Will These Home-made Dinghy Davits Break?? | Sailboat Trawler Restoration (Ep58)

Will these DIY Composite Dinghy Davits break? During a recent boat restoration project, I built a pair of Composite Dinghy Davits made from Coosa Board and Fiberglass Epoxy. They weight just 17 pounds each. I plan to use them to lift my ultra-light dinghy onboard my Albin 27 pocket trawler. Welcome to my boat building channel! This is my trawler restoration of an Albin 27 pocket trawler. Every couple of weeks I post a boat building or boat repair video to document various boat projects, sailboat restorations, or boat repairs. And when all else fails, I tell stories of boat motivation.
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Equipment featured this episode:
Digital Angle Finder - Der Winkle
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TotalBoat Epoxy Fairing Compound
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[@davetowz]

All is not lost. Give it a spine, Drill into davits and epoxy all thread up through base, use these as mounting fasteners also. I like the idea of the epoxy davits. Get the Alu davits on the boat and keep the coosa davits for when you run out of projects, never give up. Drive on!

[@motorcityboatwerks]

Thanks Dave. I’m not sure what I will do with the composite Davits. It’s a good lesson though 👍

[@thetruejuanalto]

A+ for effort!

[@motorcityboatwerks]

😁

[@SVSeeker]

Love the creative and inventive work on the davits. Sort of makes sense that the weak link is at the end of the fulcrum arm where all the load must pass into the deck. I think you were definitely on the right path for strengthening that joint. If you are going to toss them it would be interesting to see what failure load would be if you just put in multiple through bolts or set the base into concrete. Anyway glad to see the work and go easy on those who like to invent. It seems a bit masochistic.

[@motorcityboatwerks]

😀Welcome to the channel. Thank you so much for the comments! I sent you an email long ago about asking for advice as a KZbin creator and never got a reply 🤓 Let’s connect 👍 If you watch my channel you’ll know I’m often for thinking outside the box or inventing a clever solution. I’m sure you know for the amateur there’s always a fine line between that and Mad Scientist Syndrome. Airship captains and submarine skippers exempted. 😉

[@907T]

Keep it going Joe! Lessons learned are not a waste of time. I'd try out the used davits and if they're strong enough maybe get them powder coated.

[@motorcityboatwerks]

Thanks Joe 😁👍

[@JaranMckenzie]

Thanks!

[@motorcityboatwerks]

Thank You Jaran! You are a top shelf🤩🫡

[@davidbauerdorf1324]

Trial and error! But that’s how we learn. The fab work was really impressive and I felt the “ gut punch “ at the end. Heck of a deal on the aluminum davits tho. Great episode as always

[@motorcityboatwerks]

Thanks David! I think the new old davits are going to be the solution 😎

[@reinierrautenberg4146]

I had a dinghy on davits fill up with water one day. The wave from the overtaking Coast Guard vessel [of all people...] made such a breaking wave that the dinghy (3.5ft above WL) filled up in a slashing wave. With which I want to say that for weight calculations it's best to use the weight of the dinghy full of water. And with 8# per gallon, it adds up quickly. Another way of looking at it, sitting comfortably in my armchair, is that two adults and fully loaded have to be able to stand in the dinghy when it's hanging in the davits. This gives you an idea of the bolts and back plate to use at the base. [hint; the torque is insane!] Looking fwd to the next episode! thx

[@motorcityboatwerks]

No doubt! It was a tough lesson but not done yet !

[@JohansGrandBanksSaabEtc]

Just use those failed davits as garden decoration and never look back. Great experiment and we learned alot. The alu davits you got there looks nice, I hope they can take the loads. My old SS classic Simpson davits are rated at 300 lbs (each) and they're massive in comparison. Anyways great video at usual Joe keep it up!

[@motorcityboatwerks]

Thanks Johan! Yes they’re sitting on the shop floor and I think it’s time they get sent to the boat yard 😁👍

[@KA-zh3jg]

Great video! Seeing what fails, with the prospect of success at the outset is the best kind of education. As an engineer, I can attest that over history most good design started this way. Of course now there is finite element analysis, but it still would be easier to just build it (and jump in the tender to introduce some dynamic stress, as would be seen in rough seas at the back of your boat).

[@motorcityboatwerks]

Thanks of to the comment 🐙

[@mckenziekeith7434]

It is definitely possible to fabricate dinghy davits from composites. But you have to have some understanding of the load paths and whatnot. A simple box beam with continuous fibers (glass or carbon) on the upper and lower outer surfaces from baseplate all the way to the tip would tremendously increase the strength.

[@motorcityboatwerks]

🤓

[@brianmacadam4793]

Your on the right track with the base plate, carefully line up pilot holes up into the upright portion of the Davit, thread bolts up through the new base and into coos, it may require alot of theads engaged in the coosa to provide the strength, but it will work.

[@motorcityboatwerks]

Thanks Brian! Be sure to subscribe 😎

[@JaranMckenzie]

Hello, I really appreciate all your videos from this last to the begining. In fact YOU are one of the creators that have motivated me to start and document my own build. Im not sure if this is the venue to reach out and connect? Like you reached out to others in your last video. But I want you to know that your vast effort and "on point" content has been recieved with such positivity but me and my friends in the pacific north west that we hope you know it does reach people. And the people it reaches care. You will succeed. And you will sail the pacific! I hope to join you there. Preferably in Cabo..lol. Please chanel positivity and motivation, as you never know when and where the allgorithim will knight you! PS... my wife/bestie suggests you show your beautiful smile more often.... we think your smile deserves as much camera time as your serious face.. lol With the warmest hand shake.... Jaran from Rebuild Projects. I hope to conflab soon.

[@motorcityboatwerks]

Thank you Jaran that’s very kind. The best way to connect is by joining The Werkers. Not every project is a success but we keep going forward. Before you start your KZbin Channel be sure to watch my episode on KZbin vs My Boat Building. Thanks again for the support and please spread the word about MotorCity Boat Werks. 😁👍

[@vincentdsnt]

Live and learn ! Just more work

[@motorcityboatwerks]

😁👍

[@dannyjones3840]

Hey brother, like someone else said, you have to glass the bases to the arms with 1708. Bond the arm to the base with epoxy, put a nice fillet in the corner, then run at least 2 layers of 1708 covering the entire base and at least 6" up the arm. Or, just use the aluminum ones you bought lol

[@motorcityboatwerks]

Thanks Danny !

[@WaveSweepertheAdventureD-rn4nx]

That is disappointing, but sometimes the only way to know for sure is to go all in and try it. Maybe you could get aluminum or stainless bases welded up and use the Coosa board arms? Or make your fancy "new" aluminum arms pivot somehow for easy storage? .... that of course makes the pivot the weakest link right where you need it to be the strongest. Always an adventure.

[@motorcityboatwerks]

I think you’re exactly right. Thanks for the support 👍

[@mickey1299]

What a really interesting idea , just a shame it failed . Sorry mate i feel your pain . The interesting part is it only failed in one area though , so your general thought pattern did hold water . Even worse in the fact the davits actually did match the boat as well . My concerns would be the extra weight of a dinghy that had shipped water . Rain or even spray would add this weight , so i wouldn't follow your lead anyway . But even so , a really good idea , and worthy of being aired , just a real shame it didn't work out .

[@motorcityboatwerks]

Thanks Mickey. Be sure to subscribe to see what comes next 😁👍

[@jeffmelton6875]

Good video. I'm curious about a couple things: Why did you make the davits in two pieces? It seems like that doubles the build complexity. Second, why abandon the project? You may have to do a complete redesign of the base but I think your basic design is sound and super cool. Of course, the aluminum davits will save a bunch of time.

[@motorcityboatwerks]

I explained the design principles and parameters in one of the earlier live streams in detail. There comes a point in some projects when you have to rethink your plan and pivot to newer better idea. Stay tuned 😁👍

[@markgallagher1376]

I think if you fiberglass the arms to the base with some 1708 or other heavy bi-ax glass it would be strong enough. It looks like you only had a glue bond there and no glass. I really like the rest of the design though.

[@motorcityboatwerks]

Could well be. But There maybe some other fundamental problems.

[@jmkikkawa]

I like watching videos like this to learn. For the main thing that broke here, you didn't ever really explain how you attached the davit arms to the bases. We didn't see the lamination schedule. I'm not sure if the Coosa failed or maybe just the bond to the Coosa. Based on your last video I think you wanted feedback, so mine is to show more so we can understand what went wrong.

[@motorcityboatwerks]

Thanks James. You are keen to note there are some design flaws in the base attachment and elsewhere that I did not address in the video. These are not worth addressing at this time. And so we move on. The big picture is that this is not the right material for the project. Thanks for your support 👍

[@martylasher539]

Thanks for taking that gut punch in public so we can learn from your experience.

[@motorcityboatwerks]

Any time! 😂

[@commoncents9417]

i love it just buy a used one better and cheaper

[@motorcityboatwerks]

Indeed

[@davekimbler2308]

I believe your idea is sound just minor flawed , by angling away from the transom your pressure point is the joint towards the bow . If you went vertical then horizontal it should move the point closer to the stern ( like a ? and anchoring the cables at the base stern side . The little Harbor Freight cranes lift 500 lbs with ease !

[@motorcityboatwerks]

Thanks for your comments. Unfortunately There are several mistakes at play here. Better luck next time

[@_r_ma_]

The Coosa is not the problem, the problem is you are using it as though it's plywood. Coosa is a "core" material designed for use in a sandwich composite structure. It's designed purpose as a core is to increase the distance between the laminate skins in a composite sturcture (i.e. increase the moment of inertia, thereby increasing the stiffness, precisely by the square of core thickness). Your laminate skins are way too thin to function as an effective sandwich structure. You're essentially relying on the core's shear strength to do all the heavy lifting. Imagine replacing the Coosa with XPS foam insulation, you would never assume that would hold your dinghy, would you? A composite sandwich is a carefully designed balance of glass skin thickness and material properties (fabric type, fiber orientation, layup technique, etc.) and core dimensions (thickness) and material properties (density, shear resistance). Reply to my comment if you want some help designing a proper laminate schedule to take the loads of your dinghy.

[@motorcityboatwerks]

There are a variety of problems in the design, not just necessarily what you’re talking about. But thank you for the comment 😁👍