89er

[JulianB]

HI, so it (the rudder) ended up weighing 4.6kgs, and it more than passed the "whale test" it's given me extra confidence in the fin as it's only 34mm thick at the lower gudgeon where as the fin is 55mm thich, I have used almost the same laminate thickness, so if 4.5mm of Basalt is in the rudder at 1200mm easily passes the Whale test, then the 55mm thick fin, with 4.5mm thickness of basalt at the keel, at 1400mm should have no issue.

Some issues with the brass pivot and crap going down the hole, but I have a 12mm OD x 700mm LOA drill coming and that should clear it out.

Moulds unfortunatly are completly F--ked". Lucky I don't think I will need a 2nd anytime soon, but I will take this for a sail and see how it goes before getting excited about modifications. I'm guessing I can chop 100mm off the bottom, but a few sails before now and then.

49ers, if you are not dilligent, you can sheer a M8 SS pin. M8 pin is good for 2700kgs.
49er rudder goes 760mm into the water and is held by just under 200mm rudders stock (LOA is 960mm)
So say at extreme loading CoE of the rudder is 400-420mm down, (nb1) so it's pulling, very hard to believe but 1 tonne.

nb1 it's below 1/2 way because the rudder at the surface would be venting or ventalating.

The 89er has a M12 Ti TC4 pin, sheer load on that is up around 5500kgs, 1200 down and 500mm up.
Hard to believe you would get 4 tonne on it and 4 tonne pulling on the back of Scallywag or Commanchee will get a lot of motion, on the back of Don't Panic it should be sending us in pirquets! .

Scary loads, can't tell you the load we put on a 49er rudder blade tip went certifying, because I will get crucified by WS but every rudder (and centerboard) is tested to that load and then another lesser load where the deflection is measured. What I can tell you is the load we put on a 49er is a lot less than the 120 + kgs I put on the 89er rudder (within 100mm of the tip) and it came up trumps, did not even move that far, maybe 100mm.

Very happy boy at the moment, it's all coming together!

jB

 

[allweather]

Very happy boy at the moment, it's all coming together!

Really fun to follow the progress, occasional snag included.
Plus all the trivia you end up referencing(49er and so on) is interesting to me!

Did you have issues demoulding or what ended up screwing up them? And I felt that regarding having to drill out the brass pivot. Minus getting a drill effing long enough and not ending up with a reamed out? hole that leaves too much slag for the pin to feel good steering.

 

[JulianB]

It stuck up, don't know why, the CNC Miller is also confused, but shit happens.

 

[gazasmith]

I've had stick up issues.
using semi permanent now no issues on different surfaces and finishes.
more expensive than wax but worth it.
what paint was on the mould?

very interested in your foam, do you have more info on what it is?

 

[JulianB]

Really fun to follow the progress, occasional snag included.
Plus all the trivia you end up referencing(49er and so on) is interesting to me!

Did you have issues demoulding or what ended up screwing up them? And I felt that regarding having to drill out the brass pivot. Minus getting a drill effing long enough and not ending up with a reamed out? hole that leaves too much slag for the pin to feel good steering.

I go back to 49er and 18teens because we did so many of them we know emperically exactly how strong things need to be.
That's my only reason. I'm guessing that M12 rudder pin on a 1/5 toone sport boat is a "overkill" probably get away with a M10, but I know a M8 is going to be too small.

That's why I go back to hallowed tuff! jB

 

[JulianB]

I've had stick up issues.
using semi permanent now no issues on different surfaces and finishes.
more expensive than wax but worth it.
what paint was on the mould?

very interested in your foam, do you have more info on what it is?

So I did 10 x waxes, 2 hrs apart and then PVA-ed the mould.
I when straight on with epoxy, which I find to be far less agresive than polyester, and I had done a test, and subsequently, even the stick up areas released effortlessly, which is what has got the CNC miller confused.
We think we may have got a dud batch of MDF milling board, anyway, I have a rudder, and I'm very happy.

The foam, I am using a Pu, H160 density 2 part blow foam, it happens to be eco friendly, so it's water blown.
The temp of the 2 parts of Pu and the mould are very critical, got to be 25c plus.
And I let the foam sit for 4-5 days.

Re Pu's, I am sure you can find a good one, the stuff I use is Australian, made by Era Chemicals.
We took a while to find the good Italian stuff, it anit easy and don't belive the salesman, ever.

jB

 

[allweather]

Re Pu's, I am sure you can find a good one, the stuff I use is Australian, made by Era Chemicals.
We took a while to find the good Italian stuff, it anit easy and don't belive the salesman, ever.

That is good to know. I don't currently have any projects like that in mind, but last time I checked selling two part foam is only permissible to professionals in the EU and unavailable to me as a hobbyist.(without some connections) Something about toxicity and environmental issues.

Which isn't unreasonable, but looks like I have to do some reading to do regarding the eco friendly version you mentioned.

 

[JulianB]

That is good to know. I don't currently have any projects like that in mind, but last time I checked selling two part foam is only permissible to professionals in the EU and unavailable to me as a hobbyist.(without some connections) Something about toxicity and environmental issues.

Which isn't unreasonable, but looks like I have to do some reading to do regarding the eco friendly version you mentioned.

I am aware that the EU required some changes to Pu formulation and that put a end to Alloy Foils on 29ers, because the new formulation swelled in salt water that and also at the same time downgraded the Urethane that we used in the end caps, the alloy ended up fatter at the tip, than it was in the truck.

But in Italy, we had no issue sourcing it.

 

[huey 2]

Hi there JB , What did you seal the rudder molds with..., did you allow plenty of time between coats. Problems i have had with stickups are because solvents that hadn't flashed off and the surface is dry but underneath rubbery locking underneath solvents in....Especially with MDF as it retains solvents. Sometimes it causes wax to buff off leaving little on the surface. We often use ERARelease and it also has high content of solvents,....and have to be very aware sealer/gloss on molds that needs to be fully setup...Often use shellac on MDF as first coat then sealer/primer gloss then put in low temp hot box to minimise warpage....but to remove solvents in build up....combination of gentle airflow and heat.
Some of the PU foams for surfboards , are now stable eco / water setup with low VOCs...and are being brought into the country. You could use these with Alloy. I use foam to fill / seal alloy tubes. A problem is some importers have collapsed during covid and hard to get a regular supply. So have imported directly from US and EU...not cheap and only works with a very supportive supplier to airfreight in. Can still use Era for certain Items/jobs and keep some in the workshop fire cabinet store.

 

[JulianB]

Guys, bit over the mould issue, its f--ked, and there is little I can do about it.
The moulds were finished prior to me traveling OS, so they sat for atleast 10-12 days.
They were finsihed with 2:1 polyurethane and the CNC miller, they looked fine
They were then waxed, as stated before 10 time 2 hrs apart with std mould release wax,
They were then PVA-ed prior to the process.
Yes I know ERA Release, very impressive stuff.
Yes I have used Free-coat, and a range of other release agents.

Bottom line, as occasionally happens, it did not work.

Can we move on please!??????????

 

[huey 2]

No worries...Good Luck in the final stages of prep...great to look over the shoulder at your impressive group output Thanks

 

[Beatrix]

Guys, bit over the mould issue, its f--ked, and there is little I can do about it.
The moulds were finished prior to me traveling OS, so they sat for atleast 10-12 days.
They were finsihed with 2:1 polyurethane and the CNC miller, they looked fine
They were then waxed, as stated before 10 time 2 hrs apart with std mould release wax,
They were then PVA-ed prior to the process.
Yes I know ERA Release, very impressive stuff.
Yes I have used Free-coat, and a range of other release agents.

Bottom line, as occasionally happens, it did not work.

Can we move on please!??????????

Julian, I’m loving this thread. The generosity in passing on your knowledge is amazing.. thanks.
I must be dim, but I haven’t got my head around the final assembly of your foils.
I get that you create two outer skins and then blow a foam core inside the skins, so now you have three pieces. Do you just glue these together? What stops the leading and trailing edges from splitting apart as the fin bends and twists?

 

[allweather]

Can we move on please!??????????

Happily, say, have you ever considered 3D printing for these particular moulds? Probably not really any advantages due to the flat profile, but after watching a local shop print out a plug for fourteen footer outriggers I wondered about your opinion in that regard.

Swear it came up before, but can't find it right now.

 

[JulianB]

Julian, I’m loving this thread. The generosity in passing on your knowledge is amazing.. thanks.
I must be dim, but I haven’t got my head around the final assembly of your foils.
I get that you create two outer skins and then blow a foam core inside the skins, so now you have three pieces. Do you just glue these together? What stops the leading and trailing edges from splitting apart as the fin bends and twists?

Hi Beatrix,

You have a LE wrap, so this is bi-axial glass, think its 325gm and there are 2 layers, one is approx 100mm wide, the other is approx 80mm wide, full length of the LE, then around the tip and that is applied on the lower side directly against the basalt/fibre and then in the final stages of bonding, it is wrapped over the foam core so that when the top mould/laminate comes down, it's pressed directly and firmly into the basalt/laminate on the upper side.
Same deal with the spar, (this happens before the LE foam is put in place) in the case of the rudder there was 1 transverse blade, but at the bottom gudgeon it was 6 layers, of the previously mentioned bi-axial (4) and then an additional 2 layers of Basalt, which is 370gm. 6 x approx 0.34mm = tad over 2mm, but interspersed in those layers is a slurry, so it's more than likely 3 - 3.5mm think, again bonded directly to the laminate on the lower surface and pressed directly into the upper laminate.
And with something like this we do also do a TE wrap, probably 20mm inside the TE, again the Bi-Axial, same deal.

All the bi-axial is at 45°-45°.

The Basalt is 0-90°

The gluing surface, 40-50mm wide.

So you have effectively 3 fibre ties between the 2 - ½ shells/sides

Happy to do you a render/dwg if that’s not clear?

If you go back a few posts, the fin is a 4 blade spar, (I did do a render) and I do that because the fin is constantly flexing under side load, and a bit of lead induced wobble. The rudder is only loaded to 1/10th the fin load 99% of the time, plus the load on the rudder is very concentrated within 20mm of the lower gudgeon.

The way I do these rudders the lower gedgeon is at or below the Water Level, so that reduces arm which has to be a good thing.

Pick up my M12 x 700mm long dril in a few hours to clear out the pivot. Stupid, the bog had to go somewhere and I did not block the pivot, so I have a brass tube full of bog.

jB

 

[JulianB]

I use 3d printed moulds in other capacities often, even quite big ones and for full industrial process, and they work very well.

Not sure why I have not done it here, have not really though about it that much, just always have done Milling board.
Maybe next time, and that could be very soon (not SB related)!

jB

 

[Steve Clark]

When only use PU foam for the foils we make all in one go. Molds masked and sprayed with gel coat. Accurately cut reinforcements that exactly fit the foil (CNC cut stack that is held together with reactive tackifier) are then put in place and wet out with a generous amount of resin. The core has a sheer web made by cutting two slots across the core and inserting a piece of carbon. The mold is closed and put in a 5 ton press.
This is only practical if you are doing it many times. For one off or semi custom molds I still bag core into the port and starboard sides and then mill the centerline flat. As a bonus, you can squish a layer of coth on centerline. This helps transfers the shear from one side to the other, but also makes a super rugged trailing edge you can practically use to drive nails.
This Basalt shit looks pretty interesting as a halfway house between carbon and glass. I have done some tests with Flax and Bamboo and can’t say I’m wicked impressed. It was fun to sandwich some +/-45 Flax between two 3mm pieces of cedar veneer. Not lighter than 6mm plywood, but very attractive.
SHC
We are starting to set up the CNC110 this week. Maybe I should follow Julian’s example and share the process. Not exactly a Sport Boat by the modern definition, but it isn’t a straight keel boat either....

 

[WCB]

When only use PU foam for the foils we make all in one go. Molds masked and sprayed with gel coat. Accurately cut reinforcements that exactly fit the foil (CNC cut stack that is held together with reactive tackifier) are then put in place and wet out with a generous amount of resin. The core has a sheer web made by cutting two slots across the core and inserting a piece of carbon. The mold is closed and put in a 5 ton press.
This is only practical if you are doing it many times. For one off or semi custom molds I still bag core into the port and starboard sides and then mill the centerline flat. As a bonus, you can squish a layer of coth on centerline. This helps transfers the shear from one side to the other, but also makes a super rugged trailing edge you can practically use to drive nails.
This Basalt shit looks pretty interesting as a halfway house between carbon and glass. I have done some tests with Flax and Bamboo and can’t say I’m wicked impressed. It was fun to sandwich some +/-45 Flax between two 3mm pieces of cedar veneer. Not lighter than 6mm plywood, but very attractive.
SHC
We are starting to set up the CNC110 this week. Maybe I should follow Julian’s example and share the process. Not exactly a Sport Boat by the modern definition, but it isn’t a straight keel boat either....

Please do share the CNC110 process! Great advertising for the class as well.

I am working on a new foam cored rudder for my 110 and I was going to sandwich some cloth between the foam layers and after reading this, I know it's a good idea.

 

[Jethrow]

Maybe I should follow Julian’s example and share the process

Yes please!

 

[JulianB]

Mr Clark, how the f--k are you, growing some grey hair and looking mature in you recent pics.
Still need to make my way to RI and that drink you owe me.

We don't use Pu foaming in what I call "live" moulding, where everything is wet because it has a tendancy to shrink, post expansion, which is one of the reason we let it sit for 4-5 days after foaming.

We do how ever use epoxy foaming material in "live" moulding, especially if using epoxy laminates. There is a French company call Sicomen and ther stuff is particularly good, there is also some Chinese material that is truly sensational but I can't remember it's name let alone how to spell it.

The bulk of 29er foils are made this way, failure rate is very very low, like less than 1%.

So need some pretty picture of a CNC110 (I thought it was a milling machine)

July, I'm hopefully Log boat sailing in Annapolis. RI after that, and that drink!

 

[JulianB]

BTW, I though Flax was the ducks’ guts, I was in Einstein’s Cafe in Zurich (was back there 15 days ago, but different person) being told all about the stuff and went full hog into it, but it's hollow tubes and it wicks, so away from water I'm guessing it's fabulous, near water not so.

Need to stress even Carbon and Glass wicks. One of the up side of basalt is that it does not, and it's long been use (30-40 years) in water tanks and pressure vessels because of it.
But it has greater elongation than Carbon, not as much as Glass and that means you will get greater flex than Carbon, therefor greater tenacity with similar UTS.

So I have gone for greater core thickness which negates the elongation issues, and I get greater idiot factor, a +,+ from my POV.