Did Naval Architects Scam Us on Our Houseboat Analysis?

[@diyboat1872]

It's fine to put reinforcement across the boat with small bulkheads, but may I suggest you make at least two longitudinal stringers, they will stiffen the boat considerably, and make it as high as possible

[@cz2681]

So the main concern with this kind of connection is about how stresses are transferred through the joint, the failures you are seeing (on either side of the joint) are exactly what would be expected. The scarf joint needs to be as long as possible to give as much space as possible to transmit the load to the original structure over a wide area, because of how much composites flex the stiffer sections are going to cause more stresses in the weaker sections.

[@catfisher420]

I have a little fiberglass experience. I would recommend using woven mat as your extra few layers on top of the repair and I would also lay those layers extending a couple feet further than the patch. A few extra stringers fiberglassed in across the cuts would also be a great idea.

[@DouglasRees-c6j]

Not discussed is that fundementally you are making a larger vessel with the design parameters of a smaller vessel. That is the parts you are not touching, the front and rear will now be underdesigned to some unknown degree. Its probably not hard to make the splice stronger than the material around it but its likely the weak point is going to be an area not modified. Example: stretching a car or truck often requires added frame in areas outside of the stretch. The larger and heavier the vessel the thicker and stronger the hull throughout. Ask your marine experts to comment on this and be safe.

[@winningwithoutracing7811]

I'm one minute in to the video and already confidant that you're extension will perform admirably. In actually taking the time to make sample coupons and evaluate the physical realities of what you're trying to accomplish a successful outcome is damn near guaranteed. I'm a degree mechanical engineer who passed his EIT and I can tell you with confidence that 95% of those that I graduated with (back when the degree programs were significantly more robust) have little interest or aptitude in the physical realities of what you're undertaking.

[@jaycalcott9600]

I used to drive a stretched limousine "land yacht", they're built in, essentially, the same way. Your Stretch is the coolest one I've seen yet!

[@joshuatylergeorge]

Yes! Another houseboat video!

[@superstitiousfishes1247]

the whole idea was a scam. a beautiful, irresistible, can't stop watching scam. glad to see the yacht back in the channel! thumbs up!

[@Motiv8Labs]

I honestly thought it might work out from their resumes. They sounded like they really knew what they were doing.

[@MrKunzeification]

I wild suggest skeletal rib with back bone. Your adding in bulkheads (ribs), might as well add in backbones length of the boat. Glassed in wood is good, but gets heavy quick, therefore changing the formula for weight dispersement from the original calculation. Newer designs are utilizing welded aluminum reinforcements that are glassed over.

[@DouglasRees-c6j]

Yes exactly the rest of the now larger and heavier hull needs reinforcing

[@MakingStuff]

I love seeing projects like this. Keep it up!

[@Motiv8Labs]

Thanks I’m still trying to hack away at them!

[@thieltech1]

Cant wait to see more ! This build with bring in alot of viewers!!!!

[@barrygreen8884]

This is awesome! Glad you’re back!

[@Motiv8Labs]

Thank you we are still at it!

[@Sidelinechatswithrobandtim]

KZbin algorithm did its job love this project and enjoyed your latest video keep up the great work

[@Motiv8Labs]

Thank you sir! We'll keep at it.

[@dfabeagle718]

WOW not what I was expecting when I clicked... to be honest, I'm not sure what I was expecting. :) Great video though, so I figured I would feed the algorithm. I think I'll go on and subscribe too. I had a place at Texans next to the VFW, miss it badly. Oh, sorry about the AI Dirtbag scam (more expletives deleted) situation. That hurts. Good on you for testing and mathing it out!

[@Motiv8Labs]

Thanks for the feedback! Appreciate it!

[@daveevans7438]

I'm glad to see you back on the houseboat project. I'm just curious: Wouldn't a deflection test be more useful. Set up a test bench on your hydraulic press and see what a stock piece of fiberglass deflects compared to your layups. I'm just thinking. But whatever you're comfortable with, i would add a couple extra stringers all the way across the middle section and glass the hell out of it. 👍

[@Motiv8Labs]

Doing a proper 3 point deflection test is probably a good idea, good suggestion.

[@MeltedElf]

Love seeing progress on the house boat! Considering it's already blown up, probably pertinent to make sure it doesn't titanic either haha

[@Motiv8Labs]

Yessir I don’t think I’d ever have a good time on it again if I was worried about it breaking in half and titanic-ing.

[@scottsmith2869]

I just found your KZbin channel!!! I’m really enjoying your Red Neck Engineering!! I restor,remodel and rebuild Boats too! Make them what I want them to be! If it doesn’t have what I want it to have,,, I make it! If I don’t have a tool, I make it! Thank you for all your hard work making these videos! I’m visiting Dallas today! Wish you were close enough so I could visit!!! Take care! Scott from Arkansas

[@Motiv8Labs]

Thanks for the feedback and for watching the channel!

[@sirzason]

Production value A++

[@Motiv8Labs]

Thanks brotha!

[@Dave_Dickinson]

Another great episode.

[@Motiv8Labs]

Thanks man I’m tryin!

[@winningwithoutracing7811]

The biggest liability with extending a boat as you are isn't the addition strain that you're imparting on the joints but rather the additional stresses imparted on the vessel as a whole. Being that you're only adding a small bit and its a lake boat I'm fairly confident you'll be fine. I've long dreamed of stitching two smaller boats together to build a massive stepped hull 30+ foot vessel on the cheap. Provided the two hulls could be allowed to flex somewhat independently I suspect that the vessel would wind up weighing significantly less than similarly sized conventional hulls. The weight of boats goes up almost exponentially with length because addition length puts much greater moment loads on the hull as a whole.

[@Motiv8Labs]

Awesome, thank you for the feedback!

[@anygasmotorswilldo]

I'll say I learned a lot! I'd trust it with the extra layer!

[@Motiv8Labs]

Hope so we will see!

[@craigjones9244]

What ever laminate schedule you decide make sure you use vynal ester inside and out yes gelcoat as well

[@DoRullings]

I think you can easily make the joints strong enough. What I might have worried about is that the hull will now be almost 20% longer than it was designed for and that will both increase and change the load on the entire hull. Note: I am by no means a boat designer, just a guy who grew up by a fjord in Norway and has therefore been at sea a lot.

[@Motiv8Labs]

Definitely a good point. Nautaline had a longer version of this houseboat that was a 48’, so I think we are still in the ballpark for what might be normal on this type of design. We will see though!

[@sonnyjones426]

I would also glass in half rounds length wise for 2-3 bulkheads and remember 5/8 radius on all 90 degrees.

[@manfredfritz6068]

Excellent Job!!!!

[@Motiv8Labs]

Thank you!

[@KristiWade-k9u]

With all of your testing and math, I retract my comment that I won't go on the maiden voyage of the rebuild......I absolutely want an invite now!

[@SPYDER990]

ide run 4 stringers up the boat ..it would keep the bottom nice and rigid glass that all in and it will be more than good!

[@kencraig6526]

look up the duracell project, the guy has a real engineer helping him redesign a racing sailboat into a cruiser.

[@pappydoc69]

I have been reading the comments I have lofted 100s of boats in my years of boat building all you need to do is repair the glass as you stated tie into your stringers and we're you join the hulls put bulkhead .

[@Motiv8Labs]

Thanks for the reply, sounds like we should be on the right track then. Thanks!

[@nickg421]

Were those test pieces cut out of old boat scraps, or made of new fiberglass? The old material may bond and behave differently under tension. Especially if it has ever had oily water left on it, which happens a lot in a bilge.

[@Motiv8Labs]

Correct those test pieces were from the original boat so that we could see how the actual boat might behave as we fiberglass it back together.

[@Luke-pb9oz]

Bro, just glass it up using woven rovings and chopped strand it only needs a 200 mm wide patch on each side, maybe a bit more 4 lamination on each side .

[@drfrancky]

You are testing stretching (tension force) of the material but what you really need to test is bending. Bending is much more complex because it involves both tension and compression forces all together. The force required to break the plank in tension is not the same as the force required to break it when bent.

[@Motiv8Labs]

Good point thank you! We did some small 3 point bending tests with the fiberglass a while back using the harbor freight press in the shop. Need to keep working on that though.

[@Waveluth]

About 36 years ago I did a similar thing changing my 36’ cabin cruiser to a 44’ cruiser. I found that using the same math that I used when figuring out cantilevers in construction. It was a successful project and to my knowledge the boat is still going strong. I haven’t owned it for 20 years but it’s moored a half mile from my house in the southern shores of Massachusetts. I used 8 layers of West System with alternating layers of a very particular fabric ( cheap polyester fabric)instead of fiberglass mats. (Inside) and on the outside it was faired out with 6 layers of Mat fiberglass and then 2 finish coats and two additional layers of fiberglass roll over the ENTIRE HULL. After skarfing the joints, router out a 1/4”-3/8” of the hull and lay solid mats into the route. After they are at the same profile you can then start the West System and layers of fabric in and out. Why CHEAP polyester?? Because the West System essentially melts into the fabric and makes a surface SO UNBELIEVABLE STRONG it will shock you. I got the idea from a book written about building with West System and plywood. I hope it works for you. It worked for me. Good luck!! 👍🇺🇸

[@Motiv8Labs]

This is awesome! Thanks for sharing that story, because it’s tough to find many examples of people doing heavy modifications like this.

[@ready4pullback]

Soooo off topic, but just wondering if you guys are going to make the deadline for the budget jet boat build- Texoma Throwdown poker run is this weekend. Will we see you?

[@Motiv8Labs]

It appears we have…failed. More to come soon lol.

[@EvenNinegaming]

My concern is with the lifespan of that joint. Composite materials don't have the ductile properties of something like steel they are more effected by the cumulative effects of stress. I'm not a naval architect but I feel you should add some kind of a stiffener to tie the 3 parts of the boat together while lessening the effects of wave action and loading of the boat.

[@EvenNinegaming]

It might also be a good idea to put a few layers of fresh fiberglass mat over the joint aswell just to ensure the repair remains water tight.

[@EvenNinegaming]

Additionally, I worry about the thought that this modification may be stronger than the original design. Well, I agree you ha e done some good math on this. You have to remember that no joint will ever be as strong as a whole piece of a material. Fiberglass being a composite does help a lot in this case, but even then, you are relying on the epoxy across the entire joint and not the individual fibers of fiberglass. The fibers give fiber glass its strength, that's the other reason I feel you should look at limiting torqe applied to that joint.

[@Motiv8Labs]

All good points! We were definitely thinking of doing the additional supports in these areas to keep that joint from being able to move. The only question is on another message board some people said you wouldn't put the support bulkhead directly over the bonded area, but just near it. I don't know the reasoning behind not having a bulkhead support directly on top of the joint, seems like that would be the best place to keep a joint from flexing.

[@EvenNinegaming]

@Motiv8Labs I can think of a few reasons this may be the case, but I would like to test them. I'll send you an email with what I find. But tldr I think it would have something to do with water tight integrity and forces being directly applied to the weakened part of the boat.

[@kharn4624]

Just goes to show the internet is a strange and magical place. Everything is going on out there a lot more than we think it is.

[@michelplourde9831]

Not a naval expert but the way we repair smc and fiberglass in structural autobody repair you need to bevel boat side of the fiberglass and fill with new fiber mat and resin by only patch one side you still have a breaking point at the joint. If you bevel both side it's almost impossible to broke at the repair area.

[@Motiv8Labs]

I’m glad to hear that. In some of our other videos I was talking about doing a double sided scarf joint, just like you mention. This is the plan, I’ll bevel back on both sides of the boat. Thanks for the input!

[@novavroomvroom3435]

GORILLA GLUE AND GORILLA DUCT TAPE...!!!!!

[@scotthogan4558]

Call the guy who made the flex seal commercial he cut a boat in half and was on the water all day with no leaks. I trust him more than any architect or engineer.

[@Motiv8Labs]

I’d definitely trust the boat if we flex sealed it together. Would probably need a loan to buy enough of it though.

[@carlbeaver7112]

Why not glass in a 'x' cross-lap joint on each side and one on either side of the keel (between the stingers), along with your beveled over-laps? Nobody could deny their added 'stitch' strength in all directions.

[@AnvilDragon]

I don't feel your limit is in tension but in buckling. Using your simply supported beam model you are increasing both weight and length. That model for the same section is linear for both weight and length. If all the weight was evenly distributed that is about 19%. So the baseline would be 1.19 x 1.19 = 1.416 times the original design stress. However the weight isn't evenly distributed. The book you have is good. The stringers will be required and the additional bits to retain shape and prevent the skin from beer canning. Lighter stringers along the roof skin and what on the sides will take a dock bump will take some thought. Just don't stick it together and call that good. It does looks a bit light to begin with. So, following the book is a good start. It will likely require a design review and will require an inspection if you expect to insure it. Insuring boats over 30 years is problematic so you have to shop around a bit and do extra to make sure they're happy. Rates get real silly when they're nervous.

[@Motiv8Labs]

Thanks for the feedback. It took a while to find someone to insure it when we first bought the houseboat 10 years ago. Now that we are modifying it I'm sure it will be even tougher. We'll see!

[@JoeKyser]

Should have had a solid works model made up.

[@tehpanda64]

If you want to make your 40 foot house boat 50 feet long I'd start by looking at how a 50 foot boat is made and see where the additional strength is coming from. And Alternatively talk to a 50 foot boat manufacturer to see what they recommend and why. I didn't pay attention to your actual lengths I was just giving examples.

[@Motiv8Labs]

That's true. Looking at a boat already built to that length would definitely show what works.

[@parisswain5403]

What kind of boat stands and you using ?? 🤔👀

[@Motiv8Labs]

If you Google for Hostar Marine you should be able to find their website. I ordered directly from them a couple years ago. They were good to work with and had them here on a pallet a week or so later.

[@brandonlourie6027]

The amount you spent I could of done the work for you and it would never break 🤙

[@Motiv8Labs]

Yeah I’d have been better off spending the money on more of the fiberglass and epoxy instead of those reports.

[@ps3dropzone187]

I would literally run me to I beams in the subfloor on the bottom of the hull I would do your 20 degree bevels fiberglass all that and then fiberglass the i-beams to the floor as much as you can and that should give you a lot of support you know Brian down into the stuff for a little bit when are you fiberglass your I beam send

[@cz2681]

wait sketch up is still a thing?

[@Motiv8Labs]

Probably not the best choice. For everything else I’ve been using Fusion360 but I thought the houseboat was closer to a “house” and figured Sketchup might be easier.

[@cz2681]

@Motiv8Labs I was just surprised to see it, I thought it was discontinued.

[@snifnor]

ASK A BOAT MANUFACTURER IF THEY HAVE IDEAS.

[@BPHwweez436]

Why just go to a good boat builder ? Would think could add couple girders an beams tieing both toghter first before glassing her back toghter ? An NC has some of the best

[@GoofieNewfie69]

hehehe "naval architects" , The 12 - 1 scarf is a bit over-kill but doable. Your strength is in the stringers, chines and gunwals. You don't have to worry about the boat sagging in water, there a plenty of boat of similar design 50' and longer. Your making mountains out of molehills' Run extra stringers if your uncomfortable with existing strength Your test proves very little. Bulkheads give more lateral support than longitudinal(look at long open fishing boats. It's the stringers and keel that give the support.

[@eduzick]

Joel Sodowsky OPDM Solutions might be able to help.

[@FreezyAbitKT7A]

Idea... laminate carbon fiber, kevlar or dyneema cloth over the whole splice. btw Cars and Cameras are doing a Crosley.

[@Motiv8Labs]

I saw that Crosley video pop up in my recommendations! Never thought I’d see another one of those. The carbon fiber strength idea isn’t bad, unless a small roll is like $5,000 or something. I’ll look into it.

[@FreezyAbitKT7A]

@@Motiv8Labs I don't know if they saw my message but I warned them you eventually did a body swap. How many feet of carbon fiber would you need?

[@FreezyAbitKT7A]

@@Motiv8Labs Shopping online, I found the prices of carbon fiber wasn't that bad. I'm not sure what grade or eventual thickness that would be required.. Maybe do a stress test on a chunk of hull with the carbon fiber. I think it would act like a strain reliever on a power tool cord.

[@watsisbuttndo829]

I used to work at a agricultural fibreglass company years ago. When building tanks for molasses we used to add carbon/kevlar woven mat at any wall splices. The kevlar cloth was extremely hard to cut through with the heavy scissors when compared to plain glass or carbon.

[@ncikb2093]

Don't add carbon to a fibreglass laminate unless you add enough to take all the load, at which point you can just ditch the fibreglass altogether. It's so much stiffer than fibreglass is. Just stick to glass.

[@derrick7184]

Scab the stringgers front to back fiberglass Three feet out to flow inside and out..

[@mattmcgellin6607]

The algorithm bought me here, but Im an actual naval architect lol. Admire the hard work and dedication to testing but a few of your assumptions are a ways off w.r.t the calculation of stresses in the hull. Not that itll matter im sure if you just want to cruise around the lake.

[@Motiv8Labs]

Thanks for the feedback. If you or any NA you know ever wants to give any of the data a second look we’d love to have it! As right now the only thing I’ve got are two reports from these “freelance NAs” and the testing I’ve done.

[@mattmcgellin6607]

@@Motiv8Labs if you send some basic drawings or measurements I can do some quick hand calcs that shouldn't take more than an hour or so lol. What I need is: - Basic arrangement including locations and weight estimates of all equipment/hull - midship section, showing glass thickness, location/dimensions of longitudinals. This should be the hull only, not including the superstructure unless it's very well attached (moulded) into the hull. This will give you a, hopefully correct, global hogging and sagging stress... But remember that on small craft local stresses are often a lot higher. Things like wave slamming can cause cracking which over time will create big problems.

[@mtw1234]

Don't take a houeboat out into open water, they are for lakes or intracoastal waterway cruises.....also install all new stringer bow to stern gunnel to gunnel. Good luck, can't wait to take thís project on with yoú.😅

[@Motiv8Labs]

The intracoastal might be fun one day, but for now we will be lake bound once this thing is done. Unless one of us win the lottery. Thanks for the feedback!

[@JoeKyser]

If they gave you a plan, you were ripped off

[@kizerdude59]

The test your doing is a pull strength test. You need to be testing the up and down breaking point highly unlikely the boat would pull apart. I'm sure it would just snap in half. You should be doing a Horizontal test with weight pushing down on where both sides of the boat come together. That is your weakest point.

[@timeobserver8220]

You used a freelance website then are surprised why this outcome? lol

[@ncikb2093]

Did you actually expect a proper answer from an online "expert"?

[@diywaterworld]

Just because someone can calculate the circumference of an apple, doesn’t mean they know how to eat it…. From the performance of your two guys, they couldn’t even get you the circumference 🤦🏻‍♂️ doh! I’ve seen quite a few times where supposed “ naval architects “ battle with experienced builders whom of which don’t have a single degree. Can you guess who is always right in design / function / strength? Haha. What you have here is a simple process ( relatively speaking) It’s one simple question: what’s the strength of existing hull/structural layup… then multiply that number, and use superior products ( epoxy and better fiberglass) to achieve this new goal and you’re golden 😎. Obviously there’s some more to it ( structure and new loads on other parts of the boat) but overall it’s that basic. Happy to see you find solution and make headway! Looks like you’ve got a handle on it and are on your way to a great project! Thanks for sharing this process! Awesome video , excellent production quality and such a cool project!!! I wish you were closer, I’d volunteer a helping hand ! Cheers!

[@Motiv8Labs]

Thanks for the feedback! I wish I was closer to the ocean or maybe in Florida near some shipyards with hands on experts, but hopefully we are going in the right direction.

[@charlesurrea1451]

Shame you can't actually trust anything/anyone online anymore. Solely from what I've seen in this video, I would say you're going to need aluminium extrusions 50 ft long each that fit into your stringers. That should sufficiently eliminate any potential deflection in the horizontal. Extrusions such as 80/20 and the like are much stronger laterally than a piece of channel but are more expensive. Scarfing not skiving?

[@ncikb2093]

Nothing on the internet has ever been trustworthy. Hiring an engineer online for a few bucks is bonkers.