sshhh

...

is that really as fat as it looks or is it just the perspective that makes it look that way ?

It is wider than the first iteration, but still wouldn't consider it fat. Designed for 120kg displacement.

RG, The parents are almost more interested than the kids in sailind the F12:s so a little bit wolume is not so bad... <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

and at 120, or even 125kg design displacement, doesn't this makes the F12 more marketable? May be sold also as an adult trainer or appealing for Mom/Dad to sneak a ride on when the kids aren't around.

Didn't we realize this from the beginning ?

That we would have to design these boats to take also an adult and small kid (up to ten years old) or two kids simulatiniously; ergo at least 100 kg crew carrying ability for the F12 !

Combined with min boat weight this makes a minimal displacement of 150 kg ?

It is always better to sail a volumious boat light then sail a light displacement boat heavy.

Scarecrow, for what range of displacement is your DS12 designed ?

Wouter

Yes we did, but that seems like a long time ago now, and I wanted to take the opportunity to reiterate. The latest designs seem, to me, more like scaled down A's and, at least by appearance, seem to have lost any bouyancy (compared to early conceptual drawings) but obviously I'm no designer.

I won the set of DS-12 plans (thanks again!) but have been reluctant to proceed with a build as yet due to my "perception" of a limited upper range of weight carrying capacity. Is was awaiting more reviews, so Wouter thanks for asking the question.

here, here

I still think that we should design with the kids in mind, so a crew weight between 40 and 60kgs. If there is room for an easy boat for the adults, I think it should be wise to go up to 14 feet and design with the same idea cheap, light and simple.
For me it's those three things that makes the F12 interesting.
Btw. I'm starting to build the sshhh tomorow...
flathlander18, don't be a coward go ahead and build the DS12 it's a great boat and you don't risk a lot of money and we need boats out on the beaches

thats less than I imagined, must be the perspective. The Vudu's DWL is set at 100 kg, but even at 150 kg it sits in less than 40mm.

Total weight or just crew weight ?

Wouter

The DS12 is at 115. When it was drawn we were talking about a min weight of 60 kg...

If you built it to 55kg that gives you 60kg "optimum" crew weight(heaps for a young teen or small women, although as RG mentions extra weight won't be that big a killer. The main issue with putting a larger weight on is weight placement will become critical when the crew weighs more than the boat.

The overall plan and profile views actually came out fairly close to the DS12 without any reverse engineering. It does have slightly less rocker which may be a result of the sectional "fullness" compared with the DS12.

I'm still designing/thinking of the F12 as a kids cat trainer class similar to the purpose of the Optimist. Adults can make their own fun. Every so often my local club holds "regattas" with adults in optis...it's a funny sight.

I agree that seeing adults on little boats is funny but they can take it serious too this adult is sailing an 11 ft marine ply, Arafura Cadet, designed 30 years ago, in heaps of wind and 2.3metre waves off Adelaide a month ago. Picture courtesy of Peter Muirhead's site.

and another photo this boat is lighter than the DS12 despite being built 20 years ago.
I was so impressed I've purchased 2 to use at the club.

Which makes sense given the local fleet, kids will learn more sailing boat on boat then sailing an orphan, no matter how attractive the one off may be.

Your building a pair of F12s aren't you Jeff? AC rig would help get them on the water fast and you could compare the hull designs with the same rig.

Interesting stuff this F12, I have no use for one but still a great direction to go in for cat sailing.

Darryn
Mozzie
1782

Post deleted by ncik

I've also bought a couple of Arrows that I can mix and match with rigs, I think the Arrow rig would more suit the F12 and I will play with those rigs on the F12 hulls before I buy F12 sails. Once I build the F12's though my plan is to have 6 cats here. As soon as someone says they want to buy one to sail here I will let them buy it at what it cost me. But at least I can strike while the irons hot. I think lightweight F12's, with homebuilt carbon masts will be very practical boats for my kids and enable me to travel with 4 boats, but I think my enthusiasm for building a new class went with the extra weight.
On a good note I'm hoping to get to Lake Bonney for their September winter series with the 5.8, two AC's and an Arrow quad stacked, what a sight <img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" />
regards

Arafura's are minimum 36kg with all fixed fittings.
Heres a link to their sight
http://www.arrowarafura.com/
The 14ft Arrow is minimum 50kg thats why I dont see the F12 minimum weight as planned to be a miracle of modern engineering.

What is the Arafuras rigged weight? I'd estimate a 15kg minimum for the rig which brings it up to approx. 50kg, for a boat that is a foot shorter and without centreboard cases.

Are the rudders and centreboard included in that minimum weight?

Not bagging the Arafura or Arrow, just trying to make sure apples are being compared to apples.

Jeff,

Don't forget that we've brought the minium weigh down in the newer draft rules and I suspect it will get even lower once the class is in the hands of the owners/builders. The arrow weighs the same as the DS12 total weight with all the gear removed.

Don't loose faith.

ps. I had word yesturday that your gear was at the anodisers. Almost there.

It has a fixed ali frame similar to Wouters F12 that holds one swing down centreplate. I'm not a fan of that metal. The Arafura and Arrow were designed by the same designer as the Mozzie and that was a mini Stingray which was a mini Tornado. I really bought up the weight to show that in my opinion the modern boat should be lighter as per the original discussion with the F12 design. Specifically a cheap cat that kids can rig themselves, light weight, practical, exciting to look at, safe easy to homebuild cat.

As a comparison, the lightest carbon foiler moth hull ever made was 6.9kg delivered. After some time it increased to about 9kg which is similar to what most new foiling moth hulls are built at now in pre-preg carbon and foam (Fastacraft advertise 9.5kg once painted).

My mates and I have built a hand-laid glass foam moth hull which started at about 12kg and ended up about 14-15kg once we made local repairs where it wasn't strong enough (mast chock, transom).

Moth hulls are of a similar size to F12's and these bare hull weights are in the vicinity of what the F12's are being designed/built to.

So I don't think there is much weight to save in the hull structure. Centreboards and rudders are pretty well known so not a lot of weight to save there. Beams - going to carbon is an option to save weight but cost could be an issue (filament wound tube 50 x 2.5 x 1330mm = $350). Not much weight to save in the rig without going to a carbon mast or light sail materials.

High technology and low cost for home builders are opposing goals.

Carbon Fibre Express

Nothing high teck Ncik Rg and Scarecrow went to a lot of trouble with their designs to keep weight down. Gato built his "heavy" with 4mm instead of 3mm ply and used wood inside his mast instead of foam. The boat came out perfect in my opinion. RG's boat will probably weigh even less, the new class rules want more weight instead of being the original design weight of under 50kg.
regards

Wouter, the 100 kg is the all up weight
I should explain that as this isn't a one design class I offer the same basic design in displacements of 100, 110, 115, 120 and 130kg, all you have to do is ask for the displacement you want. Much over 130 and I think it will be a pig, so Im not going to do anything past that number.
The 4 boats that Billy is building now are all the 100 kg version and if you look at the link to the multihull article and the pics of the kids in it....none are remotely close to 50kg yet and probably won't be for quite some time to come, so that version will suit them.
As for boat weight, I don't think the finished boat will make 50kg, probably closer to 46kg when I last redid the numbers, so the design as it stands look right at a max of 54kg for the crew and probably won't be sailed at that weight for some time yet.
Cheers
RG

Last time I checked the weights of these and similar classes the quoted weights didn't included everything needed to go sailing. There tends to be a tradition of quoting weights that only comprises a hull or the platform and present that as a boatweight. The newly launched Weta is the same. It is quoted at 85 kg but independently measured at 126 kg.

So you are confusing the matter here Jeff; you should have know that the Arrow rules actually state :



Source : http://www.arrowarafura.com/Arrow%20Restrictions%20-%20current.pdf

We have to compare apples to apples here. The proposed minimum weight for the F12's INCLUDES EVERYTHING NEEDED TO GO SAILING, as is THE standard in a formula class.

Basically, any F12 coming off the water with the water drained and the sand rubbed off must go past this limit when put directly onto the scales. The Arafure and Arrow have significantly different weight definations and will be significantly heavier in their ready-to-sail attire. Didn't we cover this several times before already, when are people going to pay attention ?

Additionally, the F12 was never started as a showcase of "modern engineering" remember. It is supposed to be a low-cost, good looking and generally available, but yet effective and performant, entry catamaran.

Wouter

How many times can you be wrong in one thread ?

My F12 DOESN'T have this metal work. It only has an unstayed mast that is supported by two 30x2 mm pushrods of 1.5 kg combined weight including fasteners.

I agree with the others here the Arafure Cadet will be heavier then the F12 when it is ready to be sailed so your point is mute.

May I advice you as a well intending person to do your research more thoroughly the next time. No-one is benefiting from any wild goose chases that are based on falty intepretations.

Wouter

Like I said how many times can you be wrong in one single thread ?




I'm working on these rules right now; most working on the wording rather then the numbers or intent of the rules and your "assumption" is unfounded. The F12 never had an orginal established weight rule as we never reach agreement on it till recently. But even in the proposed rules the ready-to-sail weight was never "under 50 kg"; I don't know where this perception is coming from. The most original F12 rule come from me and had a 60 kg minimum weight limits, that in fact WILL BE lowered in the new class rules as a result of the recent discussions on this matter. So as a FACT the new (proposed) rules will indeed "want" less weight rather then more as you have errornously stated.


Forgive me my inflammatory style of writing but I have a hard time "understanding" anyone making a fuss without having checked the validity of his claims before hand. And checking your facts is such a simple thing to do with the internet these days !

Wouter

Wouter, I don't think we used a hell of a lot of engineering at all, in fact a good deal of it was seat of the pants stuff. We only went for Foam/Glass because we thought it would be easier to build than plywood.
I have done a set of drawings for a plywood version of the hard chine hull, but so far not a single person has taken a set of plans for it.
Cheers
RG

Wouter,

Shut the [censored] up. You've put a lot of people off F16 by being a pedantic wanker, don't do the same for F12. While your contribution to the F12 has not been insignificant we can do without a three posts in a row correcting people in a rather impolite fashion. It doesn't actually matter if people make slightly incorrect assumptions or mistakes. We're all working towards the same goal.

Chris.

RG, that assertion was made by JeffS, not Wouter.

Aside from that, the fact is that the F12's currently being designed and built are under or very close to the weights of similarly sized existing classes, which shouldn't be unexpected. There seems to be some confusion about platform and rigged weights.

To clarify my previous posts, my platform weight estimate is 35.4kg and rigged weight is 50.9kg (with a very crude rig weight estimate). So this isn't far from the proposed rule weight of 50kg.

From a design point of view, I could've dropped the design displacement down a fraction to 100-110kg, but to tell you the truth at this size of vessel my opinion is that it is best to design for the heavy side of the weight range, hence 120kg. Unless ofcourse you have a range of designs to offer.

Ncik I may be wrong but I was under the impression the proposed minimum rule was going to be upwards of 55kg. Earier discussions had weight being added on top of Gato's, not using his as a benchmark. If its only going to be 50kg then its back on track.
regards

News from the workshop, two halves made.
http://www.gust.ax/gallery/f12/08-08-12/

You are impressively fast Gato! Looks like foam stripping, but without the glass in place?

How did you cut the mould, by hand with a jigsaw?

Are those two Blade hulls I see beneath the F12? What is up with those?

Thats a really pretty hull....nice work Nick & Gato :_)
Cheers
RG

It's foam stripping, the glass on the inside. I will make up a better thing on the blog when I get the time. The two Blade hulls. lost the inspiration whit the discussions on the forum and the fact that the CHAIRMAN of the F16 class sold us some junk yard stuff at the price of super duper stuff..., but thats another story.

Thanks. Really impressed with how fast it is coming together. Still haven't come up with a name though, any ideas?

very impressive Gato nice work

It has no name yet, I'm behind on the blog, and it's my first boat done in foam...
http://www.gust.ax/gallery/f12/08-08-20/

A little bit less behind on the blog...
http://www.gust.ax/gallery/f12/08-08-21/

Gato,

I hope you've got some lead left over from one of your last projects. This boat looks like it will set a new bar weight wise.

It will end up under 50 kg but not that much. I have very little experience in foam building and the foam is eating a lot of epoxy...

Try brushing on a layer and letting it kick before putting on the actual laminate. Or wetout and squeeggee your cloth off the part and then lay it on, the foam shouldn't wick resin out of the glass if you have the right amount there.

Do you know how much resin you used on the DS?

Squeegee a thin bog of honey consistency on the foam right before glassing. No need to let it cure, glass straight onto the wet bog. This will require "half" as much resin.

Thanks for the advises!!! The epoxy for the DS12, yes I have it written somewhere, will try to find it when I get back to the workshop.

The filler works,using peelply helps with weight to (shower curtain nylon works well)bill

The 4 halves are joined together, now it's up to the Nice Lady if we get some pics...

Gato, do you ever sleep ? <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />
As this is actually a retorical question, judging by your activity - then the most interesting question is: how do you do it ?
Now seriously, great work !!!

How do you find working with foam compared to wood/plywood ?

The trick is; A bad carpenter has to cut a plank 3 times before it's to short, a good one does it at once...
Working with foam is great, fast, giving a good result and the cost is about the same. In fact for the moment I don't see the reason why to work with ply.

You can not enjoy the smell of wood, and the pleasure of using your plane with foam <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Can you buy sheets of foam, or do you have to buy a whole package.

Well, the okume ply dosen't smell so good, it would be different if you built a real wooden boat.
As for the foam, you can buy a single sheet. I will try to get some pics for Monday.

Pics!!!!!!!!
http://www.gust.ax/gallery/f12/08-08-30/

Great stuff!!!!!!!

Almost looks like strip plank boats. Interesting shape to the hulls!

I would be very interested in hearing how you did the join of the two halves. Bulkheads inside etc.

Don’t know if I shall recommend the way I joined the halves, at least not before I have smashed the cat into a big wave... The good way is with flanges, but I wanted to go fast...

Usually the worst loads are beaching and trailing, not necessarily sailing.

I know Farrier designed home-built hull halves are never flanged. They do have some tape applied though... I guess you did that too. Never heard of any problems with those.

I did a small rebate and added some extra glass BX+/-45deg over the joint. I’m not really scared of it breaking. The two hulls are glassed and I will try to get the time to make the beams and landings for them the next weekend.

So here we are, a new cat in the water. It’s not painted yet, just a little bit of primer, and the rig is borrowed from the DS12, but I could not resist. There was not a lot of wind so it’s still hard to say anything about how it’s sailing, but even with this light wind it was easy to tack.
http://www.gust.ax/gallery/f12/08-09-12/

WOOHOO!

Gato, congratulations! You are amazing. I want to grow up and be like you <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />

Tested the new boat on the kids yet?

Have you weighted the complete boat yet? What would the weight difference be between the two boats?
I was wondering how it would be to cartop these on a regular sedan, nothing else.

There is a weight difference of about 10% (5kg) between the boats, and as most of the regular sedans can carry about 100kg on the roof there is no problem car toping a cat around 50 kg all included.
As to the construction, I think it’s really up to what material you prefer wood or foam. As the cats are rather small there is no significant difference in building costs, the foam maybe a little bit more expensive. The time to build is about the same, also depending on previous experience with the materials. If you want to build a round bilged hull the foam is the solution, the tortured ply is asking a lot more hours of work for the same result, with the foam there is almost no filler and sanding and filler and sanding...
An other advantage with the foam is that you need very few and simple tools.
No test with kids yet if I dosen't count <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Had to go out once more before painting. There was 15-20 knots of wind. This is a fast cat.
<img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
http://www.gust.ax/gallery/f12/08-09-25/

W00T!

Good to see the hulls had enough volume. Grown man on one hull!

Was it tempted to nose-dive?

She is not prone to diving. Did dig in once, but that was asking for it. The DS 12 is diving faster.
It's sad that I don't have a rig for them both for the moment, it would be easier to compare, still I have the feeling that your cat is a little bit faster at least when it comes to max speed.

Interesting! I wouldn't expect that because the developed linesplan was only aiming for a forgiving boat to drive, not necessarily a fast boat.

How long till you get a second rig and on the race course?

The cat is both safe and forgiving, but in winds of +15 knots i'ts deffenetly alive.
As for the two boats together I will try my best, but honestly we soon start to think about Ice-boat sailing here...
http://www.gust.ax/gallery/josh/07-03-12/

ncik,

does the design have a name yet? Have I missed it? Also do you have plans that can be issued to everyday builders or are they Gato specific at this stage?

No name yet. AN12, i12, Fuse, Sprint, BG12, Kitten...? Just some ideas.

The extent of the plans at the moment is basically a linesplan only. There is a 3d model of a half mould also, and some sketches of structure, but no construction plans. I would consider preparing plans if there was significant interest.

If somebody want to build one it can be done with the plans ncik already have and a little bit help from me

Decided to call the design the Tabby.

They are both really flattered and send you their best purrrrrr

Gato,

I was looking through the Tabby building blog on your website again and have a question: In our Blade F16 strip plank project, I spend a lot of time sanding the hulls after planking+gluing. A lot more than I would on a ply hull. How would you compare the outside fairing/sanding on the tabby before glassing to sanding/fairing your ply and strip plank projects (you did a fair bit of sanding on the mast, did you not)?

Did you do anything to make the foam planks get a tight and clean fit in the curves, or did you just fill them from the outside before sanding/fairing? We are planking with 4mm spruce strips, and use a plane to get a tight fit between planks. This also adds to the time spent building.

I think I said it somewhere already, the strip foam is the easiest and fastest way I have tried so far.
I user 15mm wide and 5mm thick strips all over and I did not glue them together at all they are hold together by the double faced tape in the moulds, then the inside is glassed and the frames and all the other details on the inside are coved and glassed before the epoxy has set. That saves already a lot of time and sanding.
As I use narrow strips (15mm) there is no need to make them fit together. The only tool used when putting the strips was a sharp knife.
When the hull halves comes out of the mould and are joined together it’s about 30 minutes of sanding to fair the outside. Then a layer of epoxy mixed with filler to seal the foam and the joints, and then the glass laminated directly to that. It took me five weekends to make the Tabby.

!!!
Surely that is with the strips already ripped and the mould set up? Still a great building time. You had the hull panels done in two weeks then! Makes me wonder about our choosen building method

Thanks for the information!

Ripping the strips was done with a bandsaw and it took about half an hour/hull half.
I have been a wood enthusiast myself, but when it comes to modern designs I have changed my mind...

I will have to do a foam boat as well, just to test it against the woodies.

Why not a Tabby, I'm thinking of making a 14 feet version

If my youngest girl and Omars boy show any interest when they are 5-6, I'll ask Ncik for building plans!
I am into F16s, and possibly the F18 class if they get some class racing going here (which it looks like they will do). Going into a potential F14 class becomes a bit too much even for me :-)

Or did was it a 16 footer you hinted about?

I was not thinking for racing purpose, just for having fun before you get the rest ready for sailing. I can tell you, it's great fun to have a cat of just 50kg that you can rig in no time and be on the water and sail in winds of +30 knots...

I see. Tempting.. But I fear that if I sidetrack I'll never finish the current project!

Well, that would make you save a lot of money and get you the time to go sailing

Oh, you are a nasty piece of work