Stuck on 36knots in flat water on my slalom board 58 wide. Am I going to be
any faster on a speed board ? Approx how many knots ? Any throughts
anyone. Cheers
Depends. Best thing you could do is get a proper speed fin if you don't already. Something around 25-26cm. That should add a few knots on in ideal downwind conditions - but make sure you're sailing very broad and overpowered. Ultimately, you need to work out if a speed board will be used enough to justify the expense. I think the answer you're looking for is yes, a speed board will always be faster than a slalom board in good-ideal speed sailing conditions because of the reduced water and wind drag, flatter trim and optimised outline and rail profile.
The other question you need to ask yourself is "Am I having enough fun sailing at 36knots on my slalom board?" or do you want to aim for the best speed you can achieve in most conditions and sacrifice other things like upwind performance, safety when the wind drops out, ease of gybing, performance in chop etc.
I have both. Covers all scenarios. Hope this helps. 
Is jumping on say a 44 CA with a 24cm fin and a 6.2 sail (use this mostly) going
to increase my speed by 1 or say 5 knots approx ? Trying to justify buying one.
IF you have the right conditions.... flat water and plenty of wind IMHO it will make at least a couple of knots difference. In choppy/ gusty conditions you may not go any faster. Only based on personal experience.
Thanks guys.Normally use 32 techtonics. What brand/size speed fin do you recommend for a 58 slalom ?
Speed boards definitely quicker by a good 3-4 knots in the right conditions.
I also hit a wall at 36K on my slalom board, admittedly it was a Manta 59 which has a widish tail. This was in a nuking 30K+ seabreeze on pretty flat water (Woodies Point).
www.gpsteamchallenge.com.au/sailor_session/show?date=2009-02-04&team=12
I bought a CA47 a week after that session 
Had to wait 9 months for a decent breeze to fire it up in anger and this was the result...
www.gpsteamchallenge.com.au/sailor_session/show?date=2009-11-19&team=12
A 2 knot improvement in peak and average.
Three months later I got a 40 on it
www.gpsteamchallenge.com.au/sailor_session/show?date=2010-02-02&team=12
So no regrets, glad I made the investment. If you can afford it, go the speed board. At your weight it will get plenty of use.
