Scarab 16

Discussion in 'Multihulls' started by Brorsan, Feb 6, 2011.

  1. Brorsan
    Joined: Nov 2007
    Posts: 77
    Likes: 3, Points: 0, Legacy Rep: 43
    Location: Gothenburg/Sweden

    Brorsan Junior Member

    I'm thinking of building the scarab 16 (http://www.teamscarab.com.au/scarab16/design.html), but there is so little info about it. Seams like only 1 boat has been built. 5m tri at say 500kg fully loaded, that wount be very fast, will it? All info is appresiated. Thoughts of it? Is it simply TO small for a tri?
     
  2. Brorsan
    Joined: Nov 2007
    Posts: 77
    Likes: 3, Points: 0, Legacy Rep: 43
    Location: Gothenburg/Sweden

    Brorsan Junior Member

    I think i was rather unclear in my last post....

    I'll take it from the beginning.
    I'm interested in building a small trimaran, and i dont want to spend a fortune neither spend to long building it, one year buildig time maximum, starting about half a year from now. I will use the boat mostly for daysailing but allso some weekend sailing. I got all fittings, mast, boom and sails from an flipper dinghy, that is a total sailarea of 11sqm upwind.

    So, i'm interested in building a scarab 16 and use the flipper stuff to build a really cheap boat for me, and i do know that this will be a little underpowered but i live on the west coast of sweden and a avarage summer day we got around 5-7 m/s wind. If it turns out to be a nice vessel and i find a used beach cat for a good price i will later upgrade to more sailarea.

    What i've been thinking of is if this is to small to be a good boat, maybe the interior is to small to be useble at all, and the waterline simply to short for getting up speed. I would like to sail at the same speed or faster than a 9m older monohull, could that be possible (with larger cat mast and sails)?
    I've allso been thinking that going up in size to the scarab 18 would greatly increase both performance and interior volume, but the cost would allso increase. Small boats small problems has been said alot of times.
    Farrier from f-boats have said that the F23 is the smallest trimaran he will ever build because of just speed, interior and seaworthiness.
    I should allso add that i have ordered and looked closly through the study plans for the scarab 16, and that i have built a monohull with pinestrips before(more like a bigger canoe).
    So i kindly ask for your thoughts about this, you dont have to know anything about it, just give me your thoughts. I have never sailed a multihull. The scarab 16 got a sailaway weight of 200kg, that sound pretty much to me, thinking of using thinner plywood and reinforcing it on the inside to save some weight.

    Sorry for that massive wall of text, but please give me your thought, especialy on the sailing performance and seaworthiness. Is this to be seen as a toy? Or is it really a micro cruser?
    Thanks in regard
    /Brorsan
     
  3. rayaldridge
    Joined: Jun 2006
    Posts: 581
    Likes: 26, Points: 0, Legacy Rep: 322
    Location: USA

    rayaldridge Senior Member

    I don't think the size of the boat is the limitation you should be concerned about. Your proposed rig is very small-- about half the sail area of a beach cat.

    My little 16 foot cruising cat has been criticized as being under-rigged, but has 140 sq. ft. of sail-- more than the flipper rig. But Slider has that small rig because she has only 8.5 feet of beam. Still, even though she is a heavy boat-- may displace 1100 lbs when loaded for cruising, she still is faster than many monohull yachts that are much larger.

    I don't think you have to worry about the boat being slow, if you have an adequate rig. The question of accommodation is something you have to decide in personal terms-- can you overnight in a cabin that small? If so, it's big enough.
     
  4. Brorsan
    Joined: Nov 2007
    Posts: 77
    Likes: 3, Points: 0, Legacy Rep: 43
    Location: Gothenburg/Sweden

    Brorsan Junior Member

    Thank you Ray for your thoughts, discussion and thought sharing is allways good for decisions.
    I know that the proposed rig is very small, and it would only be used initialy i think. Also i was wrong about the wheight, 400kg (880lbs) is probably more likely crusing wheight.

    What do you (and others) think about the seaworthiness of the scarab 16?
     
  5. rayaldridge
    Joined: Jun 2006
    Posts: 581
    Likes: 26, Points: 0, Legacy Rep: 322
    Location: USA

    rayaldridge Senior Member

    Well, the problem with any small multihull, when discussing seaworthiness, is that stability goes up so fast with size. Big multihulls can be extremely safe, because the forces needed to capsize them are enormous. Since multihulls do not recover from capsize as ballasted monohulls do, in that sense you are always taking more of a chance with a very small multi than you take with a very small monohull. On the other hand, it will be harder to capsize that multi than that monohull, and monohulls can sink.

    Much depends on where you intend to sail the boat. One good thing about a small multi is that it will be unsinkable (or should be.) If you have an EPIRB and an immersion suit, you should be able to survive a capsize, but most of us would not want to find ourselves on a capsized boat of any kind in cold northern waters.
     
  6. luckystrike
    Joined: Feb 2010
    Posts: 230
    Likes: 14, Points: 18, Legacy Rep: 92
    Location: Germany

    luckystrike Power Kraut

    Hi Brosan,

    the Scarab 16 and 18 are for protected waters only. If you want to cruise the baltic you should have an eye on the local weather the weather forecast and seek shelter if it starts to get bad. But it can be done! No problem between the danish isles.
    For my feeling the smallest boat that can face bad weather and waves in is the Scarab 650.

    If you can afford it, take the 18 (or stretch the 16 a little only in length to pimp the "fat" mainhull for better performance). Its more than small enough in a seaway. Don't care about your small rig, you will not install it on your boat anyway. This is waste of time, because you will never experience the real performance of your boat. Building time is long and if you keep an open eye on ebay to collect cheap equipment, you will find a very old and cheap Hobie 16 or 18 and use its rig. Or you build a wooden wingmast which is also cheap and light in your small dimensions, or ... or ... or ... there are a lot of cheap solutions for rigging a 18 footer, while the new "off the shelf" parts for the beach cats are very very expensive. The sails can be second hand from class boats too. The sails of top-racesailers are normally in very good shape when they sell them as used. Top sailors have tons of good material in their garage that will never been used again. You just have to find it.

    A Plywood built boat will be mainly built from 1/4'' (6mm, 5ply) Okume Plywood (I guess). The weight penalty is not so big over the foam sandwich preferred by Ray Kendrick. His sandwich requires a lot of glass tapes and fairing in the seams. Our 6mm plywood is 0.5mm thinner than the international standart of 1/4', around 250 gr lighter every m² of surface.

    Check out the plywood plans very carefull. Plywood is Kendriks second choice of material so his calculated scantlings will be not be as careful and some parts might be lighter to save some weight. A few years ago Kendrick had his ply scantlings for the 670 on his website and i found a lot of parts that could have been much lighter. If you decide to build a Scarab, send me the plans and I will check them out for a lighter boat.

    Grreetings from the German North Sea Coast, Michel

    p.s. Scarab 16: empty weight 180kg .... Scarab 18 empty weight 345kg, Displ. 500kg
     
  7. Brorsan
    Joined: Nov 2007
    Posts: 77
    Likes: 3, Points: 0, Legacy Rep: 43
    Location: Gothenburg/Sweden

    Brorsan Junior Member

    Thank you again Ray, and a huge thanks to you Luckystrike, that was exactly the kind of thoughts and information i was looking for. I allso think it looks to be made heavier than necessary, and actualy mailed Ray Kendrick about it a few days ago. I will be very very glad if you would like to have a look at the drawings if/when i order the plans. Funny that you mention stretching out the mainhull, caus that thought have passed my mind aswell.
    I'll get back here a little later and ask some more questions when i got a little more time.
    Regards
    /Brorsan
     
  8. Brorsan
    Joined: Nov 2007
    Posts: 77
    Likes: 3, Points: 0, Legacy Rep: 43
    Location: Gothenburg/Sweden

    Brorsan Junior Member

    the scarab 18 is allmost the double wheight compared to the 16,a the sail area 16m2 compared to about 22m2 for the scarab 18. I guess this means that the 18 will cost aprox 70-80% more than the 16, does that guess seam fair?
    My plan is to build this boat and use it for a couple of years, and when i hopefully get children (about 5 years from now or something like that hehe) i'll sell the boat, and i guess i wount get much for it weather it is 16, 18 or 20 foot long. And some years after that there will probably be a bigger tri or cat, but that is to far from now to speculate on. I'll think about the scarab 16 for a while, but it sure looks lik a good multi hul entryboat for me considering cost and buildtime.
     
  9. luckystrike
    Joined: Feb 2010
    Posts: 230
    Likes: 14, Points: 18, Legacy Rep: 92
    Location: Germany

    luckystrike Power Kraut

    Hi Brorsan,

    no, for a Tri with a Cabin the 16 is not heavy, remember that a Formula 18 is at 160kg (or 180kg???*not sure*) sailing weight, so thats ok. But it can be improved anyway.

    Yes, you are right, the 18 is around 70% more money than the 16. A stretched 16 needs around 2 sheets plywood, may be 3 kg Epoxy and 6m² glasfibres more than the original, (very roughly estimated).

    The big weight difference between the 16 and18 is Volume and this is growing in the cube . Example: Lets say Kendrick wants to scale up the 16 from 16' to 32' feet. Thats the factor of two (x2). All Areas (surfaces, sailareas) will grow in m² (2x2=4) and weights and Volume with a factor of m³ (2x2x2=8). Of course the 18 is no scaled up version of the 16, its a new design. If you are a designer you want to have the volume, because this means cabin space!
    This is the reason why the 18 seems to be so heavy in comparison.

    If you stretch out the sixteen just in length, the rise in weight is not so dramatic.

    As said before, if you can sleep in it and find some place to sit inside the cabin it will work out for you. I have seen a few couples who had a long and lucky holiday in the Baltic, sailing 18' Microcuppers. With a tent over the cockpit you gain a lot of living space.

    According to the drawing on the website the bunk measures 185 x 1,00m but should be extendable aft to the main bulkhead and you have 1,12m max headroom, this is just enough for sitting. Mainhull beam is 1,5m at deck level.

    Grreeetings from the North Sea Coast, Michel
     
  10. luckystrike
    Joined: Feb 2010
    Posts: 230
    Likes: 14, Points: 18, Legacy Rep: 92
    Location: Germany

    luckystrike Power Kraut

    Hi, its me again ... the guy with the sick brain!

    Just played around a little bit :idea: , because I wait for a buisiness date, but have a look and have fun! :D

    The Data on the upper left corner are for the Original. The Mainhull seems to be a little fat now, but thats because the now black mainhull is "melting" together with the cabin windows. If you do the "stretching" the length of the Amas (floats, outriggers) should follow their mainhull in length, of course. I just gained 5 cm of sitting headroom too!

    To be honest, I would'nt tell this Ray Kendrick! :p:D:D:D

    Michel
     

    Attached Files:

    • IMG.jpg
      IMG.jpg
      File size:
      111.3 KB
      Views:
      4,843
  11. Brorsan
    Joined: Nov 2007
    Posts: 77
    Likes: 3, Points: 0, Legacy Rep: 43
    Location: Gothenburg/Sweden

    Brorsan Junior Member

    Hehe, funny again, i've also played with the thought of doing a wavepiercing bow, and made some simple sketches. Your sketch show how i really would like the boat, but then the drawings would have to be redrawn completly for the hull and amas, right? It could be done relativly easy in "carsson hull design" though. How did you gain 5cm of headroom? Was it by adding volume under water?
     
  12. luckystrike
    Joined: Feb 2010
    Posts: 230
    Likes: 14, Points: 18, Legacy Rep: 92
    Location: Germany

    luckystrike Power Kraut

    Hello Brorsan,

    no, you have not to redraw the lines. A little extra volume under water comes just from the new length, the hull is not deeper than before! When you get your table of offsets for the scarab 16 to loft the planks, you just stretch the distance between the measuring points on the baseline lengthwise so that you now get panels for 18' instead of 16'. Normally these points are 50cm apart and now you are marking tham at 55cm. This is the way you gain the extra length without changing the lines. All bulkheads stay original.

    The new bow is of course not piercing waves. Its that just in look not in function. Its to save some material and therefore weight. The flat bottom panel and the first pair of side panels will stay as they are. The modification on the following panels at the bow you will do during the build when the hull is wired but not glassed. Start with the original panels as lofted and cut away small triangular piece in small steps and pull the hullpanels together at the bow. You have to make the first bulkhead fit into this. Remember that your stetched hull is longer now and therefore more slender. So on Deck level you have just the curve of the original unstretched hull. No more curve than before.

    The extra headroom is gained by alter the positive sheer (middle sheer low and bow up) into a straight- or light negative one (bow down). A wavepiercer bow does not look good together with a positive sheer.

    This is done with a little extra width on top of the last panel next to the deck. Of course the bulkheads have to follow, but just in the same line as they are.

    If you put your cabin on top (you have to make it fit now) you gained a little in height.

    I hope you can understand what I have written! If not, please ask again.

    In my eyes the cockpit has to be 2m in length minimum, so that you can sleep in it in hot summer nights.

    Grreetings from the Noth Sea Coast, Michel
     
  13. Brorsan
    Joined: Nov 2007
    Posts: 77
    Likes: 3, Points: 0, Legacy Rep: 43
    Location: Gothenburg/Sweden

    Brorsan Junior Member

    Very informative and interesting i must say! The 2m cockpit leangth is a very good thought, really make sense, specialy in a boat with this low volume inside (and no foredeck hatch) can for sure be pretty hot as you mentioned.
    I get it all, except the deck part. Will the deck, the cabin, and the cockpit be strecthed too? (that means the whole boat streched leangth wise) And dont you think it will be rather problematic to cut off parts of the bow considering the 45 degree angled panels? (second from the deck)
     
  14. DriesLaas
    Joined: Aug 2009
    Posts: 159
    Likes: 4, Points: 18, Legacy Rep: 48
    Location: South Africa

    DriesLaas Weekend Warrior

    how about 17 feet

    Hi Brorsan,

    I have just finished the concept sketches of a boat which I want to build for myself.
    It is 17 feet long, I think the Scarab 16 is just too small. I have a rig with 20 square metres of sail area (Prindle 18 beachcat) which is a lot, but I think the boat will sail really well. I have increased the size of the cabin enough to make comfortable upright seating, and there is two pilot berths for sleeping.

    The galley and toilet will all be removable for racing to keep the mass down.

    The volume of the amas is 670 kg, which is ample for even the cruising weight.

    I hope to build the boat of marine ply, to a weight of 250kg rig included. Racing weight is then 400 kg with two crew, and cruising weight is about 120 kg more (food, water, battery, sleeping bags, galley, porta-potti toilet etc.)

    The beams will fold in the style of Farrier and Scarab.

    The foils will be very nice modern 505 centerboards and rudder, racing mode will have the centerboards in the ama's. For cruising one centerboard in the main hull.

    Rudders mounted on the ama's for now, I want to try it to see.

    I can give you the drawings when they are done to have a look at.
     

    Attached Files:

    1 person likes this.

  15. Brorsan
    Joined: Nov 2007
    Posts: 77
    Likes: 3, Points: 0, Legacy Rep: 43
    Location: Gothenburg/Sweden

    Brorsan Junior Member

    That look very nice DriesLaas :)
    But i must ask, dont you think it will be back heavy with the cockpit that far aft? And you also need some space for the rudderstick in the cockpit (about 1m)
    Are you building right now, or how long until planned building start?
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.