Scarab 16

Oh, and Lucky, why would that bow you draw not work as a wave piercing bow?

 

Yes, every single part lengthwise will be stretched a little (10%), your cabin your bunk, your cockpit, everything. Just your "dickie" will not become longer

The Foredeck theoretically also but not in the real world, because you fit your deck when the modification on the bow is finished. You will just trim the deck to the new shape ... really no big deal.

The most radical and succesfull "stretching" in history of boating were done by the Waarschip boatyard in the Netherlands. Google some pictures of the "Waarschip 660" and the "Waarschip 1010" and compare them. Would you believe that these boats share the same bulkheads? Really, no joke!

Michel

 

A wavepiercer ist not just a negative swept bowline, its a different hull overall. It has a different distribution of volume, different Bulkheads and a much narrower and highly rounded deck, that can shed water without resistance. The whole forward part of the hull has very low volume. The whole rig is shifted aftwards. These hulls are designed to pierce through the waves, not over them as normal boats. Believe me, this is no good concept for a 18' cabin boat.

Michel

 

Amazing!
Waarschip 1010, is a really nice looking boat, and almost unbeliveble that it is made from the "same" drawings as that other chubby thing
So how do i get my "dickie" longer then? (j/k)
Is it possible to relativly simply cut off parts of the bow to a nice straight back leaned bow? just to cut and polish it down and bend it together?
Anyway, that is something that can be tryed out with paper and a sissor before actualy cutting in the wood. It is still only a "add on" or "take away" with cutting it off, it is good but not necessary. How much extra wheight to you think we are talking about? 250kg total?

 

Interesting Concept,

think over again your ama design, in this configuration you have not enough longitudual stability so your boatwill hobbyhorse. Kendricks new amas (Scarab 18, 650) are good at that, take a look.

Its wise to have just one centerboard system, not two! In this length I would like to have them in the amas, to save space in the cabin. Three centerboard trunks are to much weight for such a small boat.

ichel

 

Hey, the 660 is a very good boat! Its fast and seaworthy!

Yes its a model building operation first, you are right. Modelmaking of that boat you want to build is always a good idea, when you never built a boat before. It gives you the feeling what to do in every step of the built.

To say what the weight penalty would be if you do the stretching I have to calculate a little. Can't do it before next week, but I will do it! A rough estimate (very rough) is 20 to 30 kg.

 

Thank you Lucky. I'm very serious with this and i really preciate your help and wise words.
I said that i cannot start building until after the summer, but i could start building small things like rudder, centerboards, beams and such to speed up the buildprocess.
I'll be offline for one week now, so no hurry with that calculation (and honestly, if it is 20kg or 50kg extra is not that much of a deal, it will still be worth the modification)
I've built (partly) a stripplank sailor, and a number of models made out of paper of monohulls i designed my own, surtenly not count at "built a boat before" but i got a hint of how it's like, i hope

 

Brorsan,

I have spent quite some thoughts on exactly the same topic than you did, though tending a bit more towards the Scarab18 due to performance and accomodation issues.

I have done a fairly detailed calculation on both boats which I have in an Excel spreadsheet, so just let me know if you're interested in that.


Best regards from Kiel,
Cord

 

Hi Brorson

My partner Trevor and I built a Scarab 16 5 years ago. She was alot of fun, but we only ever harbour sailed her, as we felt she would not handle a reasonable sea. When fully crewed with 2 people on board, she sits heavy in the stern, and the stern sits only 10 cm above the water. The cabin is small, and we found it was not big enough for us and our son to overnight in. The v-berth is very cosy .

However, she is a brilliant fun day sailer, with a small cabin to escape showers. Our fasted clocked speed was 13.8kt, on a reach. She did not like light breezes, and really came into her own at 15kt. We never reefed her down, not even in 25kt plus - we just moved further out on the ama.

Trevor felt she was overbuilt. He said he would build the amas out of 4mm rather than 6mm ply. We built the beams as per the plans, and they also were very heavy and overdone. We started out with a cut down Hobie 16 rig and sails, for a season. Then had a new jib and main designed for the boat. We had hoped to beat our top speed, but the bigger sails seemed to make little difference to our speed.

Trevor often said that the 18 would have been better for us. But the 16 took only 9 months for him to build. You will find some of our sailing videos here http://www.youtube.com/user/megwyn63

All the best
Ms

 

Hi Megwyn,

good to have you here to gain some 1st hand information. Do you know how heavy your srarab was, when finished? If I got Brorsan right he wants to do singlehanded sailing, perhaps sometimes with his girlfriend, so a cosy bunk should be suitable. Whats about sitting headroom? Is it enough inside the 16?
So my estimations where not so bad at all saying that the 16 is good for sheltered waters.
What do you thing about our thoughts to stretch the 16 to 18' and remain all the hull breadth's original. Shoud be a good idea to increase performance, trim and keeping building costs just slightly raised. Did you make a detailed cost comparison between the 16 and 18 before you decided yourself for the 16? What were your reasons to choose the 16?

Greetings from the North Sea Coast, Michel

 

Hi Cord,

for a better comparison it would be very helpful to have your information and if you can post it here.

Michel

 

take two on my trimaran concept

I have thought a lot about the comments received on my concept design.
I shortened the coachroof to extend the cockpit, which is now 2 meters long.
There is still sitting room inside, and two pilot berths.
The ama's were changed in section and volume increased to have more volume forward.
I have taken the decision to build this boat as simple as I can, so no nonsense of two daggerboard configurations. Daggerboards will go in the ama's.
Rudders go on the ama's for now, I still reserve judgement on this.
I have compared with the Strike 16, and Richard Woods' actual mass seems on par with my estimate.

Please have a look at my revised lines and comment, this is really helpful.

 

weight calculations

Dear Brorsan,

I've done some generous weight calculations and stretching to 18' will cost you a additional weight of 18.9kg maximum. The surface will grow around 4,2m² and I estimated 4.5kg per m², which is heavy for 6mm Plywood, light glass and paint.

You see, there is some serious weight advantages over the original Scarab 18.

I've also some clean scetches of the main hull. The cabin isdrawn a little to small. Hard to believe that these are the lines of the scarab 16 isn't it?

Michel

 

Hi Michel,

I will post the latest version sometime tomorrow...I have it in the USB drive in the office and need to translate it, so our english speaking friends will know what it's all about

Re the weight of the S16/S18: I have a problem understanding the huge difference between both boats...I went through the material lists and added them up...there is some difference, but I didn't find 150 or si kilos...taking into consideration that a Hobie Tiger or similar F18 catamaran weighs in at around 180kg (ok, that's per the class rules...), I can't believe, that the S16 should only weigh 180kg ready to sail. I emailed Ray about that quite some time ago and he promised to look into the calcs again, but I haven't heard from him since...

Cord

 

Hi Cord,

I have the same feelings, but I have no time to make a complete calculation, as I would have to redraw the whole scarab 16 or wait to see the plans. I would estimate one Ama at 35kg (compaired to a Seakayak which is at 22kg 4mm ply) and the Rig and Sails at around 25kg. That would leave 85kg for the mainhull and beams. A very tight schedule, thats for sure! And no room for gimmicks. I think the weight is for the foam sandwich and we have to add a little for plywood.

On the other hand the f 18 is a very heavy boat, at 180kg - good for cheap mass production which the formula is designed for. Compare it to the 20' Tornado (160kg), the f16 (105kg) or old ply versions of the A-Cat (90kg).

Scarab 16 and 18 are just two feet apart or ~10%, but that sums up in surface and volume (I explained it in one of my earlier posts more precise) and therefore weight. If you look at the pdf drawing you see that the 18 has much more freebord, interior volume and the subdeck forms 4 bunks. The rig and overall beam is also very large. That means longer, stronger and heavier spars and beams.
This all together sums up ... but you are right, I cannot see the big difference too. Maybe (and I mean "maybe") the 16 can be built with 200 to 220kg from plywood. If we add the "stretches" we would end at 240kg and thats more than a light boat and will work out perfectly.

Greetings from the North Sea Coast, Michel