Cosmetic strakes on welded aluminum hull?

Gentlemen; It is a nice day in the neighborhood, don't let us start a pissing contest please. The OP has sufficient answers. His boat is good to go.

FWIW, Lone Star made some faux lapstrakers too. MFG made fiberglass Lapstrakers as well. Damn those MFGs were heavy beasts but stiff considering that they were mostly chopper gun layups. (Ancient history)

 

Tunnels has this thing, about asking for a description of something from the engineers or designers, then declaring the replies meaningless and useless when he doesn't comprehend the dynamics or math or physics, etc. He's made these blanket statements previously about strakes - he's had their dynamics explained to him in simple terms, but he of course knows better.

I've worked on some of those early MFG (you can guess the acronym we supplanted). I've seen 18' bow riders with 1" thick hulls.

 

Why are strakes used on hulls ??
what is the purpose ??
should the run full length from the chine at the front or stop short of the transom??
What part of the boat you think you trying to lift ??
is it the front you trying to lift or the middle or the back where all the weight is ??
Mentally I divide any hull into thirds ! front third is for water and wave entry the next third is the beginning of load carrying and the back third is where all the weight is on most every boat ! so next time you get to look around a boat yard check out the different parts of the hull and see what you find!!
Narrow strakes used on hulls really are just ornaments and don't do very much at all ,
If its a glass hull and they built in they do actually weaken the structure if there's no frame work inside the hull bonded into the strake , if you get a mysterious leaks its always the first place to look for cracks in the gel coat where the strakes are !! the hull skin moves and delaminates the glass over time !!
Should strakes be the same width all the way or be tapered and be much wider at the after end of the hull ??
where should they start from ??
why do so many get cut short as they go back when really its where they should be producing lift ??
I know from personal experience they should be kept back from the bow but how far back that's the burning question !!
Is there a formula for all these things ??
In all my travels and looking at different boats its really just plain guess work and looks cool to have strakes !
I have worked with and asked many designers all these questions and not one has given a logical explanation or had any sort of formulary to be able to work to for the fitting of strakes to any size of boat .
I did observe quite recently part of a range of very popular sports and pleasure boats that have been round for long time and are classed as top of the range they have strake ,but added during there life were chines that were more than 150 mm wide starting from quite close to the front of the hull running all the way aft !! obviously they are to make the boat get on the plane quickly and deflect the spray out and away and downwards . these are boats that have sterndrives in most all of them !!most of these boats are in the 20 foot to 27 foot range ! interesting !!
For inflatable boats with ridged hulls the early boats had the tubes dragging in the water so to get the tube up and away to reduce water clinging to the tube a chine with a step was introduces that worked fine then strakes began to appear and some builders experienced the hulls sucked to the water ! hull without strakes never had this problem but the moment strakes were added the problem started , So the placement of strakes and there shape in relation to the shape of the hull is really vitally important !!. lesson learned by the builder they can have an opposite effect and kill speed instead of making the boat go faster .
They only work with speed !!
the number used and there size and shape again is just guess work !! do I have figures and formula's !! no I don't ,
I worked in a company making off shore power boats and strakes were added later to help solve problems . they were always just wooden shapes stuck to the hull , bigger than was needed so after testing in different conditions it was time to reduce there size little by little with a electric planer till the crew got exactly what they wanted!! Most of the shapes were much wider at the after end starting from just aft of mid ships as boats inflight only the last 1/3 of the hull really is in or touching the water most of the time !
Smaller F1 or F3 tunnel boats were a whole different scenario but they to had strakes but much smaller and there placement on the hull bottom was there key . anyone guess why ??
So on slower boats less than 35 to 45 mph its just about pointless fitting them and if its a family boat they are just protection for when you beach the boat to have lunch !!
But what do I know !!

 

The wife been getting at you again has she?? that'll teach you for having one !! wife I mean !!

 

Lots of plate aluminium boats are free of bottom strakes, although they usually have a "flat" at the chine. The convex sections forward don't allow water to "climb" like a straight section, which is the norm in glass, so the need to reduce wetted area is not so demanding of strakes.

 

You've asked these questions before Tunnels and had them answered, yet you still refuse to absorb the information. If you're unwilling to learn, leave it at that and not bait unsuspecting posters, with your continued dribble about things you clearly are unwilling to accept. This coupled with insults about designers and NA's in general, plus personal remarks of things you obviously also haven't a clue about, just points to the caliber of participation you offer any particular thread. Making comments about my better half, is way over the line and another indication of the type of individual you actually are.

Anyone with a reasonable grasp on design would read your comments above and know precisely what I've suggested - that you're absolutely kidding yourself in regard to understanding the dynamics of high power craft. The moment they see the "suction" theory in your last post, it's obvious how little you know, so the best advise for you, is to stick with the poly lamination threads, where you have shown some expertise and leave the idle speculation, about debunked, half century old theory, to the folks that have actual studied it.

 

strakes

Why should they be kept back from the bow? Fountains, Apaches, Cigarettes and most others run strakes to the bow

 

Asking Tunnels about strakes is akin to asking a framing carpenter about 460 volt 3 phase wiring systems. You're just feeding the carp, IMP-ish.

 

Don't want to add to a pissing contest -- only wondered where that observation came from. Don't think they do any harm going to the bow like they've been on all my boats.

 

Don't take any notice of the negative remarks !! It happens

Depending on what the shape of the hull is in the forward sections and as long as the strakes are quite small when the hull hits a wave head on big strakes will hit hard and make the hull want to lift because the front of most every boat is really light weight and it could be quite severe !! the old family boat I used to have had wide strakes all the way to the chine and it was a real hard riding hull even at 25 to 30 mph . The hull I have now has no strakes and is much softer riding but because I have a big motor on a smallish boat the 3 tote tanks I carry are way up forward to get the nose down and it helps .
I worked in a factory and we repaired and did modifications to races boats as well as building them and the designers were all the time just guessing when it came to strakes , the placement and how many and like I described they were always solid timber resin coated and started there life wide and long and gradually got changed as time went by till the crew were satisfied then we sealed then up properly and painted them !!I have lost count the number of strake repairs iv done over the years where the skin has bent and the glass layers separated and cracks in the gel coat from the outside !!.

 

Take the matter in hand !!

You really need to take a big pill or two and lay down !! or go sit on the loo for a while with a penthouse magazine maybe and re-leave yourself of your frustrations !!

 

Another thread that ran off the (spray) rails, imo.

 

has any one got the formular ???or a formular ??

It would be really helpful of some one had a formula or a reprinted article from a book , even from a really old power boating book or pictures or drawings describing strakes and what they do , how they work , advantages and disadvantages , just anything at all !! graphs or charts of lift predictions for widths and lengths at different speeds and designs !! flat, curved, rounded, sharp edges ,rounded edges , angles down and how much ,what ever!.
Some one some where at sometime must had done some testing and come up with a load of information that would be really helpful to a whole bunch of inquisitive people like myself.
I read books and looked at power boat drawings on boats of all sizes but never found ever any information about strakes !! now there are some pretty smart clever people here on the site so how about sharing what's scribbled on the wall some were !!

 

Okay, we give up Tunnels, you're right, there's no information about strakes, it's just a styling exercise that's been employed for the last 3/4's of a century and all NA's hold all this a secret, just to baffle the likes of people like you. Your "observations" (obviously not empirical in nature) are absolutely correct and your understanding is significantly superior, than the likes of me and the several other professionals, who've attempted to explain these things to you previously, on more than one occasion. Would you need a link to the previous threads, where you've shown a similar ignorance (or simple arrogance) of these hydrodynamic realities, when placed at your feet (if I remember correctly, you complained of the technical aspects and wanted a "Cliff's Notes" version)? In spite of countless tests, preformed countless times and huge piles of data, you can't find any, even when told where to find it or literally had it forced fed to you in these previous threads. Yep, you're beyond us . . .

 

The fake planked look helped strengthen what would otherwise be flat panels, added to the looks of what otherwise be plain flat panels and would help the big flat panels expand and contract without developing the 'starved horse' look common to flat panels of metal.

The strakes on the bottom would add strength, add some lift, deflect spray and direct the course of water and what seems important to me, they would give directional stability to the path the boat traveled. They would help control any squirreliness or wandering in trying to steer a straight or consistent path and most important to me is they would give control in turns. A boat that loses it's grip on the water in a turn is not enjoyable.

Whether they are totally efficient or not is secondary in a boat made for the masses, where any fool is expected to be the driver and where any fool will do whatever is possible at the fastest speed that can be achieved while the boat is loaded or overloaded with a shifting load of the maximum number of people and the driver is often drunk.

I wouldn't think that anchor arrangement would be very sturdy and looks susceptible to being bent, wrenched, torn off or otherwise abused by other boats, docks, trees etc., if not just worked loose in pounding waves. ?