24 ft "picnic cruiser" designing

[brian eiland]

Haven't had time to read thru your subject thread, but I would suggest you look thru this forum for many other ideas.

Have a look at this vessel for some pretty simply construction ideas
http://markvdesigns.tripod.com/boatbuilding/id12.html

 

[hirvi49]

Brian: That Mark V 39 looks nice and easy to build. I'm not very satisfied of the flat-bottom, but I've to think about it.

TANSL questioned my knowledge about boats, so I'll tell shortly about my self.:

I've designed and built two boats before this one. Those were <5m planing boats,
made of plywood. They were built without any proper plans or calculations (I was 13 and 16 years old).
I've worked as a boat mechanic for few years.
For long time my hobby was restoring old glass fiber boats and I've restored/rebuilt 4 boats ever since.

Now I'm M.Sc (mechanical engineering) and I would like to build a bit better
boat than I built over 10 years ago, using my new knowledge.

I know a lot about structures and strength, but I know only basics about hydrodynamics. I'm born with an attitude: "How hard can it be?", which is a slight problem.

About boat stability:
I tried to imitate a sailing boat hull and I made some calculations with DelftShip.
It gives me: transverce metacentric height (2,2 m) and longitudinal metacentric height (14 m).
I think those both are quite good values.
Boat length: 7,2 m, beam: 2,4 m, draft: 0,3 m, displacement: 2000 kg

 

[Pericles]

hirvi49,

Knowing more about your background & experience does help us to help you. The Mark V 39 & other designs have a good reputation.

http://duckworksbbs.com/plans/markv/39/index.htm

http://markvdesigns.tripod.com/boatbuilding/id16.html

http://www.duckworksbbs.com/plans/markv/28/index.htm

Other useful sites.

http://www.bateau.com/

http://www.selway-fisher.com/

http://www.cmdboats.com/index.htm

http://www.glen-l.com/boat-plans-catalog-300-boats-you-can-build/

From years ago.

http://www.atkinboatplans.com/

Simplicity itself.

http://www.oldwharf.com/ow_workskiffs.html

How to make a proper job of painting a LYS.

http://forum.woodenboat.com/showthread.php?138899-lumber-yard-skiff&p=3186069&highlight=#post3186069

Good luck.

 

[TANSL]

TANSL questioned my knowledge about boats,

I do not question your knowledge, I have not tried to at any time. Like I said, in many countries amateur boat building is highly regulated and difficult, very difficult, an amateur get the "approval" of the administration. One of the most important, but not the only things, is to prove (usually by the signature of a recognized professional) that the ship complies with the standards that apply.
No doubt about your knowledge but I can assure you that the legislation is, in general, a hell and that few professionals dominate. I think, if I'm wrong you correct me, that's not the field on which you play better.

About boat stability:
I tried to imitate a sailing boat hull and I made some calculations with DelftShip.

Be careful, that may not be correct, you could get too much stability for your boat.

 

[hirvi49]

Be careful, that may not be correct, you could get too much stability for your boat.

Too much stability? How that can be a problem? I think flat-bottom hull is even more stable than a round shaped sailing boat hull?

How about resistance of flat-bottom hull? Is the resistance higher than with a round shaped hull? Or is it even significant?

 

[TANSL]

Hirvi, the numbers are very stubborn and that "it seems to me" can be easily refuted by the numbers.
Too large stability can become a serious problem but not think I need to explain this.
To say that a flat bottom hull is more stable or less than a rounded hull, without more data, it makes no sense.
Try a motor boat that has the same stability, or the like, a sailboat, it makes no sense.
With the knowledge that you have, if you think about it, you will see that I am not too wrong.

 

[aa86]

looks brilliant, you should to take it to a naval architecht



car servicing

 

[DCockey]

Principles of Yacht Design is a very good text for someone interested in learning about the more technical aspects of boat and yacht design. http://www.isyd.org/?page_id=75

 

[gulo]

Hi,

This concept reminded me of another Finnish project.

http://www.facebook.com/KyamkCatamaran?fref=ts

Same targets, different approach...Interesting.

Good Luck!

 

[hirvi49]

Principles of Yacht Design is a very good text for someone interested in learning about the more technical aspects of boat and yacht design. http://www.isyd.org/?page_id=75

I have that book (a bit older version) and I started to read it again with better focus on it.

I know that Kyamk catamaran. I've seen it and talked with its designers. They have also an electric trimaran called Midnight Sun. Very interesting projects.

Catamaran has (mostly) better performance and stability than mono hull but I want the boat to be trailerable with standard trailer.
Few days ago I was driving a catamaran (planing) and I didn't really like it. It leans to the wrong direction while turning and it feels stupid in a boat.

 

[bjn]

I just bought a lot of 2nd grade from the factory (ie slight measurement variance, compressive strength guaranteed to be 300kpa even though it might be from a 700kpa run).
That was 2"/5cm stuff. Its pretty good, you can walk on it without any worries of leaving foot prints, and yes it does bounce back pretty good. The surface is very nice, especially on the thinner (~1") boards. You can bend those thinner panels to an extent but not much. Still it would seem that using the boards as boards would make more sense (over the thick block idea), be more efficient and save a ton of epoxy.

and I am talking about the Finnfoam though I doubt there is huge difference between brands.

After playing with it some more, do you think it's still a good foam core material for boat building?

Did you make a test/infuse a panel to compare to other foam cores, or similar?

 

[kerosene]

I have very limited experience and no I have not laminated anything yet. Also I have never used proper cores so I can't really to say this or that in terms of comparisons.

 

[PAR]

Having done a custom design for a fellow in Finland a few years ago, I can tell you that they can build pretty much anything they want, self designed, non-EU compliance or not, so long as they don't intend to sell it for a minimum of 5 years and certainly not for resale or mass production.