strakes vs pads / rocker vs hook ?????

[tunnels]

Strakes any sort of a formula for length and width , placement and how many ?
Hook vs rocker the pros and cons of each , whats good and whats bad about each ?:confused:

Working on a 14.6 semi cabin runabout with a 115 Yamaha ,speed 100km/h so far but rising :D

[Carter Powell]

Well here goes! This is the simple answer. A hook or a rocker are both bad news! A hook of any kind will keep pushing the nose of the boat into the water as speed increases. If you never wanted to go any faster than about 25MPH a hook might be a good idea. The hook keeps lifting the rear of the hull and continually forces the front down. A rocker is just the opposite. As speed increases in is continually trying to ride on the rear most portion of the hull and will continually let the front of the hull fall to the water and then rise and fall= now you have a porpise that can't be controlled! For 99.9 % of us a dead straight bottom is the ticket to a good handling fast boat. Now to a pad! A properly designed pad with a perfectly balanced boat will be about as fast as you are going to get. But, a set of close coupled lifting strakes near the center line of the hull will also give you an increase in top speed. I installed a set, actually just extended them to the trailing edge of a 1985 Sanger outboard last summer. The Sanger did have a flat section on the bottom about ten inches wide from the transom forward about six feet but it is not a true pad. After bringing the lifting strakes all the way to the transom it acts like a pad of about 22" wide. The hull just jumps up on plane and is much more stable at high speeds. This hull used to chine walk pretty good at about 70MPH. Now at 80MPH it is super stable. These are just my opinions but I feel they are accurate.

Best wishes, Carter Powell

[tunnels]

Well here goes! This is the simple answer. A hook or a rocker are both bad news! A hook of any kind will keep pushing the nose of the boat into the water as speed increases. If you never wanted to go any faster than about 25MPH a hook might be a good idea. The hook keeps lifting the rear of the hull and continually forces the front down. A rocker is just the opposite. As speed increases in is continually trying to ride on the rear most portion of the hull and will continually let the front of the hull fall to the water and then rise and fall= now you have a porpise that can't be controlled! For 99.9 % of us a dead straight bottom is the ticket to a good handling fast boat. Now to a pad! A properly designed pad with a perfectly balanced boat will be about as fast as you are going to get. But, a set of close coupled lifting strakes near the center line of the hull will also give you an increase in top speed. I installed a set, actually just extended them to the trailing edge of a 1985 Sanger outboard last summer. The Sanger did have a flat section on the bottom about ten inches wide from the transom forward about six feet but it is not a true pad. After bringing the lifting strakes all the way to the transom it acts like a pad of about 22" wide. The hull just jumps up on plane and is much more stable at high speeds. This hull used to chine walk pretty good at about 70MPH. Now at 80MPH it is super stable. These are just my opinions but I feel they are accurate.

Best wishes, Carter Powell

Thank you !
you have confirmed what i have been thinking all along ,setting strakes 22inch's apart is about what i had been figuring on anyway and the width of the strake its self??? , how wide is the flat area at the rear end ?? :confused:
Strakes seem to be miss thought of as a part to fixing chine walk phenomenon that people like to keep playing with but getting no where

THE flat on the bottom is also another thought as i have a big radius that goes way up near the fore foot of the stem , it gradually gets smaller as it goes along and at speed it pounds harder as speed increases.

The hook and rocker is something i understand, I have planned a form of rocker but with a difference, i want to build into the bottom to help get the bow up just above the water at speed .It will be straight to the rear but the point along the keel near the front still has to be determined as the point of the rocker . Need to get some good pictures of the boat almost at water level in different degrees of trim and speed in dead smooth water .
Have done this with a video camera on new tunnel boats and it really is interesting !!

This is going to be my wintertime project to remove the motor and flip the boat to work on the bottom , Its got signs of stress and time sitting on a trailer has not been good to it with rollers in wrong places ,need i say more !.

Thank you so much for your help !:D

[Carter Powell]

Send me an e-mail address and I will send you some pictures of the Sanger that I did. I will also send you a sample of the material that I use to build up the strakes. It is a fiberglass extrusion. I have done this many times and would be glad to give my ideas if you wish. I will also share a very simple way to turn the boat upside down by yourself if needed.

Best wishes, Carter

[propmanjay]

Allison boats all come with a lip at the back of the pad. Allison holds the record at 120 + with this lip. The lip is usualy around 60 thou at the center of the pad.

[tunnels]

Send me an e-mail address and I will send you some pictures of the Sanger that I did. I will also send you a sample of the material that I use to build up the strakes. It is a fiberglass extrusion. I have done this many times and would be glad to give my ideas if you wish. I will also share a very simple way to turn the boat upside down by yourself if needed.

Best wishes, Carter

stuartwrcom@gmail.com
I was going to make a light glass shape on the strake on the bench of the whole length for each side , fill it with pvc hi density foam (divinicell h 90 )and then introduce it to the hull and then vac bag and glass them on .
Thanks,
Wayne C.:cheers:

[afr]

we picked up 16 mph the first time we played with adding strakes to the rear of the hull on a 28 magnum twin 3.4,s 30 inch set back 106 mph

[tunnels]

we picked up 16 mph the first time we played with adding strakes to the rear of the hull on a 28 magnum twin 3.4,s 30 inch set back 106 mph


Its only 14.6 long semi cabin boat, built 1975 probably had a 40 hp when it was new now its a 115 yamaha on a 450mm set back transom i made . Most of these boats have long since departed this earth along with the people that bought them new .
Its a fun thing to play with and each little mod improves its performance just that bit more . It was never meant to do what i have planed for it.
:cheers::cheers::cheers:

[Carter Powell]

Don't wast your time on trying to figure out the strakes. Send me your address and I will send you a sample of what I have been using for years. Trust me on this. It will save you tons of time and grief! You will want to use an epoxy like West Systems with their 404 filler to make the epoxy real thick like peanut butter. Then after the fiberglass on the hull has been scuffed up good you will just lay on the ready made strakes with the epoxy goop inside them and just tape them tightly to the bottom and walk away. When the epoxy is almost cured take a sharp wood chisel and just scrap off any excess goop. After everything has cured up for a couple of days start your finish work and you are home free.

Best wishes, Carter Powell

[tunnels]

Don't wast your time on trying to figure out the strakes. Send me your address and I will send you a sample of what I have been using for years. Trust me on this. It will save you tons of time and grief! You will want to use an epoxy like West Systems with their 404 filler to make the epoxy real thick like peanut butter. Then after the fiberglass on the hull has been scuffed up good you will just lay on the ready made strakes with the epoxy goop inside them and just tape them tightly to the bottom and walk away. When the epoxy is almost cured take a sharp wood chisel and just scrap off any excess goop. After everything has cured up for a couple of days start your finish work and you are home free.

Best wishes, Carter Powell

Just a picture with a ruler along side and i can see what you have in mind plus its quicker .
Im a polyester or vinylester man myself and would like to stay that way .
I know all about the merits of epoxy just dont want to go down that road.
I have a chine to chine fairing job from stem to stern . I will have to grind off all the gel coat back to the bare glass then vac on a skin of 3mm pvc high density foam almost all over then set to and long board it totally to get shot of the hollows that it has on both sides ,during all this build a vee in the front end ,a flat at the back coming forward 6 or 8 feet in combination to getting rid of the rounded shape ,along with all this sort the rocker i was talking about earlyer !
Sounds like a long and roundabout way of doing it but the bottom has stress areas and all the cracks in the gel to go with it . Its one of the resons i havent opened the old girl up flat out as i dont want the bottom to get blown apart just yet .
Its going to be a mamoth job but i really am looking forward to it . :D:cheers::thumbsup::cheers::rolleyes::rolleyes::rolleyes:

[Raceman]

Well here goes! This is the simple answer. A hook or a rocker are both bad news! A hook of any kind will keep pushing the nose of the boat into the water as speed increases. If you never wanted to go any faster than about 25MPH a hook might be a good idea. The hook keeps lifting the rear of the hull and continually forces the front down. A rocker is just the opposite. As speed increases in is continually trying to ride on the rear most portion of the hull and will continually let the front of the hull fall to the water and then rise and fall= now you have a porpise that can't be controlled! For 99.9 % of us a dead straight bottom is the ticket to a good handling fast boat.

Carter, I've gotta' disagree with you on the "simple answer". The fact is, a well designed hook can give significant speed increases, with the key phrase being well designed. Many boats, such as the HydroStream Vipers and Vectors have hooks in the center pad. As was previously mentioned, many Allisons have a designed lip on the rear of the pad, which is essentially a small hook. While it's correct that "the hook keeps lifiting the rear", proper design and setup will cause it to lift the boat off the water, unwetting more bottom at a given trim angle, AGAIN assuming proper design and setup, AND they don't necessarily bury the bow in the process. A boat that unwets more bottom while running at a flatter trim angle punches a smaller hole through the air than one that has to run extremely bow high to lose the same amount of bottom drag/running surface. Think of it as the reverse of a spoiler on the rear of a car, giving downforce, while NOT trying to lift the nose of the car. Not exactly a parallel, but kind of puts you thinking in the right direction. I have also seen cases where a rocker can enhance a boat's performance, but it's usually because it fixes another problem of some type. The very early designed tunnelboats with a lot of lift built into the tunnel were actually rockerbottoms to some degree.

When I was running kilo's with my 16' Ally in the dark ages, we tried the lip on the back of the pad per Paul Allison's suggestion, and discovered it was lifting the boat virtually off the water, and became undriveable. In a rush to get the lip off and back to a flat pad in the last hours before the trip, we inadvertently ground a rocker in the pad. The boat ran very well with less trim angle than before, although nose higher than I preferred. In this case, somewhere between the dead flat pad, and a MUCH LESS drastic lip than the 1/8" or so would have probably been the majic combination, but we learned about rockers from that mistake, and after coming back, grinding one in the rear of my 18' Super Sidewinder yielded a couple of MPH because the boat, although dead straight wanted to run wet, and it wasn't fast enough to be a blowover risk OR for the aerodynamics to be significant. It's possible that a jackplate with some setback would have produced similar results with a dead straight bottom.

So I guess there is NO simple answer. There're a lot of variables, and a lot of different ways to skin the goose.

[tunnels]

Carter, I've gotta' disagree with you on the "simple answer". The fact is, a well designed hook can give significant speed increases, with the key phrase being well designed. Many boats, such as the HydroStream Vipers and Vectors have hooks in the center pad. As was previously mentioned, many Allisons have a designed lip on the rear of the pad, which is essentially a small hook. While it's correct that "the hook keeps lifiting the rear", proper design and setup will cause it to lift the boat off the water, unwetting more bottom at a given trim angle, AGAIN assuming proper design and setup, AND they don't necessarily bury the bow in the process. A boat that unwets more bottom while running at a flatter trim angle punches a smaller hole through the air than one that has to run extremely bow high to lose the same amount of bottom drag/running surface. Think of it as the reverse of a spoiler on the rear of a car, giving downforce, while NOT trying to lift the nose of the car. Not exactly a parallel, but kind of puts you thinking in the right direction. I have also seen cases where a rocker can enhance a boat's performance, but it's usually because it fixes another problem of some type. The very early designed tunnelboats with a lot of lift built into the tunnel were actually rockerbottoms to some degree.

When I was running kilo's with my 16' Ally in the dark ages, we tried the lip on the back of the pad per Paul Allison's suggestion, and discovered it was lifting the boat virtually off the water, and became undriveable. In a rush to get the lip off and back to a flat pad in the last hours before the trip, we inadvertently ground a rocker in the pad. The boat ran very well with less trim angle than before, although nose higher than I preferred. In this case, somewhere between the dead flat pad, and a MUCH LESS drastic lip than the 1/8" or so would have probably been the majic combination, but we learned about rockers from that mistake, and after coming back, grinding one in the rear of my 18' Super Sidewinder yielded a couple of MPH because the boat, although dead straight wanted to run wet, and it wasn't fast enough to be a blowover risk OR for the aerodynamics to be significant. It's possible that a jackplate with some setback would have produced similar results with a dead straight bottom.

So I guess there is NO simple answer. There're a lot of variables, and a lot of different ways to skin the goose.

The type of hull you are refering to has a lot of topside over the water up in the bow area and its creating an air cushion effect ,a hook is needed to get the back up and loose off the water.

Rocker on the other hand does not mean it has a gentle curve over the length of the keel but straight and flat from the back to a predetermaned point somewhere in the forefoot where the stem joins the keel then a gentle but distink change in dirrection from there to the bow and up the stem .
The big Wally power boat us a pronounced version of what i am refering to,they look fast in the water even when they are not moving .

The 1/8 lip you mention is that a turndown at the very rear of the pad to raise the back at speed ?? :confused::confused::D

[tunnels]

Gentle men there are some interesting things starting to surface and others could get a lot from where it going i hope . lets keep the ball rolling !. :cheers:

[fast fun 2]

we picked up 16 mph the first time we played with adding strakes to the rear of the hull on a 28 magnum twin 3.4,s 30 inch set back 106 mph
Magnum Marine Magnum? Maltese?

[Carter Powell]

Still got to disagree with you a little. What I was referring to was a full length hook from setting on a poorly designed trailer where the center of the hull has degenerated over time!
That type of situation will never get out of its own way. What you are referring to as maybe a small hook towards the rear of the pad or a section of the rear of the hull that won't be touching as the hull rises out of the water, then I concur that you are correct.

Best wishes, Carter Powell

[vnemous]

I think all of us would like to know an easy way to flip a boat. How about posting it or email me at mfranzoso@co.ocean.nj.us Thanks Mike

[1BadAction]

I think all of us would like to know an easy way to flip a boat. How about posting it or email me at mfranzoso@co.ocean.nj.us Thanks Mike

I can flip mine by myself (I'm a pro at it :rolleyes: ) but the easiest way is a grassy spot, 4 old tires, 5 or 6 buddys and a case of beer to bribe them with. turn it up on its side on 2 tires, have a guy hold it there while the others go to the other side, and let it down on the other 2 tires.

[Carter Powell]

I will break out the pictures tonight and see what everyone thinks. I have done it myself many times but the last time I got my wife to help. She was scared that it was going to roll away with the big wheel on the back ( what wheel )

Later, Carter

[tunnels]

Still got to disagree with you a little. What I was referring to was a full length hook from setting on a poorly designed trailer where the center of the hull has degenerated over time!
That type of situation will never get out of its own way. What you are referring to as maybe a small hook towards the rear of the pad or a section of the rear of the hull that won't be touching as the hull rises out of the water, then I concur that you are correct.

Best wishes, Carter Powell

I agree there as well !
A natural hook from the fore foot of the bow to the stren is what happens from sitting on centre line rollers on a trailer sometimes or insufficent structure inside the hull to hold its shape properly . :rolleyes:
A small turn down at or near the back is there for a purpose .
My boat was a family boat, it was good with the old motor but its taking it few steps further that i am interested in and i have found the faults and need to address them .
Tricks and small add ons that tweak and fine tune are where its at ,at the end of the day, the little things that make a good hull a better hull as speed increases . Safety and predictability is always paramount with any of the things that get changed . :D
Some interesting thoughts coming out along the way ! Thank you !!:cheers::cheers::cheers:

[afr]

flipping a boat
is just a matter of putting a engine stand mount on the transom in the outboard holes and a chain
then a rope on the front hang the boat in the air high enoph so it wont hit the ground and roll it over
its really just 123 done

i dont remember what the name of the magnum was just a 28 ft closed bow
we gutted it and re built it with h 80 divinecell

[150aintenuff]

there were several variations of the brand MAGNUM. but for reference sake do you know if it was the arronow hull design

[afr]

it was so many years ago it would had to of been a arronow
it was twin inboard when we first gutted it
the boats race name was no fear before that it was too intense b 121
no fear people bought it from us

[tunnels]

We have a tidal greek that the water ski club use ,its smooth water, and able to stand right on the edge of the creek , its a excillent place to get pictures /video down at water level .
I have a couple of friends with camera's and a video to get some footage of what i have now doing differant things ,mainly trim angles at differant speeds etc etc then to sit with a few beers and pick holes in what needs doing and where and to what exstent .:confused::cheers::D
Just had a look at the Allison boat site and that was interesting . :cool:

[XstreamVking]

Tunnells.. I have a 26.5' center console outboard boat that has two full length strakes and one strake that runs a little over half way back per side. Also a pad that starts one third of the way back and gets wider as it goes to the stern. This design will plane quickly and will carry a lot of weight with no problem. Also very stable. Seems to be a good general design for a hull.....Wider strakes give more lift, pads usually carry the stern..

[tunnels]

Tunnells.. I have a 26.5' center console outboard boat that has two full length strakes and one strake that runs a little over half way back per side. Also a pad that starts one third of the way back and gets wider as it goes to the stern. This design will plane quickly and will carry a lot of weight with no problem. Also very stable. Seems to be a good general design for a hull.....Wider strakes give more lift, pads usually carry the stern..


Thank you for that !:thumbsup:
Getting on the plane at low speed quickly is what i want and carrying that through as speed increases is the other side of it . I was against a pad to start off with but had a change of heart in the last couple of days . Was looking at 2 strakes a side but settled for 1 each side now . have picked up some little snippets of info from the postings that i will try as well .
Thank you again !!:cheers:

[afr]

like i said best bang for the buck is to exstend the two center chine,s / strakes to the transom
with or without a pad this works nice

[tunnels]

like i said best bang for the buck is to exstend the two center chine,s / strakes to the transom
with or without a pad this works nice


When i get a load a fish in the back i want all the lift i can get ! and a bow that cuts through those waves on the long haul home ! .:thumbsup:
I have an idea of the width for the 2 strakes and a flat on the bottom but everyone is gonna laught ,so im keepin quiet for now . :rolleyes:

[1BadAction]

When i get a load a fish in the back i want all the lift i can get ! and a bow that cuts through those waves on the long haul home ! .:thumbsup:
I have an idea of the width for the 2 strakes and a flat on the bottom but everyone is gonna laught ,so im keepin quiet for now . :rolleyes:

do you have trim tabs on it?

[bluecheckmate]

I can flip mine by myself (I'm a pro at it :rolleyes: ) but the easiest way is a grassy spot, 4 old tires, 5 or 6 buddys and a case of beer to bribe them with. turn it up on its side on 2 tires, have a guy hold it there while the others go to the other side, and let it down on the other 2 tires.


Yup that's what i did. I threw some covers on the grass and some motorcycle tires and between three of us we were able to flip it and also got a forklift and cherry picker to put it on top of the trailer.

[tunnels]

do you have trim tabs on it?

Why dont i have a merc ! couldnt find a vertical 4 cylinder, 110 hp fishing motor ,with a 25 inch shaft at the time i needed one . :(

Trim tabs ! not possible to mount them on the back without a lot of cutting , reglassing to make a place for them to mount . It had crossed my mind but thats all !:nonod:

[1BadAction]

Trim tabs ! not possible to mount them on the back without a lot of cutting , reglassing to make a place for them to mount . It had crossed my mind but thats all !:nonod:
ahh... yea, there are some boats like that, figured it might be the case with yours. good luck with the bottom mods. :thumbsup: