New member presentation / Roca Speed Rails wanted
12-16-2021, 04:26 PM
#1
Registered
Thread Starter
+ Pictures: New member presentation / Roca Speed Rails wanted
Hello from España, ole!
I’m reading you guys from many years ago, and finally join formally the OSO Community.
We are a bunch of friends located in Palma de Mallorca and Marbella (Spain) with some nice boats and GAS in veins.
Today I want to show you an special boat I was restoring. It’s a beautiful 25ft Tullio Abbate, an Italian well recognised manufacturer.
The model was originally designed for I/O, but they built some units with kevlar hull (I guess not the best kevlar 49 McMannus) for single outboard racing. And as I know probably the unique with twins.
This boat was built by Offshore Agency Prettin in collab with Abbate. It has an oversized tubular bracket with strong torsion bars along the hull and an a 3” wood core stern.
Non cracks or stress signals after the years. It’s true that the boat was only in the hands of OA Prettin and very well cared.
***
Let’s deep in materia!
- The boat is 1.300 pounds + 250 in inox. Steel + 850 engines (Twin Merc V6 200HP 2T Carb 200hrs);
- Has 23” Attwood Ballistic Couped & Labed Props with over ventilation (0.6” holes).
- Considering my Props as 24” because of couped design + 1.87:1 gear relation, my numbers are:
45 MPH at 4.000RPM, 7% Slip (cruiser speed)
50 MPH at 4.400RPM, 7% Slip
55 MPH at 4.800RPM, 6.5% Slip
you can run 45MPH, just at half gas and 55MPH with no more tan 2/3 gas.
It runs amazing, nice attitude, very low consumption, but!!!! At 55MPH it develops terrible CHINE WALKING!!!
My max. Speed “driving through” was 62MPH. If you push the hummers it revs immediately fast. It seems will not has any problem to touch 5.700RPM with 0º Trim and current lower engines. I guess, when they will on point could reach 5.900RPM
***
I was reading all post about in this amazing forum and got very deep researching before come here to ask, because I appreciate a lot your knowledge.
The main problem is a longitudinal sustainability lack
ISSUES:
1º the bracket: I know it’s almost double sized of you recommend + the transom has also a severe angle. I guess the props it can be 60” away from the bottom.
But I can’t cut it, it’s an identity of this
boat. Thus, my plan is to improve as much as I can with this thing.
2º the engines height: The boat will be out of the water in one month, then I will measure them properly. I guess the cav plate is 0 or 1” bellow the bottom.
I learn from you guys and from Gill standards that around 60MPH the water after the bottom exits at 4% inclination. This is translated to the rule of going up 1/12” for every 1”. Probably I will be 4 or 5” lower than I must.
As I have standard lower units, I will give 1/2” of prudence when I will raise them + install PSI gauges.
when boat will by at my garage, and I will measure it good, I will ask you all and together we will find the proper height.
(Mikel’s explanations)
3º make the steering stronger: I have single hyd + standard tie bar. I have purchased a heavy dutty rear bar. I’m 1/3 Toe in.
4º trim tabs: I will install parallel to the water a pair of lencos with led position indicators + squared “custom” trim tabs. It will be mounted just as a continuation of the strakes, with customized T-fins at the external side of the tab designed my friend Mikel.
they will be mounted just on the limit of the bottom, and will run normally in negative trims. Also will make the bracket smaller (based on Arneson Rockers ideas)
5º The Strakes: they are very classical european style. Very thin, not prominent, and even not parallel to the water. It’s with the height of the engines the biggest issue.
With such low engines I got to much stern lift, then It leads to a longitudinal lack of sustainability.
When I will rise the engines, If I don’t give the boat also a good stand points, it will be loosing again the equilibrium.
For this I have found the best solution. The Ocke Mannerfelt Speed Rails. For those who don’t know them. They are just a simple aluminium slats fixed to the strakes. They make te strakes more prominent and with a concave design, they make more lift using the energy of the lateral displacement of the water.
Roca was a Swedish company which stops making the Mannerfelt Speed Rails 10 years ago.
The “Roca Speed Rails” weren’t very popular in USA. I guess because in USA you use to build boats with wide and strong strakes. Then non extra is needed.
I wish an OSO fellow still had a set of this old Roca Speed Rails and would be open to sell them. It would be very very helpful!!
Im very happy writing my first post, I will be active in the forum.
Javier.
I’m reading you guys from many years ago, and finally join formally the OSO Community.
We are a bunch of friends located in Palma de Mallorca and Marbella (Spain) with some nice boats and GAS in veins.
Today I want to show you an special boat I was restoring. It’s a beautiful 25ft Tullio Abbate, an Italian well recognised manufacturer.
The model was originally designed for I/O, but they built some units with kevlar hull (I guess not the best kevlar 49 McMannus) for single outboard racing. And as I know probably the unique with twins.
This boat was built by Offshore Agency Prettin in collab with Abbate. It has an oversized tubular bracket with strong torsion bars along the hull and an a 3” wood core stern.
Non cracks or stress signals after the years. It’s true that the boat was only in the hands of OA Prettin and very well cared.
***
Let’s deep in materia!
- The boat is 1.300 pounds + 250 in inox. Steel + 850 engines (Twin Merc V6 200HP 2T Carb 200hrs);
- Has 23” Attwood Ballistic Couped & Labed Props with over ventilation (0.6” holes).
- Considering my Props as 24” because of couped design + 1.87:1 gear relation, my numbers are:
45 MPH at 4.000RPM, 7% Slip (cruiser speed)
50 MPH at 4.400RPM, 7% Slip
55 MPH at 4.800RPM, 6.5% Slip
you can run 45MPH, just at half gas and 55MPH with no more tan 2/3 gas.
It runs amazing, nice attitude, very low consumption, but!!!! At 55MPH it develops terrible CHINE WALKING!!!
My max. Speed “driving through” was 62MPH. If you push the hummers it revs immediately fast. It seems will not has any problem to touch 5.700RPM with 0º Trim and current lower engines. I guess, when they will on point could reach 5.900RPM
***
I was reading all post about in this amazing forum and got very deep researching before come here to ask, because I appreciate a lot your knowledge.
The main problem is a longitudinal sustainability lack
ISSUES:
1º the bracket: I know it’s almost double sized of you recommend + the transom has also a severe angle. I guess the props it can be 60” away from the bottom.
But I can’t cut it, it’s an identity of this
boat. Thus, my plan is to improve as much as I can with this thing.
2º the engines height: The boat will be out of the water in one month, then I will measure them properly. I guess the cav plate is 0 or 1” bellow the bottom.
I learn from you guys and from Gill standards that around 60MPH the water after the bottom exits at 4% inclination. This is translated to the rule of going up 1/12” for every 1”. Probably I will be 4 or 5” lower than I must.
As I have standard lower units, I will give 1/2” of prudence when I will raise them + install PSI gauges.
when boat will by at my garage, and I will measure it good, I will ask you all and together we will find the proper height.
(Mikel’s explanations)
3º make the steering stronger: I have single hyd + standard tie bar. I have purchased a heavy dutty rear bar. I’m 1/3 Toe in.
4º trim tabs: I will install parallel to the water a pair of lencos with led position indicators + squared “custom” trim tabs. It will be mounted just as a continuation of the strakes, with customized T-fins at the external side of the tab designed my friend Mikel.
they will be mounted just on the limit of the bottom, and will run normally in negative trims. Also will make the bracket smaller (based on Arneson Rockers ideas)
5º The Strakes: they are very classical european style. Very thin, not prominent, and even not parallel to the water. It’s with the height of the engines the biggest issue.
With such low engines I got to much stern lift, then It leads to a longitudinal lack of sustainability.
When I will rise the engines, If I don’t give the boat also a good stand points, it will be loosing again the equilibrium.
For this I have found the best solution. The Ocke Mannerfelt Speed Rails. For those who don’t know them. They are just a simple aluminium slats fixed to the strakes. They make te strakes more prominent and with a concave design, they make more lift using the energy of the lateral displacement of the water.
Roca was a Swedish company which stops making the Mannerfelt Speed Rails 10 years ago.
The “Roca Speed Rails” weren’t very popular in USA. I guess because in USA you use to build boats with wide and strong strakes. Then non extra is needed.
I wish an OSO fellow still had a set of this old Roca Speed Rails and would be open to sell them. It would be very very helpful!!
Im very happy writing my first post, I will be active in the forum.
Javier.
Last edited by El Espanol; 12-17-2021 at 05:46 PM.
12-16-2021, 04:40 PM
#4
Platinum Member
Platinum Member
iTrader: (6)
Welcome to OSO, just keep posting 1 post 2 post 3 post til you get to 10
Charter Member
12-17-2021, 04:46 AM
#6
Registered
Thread Starter
Thanks for the answers! As #Griff mention, 280K Plates would be the real deal! I would like to have them + Latham “side fins”.
I have the lencos in the servings and I decided to modify them to be used mostly in negative angles.
This boat runs in the calm Mediterranean seas. I guess non the lencos or the bracket will be surviving in rough oceans!
I have the lencos in the servings and I decided to modify them to be used mostly in negative angles.
This boat runs in the calm Mediterranean seas. I guess non the lencos or the bracket will be surviving in rough oceans!
The following users liked this post:
Griff (12-17-2021)
