Prout Catamarans - bow bulbs

[Bob_Ranft]

During the mid 1980's Prout's fitted bow bulbs to several Snowgoose 37's and Snowgoose Elite's. I remember reading a write up in Prout World around that time concerning the research and the list of claimed improvements. Less pitching, more bouyancy up front, very marginal speed gain etc. From memory the bulbs were not that big, about 12 inch diameter, and stuck out from the original bow by about the same dimension. The owner of the Snowgoose 37 Psychic Flight was a regular contributor to Prout World and in one article he lost a bow bulb due to a mid ocean collision with whatever. He reckoned the bow bulb took the brunt of the collision and saved the bow. Any Prout owners out there with any before or after comments. My only comment is that I once pulled alongside a liveaboard Snowgoose Elite fitted with bow bulbs, with a standard Elite and noticed that his foredeck was almost 2 inch higher. Thinking he was trimed down by the stern, as a liveaboard, I checked, his stern was floating has high as the lightly loaded standard Elite, so the bulbs certainly appeared to produce lift at the bows. Unfortunately I had no time to ask the owner for any positive or negative comments. So, over to the gang, should I make a pair up, or go out for a few pints.

 

[boatmike]

Bob old chum, Go out for a few pints!
The whole bow bulb fiasco was smoke and mirrors. They don't do diddly-squat. Proven definitively by Prout and discontinued. If they had any effect at all you would see them on all boats. And the size of them is not sufficient to effect bouyancy either so if you saw a Prout floating high on the bows (not a good thing anyway) it was not due to that!

 

[Bob_Ranft]

Thanks Mike, that's one pint at least, thirsty work just thinking about it. I was wondering why Prout suddenly appeared to drop the idea, suppose they had a valid reason based on experience. Did ask one time at the Boat Show, but never got a clear yes or no.

 

[boatbuilder]

I have sailed a wharram with bulbs on the stem and stern, all it did was make a lot of noise . Mind you I think that just about every idea has been tried on a wharram, but as no two where ever built the same nobody knows if any work.
I even modified my own Tangaroa to suit. /forums/images/graemlins/smile.gif

 

[bigwow]

There is one in my marina, it looks ridiculous!

 

[Talbot]

I know that BoatMike doesnt rate them, and he should know, but I do recall am article on multihull forum from the owner of Red Twin (if I Recall Correcetly) who reckoned they did make a deifference. I have also seen a couple of artcles by people who have fitted them, and have hit simething solid enough to splinter a bulbed bow.

I have always considered that the best way to make them is to star with a bow thruster tube.

 

[Rickm505]

[ QUOTE ]
The owner of the Snowgoose 37 Psychic Flight was a regular contributor to Prout World and in one article he lost a bow bulb due to a mid ocean collision with whatever.

[/ QUOTE ]

The owner of that boat was Neal Ensign. We live in the same town. He stopped by my boat last week and we actually spoke about this subject. He figures he hit a submerged pole and it certainly took that bow bulb clean off the bow. He figures that if it wasn't there, he would have sustained hull damage. I believe he was just entering the Indian Ocean at the time.

Sounds like it's worth having them.

Rick in Florida, USA

 

[mobeydick]

Doesn't necessarily follow. An object (such as poll, fishing line etc) that might roll under a normal bow causing no damage could get caught over a projecting bow bulb and tear it off.

Also depends how firmly they are fixed on - not very, if the bow did not suffer damage it was ripped off.

 

[davidbains]

There are several cat fishing boats with bulb bows in Brighton Marina. They definitely float higher than the ones without, in fact they are so bouyant they create alot of spray when the boats return home at speed.
This idea was first used by Crowther on fine trimaran float bows. Although they were later dropped, the later boats were designed with more bouyant bows, almost vestigial bulbs in fact.
I was impressed enough to fit bulb bows on the rather fine float bows of Aqua Blue.
They don't slow the boat down, but do damp out pitching, and at speed when they are depressed below the waterline there is virtually no bow wave.
However I suspect any improvement on a cat with it's wider more bouyant bows would be marginal.
You have to remember that most ocean going ships fit them now, I think because reduced wave making means lower fuel consumption.
I used polypropylene gas pipe. A big mistake 'cos epoxy does not stick to polypropylene! However I filled them with polyurethane building foam which did stick to the hull so they have stayed on!! They are add ons so if lost, the original watertight hull remains.
If I did it again I'd start with PVC tube for a good bond. Or as Talbot says use bow thruster tube. But it's a lot of work for a possible slight improvement on a Prout.
Anybody remember Phantom Wake, a Prout with asymmetrical hulls, flat side on the inside. It really had no wake!!

 

[boatmike]

Did you ever meet anyone who did something like this and then admitted it to be a failure? Most radical additions result in the owner justifying the fact that he did it afterwards. /forums/images/graemlins/frown.gif And if the idea is to reinforce the bow stem then do what I did when building Peregrine. Layup a gert big carbon fibre tow in the bow encapsulated with biaxial woven Kevlar then fill the forward compartment with syntactic foam up to the waterline. /forums/images/graemlins/smile.gif Slightly stronger than sacrificial blobs I think! Before anyone bleats the obvious, yes of course it added weight. 14 Kilos to be precise, but anyone who has sailed a snowgoose (especially with twin engines) knows that they are usually trimmed stern heavy anyway. If you argue that they are there as bumpers perhaps we should fit them to all boats......... Rather see an old fashioned stainless steel bow shoe though if thats the intended function of these silly things.

 

[simonfraser]

look at the tri's currently racing round, none of those have bulbs . . .

 

[Scillypete]

Why make work for yourself. A Prout is not a racing machine and never will be, any gain is just not going to be worth the effort. Mine is a great cruising boat and there's enough other things to do to keep it that way without thinking up unneccesary work

 

[Bob_Ranft]

Thanks for all your comments. I was never really interested in them as bumpers, if I remember correctly Prout's used to stick them on with sealant, so they would be relatively easy to knock off in any case. Only slight improvements to be gained I think, so I'll keep this on the back burner until the 1001 other things are sorted.

Yes, I remember Phantom Wake, went like something off a shovel.

Thanks again