that I bought because it was cheap but didn’t Think I would Need that much power is Now just marginal to plane the fully loaded PK.

It will Still plane the boat and I can get a little over 20MPH, but not without a Lot more commotion and a Real Wake everywhere I go and an even Bigger Wake before getting over the now considerable “Hump”.

The PK has never had a serious “Trip” in corners, but I feel Very uncomfortable attempting high-speed turns, so I don’t.

In Fact, I travel at WOT only occasionally, and when the water is nearly flat and my destination is far enough that I can pretty much travel in a straight line. The big, long, flat bottom will ride over a 6” chop pretty well (kind of like running down railroad ties) but does start to pound when the waves get much over a foot and it is not a very comfortable ride.

A couple of heavy anchors in the anchor well at the bow and lots of Stuff in the cabin help to trim the boat a little, but that is a matter of sinking the front of the boat with even more weight.

I built the PK-20 with a full width bottom at the stern in hopes that it would provide extra buoyancy. I would suspect the slightly tucked in stern of the AF4 would sink even worse with the same load.

(If anybody has a theory that would disprove that assumption, please let me know.)

A rough estimate is that the PK-20 now weights almost a ton when fully loaded.

Not at All what Jim had intended when he drew plans for the AF4 series.

I can live very well at slower speeds. It Is a lot more comfortable, quieter and I can See what I came to see. I don’t Need to be in a Hurry to Get Somewhere. On the boat, on the Water is really Where I Want to be and any destination is secondary.

The One Big concern that I have with the PK-20 is that because of the windage of the high bow and cabin and the excessive depth of the stern and lack of depth at the bow (Even with all the Stuff) the bow blows off uncontrollably in even light winds at slow speed. The problem is that Only the bow blows off and not that the whole boat is blown sideways.

The boat just tends to weathervane around the motor and transom and unless I a very Lucky I cannot maintain Any directional control at slow speeds in even fairly light winds.

I don’t believe the problem would be nearly as bad if the stern were not so deeply immersed to serve as a Very good pivot point. Sideways I can handle. Spinning is another story.

Over the winter I intent to add a couple more “Keels” and deepen the one I have now. I am thinking at least 3”, or 4 layers of 3/4” lumber to help make the bending easier.

The deeper keels will make beaching not quite as nice, but far better than the bow blowing into something very hard or expensive.

I may leave them shallower at the stern so I can still pull the boat up to the beach stern to as Jim suggests for these boats.

I have even considered some sort of forward mounted kick up board that could be used at slow speed, but I think that the 3 keels would do the job as well without having to cut a hole in the bottom and have the added benefit of stiffening the bottom.

It would be my Strong Recommendation to have multiple and Deep keels on any boat that has a lot of windage forward and is going to float down by the stern at slow speed.

Or, Build the Nice, lightweight boat Jim designed.


Pat Patteson

Molalla, Oregon

Still, Very Happy with outcome of my “PK-20”.