Hi,
Reaching out to the other side of the world since I understand there are a few longboarders on this forum. I've got hold of a course racer from 1991 but it has no daggerboard and I wonder if anyone has some drawings to share (or a 3D-model)? The board is a Guy Liljegren 380 production board, I guess similar to Cobra 380, Fanatic Ultra Cat etc. It would be fun to diy a wood/fibreglass dagger just to get the board out on the water :). Cheers from Sweden - land of cold weather and little wind.

Hi, I have made a few centreboards for raceboards. When old raceboards are stored for years the centreboards sometimes get lost.

You can use the same process and materials used for making dinghy centreboards, there are some good sources of info online that detail the manufacturing process. I use red cedar or foam core and vacuum bagged carbon fibre laminate.

The NACA profiles are a reasonable starting point and are also available online. NACA 9 or 10 should be OK.

The size and outline of the centreboard may be constrained by the centreboard case. I am not familiar with the Guy Liljegren boards, can you post a photo?

Can be helpful to see a pic of the original centreboard to see how the headstock was shaped as well.

Select to expand quote

azuli said..
Hi, I have made a few centreboards for raceboards. When old raceboards are stored for years the centreboards sometimes get lost.

You can use the same process and materials used for making dinghy centreboards, there are some good sources of info online that detail the manufacturing process. I use red cedar or foam core and vacuum bagged carbon fibre laminate.

The NACA profiles are a reasonable starting point and are also available online. NACA 9 or 10 should be OK.

The size and outline of the centreboard may be constrained by the centreboard case. I am not familiar with the Guy Liljegren boards, can you post a photo?

Can be helpful to see a pic of the original centreboard to see how the headstock was shaped as well.

All I have is a side pic. I traced the centreboard and the Naca 9 but I have no idea about he headstock. I think I need to make a mockup to find the right shape. I suppose the Naca is the profile at the start of the cb and that it is more or less the same on the leading edge. I'll search foor some 3D cb's to get inspiration from. :)

There are centreboard dimensions in the lower right corner of the page:
1. "Utstick" : 66.5cm - I think this is the length measured from bottom of hull to tip of cb.
2. "avstland fran aktem till framkant" : 147cm - not sure what this is. Maybe distance from tail of board to cb leading edge?

Select to expand quote

azuli said..
There are centreboard dimensions in the lower right corner of the page:
1. "Utstick" : 66.5cm - I think this is the length measured from bottom of hull to tip of cb.
2. "avstland fran aktem till framkant" : 147cm - not sure what this is. Maybe distance from tail of board to cb leading edge?

yep for both.
That's what I used when tracing the profile from the side. I need to study the Naca profiles and profiles in general. Nice tips about Naca, didn't know that there are lots of info about profiles downloadable. I figure I model the cb in Rhino3D and at the base I use the Naca 9 and then it kind of shrinks as I make horisontal section cuts every 10 cm. I have a laser cutter at work so I can create cardboard moulds for the profile.
:)

Can you take pics of the CB case of your board from top and bottom ?

It is also helpful to make a full size template out of a stiff material like cardboard / coreflute / plywood to check that the board will fit in the case and the head stock protrudes the right amount for actuation with foot, and does not foul with mast track pedal or other deck gear.

Should be able to calculate aspect ratio / chord of the foil from the photo based on the protrusion length (650mm), but may be able to go a bit bigger, if the CB case allows it.

The CB length seems shorter than my F2 Lightning and Phantom, but the board width is also less. A comparison of board dimensions listed here (missing some of the newer models): http://windsurfraceboard.blogspot.com/p/boards.html.

Bigger boards will give more lift and upwind performance in light winds but will increase the heeling moment, and make the board rail up in stronger winds, so probably best not deviate too much from the original size.

Select to expand quote

DasM said..

azuli said..
There are centreboard dimensions in the lower right corner of the page:
1. "Utstick" : 66.5cm - I think this is the length measured from bottom of hull to tip of cb.
2. "avstland fran aktem till framkant" : 147cm - not sure what this is. Maybe distance from tail of board to cb leading edge?

yep for both.
That's what I used when tracing the profile from the side. I need to study the Naca profiles and profiles in general. Nice tips about Naca, didn't know that there are lots of info about profiles downloadable. I figure I model the cb in Rhino3D and at the base I use the Naca 9 and then it kind of shrinks as I make horisontal section cuts every 10 cm. I have a laser cutter at work so I can create cardboard moulds for the profile.
:)

A CNC machine makes it easier to cut the profile, however you can get a reasonably symmetrical shape by tracing the foil profile on the end of the blank and using a router to run grooves along length of board to the depth of the foil profile at say 15mm intervals (stations).

If using solid wood plank it should be split into strips, then end-for-end alternate strips and laminate together with epoxy to prevent the board warping.

Select to expand quote

azuli said..

DasM said..

azuli said..
There are centreboard dimensions in the lower right corner of the page:
1. "Utstick" : 66.5cm - I think this is the length measured from bottom of hull to tip of cb.
2. "avstland fran aktem till framkant" : 147cm - not sure what this is. Maybe distance from tail of board to cb leading edge?

yep for both.
That's what I used when tracing the profile from the side. I need to study the Naca profiles and profiles in general. Nice tips about Naca, didn't know that there are lots of info about profiles downloadable. I figure I model the cb in Rhino3D and at the base I use the Naca 9 and then it kind of shrinks as I make horisontal section cuts every 10 cm. I have a laser cutter at work so I can create cardboard moulds for the profile.
:)

A CNC machine makes it easier to cut the profile, however you can get a reasonably symmetrical shape by tracing the foil profile on the end of the blank and using a router to run grooves along length of board to the depth of the foil profile at say 15mm intervals (stations).

If using solid wood plank it should be split into strips, then end-for-end alternate strips and laminate together with epoxy to prevent the board warping.

Thanks for your great suggestions!
I will make the full size template for the head stock and for the watery part I think it's easiest to geet a "smooth looking" profile in Rhino and then sand my way to hapiness. May even result in me buying a nice new electrical tool :). Strips is a great suggestion and I'll go with that and cover it with fibreglass+polyester...or does it have to be epoxy?

I think the rig issue will cost a bit more more than this little fun project... I saved this board and also a tornado Div2 board from destruction and it didn't cost me anything...however trying to find rig 8.5-9.5 suitable for both seem tricky. Sailloft Traction is the only sail I've identified as a contender so far and it can't be found used in my area. I usually ride wave boards and there's an abundance of used wave equipment in good condition but raceboard stuff is almost nothing. I have nice wave masts and can get 4 used Simmer Icons 2018 for the same price as the Traction Rig... On the other hand I can wave sail just a few times each year (I logged 5 sessions 2018 and 8 sessions 2017...much work combined with awfully wind poor Sweden). Maybe I need to treat myself...hmmm...

The Guy 380 was tested along F2 Lighting, Mistral Equipe and the other 1990 and it got full ratings in everything race related. OTO 1990 was the year when board graphics suddenly changed from white with a few stickers to full colour print. BIC Bamba,,,:)

Epoxy is much better. Considering time/effort required to make a decent centreboard, it pays not to comprise on materials.
I have PDF doc that provides good description of foil build process that I can email if you PM an email address.