Looking for some tips for a glass bottom boat design

Your question wasn't directed at me but as a shade tree guy who has been using various flavors of CAD since the age 10, I can say most all your questions can be pretty easily figured out with solid modeling. Again, as a shade tree fabricator I don't care for Rhino or Autocad since they aren't solid modelers, but with something like Fusion 360 it's very intuitive for me to model the craft, including compartments and reserve buoyancy chambers, get displacements, stick to materials I understand, then remove and slice sections off, tumble the model around various axis (ie heel on waterline plane), think about how it will behave and how changing weight and balance will effect her. Right click the object -> reveal properties -> volume... Then how much does the boat weight, where is COG, how is it changing? Etc. Ideally then build a small scale model (also easy to extrapolate from the CAD) and test it in a bathtub.

Nobody is going to hire me to do an engineering write up on a 600 ton vessel, or create a racing vessel where a 2% weight difference is the span between first and last place.. and I'm not planning to build one soon, either.

 

It is clear that you do not know how to design boats but you are, yes, a sailor who does not worry about the passage on his ship. It's good to know, but it doesn't matter, your answer is very witty.

 

@socalspearit, no, I wasn't referring to you but to gonzo. With pleasure, when I have a minute, perhaps, I will analyze your last post. In the meanwhile, thanks for it, my friend.

 

@TANSL

I have Dave Gerr’s text. It offers a rudimentary understanding about boat structures. I probably used it about two times in a discussion about laminate thickness.

I had the opportunity through design/build errors on my boat to interact with a Naval Architect with a CV. The work he did was beyond anything whispered by Gerr. I am forever grateful to the man who doesn’t deserve to be dragged into this messy thread.

For anyone wanting to take passengers to sea, cutting a hole in the boat in gluing in plexiglass is not really going to be done.

There are always a few fellas who will scoff at educated persons, but please remember; they are not the majority and they don’t require your engagement.

A good friend of mine who has passed away always made the mistake of thinking others always knew better. This is the opposing and also a bad view.

If we stay on objectives; it usually results in good outcomes.

Many of us hope to contribute something here. If that is the goal of our exchanges; then all is well if the contributions don’t result in harms.

 

[Back to actual glass bottom boats...]

This is the boat in my harbor: Glass Bottom Boat Redondo Beach https://redondogbb.com/

The current captain/owner acquired it a few years ago and we exchange a hello every time I motor past, and I've retrieved a handful of dropped phones for them but I had a moment this weekend to jump on and talk to him about the vessel...

He said it was manufactured in 1995 and the company is still in business with some other projects, and that they made I think 15 of these boats. USCG classifies it as a 'semi-submersible' because so much of the boat is underwater. Also, there are no thru-hull fittings anywhere, which makes USCG very happy. Having so much boat underwater means it needs an extraordinary amount of ballast (3,000lbs in bags of lead shot). Fore and aft of the passenger/viewing area are buoyancy/ballast hulls (imagine three floating buckets in a line with the middle bucket being the viewing area and the fore and aft buckets being ballasted with bags of lead to keep the buckets submerged to the halfway point). The fore and aft hulls are not top gasketed to be watertight in the case of capsize but freeboard is quite high, and the boat never leaves the harbor to encounter weather which could cause her to heel (this is by USCG regulation because the draft is so deep), so it's a perfectly functional design for its mission. The windows are bullet proof glass and he said they've never leaked or failed. They get scrubbed once a week by the bottom cleaner. The vessel hull he said was aluminum and fiberglass. It's powered by 2 x 15hp outboards so obviously his fuel cost is virtually zero and there's no need for any kind of thru hull fittings with that set-up. Doesn't got very fast but doesn't need to.

 

@fallguy,
I think I don't understand some of your statements correctly, so if I say something wrong, I beg your pardon.
Current techniques for the scantling of FRP ships are not limited to calculating the thickness. A thickness may seem adequate, according to Dave Gerr's procedures, but when analyzing the stresses in the layers of this laminate, it could be seen that one or more of them may fail. In other words, a laminate with a thickness that is apparently sufficient according to D. Gerr, may not be adequate, may not be admissible by regulatory bodies.
It is a great achievement that you have built your own boat, congratulations, my respects, and I am sure that in the conversations with your friend NA you have learned a lot. I have spent more than 60 years living day to day, minute to minute, with a NA (also with a CV) and I believe that I have learned quite a bit as well.
A passenger ship can be built with a window of the appropriate material (not plexiglass, you are right) in the bottom. There is nothing that prevents doing so. And I say this because this NA friend of mine has designed three glass-bottomed passenger boats, one of them a catamaran, which are sailing without problems. And believe me, I trust this NA a lot, I know that what he says is true.
Kind regards.

 

Yes it can, we have done so many years ago too.
But....and it is a big but, it requires a significant amount of mitigate and approvals before Class allow it. As a general rule, they do not allow such.
But on a case by case basis they will allow it - provided the mitigation has been satisfied and proven.

 

The thread is about a glass bottom boat, which are usually very shallow draft. The one in Redondo is a semi-submersible with vertical window for the passengers to be below the water surface. Those are two very different designs.

 

Why?. Why does a glass bottom boat needs to be very shallow draft? There is no reason why, as far as I know.
This type of boat has the draft that its displacement and characteristics require, like any other boat.

 

We were going to go on the redondo boat this November during the king tides, but didn't factor in how feral my nephew and niece would be. Had wanted to see inside it.

Have seen some glass bottom boats that were essentially skiffs in Florida, they were shallow as the water was shallow.

 

Yes, of course, that is only reason, the bottom of the sea, not the type of ship.

 

Crystal Springs in Central Florida is where they built the first glass bottom boat. They are flat bottom boats.

 

OK, OK but you wrote:

and this is not correct. They don't use to be....

 

As someone whose business involves a lot of fish interaction and fish behavior, viewing the fish laterally is going to be much more engaging to the viewer than from above. I know this from freediving but also it's the difference between an aquarium viewed from above vs the side. In most seas the most engaging view will be marine life on vertical structure, seen from the side, which of course presents the most challenges to draft and hull safety. The Redondo boat works a known route in a very controlled enviroment--they always just do a lap along the inner breakwall and the resident fish are trained come to the boat. Another way to do that is for the vessel itself to be the structure if in open water.

 

I agree. The OP asked about glass bottom boats though.