Small trimarans under 20'

Doug is right on the build method, we found a 200gsm bi glass over a 200gsm carbon cloth ( its available and cheap if you take the little Epoxy used ), over a 10mm foam with again 200gsm carbon and glass makes a stunning strong structure at minimum weight. The TC601 which is 20 ft and has a cabin, comes in at just over 115kgs for what is quite a large centre hull.

 

Tiny,

You were talking about flat square shapes and the need to support them with more interior structure.
Everyone jumped to graphite, but an alternative is to make a rounded shape.
Strip planking to get a rounded shape does not need to take a lot of time if you are willing to paint the boat.
It does take design time and setting up stations to form the shape, but it will reduce the substructure required.
You can add graphite if you just have to reduce the weight some more or achieve bragging rights for using black gold.

I'm not really against graphite, but you seem to be looking for an economical build method and graphite ain't it.

 

Doug, Wayne, Upchurchmr - many thanks for your replies.

Lots to think about, and so many interactive/contradictory considerations.

Wayne - Looks like your sandwich comes in around 2kg/sq metre with foam core and resin? 4mm marine ply is also 2kg/ sq metre, (without any sheathing or resin) but I presume won't be anywhere near as stiff or strong.

Upchurchmr - ply with taped seams would be my first choice because it is very familiar to me, and speedy - I've sadly got too many things competing for my time, and can't devote the time that I'd like to a build - I'm aware that if the build gets long and drawn out it is easy to lose momentum. Having said that, the strength/stiffness for weight I know is critical, and any methods that improve that are welcome.

My thoughts are going round in circles at the moment. I'll try to put together a comprehensible post and some sketches in the next few days - no point in me wasting your time if I can't articulate where I'm up to clearly.

BTW - Wayne - looking at the buildings in your photo - are you in West Sussex/ Hampshire?

 

Sardine Run 19 nearing completion?

Some photos of Sardine Run 19 looking fairly finished on the Sardine Boats FB page:

https://www.facebook.com/media/set/?set=a.925233380868998.1073741836.221946851197658&type=3

 

Don't knock carbon, we were buying 200gsm bi for about £ 9.00 per sq metre, the equivalent approx 800gsm glass would cost more + you need 4 times the epoxy. Everyone seems to just expect carbon to cost more because its got carbon attached to its name but that is not the case anymore. There are other benefits such as lack of weight ( probably as important as cost in multihulls ) ease of use and ease to work with, strength and a host of other well discussed attributes.

Where it does fail though is in abrasion where it simply grinds away with a meerest rub, but put a small protecting layer of glass over ( forget kevlar as it is real pain to work with if something goes wrong ) to prevent print through of the weave and from abrasion and you have a delightful product to work with.

I've never quite understood why people tackle ply and not foam, all the same principals of construction can be the same, if you want to use longtitudinal lengths of ply just substitute with foam, you can buy it in 2.5m lengths afterall. But the time spent preparing and glueing can be quartered with foam, it has to be one of the easiest products to use in this manner.

I live high up in the Chiltern Hills, overlooking the Thames in Buckinghamshire, surrounded by stunning woods to cycle in and some of the deepest red sunsets you will ever see. Presently a nice layer of snow to look out on. Talking of snow, the skibike trials and experiments for the winter are going to be put up in the loft today and guess what we are going to get back on with, that lovely TC601 needs finishing and put on the water.

 

Good to hear you're continuing with the boat Wayne. I'm looking forward to seeing that beauty sailing.

 

Thanks Wayne - and in particular, thanks for your build blog. I've found and read it, and I feel much more confident about the foamcore construction.

Aah, hence the Marlow. I was born in Maidenhead, I have an uncle in Bourne End, and my stepdad is from Marlow. He has many lurid tales of a wild childhood on and in the river and the gravel pits....

 

I had read much on the foam v ply debate over the years and was a little apprehensive on using foam exclusively but now having built the TC601 centre hull in foam, I can only say why was I hesitant, the modern foams available now are easy to work with and form lovely constant curves which if the boat has been designed to fit in with this philosophy, saves hours and hours of hard sanding. Things like gorilla glue have transformed the ease of joining and getting nice fair surfaces is just a matter of a little trial and error and then going for it.

Tim and I when designing the shape of the TC601 always had ease of build in mind, thats why the shape is what it is, its all gentle curves, maybe we won't get the optimum underwater shape, but it won't be far off, the bonus being is that we faired off the hull in less than a day ready for its primer. If I was building another hull ( the hull can be stretched to 22ft which does fit in nicely with the Nacra 20 or Tornado as a donor hull ) I'm sure I would get an even fairer surface as the second half we built was much better than the first.

Marlow is a fun place and yes those lurid tales almost certainly will have been highly exagerated but my kids seem to have enjoyed growing up here ( and I'm sure will have many a tale to tell ) Do ask your relatives about the Bounty, there has been may a tale starting from there.

 

Chryz10, build and design updated

Hi, Just want to share some photos of this years project, Chryz Outlaw.
Chryz10, is soo last year. The new boat will be bigger faster... and faster
Please share your thoughts. During winter I also got exam at International School of Yacht design,which where we learned all the basics about designing floating stuff
More updates at my blog, www.chryz10.com






br
Chris

 

Outlaw

Cool! Four things to consider:
1-seems like the daggerboard may be too far aft,
2-seems like the boat could use platform dihedral so the amas don't both touch the water at the same time,
3-unless the cross arms "scissor" like Randy Smyth's SewSew(EC Challenge tri) the tramp may not be "long" enough in the fore and aft direction for moving weight aft?
4-well designed ama foils(and/or planing amas) could allow you to cut the ama weight and length in half. Either/or provide dynamic lift reducing the need for buoyancy.
Best of luck!

 

Thanks for the concerns Doug
1. Hopefully not. It is where it is.
2. This I really need to avoid! I have a plan for this
3. The Sizzor has very short tramp as well.Shorter. This will be very exciting for the first test-sailing. Maybe it will dive, maybe it will wheel over. I have bought a new action-cam for the test-sailing anyway
4. Probably some C-foils could help or others, but thats a too big step for me to be ready in the summer.

br, Chris

 

The SewSew has a small tramp alright, but the thing pivots so that the lee ama can be moved forward and the weight aft:

 

Thats a great photo of Randys wreck My amas will be close to same length as main hull. That could help some I hope. If it turns out to be a true submarine, then I have to move someting aft. The mast is placed exactly in the middle of the main hull

 

The Smyth boat could have a bigger tramp, pivoting same as it is and it would give you the option of sailor weight 2-3' farther aft in heavy weather.

Especially since the bow is very narrow with little inherent bouyancy to prevent a pitch pole.
As it is I'm assuming he has to relieve pressure with the mainsheet, in really heavy weather on a reach.
It would be better to hear it from his mouth, of course, not an armchair critic.

 

I'm not up to date on more recent changes to the mechanics of SewSew... but if memory serves, the reason for the scissoring action was originally developed to enable the boat to become narrow enough to pass under and through a fixed bridge (just before a checkpoint) that had a maximum width between pilings of just barely over 10 feet (wide enough for a Tornado). That "gate" was an intentional feature of the original EC and produced many interesting design features in it's day - the most innovative IMNSHO was SewSew.