Buccaneer 24 Trimaran

[tatoski]

Samnz,

Thanks for the advice. Do longer waterlines for cats and tris make them faster? I thought hull speed limitations apply only to displacement boats and not narrow and long hulls of cats and tris.

By the way with your 6 hp under full throttle and calm seas what speed do you get out of your bucc 24?

Thanks

Tatoski

[Samnz]

I have a 5hp, Bruce has a 6hp. I get max 6.8 knots, 6 knots with crusing gear on the boat.

Waterline is not such a big factor on multihulls as it is on monohulls, eg the bucc 24 will be faster than a 40 ft cruising cat, however more waterline will always give more speed if the power to weight ratio is maintained, because there is allways waves which slow the boat down.

[boat fan]

Originally Posted by tatoski

Samnz,

...... Do longer waterlines for cats and tris make them faster? I thought hull speed limitations apply only to displacement boats and not narrow and long hulls of cats and tris.........

Thanks

Tatoski

Narrow and long hulls of cats and tris are displacement hulls.

[bruceb]

I would mount the motor on the side - It keeps the weight off the stern, the prop stays in the water more, and it is a lot easier to start and operate the engine and not fall overboard Really! Buc 24's are very fine aft, floats and main hull, they certainly don't need any extra aft trim. I just checked my motor- an older Mariner 5!hp extra long shaft with a short shaft prop. I get about 7.2 kts in very smooth conditions with just me on the boat. Extra weight does slow it down a little. I have changed props on several very light sport and multi boats and gotten good results. The engine manufacture's usually put "pusher" pitched props on their long shaft models and speed props on the short models. The speed props usually work better on our boats. Next summer I am going to try a 15hp I have, just to see what happens

[Samnz]

Originally Posted by boat fan

Narrow and long hulls of cats and tris are displacement hulls.

not in the traditional sense. Iv seen this argument so many times before...

The formula for hull speed doesnt seem to apply for multihulls, as my 6.5m floats (main hull nearly out) can get to 19 knots in flat water, but arent planing... so?

[Samnz]

Originally Posted by bruceb

Next summer I am going to try a 15hp I have, just to see what happens

iv tried that, got 12 knots out of it!

[tatoski]

Originally Posted by Samnz

The floats how they are are very safe as they will sink under and the boat will round head to wind if overpowered. I have had many close moments when I think with bigger volume floats may have capzised! This is also why Farriers have small floats. However it would have a higher top speed and pitch less with longer floats, so I would stretch them to 7.5m if I were you but keep the rest of the measurements the same.

Samnz,

If the boat buries a float wouldn't the boat bear away and not round up? I have not sailed multihulls but on a reach I believe the leeward float will bury and cause more resistance acting like a fulcrum where the boat will pivot from and cause the boat to bear away? Thanks

Tatoski

[boat fan]

Originally Posted by Samnz

not in the traditional sense. Iv seen this argument so many times before...

Damn..... I wasn`t going to post that because I just KNEW I would get this response..... .......Because I have seen that argument too many times also.

You are right Samnz. Multies cheat the rule somehow.

my 6.5m floats (main hull nearly out) can get to 19 knots in flat water, but arent planing... so?

Well , there it is ......if the floats are not planing ......they cannot be planing hulls...Soooo...what are they ?

I still think of them as displacement hulls . its a dilemma.

[jorgejbp]

Does anybody have pictures of the building of a Buc 24?
Thks.

[dialdan]

jorgejbp
Hi
I don,t have pictures but the construction method is very simple, known as tortured ply which gives it it,s stiffness, basically the sides are cutout to the given dimensions ,both sides can be cutout at the same time ,the transom and stem are glued into place and then the rest of the frames are forced into the sides. Too easy
Al

[Samnz]

Originally Posted by dialdan

jorgejbp
Hi
I don,t have pictures but the construction method is very simple, known as tortured ply which gives it it,s stiffness, basically the sides are cutout to the given dimensions ,both sides can be cutout at the same time ,the transom and stem are glued into place and then the rest of the frames are forced into the sides. Too easy
Al

Actually I think the design is hard chine ply, not tortured ply...

I havent got any photos I have been told my boat was built by setting up the frames, butt joining (with backing plate) all the sheets of ply together (for the bottom and topsides) on the floor and cutting the shape out and attaching stringers before each panel is attached onto the frames. Whole operation is very quick and easy from all accounts...

[Samnz]

Originally Posted by tatoski

Samnz,

If the boat buries a float wouldn't the boat bear away and not round up? I have not sailed multihulls but on a reach I believe the leeward float will bury and cause more resistance acting like a fulcrum where the boat will pivot from and cause the boat to bear away? Thanks

Tatoski

The multihulls will gain some leward helm as the leward hull gains more immersion but it shouldnt cause it to bear away, unless the boat has no weather helm to start with. In my boat its the reverse of a monohull sailing to windward, there is lots of weather helm when it is light breeze, then the helm comes very light when the boat is powered up, because the float is balancing the wether helm.

Either way when a multihull is pushed to the very edge the boat will either pitchpole or round up, look at videos of the volvo x 40s...

at 1min 3 secs in this vid it is quite clear
http://www.isharescup.com/video.asp?vidid=1610677988

[tatoski]

Samnz, thanks for replying. There are many videos in the link you mentioned. Which one is it? Thanks in advance.

Tatoski

[Samnz]

Originally Posted by tatoski

Samnz, thanks for replying. There are many videos in the link you mentioned. Which one is it? Thanks in advance.

Tatoski

the one right in the middle of the screen...

[oldsailor7]

Of course multihulls are displacement boats.

Most monohulls have W/L hull to beam ratios of 4-6 :1, and make a hole in the water which the sails can't supply enough power for the hull to climb out of. This is the boats limiting hull speed.

The Late Edmund Bruce had the run of the British Govts Naval test tank facility and in the mid 1960's tested out many hull forms.
He found that as hull L/B ratios increased the wave making feature diminished untill at an L/B ratio of 12:1 there was no adverse wave at all. From that point on further increases in L/B ratio entered the area of diminishing returns, as wetted surface increase increased drag due to the diminishing displacement. This meant only the very lightest boats benefitted from very high L/B ratios, EG:- The Tornado and modern Cats like the Formula 40's.
Richard Woods "Gwahir" has an L/B ratio of 15:1 for instance, but is very light and not suitable for loading up with a lot of cruising gear. But it was designed
specifically for racing. IE:- Horses for Courses.

The Bucaneer 24 was designed to be a simple, easy to build, fast "Pocket Cruiser". It has an L/B ratio of 8:1, a compromise between good weight carrying capacity and good light wind performance. I think even Lock was suprised by the way this small boat was "Tweaked" and turned out to be a little race winner.