Navigating Through Keel Challenges: Seeking Wisdom on Sailboat Redesign

[Bastien]

ahoy sailmate

I am reaching out to this knowledgeable community with a heart full of passion for sailing and a head filled with technical challenges. I am currently navigating through the complexities of redesigning the keel system of my 20ft sailboat, and I am hopeful that the seasoned sailors and engineers among you might cast a light on my path.

**Background:**

Four years ago, I became the proud owner of a wood fiber glass sailboat. Its classic design and lightweight attributes have provided numerous joyous sails, and over the years, I have implemented several upgrades to enhance its sail-ability, splash, and load on the trailer. The boat has a center keel, equipped with a bulb at the bottom, weighing, I believe, over 700 pounds, and has a draft of 6ft.

**The Challenge:**

The crux of my dilemma lies in the keel. The current mechanism to lift it up and down involves a manual crane, which is not only cumbersome and unsafe but also practically inconvenient. Furthermore, the deep draft is prohibitive in some of the lakes where I sail, causing constant vigilance and occasional grounding. Lastly, even a 3/4 feet lift of the keel, essential for trailer loading, poses a significant challenge.

**Potential Solutions:**

1. **Redesigning the Keel Lifting Mechanism:** Ideating a new system, possibly automated and compact enough to be housed within the boat, which would push the keel up, rather than lifting it from the top.
2. **Keel Redesign:** Exploring the possibility of replacing the existing keel with a design that offers a shallower draft, while still maintaining stability – a concern even with the current 700-pound, 6ft draft keel that tends to lean quite readily.

**Your Expertise:**

I am casting a wide net here, seeking any and all suggestions, experiences, and wisdom that you might share:

• - Ideas or experiences with innovative keel lifting mechanisms
• - Recommendations for keel designs that balance stability with a shallower draft
• - Tips or warnings regarding the redesign process

Your insights can help steer this project towards success, and I am eager to share the journey, learnings, and outcomes back with this community.

Thanks in advance.

 

[messabout]

Gorgeous boat, ugly bulb!

The boat might be able to sail well enough without the fin and bulb arrangement. The fin yes, you will need that part. The fin looks to be beastly heavy. Tell us more about the sail rig. Reducing the sail and ditching the bulb is a possible alternative....maybe.. What is the function of that four part tackle?

 

[Bastien]

Thank you for getting back to me, messabout.
Just to share, the area of the main sail is 140 sqft, and the boat has a length of 20ft, with a mast that stands 26ft tall.
I've included some photos from last week when I tested the new spade rudder design.
Could you please clarify your question about the "four part tackle"? I'm not quite sure what you're asking.

 

[Skip Johnson]

It's a lovely boat. A part of the beauty is in the slippery hull shape. Which means that there isn't much form stability, the boat will always lean easily, terrifying so if you lose very much of that keel weight or it's moment arm.
That being said, if you only need to raise the keel less than a foot to trailer it a pair of heavy duty automobile scissors type jacks one on each side of keel and geared together driven by a gear motor might be worth investigating.

 

[SolGato]

If I’m understanding the challenge correctly, you would ideally like to be able to lift and lower the keel a total travel of 30 inches (based on photos of tape measure) using a system that stays on board?

You mentioned grounding, can the system be rigidly fixed to the keel or does the keel need to be able to kick up?

 

[Bastien]

I appreciate your prompt response! Essentially, our primary objective is to be able to raise and lower the keel by 30 inches using an internal mechanism. It's crucial that the keel can be raised to its maximum height for trailer loading, and lowered for sailing. I've been looking into a few systems but haven't had the chance to test them out yet:

1) Implementing trailer jacks on both sides of the keel - this seems promising, but the range of motion might be a bit limited.
2) Considering the use of some kind of rubber wheel for upward and downward movement.
3) Exploring the possibility of using a UTV or ATV electric winch, although it might be similar to my current manual crane setup, which I'm not a big fan of.​

 

[SolGato]

Got it.

The fastest (speed) and easiest push button system to integrate would probably be an ATV winch or overhead electric hoist.

You would need to build gantry support to hoist from that could be struck and stowed so it’s not taking up room on deck while sailing, and the winch could be located permanently out of the way below deck with the cable/line (consider synthetic) routed to the center pulling point atop.

Of course the whole thing could also be a complete drop in or bolt in system instead that is setup only when needed.

Other possibilities include DC linear actuators.

You could use a pair of them either side of the keel anchored to the structure that supports the keel when down.

To get 30” of travel you need around 34” of actuator body, so you would need to fabricate an extension that mounts to the current cross hole in the keel that extends the lifting point up to gain proper body clearance, and then you would need to anchor the actuator bodies at the top near the deck to support them vertically.

To be able to lift 700lbs, the actuators will have to be on the slower side, but you wouldn’t have to work hard, just push a button. And actuators are available in a wide range of specs and varying quality, with different IP ratings, voltages, etc.. One neat trick is to use X2 actuators inline to get 2X the travel while reducing speed by 1/2. Common uses for example are hospital beds and hidden TV’s.

There’s also a different style of actuator that could be used in conjunction with a battery powered drill where the moving portion would get attached to the keel and would ride up and down an acme screw that gets anchored above and below. At one end of the screw is the drive housing that has an input shaft that could be coupled to a motor or a drill for example.

Research Ball Screw Actuator and Ball Screw Jack to get a better idea of the concept.

 

[Rumars]

We need a photo of the interior arrangement of your boat, specifically the casette that holds the keel fin and its surrounding space. We also need to know if you have enough electricity to power whatever contraption you install, or if it needs to be powered by other means, and if you desire a manual backup.

Keeping in mind I don't have those details, the two arrangements that come to mind are:

1. Two hydraulic cylinders acting on a crossbar on top of the fin. Telescopic cylinders can collapse to as much as 20% of the total extended lenght, and the weight is not a problem. Actuated via (if necessary remotely mounted) electric and manual pump, cockpit switches possible. It's a small elegant system, but it's not inexpensive.

2. Scissor mechanism straddling the fin. Actuation can be via screw mechanism with electric motor or manual. Much bulkier then the telescopic cylinders (you need to accommodate the folded lenght), but a lot cheaper and ultimately flatter. You can turn the screw with a common cordless driver if necessary.

 

[forwiw]

I was involved in the building of a number of Ultimate 20's in the past and they were equipped with a very simple keel lifting mechanism mounted on a removeable crane, they had a hand winch but that could easily be replaced with a powered one. The forum below has a discussion with pictures.
Ultimate 24 Keel Lift / Ultimate 20 https://forums.sailinganarchy.com/threads/ultimate-24-keel-lift-ultimate-20.185028/

 

[Bastien]

Good morning everyone, I appreciate your swift responses during the night. I'll be sharing a more detailed picture later on. Meanwhile, I'd like to share some thoughts on your questions and suggestions.

• I'm quite taken with the concept of DC linear actuators or a hydraulic cylinder, they could be great choices. I also don't mind incorporating a 12v battery in the boat's center, which could be useful for future electronics.

The design that Forwin proposed resembles what I currently have, and I'll share a picture soon. Although it functions, it's a bit too unwieldy for my liking and doesn't allow for quick reactions if something goes wrong. Also, my crane is aging and might need replacement soon.

 

[Bastien]

Hello Rumars,

Regarding "1. Two hydraulic cylinders acting on a crossbar on top of the fin. Telescopic cylinders can collapse to as much as 20% of the total extended length, and the weight is not a problem. They can be actuated via an electric and manual pump, even remotely mounted if needed, with cockpit switches as a possibility. It's a compact and neat system, albeit not the most cost-effective."

I really appreciate this idea, but I'm having a bit of trouble finding hydraulic cylinders that can retract to 13 inches and extend to 30 (or more). I've tried searching for multistage cylinders, but I haven't had any success. Would you have any advice or suggestions? Thanks in advance for your help!

 

[SolGato]

Take a look at Progressive Automations for DC linear actuators.

If the keel weighed more and/or speed of operation was an important factor, then hydraulic might be the better way to go, but DC actuators perform the same function in the same way while being much simpler to install.

Like I said, I would considered using X4 with a pair on either side stacked together so you get 2X the actuator speed and are able to use more common length (14”/16”) actuators since 30” ones are going to be a bit more difficult to find and likely priced at a premium.

A small battery and a solar panel to keep it topped up is all you would need to power the system.

I use DC actuators for all kinds of stuff. I built a claw for my tractor bucket actuated by one so I can grab banana stalks and lift them into a dump trailer. And my solar electric boat uses X3 to lift the solar bimini hard top controlled by a wireless key fob, and I also use another pair to tilt/trim my brushless motors by wired remote.

Got a few on the shelf I’ll probably use in conjunction with a motion sensor to create a spooky feature or two in my friends annual Haunted House this year -thinking along the lines of a body rising from the grave…

 

[Rumars]

I suggest talking to your local hydraulic shop if you can't find one online. They can advise you better then I can about what's available in your market.

On my side of the pond this is a common item used on tilting bed trailers or small dump trucks. For example a basic search gives me this:

5 stage, 750mm (29.5") extension (36" from base), 282mm (11.1") retracted, 2.6t at 160bar, max speed 0.5m/s (19.6in/s), 381.45€ (~405USD) Teleskopzylinder 5-stufig Ø105/90/75/60/45mm 750mm Hub https://hydrotechnik24.de/teleskopzylinder/teleskop-hydraulikzylinder-5-stufig-105-90-75-60-45mm-750mm-hub

4 stage, 790mm (31.1") extension, 323mm (12.7") retracted, ~463USD Teleskopzylinder Hydraulik 4-stufig - 790 mm Hub - 11,7t Querbohrung, https://www.hydrauliktechnik24.de/Teleskopzylinder-Hydraulik-4-stufig-790-mm-Hub-117t-Querbohrung
At 13.8" retracted I can get 35.8" extension for 475USD from the same shop.

Provided a stiff enough bracket to connect them to the top of the fin, one of this cylinders would be enough.

A 30" extension caravan leveling jack is going to cost you a lot less. Pair with your favorite brand of cordless driver and you have a simple and low cost solution, just not as convenient. https://www.amazon.com/South-Bend-C...+inch+scissor+jack&qid=1697055161&sr=8-6&th=1

 

[Bastien]

@SalCo, thank you so much for your solution. While I am well-versed in automation and electronics (such as RPI), I have not had the opportunity to work with actuators. Could you possibly share a picture or further details about what you're discussing? I'd like to ensure I'm exploring the correct type of actuators. Also can you help me to understand how actuator can have 3 times the sizes (36inch) of what it is when retracted? from what I am reading it is only doubling the size. Do they offer the multistage like hydro?
I am not very clear on the x4 tricks. thanks for the hlep

@Rumar, I appreciate you sharing the link. I'm currently exploring it. The 30" extension seems like a viable option; I hadn't realized it could lift to such a height. I will check to see if it fits in the trunk.

 

[SolGato]

Here’s a quick sketch of what I’m proposing.

The linear actuators are only single stage.

To get full 30” travel range, you would need to fabricate an extension that moves the top lifting/upper actuator anchor point higher to allow enough space between the lower mounting point (keel box) and the upper to accommodate the total collapsed length of X2 14”-16” stacked actuators, or a X1 30” actuator positioned either side of the keel. This extension bracket would use the existing through hole you are using to lift the keel and create a stop rest when fully deployed.

By stacking two linear actuators so they are pushing against each other, you can double your speed and use more commonly sized actuators. To accomplish this, you would create a coupling that would slip over each end to connect them together. The main penalty of using X2 instead of a single actuator is that you will need a taller extension to accommodate the length of having a second motor body and additional gearing. The other drawback is synchronization although with the weight involved there will be some self regulation, but still X2 instead of X4 would be more advantageous if speed is not a factor.

I just did a quick check and 30” actuators aren’t too hard to find. Heavy duty long travel ones are popular for moving solar arrays. Some of the bigger ones need higher voltage, but would be easy enough to power them using an EBike battery for example and recharge them with solar and MPPT, or just take the battery home with you and recharge between sails.

Here’s an example of one way I use inexpensive hobbyist type actuators. These are the PA model range from Progressive Automation.

Ebay is also a great source for deals on heavy duty surplus actuators. Years ago I purchased a super heavy duty pair of 12V long travel heavy load Dana/Warner made actuators off Ebay to actuate the engine cover/sundeck on my Cigarette speed boat.