Dirk, good luck with your project! Please keep us up with the play. I know some of the drive for such a project is the creative spirit.
I have a Taipan project which could eventually gain from such a move.

Dirk,
Not sure it would be of interest to you, but I have 2) SC20 bows (maybe 4' long) in excellent condition. Would be a relatively easy splice I think.

Dave 509 276 6355 Spokane, WA

I thought the Inter 18 was around before F18 (it had a carbon mast) and was grandfathered in in hindsight after F18 came about. - I don't think that counts.

Fair comment Jake, for a yank!
The inter18 was only available in europe with a ali mast and F18 was up and running earlier over here.
SO WE CAN BOTH BE RIGHT!

Happy Christmas

Paul

Pete Melvin and Gino Morelli designed the Inter 18 specifically for the Formula 18 Class Rules and was sold with the aluminum mast in Europe. The carbon mast was an "extra cost" option sold exclusively (I think) in North America. Nacra also offered a larger mainsail for the carbon mast Inter 18 in the 2nd or 3rd year. All of the Inter 18s can be fully legal F18s if you use the aluminum rig and F18 sails.

Les:

I think the Inter 18 used the same snuffer system that the I-20s are using. They are made of carbon fiber and not allowed in Formula 18 class racing.

Of course if someone is going to change out a mast then the snuffer should be no big deal.

Let's say that someone wants to upgrade an Inter-18 to Formula 18 and has the average one. They will be trading out a carbon mast for aluminum. Let's call that $900. They will need a new sail to fit the aluminum mast, I doubt that the same sail would work on the Carbon Mast and the Aluminum Mast competitively. That sail will run $1500. Then if you need to replace the snuffer you are in at least $300 for that. Now you are in an Inter-18 for $2700 not including what the boat is worth. Say the boat is worth $3000. You are up to $5700 for a boat that may or may not be competitive with the boats sailing today. If you are in this position you may consider getting a used formula 18 for about $8000.

If you were to buy a used Formula 18 for a good price you could sell it later and not lose too much money.

Just thinking before an upgrade may save some money and grief.

Later,
Dan

Dirk,
use the blue foam you're talking about. its cheap and VERY rigid. It is every bit as rigid as the poly cores. to shape use adhesive backed 36 grit abrasive on a flat "stick" as a file. then sand with 80 grit before glassing. you will HAVE to use epoxy. everyone is right in saying that polyesters and vinylesters will melt the blue foam. I recommend Gougeon bros Pro set. stay away from the west systems. west is made for coating with light amine blush, but is not structural in anyway. in temps above 80 degs it will become soft and heat deflect. I learned this the hard way with bicycle frames. we shaped blue foam cores and wrapped carbon with west systems. I always thought it was my imagination that the bike was more flexible in hot weather until i made some flat carbon landing gear for my rc plane and watched the wheels turn outward 45 degrees in mid 80's weather. Anyway, shape away and have fun, would love to see pics of your progress

it is not the west that fails at 80, it is the foam. i just finished the molds and boat for an open 60 mono project. we used the west 105 to sheath the molds and it was fine. we also used some of the blue foam (sm) in some of the ovens and it turned into a big blue puddle.
oh, and the gougeons make west.

I agree with basket case. The blue foam is simply not a structural foam. It is designed specifically for cost effective insulating properties and it is substantially weaker in shear than the foams that are designed to be used in laminate cores. In a properly designed laminate, the core should largely resist shear loading. Use end grain balsa or the foams designed for composite core applications if you want to achieve reliable results. You will also find that you will get a much better bond to the foam (and a significantly better structure) with pressure applied to the laminate during cure (autoclave or vacuum).

I've had no heat issues with the West System epoxies...although almost all epoxies will get soft if you heat them to high temperatures. Also note that epoxies are affected by UV so if you are leaving them bare and exposed to the sun without a UV barrier, they will yellow and can get brittle.

If you really insist on cutting corners, you'll have better results using green rigid PVC foam from a floral shop than the blue stuff from a home improvement center.

correct, blue foam is not a designed structual foam as compared to say klegecell or any of the others, but its cheap and available in thickness and easily shaped and is typically lighter. we made a 3.1 lb carbon bike frame with it and got carbon bike of the year in '91 from bicycling mag. call gougoeon they will be happy to tell you west is not for structual laminates but for coating and recommend their pro-set series as they did our buisness here. we still use the west for coating thermoform tools if our customers wont swing for an aluminum tool, but for structural lams the pro-set has a fairly impressive set of physicals. Jake, how would an autoclave help you apply pressure to the surface of your laminate against your foam? the vacuum bagging works well, but room temp resins dont require an overall higher atmosphere to go through their cure cycle typically which is what the autoclave is there for. I dont see how the author here is going to keep a normal atmosphere behind his foam to allow an autoclave to work as your recommending, but again, bagging is a great suggestion to him. and i'm sorry but i disagree that the floral pvc would be better. the cells are too easily crushed. it is possible to make a ligther lam with the blue foam, its a tighter cell and holds less resin. it is not as structural, but it sounds like our author is not looking for overal structure, but simply changing shape, and the way he would be encapsulating the foam, I feel the blue would be strong enough. I definitly would not use it for a structural item where I was relying on the core as in a flatter 2-d laminate such as the skin of the hull. i used klegecell in my carbon daggers.

it is not the west that fails at 80, it is the foam. i just finished the molds and boat for an open 60 mono project. we used the west 105 to sheath the molds and it was fine. we also used some of the blue foam (sm) in some of the ovens and it turned into a big blue puddle.
oh, and the gougeons make west


yes gougeon makes both systems and they market the west to the home-built boaters due to the low amine blush. the pro-set is aimed more at industry, but the amine blush is so high its sticky when cured, but neither system is for tooling?? and you are very correct, blue foam and ovens dont mix <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

A blue foam will be MUCH lighter. the frame we designed for our client was origionally cut from structural urethane foam for its core. the core alone was 2.5 lbs which didnt leave much room for carbon. the blue foam core was .75 lbs. the "structural" cores are designed for sandwich laminates. you are not doing that. you are covering a shape. here's my analogy: if your final goal is a 10 lb structure. would you rather have a heavy core and not much skin, or a light core and 4 times the skin? theres more strength and stiffness in the additional carbon, if and only if you have a one piece design, or a solid core. the blue foam allows you to make a more similar construction. more laminate weight less core weight. they are talking about shear strenght etc....flat panel construction uses cores to give a "3rd" demension to the construction for rigidity. that rigidity depends upon the shear strenth to hold the sandwich together. this is where the designed cores shine. you are not constructing like that. you are making a SOLID shape and covering it. completely different. you will end up with a more "one piece" construction as our bike frame. boat hulls are made in multiple pieces and assembled to some degree, are very hollow, and are resonably flat. so the walls need the structural core to keep rigid. your "solid core" construction does not follow that ideal, so your choice of materials needs to follow your need, not generic construction theory. just my very humble opinion

thank you rubi, jake and the other authors again for the detailed informations and and very helpful hints.

rubi, I totaly agree that the only forces I expect the extended bows have to deal with are those from the waves.

while those can be significant, I also believe that the blue foam would be stiff enough if coated well on the outside.

how thick would you suggest to make the skin if using glassfibres? would 2 layers of 160 g /m² do the job?

I will try to use the vacuum principle to get a good connection between the glass and the foam.

anyhow, will surely keep track with a camera once action starts and will report progress than. :-)

3 plys 200 gram boat cloth. (fine woven cloth)

I honestly cant tell you how much material to use over the outside, but i can tell you to add an extra layer to allow finishing. you can easily sand through an entire layer while finishing. once the last layer is on, keep brushing a thin coat of epoxy at each "b" stage until the last weave is completely filled before sanding. filling the weave completely will not really add weight as most will be sanded off, but it will keep you from sanding into the glass too much. be sure to grind into your origional hull at the overlap at a very long taper to glass onto and to aid in finishing the seam.

I noticed some horizontal possible movement in my forestay tangs. When taking of the cover plate, I can move them about half a centimeter fore and aft. In contrast, there is no noticeable movement in the direction the forestay pulls so. Talked to Aquarius Sails earlier and they recommended to completely replace the bulkhead with a new version for it. Since than I watched what was happening to my tangs carefully and noticed that after re-mounting the cover plates again with some epoxy no more movement occured. My guess is that the discovered aft and forward movement was probably caused by the boats earlier use on a beach where people probably pulled on the forestay when pulling the boat along the beach from and to the water. While not doing something like that anymore I wonder if I still can find out more about the construction principle of the tangs as I remember to have read somewhere else that old SC indeed might have encountered some issues with the forestay tangs being pulled out. Myth or fact? Any comments/experiences on this?

No experience with the SCs, but have had a forestay tang pull out of an old Tornado while going upwind trapped (single trap those days) and full depower. This tang had just some millimeters of sideways flex on the beach. No vertical flex. Turned out it was installed in plywood with as good as no precautions to stop rot and the bolts from working on the wood. Since then I have found movement in any high load fitting holding the rig up to be unacceptable. If it was my boat, I would cut a hole for inspection and possibly remove the deck in the area for repairs/rebuilding if jugded neccesary. If Aquarius (and Bill Roberts) recommends replacing the bulkhead, it sounds like it might be the smart thing to do.


On another note:
Any hope for an F-16 report from China? Is it happening for the class there? Did you find a local sailmaker to build sails for you? If you have time, it would be good to hear from you again on the F-16 forum.

Ups! Thanks! That sounds scary! Anyone knows how the tang is fixed to the bulkhead on a 1980s SC20?

Rolf, will post on F16 regarding other topic.

If you are just adding a bit to the bow, it won't matter which foam you use since the glass and epoxy will be taking the loads. I built a pair of amas "surfboard style" with a stringer between stacked and glued pink insulation. Crappy foam? Yes. As long as the bond doesn't give way, it works great though. Think of all the surfboards that were made with less than stellar foams. Some current epoxy boards are made with what amounts to styrafoam. Your skin will be taking the loads if you don't modify the underlying hull other than roughing it up for bonding the foam and glass to it. That said, you don't need much and might be able to get some klegecell or Airex cheap.

Dan

Dirk,
I have a couple of early 80's bows, cut off 6' from the bow. I'll try to dig them out of the snow, stick me head in there and see what I can see.

Dave