Im wondering how you shape a bonzer type of concave? Ive done lots of shallow double barrel concaves by hand with no problem but im wondering how you get that deep symetrical gullwing shape bonzer concave?
Mike Eaton has a drum air sander that he uses to create the narrow/deep concaves
If you glue some sand paper to a rolling pin and hook the rolling pin up to a drill moter, that should do the job. I would think that if you kept one of the handles free, you could then use both hands to help guide the rolling pin. Just a thought.
…a coke can.Herb
Rich Pavel bonzer:
Does anyone have guidance, diagrams or close up photos of the bonzer concaves I could look at please? I want to make one, but despite the number of pics of the boards online I am yet to find one which shows the profile closely enough to try making one. I have coke cans, rolling pins and sand paper at the ready, but not sure where to start with the shaping so looking for any help I can get here, pretty please you wonderful people 
Mr Skelter , the bonzer concaves are not all exactly the same it depends in part on the size of the board , when the Campbell bros developed the Bonzer concept they did it by trial and error and ended up with what they thought was IN THEIR OPINION the optimum combination of concaves and fins , other well known board builders have also successfully made their own versions of the bonzer using IN THEIR OPINION their own combination of concaves and fins , there is no one absolute combination that works for all boards and for all surfers , in the spirit of Sways perhaps you should go down your own road and develop your own version of the Bonzer for your size board your own surfing style on the waves that you surf , you will learn more and end up a better board builder and possibly a more knowledgable and better surfer , this is not meant as a put down but encouragement , don,t just follow and copy others , you may well come up with IN YOUR OPINION a better Bonzer and if you do tell us about it post pics .
The above, is about as well said, as is possible to do.
There used to be some very clear pics on the surfy surfy blog, and if you search the archives, and the internet, you should be able to get a pretty clear picture of what others have done. As I recall Malcolm has said that Bonzers work even without the channels.
Thanks very much, there’s no way I would deem that a “put down”, it makes perfect sense. The only problem is that this is being made for someone who wants a bonzer, first board for a non family member. So I am trying to stick to the Campbell bros version as much as possible, while shaping it myself, no templates etc, just by eye but I need a starting point. Its a 3 fin, so i think two deep channels either side of the stringer with plenty V in the stringer, is roughly correct. I can see the tail of some of the boards (so I can see the channels) BUT, I have no idea (and can’t find any pics) what happens further up the board. Does it go to single concave around the mid point, and up into the nose area or… ? That’s sort of where I am. I am going with two channels and V, but where to go with it at the mid point is where I am a bit stuck.
Thanks again, and your point is totally cool with me and will apply to my next board which will be a more experimental bonzer style build for MYSELF, so i can play around with ideas more, but this one needs to be as close to a traditional original bonzer as poss. Any pics or diagrrams of the Campbells contours would be handy, I will keep searching online.
Appreciate your time replying
Thanks Huck. I have read all the threads on Sways and found the links to that mentioned by several people, but the threads are dead. I went through their archives and can’t find it either :(.
Very curious about the last point you made… “Bonzers work even without the channels” - Forgive me but if it doens’t have those channels, lets say it’s got a flat bottom, what makes it a Bonzer?! I thought it was the channels, but maybe it’s those cute sidebite fins? Grateful to know what you think makes a board a bonzer?
So you’ve read all the Bonzer threads in the archives and still haven’t figured out fin shape and placement are a key element of the bonzer design?
Did you go through the archives over at surfysurfy.net as I suggested? If so you should have a pretty clear picture of the bonzer channels and fins. Also a pretty good interview with Malcolm explaining a bit about the history and the concept behind the design
Yes I have read them all (several times) and yes I have worked out that “fin shape and placement are A key element of the bonzer design”. My question to you (unless this is your answer) was what makes it a bonzer without the concaves, if you’re saying “fin placement is what makes it a bonzer” then that helps. In all the threads I have read, it seemed like everyone referred to a board by its concaves as what made it a bonzer. Maybe I misunderstood that, sounds like I did now. Every bonzer i saw on here had nice countoured channels in the bottom so i (perhaps wrongly) assumed that’s what made it a bonzer.
“Did you go through the archives over at surfysurfy.net as I suggested?” - Sorry, my mistake. I saw a lot of people referring to http://forum.surfer.com and that’s what I thought you were referring to. I just looked at surfysurfy and i haven’t been there before. loads of great pics, not found any of a board being shaped yet, but it looks like just a list of boards for sale. I am going through the archives and “bonzer” category but still so far just sales. I can work off those images when I find enough to see the bottom shape up around the middle, but was hoping there might be a bonzer thread on here showing someone’s stages for building it, shaping pics etc. There were loads from 10+ years ago but the images are all dead unfortunately.
thanks for your input
Bottom channels and fin shape/placement are the elements of the bonzer design. You could do the fins without the channels. You could do the channels without the fins. As gbzausa pointed out, you can do whatever you want.
If you looked through all the bonzer photos in the surfysurfy archive and all you could see is a bunch of boards for sale, then I really don’t have anything more to add. I’m not a bonzer advocate, expert, or aficionado. I did build one long ago, and I liked the way it rode. I studied the archives here, and the pics on surfysurfy, and gave it my best shot.
I just tried to direct you to a source with helpful photos and information. If there’s nothing there helpful to you then maybe you might want to focus on a different design / fin setup, with better or clearer explanatory documentation.
Looking at these pics on surfy I am getting a better idea, thanks Huck.
I am still looking for a build thread for a 3 fin, need to work out where the side bites are best placed so I can start shaping. Will keep looking but if anyone has any diagrams or know of any threads please drop a link. thanks
PS - I did find this a while back on a thread:
But not sure which of the red lines applies to a three fin (if either of them apply). also not sure of the toe in angle for a three fin design
Yes and your direction helped thanks. No, i can’t change. I have been asked by a good friend to make him a bonzer and said I will. I know the length, width, general nose and tail shapes he wants, and that it needs to be a 3 fin. I will keep digging, this thread was part of that process. I will get there. thanks
You did check out the campbell bros website, right? There’s a ton of information on that site, yet strangely not too much about mid point forward. https://bonzer5.com/
The site has some valuable videos and images, i suggest you look long and hard. Of course, these are mostly focused on the more ‘modern’ bonzer. IMHO, the way these are being surfed, with a bit of slide, I would guess the nose and mid point are pretty much flat, going into a wide single convave somewhere behind mid point.
Hopefully this helps. Three fin bonzer. Look at the concave in the middle: https://www.youtube.com/embed/9XcfX4-1ZbA?
Here is one being shaped, watch this vid: https://player.vimeo.com/video/245073689
Great video with Taylor Knox on board: http://view.surfline.com/WI-5/
Here’s a CI Biscuit/Bonzer combo, explained by Malcolm, seems like bonzers are classified as utilizing the diagonal movement of the water, using a wide based set of side fins which are also canted outward. Vee in the tail as well as the double concave. Interesting, the CI biscuit looks like it uses a lot less of the concave: https://player.vimeo.com/video/201372007
Also, thanks for your interest in the bonzer. Now I think I want to try one.
Ha ha, good for you! Dying to see how mine turns out! Thanks for some great links there. I have been to bonzer5.com several times, none of the menu items suggest videos are on there. I browsed the pages and didnt see much, but will go look again. I read someone say they have forums and all sorts, but the menu at the top just looks like any standard shop type website. I must have missed the good stuff so will go find it.
3 fin for me. Hoping to find a decent idea of toe in. I read most peolpe are doing 1/4" toe-in but I am sure I read (a long time ago) something by Malcolm Cambell talking about pointing the runners at the nose or even beyond it. Need to decide my toe in before I shape the bottom concaves, i have just about finished shaping the top and bottom (flat, ready for some rolling pin action!)
thanks again, and hope to see your pics soon!