How to get the bow down on west coast style dory

[TomMcKinney]

I have a Glen-L Little Hunk Dory. 15 and 1/2 ft long, with motor in a well. Its powered by a tiller steered 50hp Tohatsu TLDI, has a dole-fin and non adjusting trim tab. When I throttle up, the bow comes way up and its hard to see. My only remaining options are ballast forward (sand bags) and a tiller extension to move my fat but forward.

Anybody have any other thoughts or ideas? Thanks

[pipefitter]

Is the motor trimmed all the way down? Thats a large motor for a 15ft dory and a tiller at that. Dories with their steep raked transoms translate to more like a 13ft boat. You would do better to get a tiller extension and move foreward like you say.Move batteries and fuel tank foreward as well.

[Peter Eikenberry]

If you are pushing this dory to plane of course the bow is going to rise up because of the rocker in the bottom. Dories were not made to go that fast.

[Dave Wright]

Try the tiller extension first and move forward. If that doesn't work, decide whether you want to replace the non adjustable trim tab with an adjustable one. Finally, you could add a hardwood wedge to the bottom of the boat, as close to the plane of the transom as you can get. Maybe full width across the bottom unless the cavitation plate of your motor is high, then leave a gap in the wedge at the center line of the boat, say 10 inches or so. Heck leave a gap no matter what. Maybe try a 1/2" X 2 " wedge (that's a right triangular cross section, 1/2" and 2" on the right angle legs, the hypotenuse goes against the bottom; the 1/2" dimension is aft - sketch it and see how it directs flow downward to raise the aft end of your boat up).

Dave Wright

[TomMcKinney]

I apppreciate the help Peter, but this boat is designed to plane. It is a Pacific coast power dory not a banks style rowboat.
http://www.boatdesigns.com/products.asp?dept=531

The fuel is forward, but batteries would be hard be move. I'll see what a tiller extension does.

Dave- the motor is in a well so there's a gap already- If no midship well than I doubt there would be a problem since I'd have 3 more sqft of planning surface. I've read about wedges before, in fact i believe Tracy O'brien's 16 ft'er calls for them in the plans. I suspect the smaller hulls need the help with their minimal bottom/planning surface compared to weight.

Thanks


Tom

[pipefitter]

I forgot to mention this but there is an outfit called "Bob's Machine Shop" that makes a bracket patterned wedge for your outboard that adds another 5º of trim to your motor. Just another thought.

www.bobsmachine.com/Products/transom_wedges.cfm

[George Ray]

Where is the cavitation plate in relation to the bottom?

pictures !!!

[RonW]

Tom, I don't believe you are getting the straight and hard core dope, other then peter's post.

I have a 18 ft. dory, and you took the plans for a 18 ft. pacific dory, which should have had a 30 horse and reduced it to a 15 footer and installed way too much power and weight.

I would suggest.
A- mount a pedestal seat on the bow with remote steering and wear a motorcylce helmet, goggles and the best life jacket that money can buy. (orange, so they can find you)
B- remove the 50 and install a 10 or maximum 20 horse.
C- take the transom off and add a couple of frames to lengthen the boat to around 21 ft.

I respect glen-l , but also see where they say 500 pounds max. weight for the motor on the 18 ft. version, that is a big screw up, they also say 25 horse for the 18 footer.That is more realistic.

Sorry but you are just way too overpowered and weighted.

[Cuyahoga Chuck]

It sounds like you are trying to climb your bow wave just like an overpowered displacemnet hull. You didn't state the boat eventually planes. The tip off that you are not getting on plane would be the enourmous amount of gas you are going thru'.
The usual suspects have to be sorted thru'.
Too much motor weight? How much heavier is your fifty than the forty that's called for? Everybody wants a bigger motor than is called for. But, if you mount a husky 4-stroke instead of the lightweight 2-stroke the designer had in mind you may be moving the CG too far aft.
Is the bottom as straight as it's supposed to be? It's not difficult to screw this up on a home-built.
How heavy are you? (An editorial question). Designers have no way to anticipate a 300 pounder on a tiller steered boat.
I'm not saying any of this applies but, stuff like this effects amatuer boatbuilders all the time.

[Steve Miller]

And Glen-L has long calcuated the weight of "people" at 150 pounds.

[Dave Fleming]

Tom, the recommeded HP for that boat from the Specs page is 25 HP.
And that is for the full sized version.

How come you went with a 50HP?

[Tar Devil]

Tom, is your boat the Wee Hunk or Little Hunk?

[RonW]

This one always intrigued me, a little shorter, but hey he only used a 40 horse.

http://www.glen-l.com/picboards/picboard11/pic587b.jpg

[TomMcKinney]

Tar devil- Its a shrunk Little Hunk. I assuem builder did it per plans which say shrink by up to 3ft by leabving out a rear frame bay.

Ron-Glad you like that boat since that's exactly the one I bought. Was happy to see it for sale and had to bite.

In between those pictures and me another owner repowered with the 50HP, said he needed the extra HP

The engine weighs around 200 lbs,probbaly 210, just like me

Motor is not too heavy given the max weight of 500 by the designer. Bot even 1/2 that weight. And I'm not sure why you agree with peter's comments on dories not going that fast. These are not displacement boats. Although this boat might have too much rocker from mid ship back (shouldn't have any in the rear, but may have some built in)

Dave- you get props for your experience, but 25hp is MINIMUM recomended per stats published on the website, so I doubt its overpowered and it came that way. Plus on the one hp per 25lbs, boat needs aat least a 40. I doubt the weight difference to the 50 makes that musch a difference but I could be wrong.

I fear that the bottom may not be perfectly done, But I need to go out with a straight edge and check. I would bet 100-200 lbs of sand placed up front would work wonders and not effect speed/fuel too much

Thanks for the info all

Pictures from previous owner can be found here
http://www.glen-l.com/picboards/picboard11/pic587a.html

[jlapratt]

......I doubt its overpowered and it came that way. Plus on the one hp per 25lbs, boat needs aat least a 40.

Just because it came that way doesn't make it right. That is an awful of of power for a 15 footer! I built my 16' San Juan Dory very heavy and only have a 30 hp on it. Now you are going to add more weight to it by way of ballast forward. You need to compare the DWL and where it sits now; that will speak volumes.

The need for trim tabs should have been a big clue that something is wrong.

Jeff

[Todd Bradshaw]

Did anybody else find it strange that the Glen-L website blurb for this design listed only a minimum Horsepower (25)? They do tend to be a bit spotty about even including HP figures in their catalog (which is pretty unusual for somebody selling motorboats) but quoting a minimum without quoting a maximum on such a small boat would seem to leave the legal liability door wide open with a sign on it that says "come on in!"

After seeing what a Simmons 18' skiff can do with a 25 in the well, I wonder if this rating is a typo on the Glen-L website and shouldn't read "maximum" rather than "minimum". There's no way on earth that that little boat should need 50 HP. It would be very interesting to see what it would do with something in the 18-25 range and about half the weight back there.

[RonW]

Well here is a whole web site dedicated to the pacific dory in the 20 to 27 ft. range roughly, and most of them carry 40 to 90 horses.

They are seaworthy enough boats, but they rock and rock hard. And when the water is rough they can only run around 12 m.p.h. or they just flat out pound so hard you can't take it.

http://home.att.net/~td2evers/index.htm

[Peter Eikenberry]

Sorry but I still think it's way overpowered. Your method of calculating horsepower is not correct. For a flat bottom hard chine boat under 20 feet in length, with a 20 inch transom height, the correct formula for horsepower is

Length (on center line) times maximum transom width times .5 minus 15.

L X B X .5 - 15 = hp (round up to nearest multiple of five)

I can't believe that Glen-L would get the wrong rating for this boat. I have talked to them many times over the years and they are meticulous at getting it right. A 25 hp motor with engine batteries and full fuel tank can weigh as nmuch as 200 lbs. A fifty with battery and fulel tank weighs close to 400 lbs. Additionally the weight you quoted is the maximu weight capacity including passenger gear, motor and fuel. You're way over that with a fifty hp motor. Even allowing for transom width same as beam the max I can caclulate is 45.

[pipefitter]

Plus when you splash trim tabs down in the water at max trim you are taking away some of the extra hp anyway.30hp with less drag is going to perform better and more economically than a 50 ran under a trim load,plus consider the bolt on cavitation plate. It starts going backwards after awhile.You may indeed end up realizing only 30hp of that motor while burning a 50hp worth of gas.

[Tom Hunter]

The comments about too much motor could easily be correct. On the bright side you can sell a 50hp and get enough money for a 30 and still have some left over.

Before you do that take the boat out with a freind and have them sit in the bow. If that solves the problem then you know you need to put wieght forward. But you will still have a lot of wieght for a 15' boat, which means increased fuel costs.

Figuring out what a 30hp weighs might be worth the trouble, you may even be able to get that information online. Figuring out what everything weighs and where it is located might also be worth the trouble.

I just looked at the other little hunk pics and noticed that the boats shown all had more horsepower and the engines out on the stern, not in a well. I am not sure what this implies for your boat, but it may mean that what works for them will work differently for you.

A previous owners statement about needing a bigger engine should be discounted unless he is a professional boat person with experience in many different types of boats. I bought my boat from a guy who sailed it for years and though many of the modifications he made were sensible some of them leave me scratching my head. For example the bilge pump could only be reached by lifting the engine out of the boat. That is what the previous owner did, but does anyone reading this think it was the best way to do things?

[David123]

Since your boat has been reduced in size, it is now closer to the Wee Hunk than the Little Hunk.

Max recommended HP for the Wee Hunk is 40 HP. (from the Geln-L site)

Don't overthink this. Just get a smaller motor if that's possible. Or run at 1/2 to 3/4 throttle to test the theory.

[Todd Bradshaw]

That will test the power part of the theory, but not the weight and balance part, which seems more likely to be causing the problem to me than power.

[Spokaloo]

Alright, Im going to dig this out of the bilges because Im looking at a Pac dory to build, scouring the web trying to find plans for what I want, and can't. The thread was a good one, but I think everyone missed the true reason for this boat's issues.

As designed, its supposed to be at a minimum 18' long. This provides a 12' flat run aft, which with the well option shortens to 9' with two side strakes beside the motor. When he shortened this boat to 15', all of the length was removed from the aft planing sections of the boat. Given our dimensions above, we have a 6' planing section, which for a planing craft is the bare minimum to plane.

By introducing a motorwell, the boat has lost much of its ability to bear weight near the transom. Parallel to the loss of buoyancy, we also see a loss of planing surface aft, in the most critical area. This boat, while trying to climb up over the bow wave, is running on less than that 6' of planing surface, and generating next to no lift aft of the motor. Compounded by the tillersman, this is an untenable situation for the boat.

Look at semi-planing boats with well mounted outboards. In order to achieve the desired performance, they are LONG (this is not), they are NARROW (this is not), and the weight is biased towards the middle 1/3 of the hull length (not all at the transom). This allows the main body to generate lift, and the aft sections to allow the water to curl back in, reducing drag.

On top of all of that, this boat is framed with what I guess to be fir and sheated in fir ply. This also makes her heavy for her length.


SOLUTIONS:

Remove the well (its easier than you would think). Just add in hull sections underneath with appropriate framing and a little fiberglass. Cut out the transom, and you will have a different boat.

Add a center console. It will distribute the weight more appropriately for the planing condition you want. Also move ALL weight (batts, fuel, supplies) out of the aft sections to amidships somewhere around the console area. KEEP IT LIGHT.

Atkin was notorious for adding hook to the hull in the aft sections to generate lift. Add some considerable wedges to those sponsons next to the motor. You have enough lift forwart to counteract all of that negative trim this will incur, which will also make the boat feel like its 1000 lbs heavier than it is, both in stability and steering. This is a good quality!

Finally, reduce the engine weight. Switch to a 2 stroke 30 with some of the above mentioned alterations. If need be, don't forget to change out the trim tabs, and make them almost as wide as the sponsons, that way you get considerable lift.

Alright, now I feel better.

Anyone know where I can find plans for a 14-16' Pacific city style power dory?

E

[Andrew]

Another possible solution it to add Cavitation Plate fins (DOL-FINS,STINGRAYS, etc). These will help bring the bow down, get on plane at lower speeds and help hold in turns. They're also easy to try and relatively inexpensive.

[Tom Lathrop]

I have a Glen-L Little Hunk Dory. 15 and 1/2 ft long, with motor in a well. Its powered by a tiller steered 50hp Tohatsu TLDI, has a dole-fin and non adjusting trim tab. When I throttle up, the bow comes way up and its hard to see. My only remaining options are ballast forward (sand bags) and a tiller extension to move my fat but forward.

Anybody have any other thoughts or ideas? Thanks

At first glance, this looks like an unlikely situation. Are you saying that there are trim tabs on the boat? Never seen a trim tab on an outboard except the torque corrector under the ventilation plate. I can't believe that a trim tab under the transom won't correct any amount of bow lift except under an extreme weight distribution unbalance.

If there are no trim tabs under the transom, Make a couple of temporary wedges and tape them on the bottom. Plastic packing tape will do for this trial. Make the wedges about 6" wide by 6" long, 3/4" thick at the aft end and zero at the leading edge. This should make a real difference and tell you which way you need to go.

[erster]

Alright, Im going to dig this out of the bilges because Im looking at a Pac dory to build, scouring the web trying to find plans for what I want, and can't. The thread was a good one, but I think everyone missed the true reason for this boat's issues.

As designed, its supposed to be at a minimum 18' long. This provides a 12' flat run aft, which with the well option shortens to 9' with two side strakes beside the motor. When he shortened this boat to 15', all of the length was removed from the aft planing sections of the boat. Given our dimensions above, we have a 6' planing section, which for a planing craft is the bare minimum to plane.

By introducing a motorwell, the boat has lost much of its ability to bear weight near the transom. Parallel to the loss of buoyancy, we also see a loss of planing surface aft, in the most critical area. This boat, while trying to climb up over the bow wave, is running on less than that 6' of planing surface, and generating next to no lift aft of the motor. Compounded by the tillersman, this is an untenable situation for the boat.

Look at semi-planing boats with well mounted outboards. In order to achieve the desired performance, they are LONG (this is not), they are NARROW (this is not), and the weight is biased towards the middle 1/3 of the hull length (not all at the transom). This allows the main body to generate lift, and the aft sections to allow the water to curl back in, reducing drag.

On top of all of that, this boat is framed with what I guess to be fir and sheated in fir ply. This also makes her heavy for her length.


SOLUTIONS:

Remove the well (its easier than you would think). Just add in hull sections underneath with appropriate framing and a little fiberglass. Cut out the transom, and you will have a different boat.

Add a center console. It will distribute the weight more appropriately for the planing condition you want. Also move ALL weight (batts, fuel, supplies) out of the aft sections to amidships somewhere around the console area. KEEP IT LIGHT.

Atkin was notorious for adding hook to the hull in the aft sections to generate lift. Add some considerable wedges to those sponsons next to the motor. You have enough lift forwart to counteract all of that negative trim this will incur, which will also make the boat feel like its 1000 lbs heavier than it is, both in stability and steering. This is a good quality!

Finally, reduce the engine weight. Switch to a 2 stroke 30 with some of the above mentioned alterations. If need be, don't forget to change out the trim tabs, and make them almost as wide as the sponsons, that way you get considerable lift.

Alright, now I feel better.

Anyone know where I can find plans for a 14-16' Pacific city style power dory?

E

You have covered some genuine issues with some of these designs. It can be done to some limited success. But you are not going to get a runabout by today's standards. What many people seem to forget is the original purpose for the dory design. You are asking for a true planing hull in a dory design. The motors were for making the boat "go ahead" not perform as an optimum runabout by today's measures.

Remember too that "ballasting" with altering the position of cargo weight does not make a hull necessarily better since its above waterline, too. This is what is known as measured success but also can create adverse conditions in the wrong types of weather with a small craft.

[erster]

I got a raw and unproven plans for Power Dory here, but I cannot let anyone have it yet till I build and test it first, and get it US Coast Guard approval...

Welcome to the world of R&D. One real issue that is evolving with modern technology in the design programs, anyone can design for eye appeal, but does not necessarily represent a good hull design. This is the real world, unfortunately. But fortunately for the real world, too, there is some oversight, especially given peoples computer's ability over and above their engineering abilities in certain areas.;) Airplanes, too, come to mind.

[kengrome]

Alright, now I feel better. Anyone know where I can find plans for a 14-16' Pacific city style power dory?Honestly I think I would build myself a Bolger Diablo before one of these boats -- maybe raise the sides a bit for offshore use. There are reports of Diablo planing on 9.9 HP 4-strokes, and others that claim it is the best handling boat of any in its 15 foot size range. And it looks good!

http://www.instantboats.com/diablostory.htm
http://www.users.bigpond.com/keb/
http://www.kolbsadventures.com/diablo_12.htm

... but it is definitely not a Pacific Power Dory by any stretch of the imagination. Then again the pictures posted of the boat discussed in this thread make it look really short and fat. I hope it's not really as short as it looks, but if it is I can see why it doesn't plane.

I guess I don't really like looks of these boats much, even the ones that look better proportioned. They look like they are built heavy though, so they can probably haul a lot of weight if need be.

[mmd]

The subject of this thread seems to me to be a fine example of The Law of Unintended Consequences. Mess with the design and you take your chances on performace.

Spokaloo has it pretty much down - it is a problem of lifting surface area and centre of lift, plus weight distribution. The installed power is a bit high, but that is not causing the problem. If the boat planed properly, it would probably be uncontrollable at WOT, but that is a problem for another day.

I, too, think that the solution is to 1.) remove weight from the boat and shift what is left forward; 2.) mount the engine on the transom and extend the planing surface over the motorwell hole, or 3.) get a new boat.

Sorry if this advice isn't what you wanted to hear.

[Spokaloo]

I actually really want a true Pacific City power dory.

I need a boat that can be beached fully and retrieved by trailer. I want to be the absolute shallowest draft possible because I have to help people on occasion near our house in extremely shallow water. I need a burdensome boat that can be used for serious shoreside work including hauling dock components and weed mitigation. I want a hull thats as efficient as possible fuel wise. I need to be able to fish readily. I need a good crabbing boat for a small protected bay we crab on the oregon coast ( many 14-18' boats are out there with us).

Here is the environment:


http://i17.photobucket.com/albums/b65/fighterama2/airlift/airlift028.jpg

On top of that, Im a displaced oregonian, so I want a boat from home, ya know?

http://voila-finearts.com/images/bretts_boat.jpg

E

[Tom Lathrop]

The subject of this thread seems to me to be a fine example of The Law of Unintended Consequences. Mess with the design and you take your chances on performace.

Spokaloo has it pretty much down - it is a problem of lifting surface area and centre of lift, plus weight distribution. The installed power is a bit high, but that is not causing the problem. If the boat planed properly, it would probably be uncontrollable at WOT, but that is a problem for another day.

I, too, think that the solution is to 1.) remove weight from the boat and shift what is left forward; 2.) mount the engine on the transom and extend the planing surface over the motorwell hole, or 3.) get a new boat.

Sorry if this advice isn't what you wanted to hear.

Michael,

There are lots of dory or semi-dory or boats that are called dories that do plane. The Pacific Dory is one of them. If this boat truly reacts like Tom McKinney describes, then there must be something wrong with it. One best measure of the ease of a boat planing is bottom loading and the dory does suffer there because of the narrow bottom of small area.

Tolman Skiffs and Simmons Skiffs are dory types that do plane and give good account of themselves in the ocean so that should not be the issue. Adding weight to any planing boat is the surest indication that something is seriously wrong. I'm not fond of dory type power boats either except for use in rough water where their flared sides and narrow bottom can be an advantage in seaworthyness when properly loaded.

Without a careful look at the boat, we are just spinning wheels here. Some other cases in my experience of similar performance have been traced to rocker (convexity) in the aft planing surface. If there is rocker back there, the boat is never going to plane properly but wedges under the transom can help.

[mmd]

Tom, I am not disputing that dory types can plane. I think that, given the description presented, that this boat has inadequate planing surface (excessive plane loading) due to the reduction in boat length at construction (messing with the plans when you don't know what you are doing) coupled with the centre of dynamic lift being too far forward of the centre of gravity (balance). Rocker probably doesn't get a chance to show its bad manners here. As the boat gets up on plane the centre of dynamic pressure on the planing surface - which is probably around midships, or slightly forward of that - lifts the hull, which rotates longitudinally about the metacentre, forcing the stern down. With the somewhat large hole in the boat thanks to the motorwell, there is not enough reserve buoyancy to resist this, so the boat assumes a bow-up attitude. In this attitude, the planing surface available is very inefficient and this, coupled with the drag induced by a large, square, open hole in the planing surface (the motor well), sucks up a large portion of the available horsepower. What is lacking is an efficient planing surface; no amount of gizmoes will compensate for that.

Trim tabs, transom wedges, wing thingies on the outboard lower unit are all, IMHO, band-aid solutions to try to compensate for the shortcomings of a badly designed or constructed hull, and they all rob power through drag.

[erster]

The LITTLE HUNK can be increased or decreased in length by up to 3' by simply adding or deleting one or two of the duplicate aft frames.


On the Glen-L site for the plans, the above is listed.

https://www.boatdesigns.com/products.asp?dept=531

This thread was created almost a year ago. We do not know what took place in the building process at all. This I feel comes into play more than anything.

Spookaloo, you need a boat built in aluminum, from my point of view after reading your reply, when you wish to have a beefy hull, but efficent hull.

Disclaimer: My comments are opinions as I am not properly trained in boat design, and feel free to weigh them accordingly. But a dory skiff designed originally for a motor even with wedges should run on a planing angle, even though most bows will be a bit higher than most runabouts. The fine line for me is the difference of pushing water when the angle is too extreme, for sure.
When looking at his profile, its been a while since Tom McKinney has been concerned further to follow up. It would be interesting to read what if any conclusion or fix took place.

[Spokaloo]

I dug this thread up because of two reasons:

1) I felt it was unresolved

2) I am planning to build a boat similar to it.

Erster, I like the idea of aluminum, but I suck at welding steel, so alu isnt going to be pretty. Ply will be the order of the day as I build it, but if I find it to lack durability, sheet alu is an option.

Thanks!

E

[erster]

I dug this thread up because of two reasons:

1) I felt it was unresolved

2) I am planning to build a boat similar to it.

Erster, I like the idea of aluminum, but I suck at welding steel, so alu isnt going to be pretty. Ply will be the order of the day as I build it, but if I find it to lack durability, sheet alu is an option.

Thanks!

E
3/8" meranti plywood with biaxall cloth, 1808 or at minimum 1208, or some folks may mention dynel or fabrics like Kevlar for the bottom would be my first choice for a medium duty hull. But there are stark differences in 14 to 18 feet hulls in all weather uses for sure. If you can find AB fir with the rescoursinal glues, I would use that in the place of meranti. But to ensure the angle is correct from your point of view, I surely would buy a set of Simmons plans and check out their setup on the strongback and framing and adjust accordingly to any other plans of simular designs.

On the Simmons site, there are links to several videos. Check out number three and you maybe surprised at the running angle of the hulls. But without some modifications to the bottom, staying with the intended hp is important to counter some of the loss of bottom planing surface in known designs, having a lot iron and dead weight in the well area. There are other ways of achieving a more desirable running angle with some changes. But to discuss this would also be modifying plans and an expensive crap shoot of serious consequences if you get it wrong doing this on your own.
http://www.simmonsseaskiff.com/Video/index.htm

The very first thing you need to do is to get your well right with the intended engine in hand before you do anything else.

[Tom Lathrop]

Yeah Michael, I agree with everything you say but was assuming the designers knew what they were doing when they said the Little Hunk could be shrunk by 3 feet. Still, a 50hp motor aught to get it on plane unless there are some lead bricks hidden away somewhere.