Select to expand quote

Gestalt said..
back in the 90's when I competed in race board class, a friend from school was on speed boards so I got to race his a few times. I was on manta boards at the time (Now NXS) and from memory it was hand laminated eps. I think the blanks were glued up as at that time you couldn't buy blocks big enough.

Do you mean the Mantra were hand laminated?

Speed were definitely moulded.

But I would be very interested in what could be done with hand laminating and foaming resin.

Just had a chat with a friend of mine who used to be on the tour. He is making himself single skin boards and he says they last him 2 years. His standard is high, he sails a lot, jumping and riding real waves. He says if they are lasting him 2 years then they are overbuilt for normal people. He has extensive experience building sandwhich boards too. The drawback is weight, they are 7.6 kg. I know his sailing style really well, and if they are lasting him they will be perfectly strong enough for most people.

Select to expand quote

sailquik said..

Gestalt said..
back in the 90's when I competed in race board class, a friend from school was on speed boards so I got to race his a few times. I was on manta boards at the time (Now NXS) and from memory it was hand laminated eps. I think the blanks were glued up as at that time you couldn't buy blocks big enough.

Do you mean the Mantra were hand laminated?

Speed were definitely moulded.

But I would be very interested in what could be done with hand laminating and foaming resin.

Yes i meant manta. I think at the time Peter (manta) was hand laminating eps and epoxy. Not sure when he did his first vac bag sandwich board. Maybe mid 90's?? I got my first sandwich board from him in 2000 and he had a few years experience already by then. Early 90's his boards were pu. He would have been a very early adopter as he's been doing sandwich boards for over 30 years.

i believe there were a couple of New Zealand guys that started doing sandwich boards long before anyone else I know of. They got the idea from looking at America cup boats. not sure why other early builders used foaming resin.

Select to expand quote

sheddweller said..
Just had a chat with a friend of mine who used to be on the tour. He is making himself single skin boards and he says they last him 2 years. His standard is high, he sails a lot, jumping and riding real waves. He says if they are lasting him 2 years then they are overbuilt for normal people. He has extensive experience building sandwhich boards too. The drawback is weight, they are 7.6 kg. I know his sailing style really well, and if they are lasting him they will be perfectly strong enough for most people.

Do you know if he's vac bagging the single skin?

if jumping is the measure then there are many windsurfers that don't jump at all.

I've certainly adjusted some of my ideas about pros and cons after this thread

Select to expand quote

sailquik said..

Gestalt said..
back in the 90's when I competed in race board class, a friend from school was on speed boards so I got to race his a few times. I was on manta boards at the time (Now NXS) and from memory it was hand laminated eps. I think the blanks were glued up as at that time you couldn't buy blocks big enough.

Do you mean the Mantra were hand laminated?

Speed were definitely moulded.

But I would be very interested in what could be done with hand laminating and foaming resin.

Andrew, sorry to read about your trailer. Hope everything sorts itself out for you.

i meant to mention with my last post,
I was told recently that Speed did introduce thin pvc towards the end of their run. .

Select to expand quote

Gestalt said..

sheddweller said..
Just had a chat with a friend of mine who used to be on the tour. He is making himself single skin boards and he says they last him 2 years. His standard is high, he sails a lot, jumping and riding real waves. He says if they are lasting him 2 years then they are overbuilt for normal people. He has extensive experience building sandwhich boards too. The drawback is weight, they are 7.6 kg. I know his sailing style really well, and if they are lasting him they will be perfectly strong enough for most people.

Do you know if he's vac bagging the single skin?

if jumping is the measure then there are many windsurfers that don't jump at all.

I've certainly adjusted some of my ideas about pros and cons after this thread

I think so, but not sure, i will ask.

Select to expand quote

sheddweller said..

Gestalt said..

sheddweller said..
Just had a chat with a friend of mine who used to be on the tour. He is making himself single skin boards and he says they last him 2 years. His standard is high, he sails a lot, jumping and riding real waves. He says if they are lasting him 2 years then they are overbuilt for normal people. He has extensive experience building sandwhich boards too. The drawback is weight, they are 7.6 kg. I know his sailing style really well, and if they are lasting him they will be perfectly strong enough for most people.

Do you know if he's vac bagging the single skin?

if jumping is the measure then there are many windsurfers that don't jump at all.

I've certainly adjusted some of my ideas about pros and cons after this thread

I think so, but not sure, i will ask.

By compacting fiber, vac bagging, allow an higher fiber/resin ratio wich increase tensil strengh by weight. But for near same quantity materials, just a bit more resin for experiment hand lam operator, it reduce thickness of laminate and so flexural strengh. Board skin suffer of flexion, break by buckling wich is flexural instability under compressive forces. Dents are foam d?formation because skin flex over. Increase skin thickness is the way to go to increase board strengh. Add layers of fiber in laminate increase strengh but weight too. Sandwich is a way to increase skin thickness and so flexural strengh without much weight, it reduce overall skin density. Use of foaming resin is also a way to reduce skin density.

Select to expand quote

Gestalt said..

Toilet plungers ?!

Select to expand quote

jn1 said..

Gestalt said..

Toilet plungers ?!

Real characters lol.

Select to expand quote

lemat said..

sheddweller said..

Gestalt said..

sheddweller said..
Just had a chat with a friend of mine who used to be on the tour. He is making himself single skin boards and he says they last him 2 years. His standard is high, he sails a lot, jumping and riding real waves. He says if they are lasting him 2 years then they are overbuilt for normal people. He has extensive experience building sandwhich boards too. The drawback is weight, they are 7.6 kg. I know his sailing style really well, and if they are lasting him they will be perfectly strong enough for most people.

Do you know if he's vac bagging the single skin?

if jumping is the measure then there are many windsurfers that don't jump at all.

I've certainly adjusted some of my ideas about pros and cons after this thread

I think so, but not sure, i will ask.

By compacting fiber, vac bagging, allow an higher fiber/resin ratio wich increase tensil strengh by weight. But for near same quantity materials, just a bit more resin for experiment hand lam operator, it reduce thickness of laminate and so flexural strengh. Board skin suffer of flexion, break by buckling wich is flexural instability under compressive forces. Dents are foam d?formation because skin flex over. Increase skin thickness is the way to go to increase board strengh. Add layers of fiber in laminate increase strengh but weight too. Sandwich is a way to increase skin thickness and so flexural strengh without much weight, it reduce overall skin density. Use of foaming resin is also a way to reduce skin density.

Yes I understand.

I am guessing that part of the reason I've not had some of the issues others have had with single skin (excluding me not pushing things as hard) could be because I used 6oz Volan for my layup. I bought a roll from mctavish surfboards when they changed their factory setup. Volan is thicker and holds more resin so acts a bit like a bulker. I used it because of its use in longboards.

I'd like to try Graphene in single skin too, however not sure if it's available for diy. Some of the figures being advertised are

The final composite showed an increase in tensile-shear strength of +122%, Compressive strength increase of +30%, increase in flexural strength of +73% and flexural modulus of +87%. Interlaminar shear strength increased by +31% when just 0.17% graphene (by weight) of graphene GS was included in the carbon fiber reinforced polymer composites

The most important is flexural strengh and stiffness. If i remember well i see test of something like this on sanded instagram. Real graphen is carbon nanoparticles, i don't think it's easily accessible for DIY. But you can easier find microparticules of graphite or orher materials that added in resin can improve some mechanical numbers. What you want is increase flexural stiffness and strengh but keep toughness so your skin resist to dynamic loads. You want hardness too to resist puncture (dings). A good material for much of this can be wood.

I looked at it long and hard a read everything I could get my hand on re: nanoparticles in order that I could make stronger boards. It is not in any way usable by us.
Firstly the size of the particles means they stick together vehemently, as the tiny size means nuclear forces are at play. Think static x1000.
So just to get it to evenly disperse in resin is impossible for us... special chems, magnetic stirrer like a lab etc. There are whole PhD theses at great length just addressing the dispersal problem.

Then its so bloody dangerous. It cannot be contained and will enter cells, not just in your lungs... it will pierce cells and kill you through your eyeballs.

Much of the reason I rant about a certain company on TV at the moment claiming graphene in their swimming pool laminate. Hmmmm

Mark, thx, Good to know

Lemat, hoop pine veneer in all my boards and the ones that were built by others for me. My single skin board has hoop and carbon in it.

1mm hardwood veneer (french ash) with biax carbon is what i will use for my next project.
Just finish my last hybrid race freerider, beefy build glass/cork/carbon.
290x72 190l step tail (kona inspired). Carbon sandwich daggerboard. 13.5kg

Looks fantastic. Love the shape.
Did you make the centreboard case as well?

Yes on this one i make all the dagerboard system.

Select to expand quote

Gestalt said..

geoITA said..
...
The result was a board that weighted much more than my similar volume RRD 281. The feel on the water was not nearly close: my RRD felt stiff and quick, his board felt soft and sluggish. Over time the stringer protruded slightly from the EPS core, so that it was possible to sense it bulging under the epoxy skin. In less than one season, that board, which was supposed to be aimed at an expert sailor, became of practically no value, as no one with the skill needed to sail it would ever consider to buy it.
On the water all the shortcomings showed even more boldly than onshore.
...

something sounds odd here. I never considered my pu boards back in the day to be soft and sluggish. i still got a speed board in the garage from the early 90's that doesn't suffer from any of those traits. An eps board should not be like that either. so i'm thinking the wrong density foam was used for the build.

i currently sail an eps board built without sandwich and it's stiff and fast. i race friends on similar gear and i'm not slower.

Indeed PU is some stiffer than EPS, and density makes a difference. But stiffness from the core is nothing compared to the stiffness added (or not) from the skin.
I once built a 3.8 meters "tentative raceboard" in PanAm fashion, with a retractable daggerboard. It was 25 kg/m3 EPS with a stringer and single skin glass/epoxy. Heavy, but still strong enough for the low speed it used to go. Going 25 - 30 knots over chop, which is what a modern slalom board do, is a different story: impacts are hard and a not stiff enough bottom would easily alter its shape. And a few 1/10 mm rocker alteration in the fin and straps area can make a huge difference in control. Such alterations happen easily even in sandwich boards, so it's all a matter of one's requirements.
Also, materials do work the way they work. Sandwich works well because it adds thickness to the laminate, separating the inside and outside fiber layers but connecting them, so that they will have better stiffness. This is at the cost of the weight of the sandwich foam, which actually adds very little to mechanic performances by itself. So one of course may think of other ways to get similar results, by means of foaming epoxy or wood veneer. Probably one may get enough stiffness, lightness and toughness form such a board if it will be used for wavesailing and/or freesailing. I also owned a wood veneer slalom board (Starboard Sonic95) and it was a nice board indeed, but the CarbonArt ones I owned after that, or the FMX's I sail now, are on a different level as for stiffness.

^^^^People have used honeycomb for the sandwhich. I was thinking of using it but it only came minimum 6 mm thick. It also came single skinned or double skinned. The double was very stiff , good for the bottom of the board. I had a fondle of an off-cut and was surprisingly strong on its own. I think the skin is resin soaked paper ? The single sided stuff would be good for the curved deck but is then open honeycomb on the top. Don't know how to deal with that. It is cheap enough and weighs nothing. I may consider using it on the bottom of my next board. I'm thinking one layer of 4 oz glass over blank and one layer 6 oz over the honeycomb , ( instead of 2 x 4 oz ), should be enough for the bottom lam ??? Also the double sided honeycomb is smooth so doesn't absorb resin like sandwhich foam. Almost no bog needed . I wonder how good resin bonds to it ? It should stick , it is designed to be used with resin. I'm sure it would be good for stopping negative rocker deformation happening at the back of the board.

Is it worth doing this ???

I gather you mean nomex honeycomb?
Helps with fire resistance also Daffy (too soon....?)

JP did it in some speed boards so its worth a bash

Select to expand quote

Imax1 said..
^^^^People have used honeycomb for the sandwhich. I was thinking of using it but it only came minimum 6 mm thick. It also came single skinned or double skinned. The double was very stiff , good for the bottom of the board. I had a fondle of an off-cut and was surprisingly strong on its own. I think the skin is resin soaked paper ? The single sided stuff would be good for the curved deck but is then open honeycomb on the top. Don't know how to deal with that. It is cheap enough and weighs nothing. I may consider using it on the bottom of my next board. I'm thinking one layer of 4 oz glass over blank and one layer 6 oz over the honeycomb , ( instead of 2 x 4 oz ), should be enough for the bottom lam ??? Also the double sided honeycomb is smooth so doesn't absorb resin like sandwhich foam. Almost no bog needed . I wonder how good resin bonds to it ? It should stick , it is designed to be used with resin. I'm sure it would be good for stopping negative rocker deformation happening at the back of the board.

Is it worth doing this ???

I once owned a 276 slalom board from Drops with Nomex inplace of sandwich foam. The board was super light and super stiff. Even too light for me, as it suffered a lot going over choppy water. I thinkk that was because of too little momentum, it tended to brake on each chop crest and needed to be re-accellerated again.
Once it started delaminating in the deck, due to a hit with my foot (!!!), it would not stop: when I pressed around the damaged area it would do a crick crick sound and delam would expand. So I had it changed with a "regular" full carbon sandwich version of the same board (it came in 3 versions: standard, full carbon, Nomex) which was about .5 kg heavier and that one sailed much better and was plenty strong.

As for negative rocker developing in front of the fin box, I am very happy with the Kinetik construction which incorporates multiple stringers in that area. My m? boards used to have 2 of those, my FMX's 3. It seems to me it works perfectly well.

Select to expand quote

geoITA said..

Imax1 said..
^^^^People have used honeycomb for the sandwhich. I was thinking of using it but it only came minimum 6 mm thick. It also came single skinned or double skinned. The double was very stiff , good for the bottom of the board. I had a fondle of an off-cut and was surprisingly strong on its own. I think the skin is resin soaked paper ? The single sided stuff would be good for the curved deck but is then open honeycomb on the top. Don't know how to deal with that. It is cheap enough and weighs nothing. I may consider using it on the bottom of my next board. I'm thinking one layer of 4 oz glass over blank and one layer 6 oz over the honeycomb , ( instead of 2 x 4 oz ), should be enough for the bottom lam ??? Also the double sided honeycomb is smooth so doesn't absorb resin like sandwhich foam. Almost no bog needed . I wonder how good resin bonds to it ? It should stick , it is designed to be used with resin. I'm sure it would be good for stopping negative rocker deformation happening at the back of the board.

Is it worth doing this ???

I once owned a 276 slalom board from Drops with Nomex inplace of sandwich foam. The board was super light and super stiff. Even too light for me, as it suffered a lot going over choppy water. I thinkk that was because of too little momentum, it tended to brake on each chop crest and needed to be re-accellerated again.
Once it started delaminating in the deck, due to a hit with my foot (!!!), it would not stop: when I pressed around the damaged area it would do a crick crick sound and delam would expand. So I had it changed with a "regular" full carbon sandwich version of the same board (it came in 3 versions: standard, full carbon, Nomex) which was about .5 kg heavier and that one sailed much better and was plenty strong.

As for negative rocker developing in front of the fin box, I am very happy with the Kinetik construction which incorporates multiple stringers in that area. My m? boards used to have 2 of those, my FMX's 3. It seems to me it works perfectly well.

Do you know if the honeycomb skin delaminated from the honeycomb or the fibreglass delaminated from the honeycomb skin ?

Looks like it's up to you imax

Select to expand quote

lemat said..
Yes on this one i make all the dagerboard system.

So impressive.

A friend builds longboards, tandems, shortboards and it's the longboards that impress me the most. you gotta have skills to build a longboard from scratch. Not sure I could do it.

Regarding Honeycomb, I built 2 wave boards with it a few years back. Made a short video of the first one including some sailing(think I posted it before). First board was 5.3kg, second 4.8kg. Still got the first one (after repaired damage in the video), second lasted a few years then it started to fall apart. Some of the drawbacks is that it handels dings porly, walls of the honeycomb colapses and if it start to take water it rather quickly travells through the cells. But rather easy to repair if inner laminate is ok, just cut outer laminate with a knife and then remove honeycomb, glue new one inplace and finnish with new outer laminate.

Good day everyone,
I have a question about the sandwich structure :
I windsurf in China and I bought in a trip to Singapore an old JP XCITE 145 from around 2007 with the cabon fiber construction, for very cheap.
When I bought the board I did not realised that the deck was entirely soft between the front foot straps and the front of the mast track.
I have decided to do the BOARD LADY extensive soft deck repair and I cut and removed the deck in the soft areas.
I am about to start the reconstruction.

I have noticed that the sandwich is made with :
- 1 layer of fiber glass 2 directions at the bottom of the sandwich : length of the board and 90 degree of it
- 3mm of PVC
- 2 layers of unidirectional carbon fiber in the direction of 45 degrees of the length of the board

I would like to rebuild the deck identically but I don't understand why the deck is made with fiber glass at the bottom of the sandwich, and with just 1 weak poor layer of it.
the fiber glass will work in pulling as my weight presses on the deck while the carbon fiber on the top of the sandwich will work in compression.
The fiber glass is much weaker than the carbon fiber in pulling, so why is there fiber glass on the bottom of the sandwich and carbon fiber on top and not the other way around ?
I can see on the Carbon Art website that they do the same so it must be the way to do but I don't understand the physics behind.
Why not carbon fiber on both sides of the sandwich (if budget is not an issue) ?

I have attached some pictures.
Cheers

my 2cents worth.
There isn't as much force on the inside layer as the top.
The top layer also needs to protect the PVC from denting under foot presure

The carbon is at 45deg so it allows a little bit of longitudinal flex, so the glass can take some of the load, it also helps stop the board twisting under sail pressure torque

The glass layer serves to stiffen the pvc foam, holding it place to better support the carbon layer. The carbon layer, being much higher modulus carries all of the bending load of the board, but can only do so if it keeps its shape (due to support from the core and sandwich)

Select to expand quote

BjornD said..
Regarding Honeycomb, I built 2 wave boards with it a few years back.

That looks like a really nice build Bj?rn, plus a nice spot-guide of Sweden. :)

Are you making custom boards commercially or is it only for your own enjoyment?

JBYaoCan, the glass under the PVC is not quite as important. You have now pulled away so much polystyrene that it needs filler. So given the age and condition of the board, plus it won't be subject to stress like a waveboard - easiest to fill all that with resin and q-cell mix to get it flat, then the PVC straight over the top with no glass under the PVC.
That is the best way of a decent result for beginner.
Then 3 x layers of 4oz glass over the top with maybe a carbon patch just where you will stand when gybing

This will be heavy - but its better than the alternative 'correct' way with lots of products that will cost more than the board