I sailed Hobie 16s for many years but stopped when my kids were born... now they are teenagers I find myself drawn back to the sea. Just designed and built a 21ft stitch and glue outrigger canoe to exercise with but have my eyes on an F16.

Looking at the Vipers and Blades that are in the club here, I want to try to design and build an F16 of my own design.

The materials I can easily get here in Singapore are clear NZ pine, meranti and meranti marine plywood ( thinnest 3.6mm ), divinycell PVC foam , epoxy resin, carbon fibre cloth ( 200g/sq m or 250 g/sq m ), glass cloth and kevlar and carbon tow. What would be the best option without having access to a female mold.?

I was thinking over male mold frames either
1) 6mm pine strip covered with carbon fibre 200g/sqm
2) meranti marine plywood sides with pine strip bottom and fibreglass ( lowest cost option )
3) 6mm divinycell cut into strips for planking and carbon fibre 250gm/sqm

4) Hot wire carve blue EPS foam into a boat shape and cover with carbon fibre cloth

what do you think?

Thanks in advance

Shane

I know that Scott McCook has been experimenting with F16 building methods. Why not have a chat with him? Especially as he knows what is available in your locale.

I'd go with the lowest cost option
A) If you make a mistake during construction it wont cost too much
B) If you make a mistake with the design it wont cost too much
C) In a couple of years you may want to adapt the design or you may feel the construction is a little heavy or not stiff enough etc you haven't wasted too much money on your hulls
D) If it gets totaled due to a collision again you wont have wasted your money.
If it works first time and you have a fast F16 then you could always make another using more exotic materials.
In the mean time keep us informed on your decision

Strip planking is very time consuming compared to bending divinycell/foam into a female mould and laminating. Ref: http://woodastic.blogspot.com/

If you go with ply, buy a sheet or two and check the quality of the wood, gluing and finished sheet. Check for delamination when boiling, voids, uneven layers of wood etc.

A quote from a boat building website :
Murphy's law for boatbuilders is that you won't find your mistake until the glue has set, and Welsfords law for boatbuilders is that the mistake that can't be fixed with lots of epoxy and fibreglass hasn't been born yet.

Think you missed a bit Mark......

Heaps of ways to go about it. I designed and built a pair of F16 hulls out of foam and double bias glass in a female mdf jig.

But to go down this route you really need a fair bit of composite building experience or a helpful friend with said experience.

PM me if you need a hand with preparing the hull shape. I'm an engineer specialising in naval architecture and do that stuff all the time. Check out Gato's bloog on his F12 builds. http://www.gust.ax/

Oh, and don't go down the blue foam route. It might be cheap and quick to build but that'll probably be the only benefits with that method.

Thanks for the quick replies, its very encouraging...

J Alani,
I will ask Scott thanks.

Mark,
Point taken, I did waste a lot of time and money with my stitch and glue canoe. But it was fun designing, solving problems and building. What a change from my day job at the bank ( used to be an engineer but banks pay better)

Rolf,
I had heard a lot of bad stories about meranti ply in the US websites but I found the marine ply here to be of good quality. I went through several sheets when I built my canoe and there were no voids and good veneers used. Only thing is that the thinnest I could get was just under 4mm thick....and I dont think meranti ply bends as well as okuoume.

NCIK,
thanks for the offer, I will take you up on that. I am thinking the underwater cross section should be semi circular and the plan view of the hulls should be 2 circular arcs. So if I put the equation of a circle into a spreadsheet and vary the radius until I get the arc i want, I should be able to get a table of offsets of the width of the hull every ft. Then I draw a semicircle at each point to get the mold frames.

Why meranti? Few good experiences with meranti in high stress applications where you want low weight, as far as I know.
3.6mm is less than 4mm, so that further reduces strength. Are you planning on glassing the boat inside and out (adds weight)?

I think on this site about 18 months ago, a group set themselves up via a blog site to design and build a F16 which would be made avaialble to all who were interested. I think a number of regular readers of this forum were involved, is that design still kicking about ?

Have a look at the method John Lindahl is campaigning in building his LR2 and LR3 A cats, gives a very strong structure and very light weight hulls plus it quite well documented. Google should find it no problem.

There is also a very good boat design and build section on this cat sailor forum at the bottom of the list of forums and also another good resource is /www.boatdesign.net/forums/

Best of luck but one tip, which is it going to be a single hander or a dual hander, they are quite different designs.

Rolf,
Your blog is very interesting since I have i have a supply of 6mm clear pine strips 5m long.... What cloth did you use for the outside and the inside of your Blade?

I made a fuselage for a scale model glider using balsa strip in the same way as you built your Blade - left /right halves but when it came to joining I had problems with warping/ twisting. Eventually I tapped them together and when it cured I discovered that the fuselage had a built in twist.... did you have any problems with twist in the left and right halves?

Thanks,

Shane

160gsm I think it is. Dont remember exactly what we bought two years ago. We apply it +-45 deg to the wood fibers.
I would consider removing 1mm or even 2mm from the strips if I was going for a min weight boat, depending on the weight of the wood and how much epoxy it soaks up.
Strip planking is slow!



We dont know yet. First match up is hopefully next week or the week after. It takes time to do 6 identical hull half panels but we are now almost done with panel #7 and well into #8.
As long as both sides are glassed the material is relatively stable. I have checked with experienced strip plank builders and they are in favour.

Before you get to carried away with your design Nick very kindly helped me with mine (still on drawing board, money being the main reason). I also initially thought of a semi circular hull cross section but after Nick crunched the numbers there wouldn't have been enough buoyancy. Now there is a relatively flat section to the bottom of the hulls.
The semi circular design had approx 250mm (10") of draft with 180kgs on one hull or 100mm (4")of draft with 80kgs on one hull.
The non semi circular design had 200mm (8") of draft with 190kgs on one hull or 120mm (5") with 90kgs on one hull, with a slightly wider flatter section between the Center board and Main beam the depth of draft would be even better.
I found an interesting article not so long back (can't find the link now) but instead of using foam (core cell) strips along the length of the hull they decided to lay a lot wider 600mm (24")foam vertically they reckon the benefits were stronger, lighter and fairer. I guess you have to be pretty handy with the hot air gun whilst forming the required curves in the core cell.

keeping it semi circular would give the minimal wetted area and make it easy to do mold frames without CAD.
My proposal for the 16ft hull

max width 13.5 inch tapering to 1.5 inch at the bow and 10.75inch at the transom...

hull would be 19 inch high at the bow, 24 inch amidship and 14inch at the transom.

Max depth and height would be 5ft from the stern, coinciding with the middle of the daggerboard.

Would that work?

Shane

PS I can imagine using 24inch wide PVC foam... its quite stiff, how wil it conform to the curves of the hull....unless you have a female frame and apply heat while vacuuming it

Shane
I'm a raw beginner when it comes to stuff like this!! So I'm basically repeating what I've heard in the past. As far as I can see if you're happy with your ideas then just go for it, you never know what the outcome will be. I just wouldn't like to see you wasting your time and money on a design which although could be easier to build doesn't perform so well on the water.
Your overall design dimensions to my mind aren't out of the ordinary so you'll have yourself a F16.....
Probably the best wet pussy you've ever ridden!! (friday night humour)

How about something like this.
I would go with a flatter bottom my self.
Where you put the center board is a function of where your center of life for upwind sail area is and how much weather helm you want.

Why consider meranti?
Its readily available here in Singapore and light red meranti is about the same density as pine. Its a bit brittle I hear but made into plywood that problem doesnt seem to manifest.

Why simple semi circular forms?
I couldn't find any plans for F16s on the Internet. So I want to make this design free and available for any home builder to build. In my other hobby, aeromodelling, scratch builders are a dying breed so I hope that all the scratch builders who are building kayaks and Moths will come over to cats so there is more info on the Internet.

MarkP,
What is the max width of your hull?

Shane

Wow Lesburn,
Thats very close to what was in my head. The only changes I would make are to have the for'ard sections go from vertical sides amidships to more of a teardrop section at the bow. that would reduce weight forward. And same for the after sections behind the trampoline so that if you trapeze way behind your footing is at a better angle to help from being slung forward in a near pitch pole. I think the Viper has a good design there.

i am thinking of adapting a method of building model airplane wings where you laminate a skin of glass/ wood strip on mylar sheets then vacuum bag to a flat surface. When cured, the mylar is peeled off, the sheet can be cut to shape and applied to the mold frames for the hull sides. It would still be flexible because only one side of the wood strips would have fibreglass, the other side would have the fibreglass applied after the rest of the sheeting is done. The advantage is that sheet has one side practically faired and finished because the mylar will leave a glossy perfectly smooth finish. If this method can be used for the hull sides, half the fairing is taken care of..

Still have to work out the details...

Need some info on scantlings..

For Okoume plywood F16s -
What weight of cloth is used and what thickness for the okoume plywood?

For strip planked F16s - What thickness wood and what weight cloth?

I can easily get Alumimium T5 hardness of circular section for the cross beams. Are these suitable? 100mmm or 125 mm?

thanks,
Shane

For strip planking: 4mm norwegian spruce and a layer of 160gsm cloth put on diagonally on each side of the wood. That is what we use.

For okume, you dont need glass as far as I know.

100mm beams are good.


One of my co-workers in the office is heavily into scale RC airplane models. He is putting the finishing touches on a Tiger Moth just now

Just some quick feed back on the lesburn design...

"Teardropping" the sections like pilgrim said would be good as it would improve the water line and decrease fore deck area.

Push the buoyancy forward. This design has no where near enough volume up front. This doesn't hurt the hydrodynamics of the boat and will give you more downwind stability. Just have a look at wing sections and how "full forward" they are.

The other recomendations if you are going to build an F16... keep the platform as stiff as you can, solid beams and stiff hulls.

Also, don't forget 80% of a boats performance comes from the rig... so give some thought to who will do this and how it will integrate with the platform design.

Besides that, I guess if you want to see how we think an F16 should be done, have a look at the VIPER.

Good luck and hope to see you on the water.