Outboard mount on rudderbox??

[bluefightingcat]

I recently acquired this boat:

It's a K-19 build from plans sold by NorthWest Marine. It's build using plywood which is then laminated with fiberglass and gelcoat.

I want to add a "transom mount" so that I can add small electric engine. Obviously this boat does not have a transom. I came up with the idea of mounting the engine on the rudderbox. This is the idea:

The mount would fit in on top of the top pin of the rudder. And then I would use the L-plates to anchor the whole system to the rudderbox to provide some support. More pictures here:

I have not done anything permanent yet. I am just concerned about whether the rudderbox can handle the weight and force of the outboard. The outboard is a e-propulsion spirit 1.0 plus. It is a 1kW/3hp electric outboard. The outboard weights 19.3kg or 42.6lbs.

What do you think? Is this a crazy idea?

 

[El Borracho]

Sailors often mount the motor to one side. Are you going to remove the rig?

 

[bluefightingcat]

Sailors often mount the motor to one side. Are you going to remove the rig?

Is there an advantage to having it on one side? With my idea I would have to remove the rudder, each time I wanted to mount the motor. But that is easy to do.
When sailing I would take the motor completely of and store it away. Most of the time I do not use the motor and it's only there to help with trailering or in case I get in a sticky situation.

 

[El Borracho]

Offset to one side because the rudder. Rudder can stay mounted for steering under power. Affixing the mount elsewhere is probably easier too. Raising and lowering the motor on its mount makes the transitions between sailing and motoring much smoother. Steel hardware store angles and timber are going to be ugly. How about the same glass over plywood techniques that were used for the hull?

 

[CaptainAhab]

That looks like a 19' Laser. The deck proportion , how the aft tucks in, even the bow. I wonder if someone scaled it up.

 

[Marty Gingras]

Cool boat.

The motor is likely overkill.

 

[Diamond Jim]

I’d ask someone who knows the boat’s structure like the designer or the builder.
Anyone else has no idea what’s behind the paint.

 

[longy]

The boat will be un controlled during the transition. In calm waters & light breezes, this would be OK. But if you need to make the transition in any sort of weather I think it will get wild quickly. Wind & waves will take the boat wherever they want. Meanwhile, you're bent over the back, pulling the rudder up, swinging it sideways & securing it somehow to the cockpit, then swing a heavier thing back over & down.
I'd make a side mount

 

[Sidecar]

Can you not mount the motor somehow off the back of the rudder?

Win. Win?

 

[Monkey]

It will handle like shit. Think of it like a jet ski. You’ll need throttle just to turn. That’s not fun.

(Yes, this is based on experience)

 

[Fortely]

Unfortunately, I do not fully understand the construction. Are the "L" plates screwed to the rudderbox or not? If so, do you need to screw every time you switch to engine?
If not, would only the top pin of the rudder hold it? That is not appropriate for a number of reasons.
- not secured against upward movement. you can loose your engine in waves
- high forward throttle can break the wooden bracket
- high forward throttle will bend the rudder pin
- repeated forward and backward throttle will break off the steering pin

 

[bluefightingcat]

Unfortunately, I do not fully understand the construction. Are the "L" plates screwed to the rudderbox or not? If so, do you need to screw every time you switch to engine?
If not, would only the top pin of the rudder hold it? That is not appropriate for a number of reasons.
- not secured against upward movement. you can loose your engine in waves
- high forward throttle can break the wooden bracket
- high forward throttle will bend the rudder pin
- repeated forward and backward throttle will break off the steering pin

The plan is to screw the L plates to the rudderbox. I haven't done so yet because I am not entirely convinced it's a good idea. Yes the plan would be to screw the mount everytime. However I don't use the motor much, so it would not be a big burden.

 

[gt-MTb]

Think of it like a jet ski. You’ll need throttle just to turn. That’s not fun.

Agree with this, you need the foil. Stop any plans that require you remove the rudder.

You will leave the motor pointing straight, and use the rudder to steer.

Lots of sailboats without transoms have motors... look at J70's for example. Something similar should work for you.

 

[bluefightingcat]

Thanks everyone. I've decided against using the rudderbox as a place to mount the motor.

 

[Monkey]

Thanks everyone. I've decided against using the rudderbox as a place to mount the motor.

Smart move. The one year we kept our B25 in a slip, we’d run it over to the hoist before every race to clean the bottom. We had the same bad idea as you one night and decided not to put the rudder on. It handled like a Mustang leaving a car show. (Back end going everywhere and trying to crash into anything it could find)