I’m looking to purchase some PU blanks to attempt to make some hand shaped boards but having trouble finding a definitive answer as to how much thicker I should order the blank compared to my desired outcome thickness. I will be using an electric planner. My desired thickness will be 2 1/2" so how much extra do I need to skin the blank and shape it down assuming the rocker in the blank is similar to what I want?
Thanks very much for any input!
I’m not sure if your trying to point out the max thickness measurement? I was assuming the max thickness meant the blank before being skinned but I have no idea what I’m doing. I’m ordering from this place http://www.southcoastfoam.com.au/product/6-3-b-shortboard-blank/ and I thought that 2 3/4" in the diagram and max thickness was before doing any mowing?
If the blank is undamaged - no gouges, dents, etc. the closer to your finished shape the better. If you can just barely skin the deck and sand it, the resulting strength will be optimal. I suppose if you could just leave the crust on it would be stronger still but aesthetics come in to play and most would agree it’s nice to have a smooth clean surface to glass over.
The farther you mow in to a blank the softer the foam gets… that’s the case with most urethane blanks made in the USA.
Anyway, check the catalog link Bud posted and try to get as close as possible to your final thickness. It’ll be stronger in the end and will require less shaping.
EDIT - just saw your latest post. Australian foam formulas might be more consistent throughout.
Thanks for that John!
As far as I know Australian foam suffers the same problem and is weaker the deeper you go.
So just to confirm before I throw some money down on some blanks, that max thickness measurement on the blank websites is after you have skinned the blank and done some minimal shaping?
Why not direct these questions at the blank manufacturer? I’m sure you’d get a better answer.
On board 1, if using a planer, more foam is better. Gives you a chance to make more passes and get a feel for the planer and the foam. At least that’s my opinion.
Just call or email South Coast. They will answer your questions. Lowel
3/8" to 1/2" extra thickness to work with to get to your finished shape should be adequate, as long as you are not changing the rocker more than that.
the measurement shown is the actual dimensions of the blank.
…mostly you are answered by the other members and that your question depends on your ability; technique etc.
Seems that this is your first attempt; sometimes in this scenario is better to have more foam; however, more bulky plugs are a no no for some designs due to too much foam on the tail and nose; regarding that, think about what type of board do you want to shape then research for the plug or plugs.
Planer technique is very important. If you do not know how to use it properly, better to go with a bit more foam (again, check the plugs and your design, cause some factories have couple of plugs that are thick in the middle area but not so much on the nose and tail; check the rocker too)
In your case and if you are not familiar with the plug or do not have enough experience, is better to use shallow passes instead of deep ones. Also, some foam and some densities do not like deep passes and speed in the movements.
Go with the “normal” density provided by the factory (Aussie foam is lighter than US foam)
Most of the times I have customized blanks so I know what to do before start. I suggest a bit more thickness only in the middle area but check for the rocker measurements regarding your desired shapes (its better to not change the rocker if you do not know exactly what s doing) and clean the blank to get almost the wanted thickness from the bottom.
If you think right and only do shallow slow passes (and a blank without holes etc) you would not have problems with the thickness (close tolerance thickness)
First, check the rocker for bumps etc; true in the blank; leveling etc; then start to shaping.
Thanks huck thoose measurements are exactly what I was after!
Go get 5 old second quality blanks off southcoast for 20 bucks each and see for your self. The only real way to know is to have a go. Most of my personal sb aee 2 1/2 and I usually shape them out of a 6’3" 3" blank. By the time you skin it, cut in concave etc its not hard to get down to where you want to be.