Finalising #001 design. Comments, please!

General Discussion
1

Swaylockians!

I’m fishing for opinions on my #001 design.

Background:

It’s for a 5’6" female rider who weighs 55-60 kg (120-130 pounds). And is married to me. So I cant afford any mistakes :wink:

She wants to go to a longer board and 8’6" seems like a good step up for her. More length/volume but she should be able to handle it without much hassle using compsand. I’ve opted for a “fairly traditional” design as she wants something she can start doing a little logging on, but still turn. So…

I have already promised that I won’t ride it myself… Except to test it out ;D Honest! :slight_smile:

Design:

8’6", square 5 1/16" tail, 14 3/8" at 1ft, 22.5" widepoint around 1" back of centre, nose 17.25" 1ft back. Mostly flat bottom. 2" thick. Turned down, sharp rails in the tail starting to round out at 1ft going to 50/50/egg at midpoint. 10" finbox and FCS for sidefins to allow some flexibility.

CAD:

I’ve found APS3000 useful for getting my ideas into an environment where I can see it and have attached my current BRD file in case anyone feels like looking at it. Keep in mind that I could have spent a whole lot of time on the design but didn’t. So there may be some things in there that aren’t exactly what I see in my mind’s eye.

Look forward to hearing any and all opinions and feedback!

Thanks and best regards.

-doug

2

Hi Doug, one thing she might really like is if you move the widepoint nearly a foot back. The hips will make it turn much easier than a parallel plan, and the shoulders will be narrower which will be easier for her to paddle.

(caveats: I can’t open your file, so I’m just guessing that it isn’t already this way; and if she’s a swimmer with superwide shoulders already, don’t worry about the pulled in front end :slight_smile: )

3

Hey Other Doug! It sounds like a good design. My only suggestion would be to make it a bit thicker. 2" seems a little thin to me. If it was for my wife and she weighed 120-130 pounds, I’d go with at least 2 3/4". Some decent V in the tail is good to facilitate turns, and I would recommend subtle double concaves for 18" at the tail. Keeps it loose. Doug

4

hey doug,

all looks great to me, and i agree with adding a little extra thickness. what about rounding out the tail a little bit? maybe a squash, or completely round? i have a 7’10 mini log that is a rounded pin, and it does all that you are talking about.

although, i have to admit it is more looks for me than anything, nice long clean curves.

5

Very nice

6

Yeah I had though of rounding out the ail a little. For the moment I have gone with the square tail for a little bite and simplicity. But I havent really made my mind up there yet. And the squash does look nicer… Anyone else have any specific thoughts on this?

Thanks for the feedback so far!

-doug

7

Looks nice Doug, although I don’t know anything about longboards so I can’t really comment on how it would perform. With the rails you’ve got in the .brd file, if you’re doing compsand with 12-16mm wide bala rails, then your rails aren’t going to be very deep. Even if you go thicker in the centre, at 8’6" you won’t have a lot of strength in the rails, so the skin will have to be engineered against snappage. You might consider something like Sab’s top hat, or say a 5mm top skin to give the board a bit of strength.

Are you going to hotwire the profile yourself, or get it done on a cnc hotwire cutter?

8

2 inches thick will snap, sure. Better to go somewhere on the high side of 2.5, say 2.75 or close to it.

I intensely dislike throwaway boards.

9

Pinhead,

I was going to go around 5mm balsa deck and thinking of up to that much again on the bottom (undecided eactly how mauch so far).

Hhhmm… Perhaps a flatter deck might be a good idea? Will certainly make hotwiring easier too!

-doug

10

Charlie,

Seems to me pinhead is saying even a bit of extra thickness in the centre isn’t going to help.

I find myself wondering how Bert does 2" thick “bulletproof”… Flat deck perhaps. Time to hit the archives!

And yes. Throwaways suck.

-doug

11

Doug,

Because you don’t have a centre stringer with compsand boards - extra thickness in the centre won’t in of itself add much strength - However if you add more thickness to the centre and keep the rails thin ie dome the deck, you will put more stiffness into the skin by virture of its shape. Alternatively if you thicken the rails, you’ll get more strength from deeper therefore stiffer “beams” in the perimeter stringers. These are two ways shape will influence the mechanical properties of your board. But the best approach is to engineer strength with the skins so you can have whatever rail shape and volume distribution you want. That’s why I suggested you look at Sab’s top hat technique. The 5 mm thick top skin might do the trick - the archives will tell.

12

Just sat here kicking myself for a few minutes :slight_smile:

I thought I had read the entire “[=1][ 2]solid balsa rails – what’s your technique?[/][/][=1][ 2]” thread properly. And now I feel like an idiot.

On the upside I feel like my understanding of how I achieve things has just increased by an order of magnitude.

NOW the problem I have is figuring out how exactly I am going to implement this :smiley: hehe! That’s OK, construction is still looking like a month or two off so I have some time to digest this properly and figure out how I am going to try to implement it.

For the moment I am thinking 5mm deck skin, 3-4mm bottom skin and emulating what sabs has done in the thread above. Can’t see any mechanical point in using anything but diamonds. And 20mm x 5mm with runnoffs sounds quite reasonable. Going to have to do a couple rough scale drawings and see how it looks to me.

Thanks pinhead. And thanks sabs! You you both heaps (along with everyone else on here).

-doug

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13

hi doug i made my 8 ft mal 2 1/2 including skin

2?@inches is probably too thin and not neccessary for flex on a longboard shape

2 1/2 thick with a slight concave in the deck would be my approach

maybe less if you use thick skins

14

Doug,

Also check the latest work of Meecrafty, Silly, Pauluk, Benny, Oneula, CMP and Yoshio (and obviously Bert) those guys have done the hard yards on balsa compsand longboards. Sabs has got the boatbuilding chops that have got him from a-b a little quicker. My compsand shortboard works very welll, but I went for small wave fish type board, which has more room for error with compsand construction. My next one is going to be a semi-gun which presents a few design challenges so I’ll need to consult the sages for advice.

15

Hey Paul,

I seem to be getting talked into this :smiley: How does 5mm top and bottom with 2" core sound? That’s going to be just under 2 7/16" in materials and probably ever so slightly over 2 7/16" when fiberglass, etc is taken into account.

Currently I am looking down the barrel of:

5mm skins - wrapped over the rails

tophats - I really like this idea

a smudge under 2.5" total thickness

Would you mind expanding a little on the concave deck?

Thanks again!

-doug

16

Cheers pinhead.

Thought I had been keeping track of their work. Obviously it’s time for a review :slight_smile:

Thanks again,

-doug

17

hi doug sorry been away surfing for a few days

lets get back to it

I think that those measurements sound great

I think your core could be 2 1/4 for a 9 footer though

Let me know how the tophat idea works

I built a longboard first exactly as per bert instructions

pre glued the skins

and i still like its flex characteristics the best

it has 15 mm balsa stringers on the rails

3mm deck and bottom core

its about 2 1/2 thick maybe a bit more

and there is a concave in the deck of about 8 mm

18

NP Paul - hope you got a stack of nice lines!

Hhmmm… so 2" core for an 8’6" (for a smaller chick) doesn’t sound any good to you?

Looking into the concave deck thing now… Whether I update the APS .BRD file depends on how long things take and whether I feel like playing with it some more :slight_smile:

-doug

19

hey doug

cheers yeah it was pumping

um measureing things has never been a strong point of mine

i tend to go by feel and look

what i do think is that a little extra thickness in your shape and materials isnt gunna hurt

Bert is the master for sure hes deffinately posted in the archives

the thickness of some of his longerboards.

my understanding is that a slight increase in core thickness makes a compsand board stiff

however the extra length and parallel outline of a longboard compensates for this somewhat.

my 8 ft mal finished at 2 1/2 with 3mm skins and it felt perfect(not overbuilt at all)

so the 5mm deck may be enough strength wise to compensate for added length, or you may need to add a bit more to the core or the balsa stringers

if it was me id go a bit thicker in the core

id do the bottom skin first then the rails

id then check its flex characteristics before i made the call on the deck

if it was reallly floppy i might put another 3mm on the rails and see what it did

or perhaps just make a call on a thicker skin… your already planning 5mm so maybe go further with sabs top hat idea would be next .

Bert and the other guys may be laughing at what im telling you though

so watch out im just saying whats working for me

or sometimes doesnt.

aim for strength in the deck skin

and you should be sweet

one thing compensates for another

change one and you change the other

hope that doesnt add to the confusion mate

20

G’day Paul!

Glad to hear you got some wave action!

Yeah, I have been pondering this whole #001 over since I’ve posted it. Really glad I did post it, in fact. The feedback has been really useful. Along with the Neutral Axis thread I am reconsidering a number of things.

I have recognised that I need to narrow my field in a number of areas so that I can make progress going ahead and still produce rideable boards early on. I may wake up with a knife between my ribs if this is a lemon :wink: Firstly I am going to restrict myself to boards 8’+ for a while (I’m mostly a longboarder so I am happy with that as a starting place). Secondly I am going to start with relatively simple construction that’s worked for a number of others. So far that looks like being minimum 2.5" thick, no wrapped rails, no T-hats, no springer, 2 EPS. Preformed skins, probably 5mm top and 3mm bottom. 3x 5mm thick rails to start. I like your idea about adding more to the rails if I really have to (before the deck goes on) - thanks for that tip. Still working through the archives and getting my “starting formula” togethor, so all advice and input still welcome :slight_smile:

Thanks for sharing your opinions and ideas. If the other s are laughing at the advice you have given me, don’t worry. It’s not you they are screwing with - it’s me :smiley: Lucky for me I give up about as easily as Pit Bull |^D

-doug