Scarab 16

Ok, here's the calculation I made for the S18 and S16. It is based on the materials list and the prices of a single supplier, who is able to deliver almost everything one needs for the boat (timeout.de). I did not perform any cherrypicking as I felt that the potential savings would be outweighed by the additional work, shipping costs and multiple contacts in case of problems...

Keep in mind that these costs are for Germany, rather a high cost country in terms of composites, as it seems.

Other costs such as rigging, costs for workshop etc. most of them are guessed on the safe side, except for the fittings which are 100% Harken stuff which I can order with a discount. Costs for waterjet cutting the folding system have not been requested yet, but it turned out that it might be difficult to get the specified aluminum in Europe. I found sources, but those are wholesales companies...

Costs may vary also with different resins used, I calculated epoxy for best possible strength. Having the painting done by a professional will also affect cost. Consumables are represented in the calculation, but keep in mind that you will need tools, which may add close to 1k€ if buying quality.

Ok, it's up to you guys now...did I miss anything? Or guessed something completely wrong? Keep in mind, that this represents a sort of worst case scenario...


Cord

 

I am sorry, we never weighed her. When I just asked Trev, his response was "too heavy". I was able to launch her in 100mm of water though

We are both 165cm tall, and I found that I had to hunch to sit in her, so no, I never felt there was enough room to sit in her. If I sat on the little seat shown in the plans, my knees were so high that I was not comfortable. It was, however, perfect for our small son. There is no room to cook in her - not even with a small gas cartridge cooker. You cannot prepare a sandwich down below. You can only lie down.

Definitely correct.

There was no 18 at the time that we bought the plans and commenced building. The 18 was made available about 4 months later. Trev would recommend the 18 over the 16 at any time, but suggests that you look at Nicky Cruz's Tri's here http://www.delaveaumultihulldesign.com/designs.php He feels that these boats would be lighter. I note that the smallest design does seem to be 6.4m though. I do know someone who is currenly building Nicky's 7.6 tri. . .

The Scarab 16 is a great wee tri. Wee being the operative word.

Good luck! Ms

 

under 20kg for that strech, that would be very nice (and it would for sure increase performance)
Lucky, that sketch looks really really nice, that slender hulls with nverted cheer line and backswept bow is a piece of art, well done.

Megwyn, first let me thank you for giving me/us real useful information from the actual boat model. Ofcourse, i got millions of more questions for you It seams like you dont trust in the boat at all for bigger waves, have i got you wrong or can you describe what the boat does that make you doubt it? Is it just the size of it and the stern beeing so close to the water? (well, the whole cockpit is rather close to the water)
Another question for you Megwyn, i can see in the videos that your daggerboards are inserted verticaly, (same as i would make them) was this included in the plans or did you and trev build them without drawings? Do you find it frustrating to raise one and put the other down each tack?

I have noticed that that the boat seams to sit rather heave on the stern on most of the videos of the boat, even when sailing on a reach in 20kts wind. Small tris like this usualy (i think) need the center of floation to be somewhat futher to the aft due to the huge weight (compared to boatweight) that two persons in the cockpit cause, so i'm not suprised, but i hoped i was wrong...
Then is the question, can it be fixed without forcing Ray to redraw the drawings or is that the only solution? The stretching will probably help a bit, but not very much. Or is it just not that big problem?

One more thing, the study plan only mention plywood as builing material, and the specified weight is 200kg (strange that is still says 180kg on the homepage...)

Lucky, do you think it is possible to build the boat with 4mm ply istead of 6? (of course thicker ply where you put your feet) the boat would then need some reinforcments in heavely loaded areas. 4mm ply got 3 layers of fibres, wich means 2 layers of fibre in the longitudinal direction, 6mmply is 5 layers = 3 layers in the same direction. Hmm well that is 50% more, but still, 4mm ply is rather tough, and the flat areas is rather small, and all of them are curved longitudinal, giving extra streangth.

Still no answers from Ray Kendrick, that aint the best service i think...

Once more, thank you all for helping me with useful information, thoughts, ideas, sketches and so on. Thank you.

 

Since I wrote the first post, a lot of thinking and doodling has happened. I vary between wild enthusiasm and trepidation, and have to keep reminding myself that this is not a very difficult boat to design or build.

I have decided to simplify things considerably in some respects. There is a certain appeal to having folding beams, and I really want to do it, so I will.
Daggerboards and rudders on the ama's, for now.
I stretched the cockpit and shortened the coachroof, gave the ama's more volume. Initial calculations indicate I can achieve my mass budget, I will run this again.

Brorsan, I drew both the stretched Scarab and the original in 2d CAD, and I really am concerned that the boat , though looking lovely with its' low profile, will be barely usable except for hiding from the weather in an emergency. I will attach some views in the near future.

I did some initial FEM work on the beams, and it seems you can build an ample beam from e-glass and epoxy (UD and fabric) that weighs about 4kg per beam ie 16 kg in total. This can be optimised further, it was just the initial guessed laminate (a rectangular section, 10 plies ud on each sparcap, shearwebs from 16 plies of 163gsm fabric at 45 degrees. Width of spar is 75mm.)

Brorsan, a good friend of mine, Fred Forsgren, used to live in Gothenburg. He is a naval architect, whom I have not heard from in years. Do you perhaps know him?

 

Hi Brorsan,

it makes me feel glad that you like my sketch. The trim problem is not as great as you think. Most modern Multihulls have digged in transoms when lying in the habour and are "bubbling" behind the transom at slow speeds. The resistence ist not so big as you think. This will disappear as soon as you go 7 or 8 knots boatspeed. The shape of the after part of the Kendrick hull is modern standart and ok!

Hmm building with 4mm is difficult because the two additional layers of veneer of the 6mm makes the thinnest ply to make a small boat usable for "every day buisiness". 4mm ply is just for very light dinghies and A-Cats and they are fragile. Not for sailing loads, but a bump in the habour or a grounding and you have a hole in the boat.

Gougeon / West System recommend to reinforce skinny plywood with a layer of 120 - 160gr/m² glass inside and outside so that you get a kind of sandwich. Maybe this is am option, but you have to do comparing breaking tests with a punctual force first.

How much glass reinvorcement ist recommended by Kendrick on the 1/4' skin and how much m² in total are used in the scarab 16??? Perhaps you can save some weight there. Remember that we saved 200gr/m² just because our european 6mm is a little skinnier than the international standart of 1/4' (6,4mm)

A mix from 6mm in normal- and exposed areas and 4 mm in low stress areas ist another option, but building will become a kind of puzzle with lots of funny scarfing. This would stretch the building time. I woud'nt do it.

So, for my feeling ... in general it is a good idea to make the hull from 6mm and all other stuff as light as possible. For example the subdeck (bunks), the whole cabin and so on. Do you really need the folding mechanism? There sits a lot of weight.

Having vertical lifting daggerboards is favorable, some more 3kg saved.

Michel

 

Hi Brorsan
It is more the chances of water influx into the boat. The small ledge at the stern is only (from memory) 1-2cm high, and then the ledge to enter the cabin is only about 2cm high. That is not a very large barrier to prevent the water entering the cabin. We only ever went out in about 1 meter swell at its highest, and that was a long swell. In the short choppy 500mm swell, she would take a little water into the cockpit, but it never ventured too far forward, due possibly to the fact that she dragged her rear a little . She could be made more seaworthy by designing a better washboard set up than the one we had, and by increasing the ledge at the entry to the cabin, and on the stern. But you would also need to look at your cockpit drainage again. She can become a bit wet when having fun, as the waves, at times, hit the beams, entering the cockpit, wetting anyone on the tramps/amas, and slowing the boat down.

Trev preferred that type of daggerboard to the kick-back type in the plans, because he was concerned regarding them leaking. This is only because he has no experience of kick back boards, not because he was suspicious of the design. He just prefers them that way. And no, I did not find it difficult to run from side to side - in fact, it was good excercise for me . I would imagine it may be frustrating if you were single handed though. . .

She did sit heavy in the stern with all of us on board. Trevor felt she was a little narrow there, and would benefit from being more beamy on the stern, but, as he did not know this until she was built, it was a little late to totally remodel her stern. From memory, I think there was space to broaden her stern beam without interferring with the folding of the ama's. This would definately give you more floatation in the stern, especially if you were to seal it off, creating an air tight section.

I think Trev felt 6mm was okay for the hull, but 4mm for the amas. The hull takes all the stress of the mast, with the step being on top of the cabin. The stress is then carried around and transferred to the hull through a bulkhead. The boat is good and strong, and will handle you really having a good yahoo, as it is designed. I would not like to speak for it's ability to hold together if you were to try and use 4mm ply throughout. That is really a question for an engineer. But I know I always felt safe on her at 6mm, with all the sailing that we did. (Harbour sailing). We sailed her extensively in the Katikati and Tauranga Harbours. Katikati can get a really good chop happening at change of tide, and she always felt safe. We sailed her a little in the Waitemata Harbour, and she was certainly able to handle that. She was mostly sailed on the lakes - and mostly Arapuni, which is a Hydro lake, and can become choppy also - with up to 1/2 metre chop. And we never needed to reef down, as I think I mentioned before. She was just a fun boat, but wet

I am sorry to hear that. I always found him quite quick to reply. How long ago did you try him? I found he was great to talk to on the phone too.

Good luck Brorsan.

Ms

 

of course. My prevous 24ft tri was 4mm ply on all three hulls with very little structure and one layer of dynel cloth on the outside. I sailed over 50 races and hit the bottom a few times with no damage whatsoever!

The only parts that were 6mm was the deck and cockpit and cabin of the main hull.

 

Samns, what sort of tri was it? if home made, do you got any pictures you could show maybe? Thank you for that info.
But with one layer of cloth on the outside (instead of just the chines) that means alot more fairing and also not that huge weight save i guess. But it should make the boat much more durable, right? Flex can take much more loads then a stiff contruction, but it is also a little slower i think.
What do you think?

Cortison, i'm probably blind, but how much didthe two boats cost to build in your calculations?

 

it was a bucc 24, covered in great detail on 2 other threads on this forum.

you wouldnt need to fair one layer of cloth at all just an extra coat of epoxy and sand and paint it?

 

Great info ... thanks! So we are coming closer to the Target step by step. My fear is that the bottom of Baltic Sea, this is where Brorsan is at home, has a lot of rocks and stones.

I think, the especially the cabin can be made of 4mm ply, because the boat is to small so nobody will walk or sit on top of it. Exept the reinforcement for the Mast.

 

Lucky, i think the cabin top must be walkeble. There will for sure be a day when someone step on it (murphys law)
I am from Gothenburg, but will move to Malmö after the summer (next to Copenhagen, but on the swedish side). Lucky, where do you live? (and when on it, what do you sail?)
Anyway, the archipilago north from Gothenburg (where i love to sail) contain rather much rocks aswell, the boat must handle a hit at moderate speed.
Lucky, i think you are right that mixing different thickness of ply will make problems not necessary.

I'm going to do a rough sketch of the boat in delfship when i get time tonight, to get a better insight of the size of the boat.

I've also been thinking about the folding system. When folding it, the mast have to be down already, so what is the purpose of folding then? Faster asebly from trailer to sailing would be one thing, but i cant find any other compared to a "demounteble" And that leads to my next question, what can be gained by doing it demounteble instead of folding?

 

a little delf sketch

I tryed to make a delf model of the scarab 16, but could not keep my fingers from doing the scarab 18 "förö version" instead (with some minor modifications. well, some changes are rather different from the stretched scarab 16 and would need new drawings) I have done "plywood" boat models out of paper using carsson hull program and delfship, maybe it is better to do the entire boat completly as i want it instead of doing the scarab? Or do i just make myself alot more work?


http://picturepush.com/showformat.php?format=img&image=5125394
(i hope the picture show correctly)

I've been thinking (as usual), one centerboard in the mainhull instead of the amas would save weight, building time and more importly make it easier to tack when sailing solo. To be able to fit a centerboard in that small cabin it needs to be of kickback type. And i guess placing it in the center of the hull would be the best. This will also decrease the load on the beams. How high above the floor would the centerboard box have to be aproximatly? 35-40cm? If so, then it will be at about the same height as the bunk(sleeping level), and can be built strong together with it. What do you people think?

Oh, and i must admit that Luckys sketch is better looking than my delf model, a little slimmer adds alot for the look of it, but does headroom inside the cabin and increased height of beams

 

Hi Brorsan,
I live in Wilhelmshaven/Germany, this is at the "Jade", a big bay next to the river "Weser". As usual here in the North Sea, we have strong tides here with the Eastern Friesian Islands and Helgoland as our home waters. We are sailing the Baltic reguarly for holiday and some racing. I sail a classic Tornado as my afterwork boat and I'am helmsman on board the "eeeasy", a Dehler 34 for racing. In the workshop under construction is my own design, a 9.2m Racer-Cruiser Trimaran.

The "look" can be refined without problems in delftship if you like my scetch so much. I would transfer the delft lines to a sheet of milimeter paper and look after the interior headroom, seat and bunk measures.

To stretch an existing design and refine the look is not risky, because the changes in design are minor. If you want to do the design all on your own you have to learn how to design a boat. Modeling a hull with delftship is only one small part of the design work. Balancing the centers of flotation and weight (mainhull and ama), the pressure points of sails and underwaterbody is the major part of the design work, requires knowledge and a lot of time. Calculation of the loads and fixing the scantlings requires engeneer skills. The risk of doing something wrong ist great. You have to decide if it is worth the effort. To design a good sailing 18' trimaran with a useable cabin is no easy task.

The centerboard can be offset of the middle without performance penalties, so you can have a clean middle of the hull with the trunk under the bunk or seat. Anyway, a daggerboard is lighter than a centerboard and hydrodramatically more efficient because of the short slot. I don't know how heavy two daggerboards in the floats are, but their trunks are the lightest you can have.

When folding a pair of short shrouds hold the mast, when the main shrouds become useless. If you don't need the folding mechanism the boat will become lighter, cheaper and faster to build. I'don't know if Kendrick has a nonfolding option in his plans.

Grreetings from the North Sea Coast, Michel

 

I always found Ray quick to reply and I was probably one of his worst tyre kickers over the course of 8 sets of study plans over 10 years or so. I can only think if he's not responding he's either away or (hopefully not) got involved in the flooding up his way.

This has been a great thread. Its always interesting to see peoples ideas for re-doing designs etc. I think a couple of feet, for a bit more disp towards the stern of the S16 would improve it for a couple of adults, but it still won't be like the S18.

Thing is multis are expensive to build and tri's (loa for Loa) tend to be more expensive than cats due to extra skin area etc. A flared topside tri is more expensive yet and you can add folding for more $$$. By way of comparison (and this is not a vote either way) Similar materials materials for the S16 will build the platform of Richard Woods new 6.5 Acorn cat. Both will sleep two, can use a beach cat rig and be a lot of fun. I think the Acorn would better handle conditions that would be uncomfortable for the S16, but of course its not so easy to trail as a folding tri. With multis there are lots of options dependant on use, budget .etc. but you have to look around. have you checked out the Sardine Run 18' tri? Maybe a better choice outside sheltered waters..............

Someone wrote earlier that ply seemed Rays second choice of material. I don't agree. With one exception (the strip Avalon) his early designs were all for a form of stitch and tape ply. IIRC the Scarab 22 was the first with a foam option and all his newer boats have this option. Foam/poly is about equal to ply/ epoxy in cost, particularly where the ply is essentially used as a load bearing core, with lots of epoxy coving and glass, rather than just a skin. The S16 is designed I think as a small knockabout type trailerable boat and needs to be robust. 6mm might seem OTT but I think it appropriate for the type of use envisaged and the construction method. After all if you were building a ply racing tri that size the whole thing would be of 3 or 4 mm either tortured or over frames and stringers and you would probably carry it to the beach to launch it. I wouldn't make a drastic - like reducing the skin thickness - alteration to the S16 without the designers ok - if you want a lighter boat maybe something else would be better.

By comparison, the 7.6m Nicky Cruz tri I'm building is all 6mm over frames and stringers except for the bottom panel (which is the cabin floor) and cockpit floor at 9mm. The new NC 6.5 has the main hull out of 6mm and the floats from 4mm. The previously mentioned Acorn is also a mix of 4 and 6mm. SamNZs old B24 is skinned in 4mm and is going on 40 years old (although it wasn't considered appropriate to jump into the cabin) .

Good luck with designing your own, I tried, but was never happy with the results. Getting a nice looking set of lines on a computer, and printing out the hydro's was the easy part.

 

Why would sardine run be better suited for my conditions? about same dimensions, only less space in the cabin. Cant find any info on the acorn 6.5, could you please post a link?
I'm totaly open for other ideas
Maybe the best option is to buy a used boat, but here in sweden there is very hard to find a multihul for under 10 000 euros. If i get a used beachcat with for around 3k euros, how much do you think it will cost aprox. to build a streched S16? Are we talking 5k or 10k euros?
Are there any good homepage for browsing used multihulls in europe?