Engineering degree project research help

[altitude2k]

I don't know if any of you remember but a while ago I posted asking for your opinions on a project idea I had as I am currently studying my final year of Design Engineering at Bournemouth University, which was based around a mooring buoy. The response wasn't great so I changed my idea. After speaking to a couple of boat owners and to the design guys at Sunseeker, I came up with an idea that is as follows:

An inflatable device, that can be compact enough to store onboard a motorboat, that can be brought out and attached to the boat to perform repairs on the propellers and prop shaft. The idea is that the product is attached whilst deflated, then inflated to raise the stern of the boat to allow quick access to the props in the event of something happening to them. The product could also be used whilst the boat is docked to perform more extensive repair. It is intended as a quick-fix whilst out at sea, and an alternative to lifting the boats onto dock, especially those that don't need to be antifouled.

I have created an online questionnaire and I would be much abliged if any boat owners could spare a couple of minutes to fill it in for me, as market research is a big part of this project. Here is a link to the questionnaire:

MARKET RESEARCH QUESTIONNAIRE 1.0

Many thanks in advance.

 

[Nautorius]

A better idea,

However it would have to be a large floatation device to lift 5-10 Ton of MOBO. I'll have a look at your questionaire but I am no Engineer...

paul

 

[Talbot]

pretty unrealistic. Anything large enough to lift that much weight is going to need strong material, and take up a LOT of stowage. The interest in such a beast would be minimal.

If you want a decent engineering task, how about a dan buoy(or also known as a man overboard buoy) that stows really small, but can be deployed immediately, and is then large enough to be seen easily, picked up on radar, and not blown over/collapsed by strong wind.

 

[office_sailor]

An interesting idea, but in all seriousness, you need to speak to a naval architect who can do some number crunching and help you look at the feasibilty.

There are two aspects to consider. Firstly. you are goind to need to lift the stern with considerable force. A rough calculation I've just done shows me that to change the trim of a generic 8m motorboat by approx half a metre would need a lifting force of around 2.5 tonnes, which is around the displacement anyway! Secondly, big changes in trim caused by lifting the stern of a vessel can have serious effects on the transverse stability as well, especially as the waterline beam forward will narrow considerably as you lift the stern.

I think the calculations would have to be based on a specific vessel to ensure safety!

 

[altitude2k]

It's too late to change the project. And it's a modification of a concept that is used in a wide number of floating lifts and buoyancy aids.

 

[office_sailor]

PM'd you.

 

[trev]

I can't see such a device being compact enough to stow on board, or very practical on a boat moving around in a seaway, especially with people left on board. - or do they all get into the tender or go for a swim while the repairs are in progress ?? My usual crew of wife etc would not be amused if I attempted such a thing - may have some use in marina as a cheaper alternative to a crane, but marina owners would be hard to pursuade to use a 'cheaper' method !!

 

[jfm]

Chris
I filled in q'aire, also did engineering degree myself so can sympathise. Some of the multichoice answers were limited so I abstained. Eg "would you use it at sea, docked, or both". You need a "neither" to do proper research

The first thing you gotta decide is not the engineering but whether the problem you are trying to fix exists, and imho it doesn't. I would define the problem that this thing is aimed at as "the existence of a significant probability that you need to get access to props without having easy access to a crane". People will tell you about ropes round props in middle of the sea, it does happen, but the probability is too low for a boater to endure the "cost" of buying/storing/deploying a massive heavy piece of kit like this.

Most people would prefer to fit ropecutters, dive in and fix the props, hobble home on one engine, or call a friend/seastart /lifeboat, etc.

Then there's the engineering. The inflated bag (if that's what it is) might have to be forward of the point where the shafts exit the hull. Otherwise it would obscure the rudders, props, shafts, the very things you want to get at to fix. That puts the bag a long way forward, and I would be massively worried about stability. Or, you have the bags level with transom and some kind of crossbar attachment thingy, eek. Gut feeling says it cant be made both safe and compact

No-one will accept attachment brackets permanently bolted to the hull of the boat. This thing has to be fully removable off the boat, when not deployed.

Storage is a big issue, even on a big boat. Much storage involves lifting the thing out, and this sounds heavy. If you can pack it small, can the user do the same afterwards, when it's wet and manky?

The whole tilting process sounds scary. I have only had to get access to props once, in many years/miles of boating, when a ropecutter came loose. I put on the scuba and did it, took half an hour, the guests carried on drinking and having lunch, unaware. You couldn't do that on a tilted boat. And the scuba gear plus dry/wetsuit is much easier to stow/deply than your machine. And loads cheaper. and can use recreationally, etc

Sorry to be negative, but good luck /forums/images/graemlins/smile.gif

 

[ShipsWoofy]

Might be handy on the mooring though Mark, to change a damaged sea cock or other such job without employing a crane.

Now if he can built an inflatable mast stepping device I will be impressed!

 

[PCUK]

It's totally impractical, may lift an outdrive boat's stern high enough to reach the prop', but then the drive can more easily be lifted on the power tilt. To lift a boat with shaft drive high enough to reach the prop' would probably cause the boat to either roll off the device or submerge the bow and sink her.

 

[KevB]

Nice idea if you can get it to work. If you need a boat to test it on.......

 

[Nick_H]

Look at a beam view of an average motor boat and see how high you would have to lift the stern to access the props, how far the bow would be submerged, and then imagine that in open water with even a slight chop? I think the guys at Sunseeker are humouring you if they told you the idea is workable, and that's a shame 'cos you've asked them for help. Good luck with your project.

 

[hlb]

It's a none starter. Besides theres similar in existance, but like a floating dock that lifts the boat up, with far more rigidity. Ones up the river at Cowes and I've seen them other places.

I can just imagine my boat bobbing about mid chanel on a big bag of air. Then sort of plopping back in, sideways probably. Ang on. I can hardly pick the dinghy up. Hpw the hell do you lump this thing about, capable of lifting 10 tons!! /forums/images/graemlins/crazy.gif

 

[Talbot]

Mast lowering requirement - Thats your fault for having a HT. Us Catalac owners can lower our masts easily by hand - done it several times on my own (and raised it on my own as well).

My seacocks are at the centre of balance, so I dont see how you could achieve that.

 

[DavidJ]

Might just be useful for debarnacling the prop on an out drive. When in the fully up position my prop is not out of the water and it's a snorkling job to scrape the stuff off. If the device could raise the boat even by a foot and you could somehow lay on it then the job would be a whole lot easier. Not sure I would have the space to keep on board but I would certainly rent one for say £25 a day
best of luck

 

[ShipsWoofy]

If you could get the whole boat out of the water rather than just trying to pitchpole her /forums/images/graemlins/grin.gif

 

[Bergman]

Don't think the 10 ton bit is the problem.

Air bags are widely used for recovery of HGV and the like and esily lift that sort of weight and more.

I think the hard bit is how it can be attached to a range of boats without having permanent fixings and in a reasonably safe and secure way.

Perhaps possible in sheltered water - but wouldn't fancy it in anything of a seaway.

PS
Maybe just lift 1 side of boat - natural righting moment will help maintain some degree of stability - sort of like a tripod - if you see what I mean

 

[jimmy_the_builder]

Chris, I'm one of those that responded to your previous idea; I'm afraid that this one is unlikely to have a market either, sorry. I used Hydrohoist lifts to store my previous two boats, and they're great - but they are very carefully engineered and professionally set up to properly maintain the boats centre of gravity. There's a real risk of losing the boat altogether if you use these devices incorrectly, and for example there is absolutely no way of making your suggestion safe to use in an open sea without it being impractically large. There was a court case a few years ago arising from the use of a boat lift where the owner had 'adjusted' the lift after it had been correctly set up and the boat was subsequently launched off the front of the lift on to the dock. Airberth have done a lot of work on inflatable lifts that have no steel components (Hydrohoist lifts are based around a steel frame) and again a lot of attention is paid to maintaining a safe centre of gravity. Might be worth looking at the products from these companies and doing some displacement calcs before going much further...

Regards
Jimmy

 

[hlb]

What amazes me, is how some on in last year of engineering degree. Could even come up with as hair brained idea.

I mean, just imagine, draft, say 3ft, so the arse end has got to raise at least six foot, to get under it. So the bow is underwater with deck awash, it's all bobing and loloping about a bit, whilst the water gushes i via anchor hole and escape hatch, suppose wife deals with these problems via a bucket and maybe a rope ladder to help her scale the hum...45deg angle to empty buchet over stern. Meanwhile hubby is presumably in the dinghy under the boat. Mid channel. Bouncing up and down, occasionally being crushed by boat, or props/ rudder puncturing dinghy in the process. Course there would need to be different designs for shaft drive boats and outdrives. Maybe others for full tanks and part full.

Besides, I'd get the job of opperating the foot pump, which I dont fancy much!! /forums/images/graemlins/crazy.gif

 

[Its_Only_Money]

If a single bag call it a "Self-capsizing Bag".

If 2 bags for stability, what happens if only one bag inflates???

Have filled in the questionnaire btw....good luck. I´m sure you can still demonstrate some good engineering disciplines however commercially successful the final design looks.