I have started a blog and new pictures will be there.

http://goodworks.livejournal.com/

I do hope to get some answers to my questions but if I cant I'll just give it my best guess and move on... If the boat works others can follow and if it breaks I'll document what I think went wrong and how I intend to fix it. Its a bit disappointing how little detailed information is available.. so I hope that others who want to try homebuilding will have a path to follow.. albeit strewn with the debris of my failures and misteps.

Shane

Looking good Shane. Sorry can't help with the technical details, never done what you are doing.

However, where did you the carbon from? XSP? Going to try an experimental mast on the moth so need to make a base for it.

Great!



How about giving some of the builders/designers around a call, or take measurements directly off a boat if you need that kind of information.

Could you restate what you need to know? I'll fill in what I know or can find out. We want to keep you going on that project.

I think Phil Brander had an indepth site for building a timber F16.

Anyone know where it is?

Without wishing to detract from what Shane has already done, IMO there are a huge loads of information about on building in Carbon and Glass and even greater amounts on boat building in general, but it is a pain to find quickly and time consuming to piece together but then if it was all so easily available then we would all be building our own boats.

Shanes approach of just getting on with things is possibly the best way in reality as I seemed to spend far to much time researching things but I'm not sure it could lead to small mistakes that turn into major problems. Fortunately the type of small scale construction we are using is pretty forgiving and with just a bit of over engineering we seem to not break to many bits.

My recommendation to anyone contemplating building a boat is to look at the LR2 blog as a possible alternative method, it is a good and easy path to follow and builds pretty good boats relatively quickly.

What Wayne said! (Unless you have perverse ideas about actually building becouse of the process and wanting to do something special like an F16 with the finish of a grand piano)
(And if Shane was building to plans, things might be a bit easier, but there would still be questions).


Here you go Pete:
http://www.thebeachcats.com/index.php?module=pictures&g2_itemId=11955

Thanks Rolf. Isn't it time to update the "View from the Office" thread?

How about use this thread as a dumping ground of good links and information that would be useful to the amateur homebuilder. Can post a link, say what was good or bad, what worked, what didn't, improvements. Would go a long way to helping people like Shane who are starting out on these projects and help grow the class.

I tried to contact a designer but no response. I would even buy a set of plans for reference but nothing modern seems available eg Blade or Viper era. I took some measurements from a Viper because I plan to use Viper sailplan and mast. Chainplate distance from main beam = 68 cm, main beam to rear beam 2m.

Questions

1. please critique my layup plan. Using 200 gm per m carbon cloth over Divinycell H80 overall, with 30g /m glass over that for a better finish. 0/90 deg orientation on th eoutside , -45/+45 inside of the hull.

Doubler of 200 g carbon starting 2m from tip of bow to 1m from transom 0/90deg orientation .

Deck doubler of 200g carbon starting 1.5m from bow tip to transom 0/90 deg orientation.

Local reinforcement of 200g /sq m cloth under beams and chainplate area -45/+45 deg oreintation. Local reinforcement of 300g/ kevlar under beams, chainplate and forestay anchor point to insulate metal from carbon and provide protection.

2. Should I have a sheer clamp to attach the deck? Timber? or Divinycell foam?

3. Bulkheads under Main Beam and Rear beam. Should I use plywood ( 10mm? ) or 200g carbon/H160 foam/carbon sandwich ?

4. Deck hardpoint under the beams - should I have 10mm plywood replacing the H80 foam or can I use H160 to replace the H80 foam?

5. Thinking of a 10mm diameter solid carbon extrusion covered in kevlar for a sidestay anchor instead of a 2,5mm stainless chainplate. More for the 'cool' factor but also to avoid crevice corrosion in the stainless steel. Worth the trouble for the cool points?

6. Broad centreboard like the Taipan or High Aspect ratio like the Viper? Asymetrical or sysmtrical foils?

7. Should there be a bulkhead at the chainplate position?

8. Do I need diagonal stringers between bulkheads as a hull stiffener and to give torsional strength?

Thanks in advance

6.

Have the topsides of the bow quite rounded. Makes a big difference when you have buried the bows, helps them to recover.

High aspect boards is definitely the way to go. Does mean you need to build them stronger to take the sideways forceloads.

I think Phill Brander still supplies the Blade F16 plywood plans?

The measurements you need is from bow to chainplate, bow to main beam, bow to daggerboard and bow to rear beam.


1: Layup schedule. I can not advice you there.

2: Unless you have a way to add a fillet and glass tapes on the inside of the hull after putting the deck in place, I would do a shear stringer. I am comfortable with wood stringers. Alternatively a flange of some form. At least you need some extra glue surface area to stop the deck from popping off.

3: 10mm bulkheads are overkill. 4mm ply with cutouts will do. Foam/carbon is lighter, but I can not help you with the laminate schedule. I have done some foam/glass bulkheads and they did fine on a Tornado, but I am not comfortable on advicing you on foam/carbon/glass.

4: Ply is a possibility, or a nice spruce or WRC plank with some hefty reinforcement in fibers. If going with foam/carbon, you will want to make this part as stiff and strong as possible to minimize flexing and wracking.

5: If I was to do carbon chainplates I would do it like Farrier does. Be careful with alignment and size it for shock loads.
http://www.f-boatmart.com/images/P/F-22chainplate400-01.jpg

6: High aspect ratio, symmetric. Important part of the boat to get right and with high quality on the build and surface. Asymmetrical have been tried in other classes and have not paid off sufficiently yet, except in the C-class AFAIK.

7: Yes.

8: Not neccesarily. Depends on your layup schedule.


To get tips on layup schedules you could try getting hold of guys like Bill Vining, Kevin Cook etc here on catsailor.com. Remember that what you get here is advice given with good intentions. The advice might be spectacularly wrong and lead to catastrophic failures..

Rolf,
I sent 2 message to Phil through the forum message utility but didnt receive any reply. Will try again.

Thanks for your reply. The layup I use is based on the LR2 layup with the extra strength of doublers in the middle part of the boat.

Think I will go with the timber sheer clamp but use carbon/h160 foam/carbon bulkheads and maybe composite chainplates.

Shane

Hi pilgrim,

1) Unless I know the loads and required stiffness, I would use a symetrical sandwich (i.e. 0/+-45/90 inside and outside) with the most fibres in direction of the main loads (from stern to bow?) but not too far from 30%/40%/30%.
If I understand you right, you want to use 200g inside and 200g outside, and midships reinforced by another 200g + 200g? Sounds a bit oversized. I would locate the areas where you need reinforcement (i.e. between the beams, along the keel, where you put the feets for trapezing and righting, around any force introduction. You can use glass instead of kevlar for insulation, does the same as good as the other.
2) yes, timber or large radius CFRP L. It needs to be strong, hence no foam. It will add so much integrity and durability for so less weight.
3) Sandwich would be enough. Add a bulkhead under the attachement for the bridle wires as well
4) I would do epoxy plugs around the bold holes, but hardwood is also possible if protected from moisture.
5) Possible, but I would prefer metal, because it will not break, just bend, if hit. And so far I bend this on all my boats...
6) if you sail single hand: symetric, if you sail dh, you could have asymteric ones. But the boards must be slightly larger, since only one is in the water. Profile and thickness are much more important than aspect ratio, area is more important than aspect ratio. A too small board with high aspect ratio will be a bad performer. DH needs more board area than SH. You can contact me for profiles better than std NACA sections.
7) yes
8) no, but you could have and reduce the weight of the carbon clothes of the sandwich skins.

Ok some words of my background:
I am an engineer with degree in aviation and working for a larger airframe builder for preliminary aircraft design, so I am neither an expert for CFRP nor manufacturing. I have never build a boat, but some parts and repair jobs. Hence be sceptical with my input.

Cheers,

Klaus

Try Phillbrander(at)bigpond.com

Wouter

thanks Klaus,

Just need to clarify..

'0/+-45/90 inside and outside" you mean either 0/90 inside and outside OR -45/+45 inside and outside but not a mixture?
I was following LR2 A class cat layup which seems a reasonable compromise between longitudinal strength and torsional resistance.

What would you recommend for the boards for this Double hander? Size and profile? I have software called Profili with which I can plot foil sections. I have most of the common sections and can donwload if you give me a source or if you provide me a .dat or.txt file. I will send you an email.

Thanks

1. Wouldn't bother with the glass for wear, except maybe right down the keel say 50mm each side. Consider 45/45 inside and out for torsional stiffness. 200gsm carbon should be enough all-round although maybe consider some carbon unis from bridle to cb case along the inboard and outboard sheers (check out CST's new carbon flat bar pultrusions). You'll likely not need the extra layers of carbon. Don't forget to take the cb case opening to single skin, probably 3-5mm thick will be enough.

Depending how quickly you are doing the hull laminates, the epoxy filler screed can be laminated straight over before it cures. Less sanding (the most painful task in boat building) and a better (chemical) bond between the foam and skins.

You haven't mentioned the core thickness? This will ofcourse impact some answers.

2. Yes for sheer clamp, at the very least for locating the deck and controlling the glue while laminating the sheer. As said above, an "L" of carbon is probably the best, can kill two birds with one stone and avoid the sheer stiffener step above.

3. Use a sandwich laminate for framing. See the frames from my home build for what I consider a neat idea (ring frame with a diagonal brace of carbon unis in tension when on one hull). Think the photos are on the F16 website.

4. I prefer a resin soaked plywood and single skin laminate for hardpoints but only because I've never bothered to buy really dense foam for the small number of areas. Either should work in theory.

5. Plenty of ways to do chainplates. May I also suggest carbon plate (c-plate) as an option, but make it very thick.

6. High-ish aspect ratio cb. Buy some off the shelf if you've got the dollars, much easier to get right first time.

7. There should be a bulkhead at the forward or aft end of the cb case which should be close enough to the chainplate to provide enough support. If it is too far away then consider a ring frame that has plenty of depth at the chainplate, and thinner depth elsewhere. As said above, add a frame at the bridle too.

8. I'm not sure what you mean by diagonal stringers, but anyway, you shouldn't need any stringers. Firstly you are using a cored laminate which does the job that stringers typically do, and secondly with a 45/45 skin or two it won't need to be diagonal, you'll get plenty of torsional stiffness from the skins. Only reason you'd need a stringer is if you're core is very thin, and then only to cut the hull panel sizes down.

Just read the other responses and I agree with them too. Love that F22 chainplate, brother has something similar on 12' skiff, but it straddles a frame.

If you need C-plate for chainplates Shane, XSP@NSC have plenty of this.

Ncik,
Good idea to use some unidirectional on the deck, that will take care of the compression stress. Iwasn't going to have the deck at the centreboard opening single skin but I was goin to use H160 foam instead of H80 foam. The whole boat is mostly Divinicell H80 foam 10mm thick ( 80kg/ sq m density ) except for high stress areas which have H160 foam.
I'll probbaly go with the timber sheer clamp since its easier to do.

The diagonal stringers I proposed run between bulkheads and ring frames diagonal to the axis of the boat so that the boat works like a truss. But I guess if I go with the -45/+45 layup on the inside, the fibers will are in the correct orientation.

Yes that chainplate is really cool but a bit overkill on a 12ft skiff... think I will do one to keep up with the Joneses. Yacht Bling...

Shane

I meant to have
a 0/90 fabric and a +-45 fabric outside
and a 0/90 fabric and a +-45 fabric inside.
There are tow ideas behind:
1) Having the same layup scheme in- and outside will not cause any bending, warping, etc. if loads are applied. (If you pull on an asymetric sandwich, it will bend, because one skin is stiffer in the direction of the load than the other)
2) Assuming that impact loads are the most critical case, I proposed to have an nearly isotropic layup (0/+-45/90 fibres), because I think it is the best for that case, but I might be wrong. I would build small square testpieces and make impact tests to find the answer)

Regarding the boards, I would start from the an existing F16 (since they have all the same sail area and mast height), check which one has the smallest area and is regarded as a good double hander in light and strong winds.
In Profili you will have plenty of sections, but probably none designed for a beach catamaran. When I broke the rudder of my friends T, I redesigned NACA 4 digit foils (e.g. NACA 0012) from 8 to 14% thickness by changing nose radius and max thickness location, to improve maximum lift (which allows to reduce board area), cavitation and drag (it is always a trade off, you can improve two of them but worsen the other one). Since my friend complaint always about cavitation we select a board with better cavitation and lift with equal drag than a NACA section. I still should have the data on my computer, so I can send sectional data, if you tell me, which NACA foil would be your starting point (I need it as reference point) and which of the parameters you want to improve.

Cheers,

Klaus

You are suggesting 2 layers of cloth but I am only planning to have one layer of 200g/sqm outside and inside. Most people think thats enough and I cant get a lighter cloth economically. A lighter carbon coth would cost more because I neeed 2 layers.

I'll probably go and measure some daggerboards tomorrow..
NACA 0012 would be a good starting point since I know its been used for this purppose before. And NACA 0015 for the rudder...

I thought we dont go fast enough for foils to cavitate... Are you modifying the foil for a higher critical angle so the foil doesnt stall? Or at least to minimise the laminar separation bubble..

Another question I want to ask you since you are working in aviation. Do you think it would help rudders work at higher angles if we introduced a turbulator at the leading edge. EG A strip of sandpaper glued to the leading edge or even roughing the LE with 60 grit sandpaper?

Shane