Catsailor.com The Man Shed News
Posted By: TheManShed The Man Shed News - 03/01/10 08:33 AM
There was action around The Man Shed today. Caught a slight break in the weather it was in the mid 60’s today but chilly tonight. Got the crew together and laid up the port side of the main hull. It may take a few days to fully cure so I'll go back to working on the connecting beam jig. I tried several methods of covering the frames. Looks like I'm going to fill the gaps with foam and fare it down. I could not get bendy plywood or 1/8" foam to wrap around the sharp radius of the ends. If the jig looks long it is. The beams will be 17 feet long the jig is 18 feet long. With the second half of the main hull laminated I’ll have plenty to do now. I'm also thinking of making curved boards that's still on the sketching pad - but I have a plan.
Description: Cutting carbon
Description: Bagged out
Description: Connecting beam jig
Posted By: erice Re: The Man Shed News - 03/01/10 11:24 AM
imho
get the #1 boat going with standard boards first before going for banana boards
tri's find it hard enough to go to weather well without having curved boards as well
if you start tweaking without having 1st established a base line you'll have too many variables
Posted By: Jake Re: The Man Shed News - 03/01/10 12:49 PM
you could also build the trunks like the latest a-cats - they can accomodate straight or curved boards. The top and bottoms of the hull are shapped to the board profile. The trunks inside the hull are simply big and flat with plenty of free play.
Posted By: TEAMVMG Re: The Man Shed News - 03/01/10 01:43 PM
The structure of the beams needs to take into account the possibility of banana boards.
Righting moment is the same as straight boards/no boards, but loadings are different.
Posted By: TurboCat Re: The Man Shed News - 03/01/10 02:02 PM
Looking good Mike!
you could also build the trunks like the latest a-cats - they can accomodate straight or curved boards. The top and bottoms of the hull are shapped to the board profile. The trunks inside the hull are simply big and flat with plenty of free play.
So like a box that you exchange the top and bottom on(permanently), depending on the board?
Keep at it Mike.
Posted By: Jake Re: The Man Shed News - 03/01/10 02:30 PM
you could also build the trunks like the latest a-cats - they can accomodate straight or curved boards. The top and bottoms of the hull are shapped to the board profile. The trunks inside the hull are simply big and flat with plenty of free play.
So like a box that you exchange the top and bottom on(permanently), depending on the board?
Keep at it Mike.
Nope - you don't change anything as long as the foil cross sectional shape is the very similar between the straight board and the curved board. The deck and hull bottom openings are thin so they don't interfere with either board shape as it goes through the opening. The trunk is fat enough to contain the curvature of the banana board and the upper / bottom openings hold it just the same.
Posted By: ThunderMuffin Re: The Man Shed News - 03/01/10 02:45 PM
I wonder how they keep the box from flooding. I can't keep my box from flooding. Anyone else have problems with flooded boxes?
Posted By: TheManShed Re: The Man Shed News - 03/01/10 08:25 PM
Jake,
That gives me an idea the trunk could be D shaped also.
Posted By: Luiz Re: The Man Shed News - 03/01/10 08:27 PM
I wonder how they keep the box from flooding. I can't keep my box from flooding. Anyone else have problems with flooded boxes?
No, but my plans for the future might include this problem
, so I'm also interested in a method to keep a fat board box from flooding.
Posted By: TheManShed Re: The Man Shed News - 03/02/10 01:29 AM
Using the fat box what support the side of the board is that not important? I know the front and back load up but isn't there side loads on the boards? Does anybody know what brands of A-cats use these types of boards I'd like to check it out?
Posted By: Jake Re: The Man Shed News - 03/02/10 01:54 AM
Using the fat box what support the side of the board is that not important? I know the front and back load up but isn't there side loads on the boards? Does anybody know what brands of A-cats use these types of boards I'd like to check it out?
The boards, even on most typical beach cat with straight boards, are only supported by the deck opening and the hull bottom opening. The daggerboard trunks usually slip outside formed and sized openings for the daggerboard and don't normally provide any support for the board (some are even paper thin and pretty much there just keep the water out - like on the nacra 6.0).
The new (v5) Geltek Flyer and I think the latest EVO has the capability of running either straight or curved boards.
Posted By: arbo06 Re: The Man Shed News - 03/02/10 02:14 AM
Are we still talking about dagger boxes? Just askin'.
Posted By: Luiz Re: The Man Shed News - 03/02/10 02:28 AM
The boards ...are only supported by the deck opening and the hull bottom opening.
The new (v5) Geltek Flyer and I think the latest EVO has the capability of running either straight or curved boards.
How do they keep the water out of the fat part of the box?
I'm afraid there's no curved board to be found in a 5000 miles radius around where I am...
Posted By: TheManShed Re: The Man Shed News - 03/02/10 05:11 PM
Hi Eric yep we got off to dagger boards.
Posted By: basket.case Re: The Man Shed News - 03/02/10 11:56 PM
mike, you should really consider using a perforated film with your lay ups.
Posted By: TheManShed Re: The Man Shed News - 03/03/10 04:24 PM
You must be looking at the last posting on my website. My supplier shorted me on the peel ply I ordered and paid for 7yrds and he delivered 5yrds. I had to make due with 3M masking film in a pinch to make up the difference. I did not know I was shorted until we had already done the lay-up and putting on the peel ply. I was pissed but in these circumstances you have to be flexible and do a work around when you have thousands of dollars of materials that could be wasted. The 3M film works for smaller areas but was not really ideal for this lay-up, I’m glad I had it available.
Posted By: basket.case Re: The Man Shed News - 03/04/10 01:25 AM
nah, the perf film is applied between the peel ply and the bleeder. it limits how much resin is pulled out and also, as a side note, makes separating the bleeder and laminate a hell of a lot easier.
Posted By: dacarls Re: The Man Shed News - 03/04/10 01:37 AM
Bimare sells DB wells for both straight and curved boards for A-class cats. I never have seen one. Please talk about how you plan to make curved boards, as several profiles are presently used/sold-- depending.
Also- I made my own perforated PE painters dropcloth- left it folded up and put a zillion little holes in it. Worked fine.
Posted By: TheManShed Re: The Man Shed News - 03/04/10 05:32 AM
Perf film - I made one up once from 4 mil plastic but never used it. I may give it go next time removing peel ply and bleeder cloth is like skinning a live gorilla. I've not had a problem with too dry of a lay-up without it.
Boards - I was thinking of makng the boards from the plans I have on the half - straight from just foam as they are not that large 2" thick at the thickest point and 12" wide. So I'd be working with 1" X 12" X 5' and bending it to a curve on a jig. Then matching the other side to the curve and glassing to the first half. If that works glassing the outside it to make a plug for a mold.
I have not seen any profiles presently used/sold any information on that?
Mike
Posted By: TheManShed Re: The Man Shed News - 03/04/10 05:55 AM
Slow work but I start to see some shape.
Posted By: erice Re: The Man Shed News - 03/04/10 06:56 AM
i was under the impression that lifting boards worked best when their section was an aero-foil style asymmetrical wing type
ie not symmetrical
somewhere on SA is a pic of the end bmwo's banana boards that showed a fat, high-lift, wing section
your build description for curved boards doesn't seem to mention a lifting section...???
straight boards can be angled to provide lift, but apparently they don't work well across a broad range of speeds so aren't used much
symmetrical curved boards aren't going to provide any lift are they???
Posted By: TheManShed Re: The Man Shed News - 03/04/10 03:34 PM
Still looking for information any technical-engineering data would be welcomed. Are the boards on the A-Cats Asymmetrical?
I think it was pointed out in the commentary from the AC that curved boards is a way to improve performance so there is going to be development in the whole concept of curved boards in an engineering aspect.
Until then the old way of build and test will have to do. On the prototype I think I like Jake's idea of making a trunk that will accept both type of boards. Then I can tell which is best.
Posted By: Jake Re: The Man Shed News - 03/04/10 09:22 PM
Still looking for information any technical-engineering data would be welcomed. Are the boards on the A-Cats Asymmetrical?
I think it was pointed out in the commentary from the AC that curved boards is a way to improve performance so there is going to be development in the whole concept of curved boards in an engineering aspect.
Until then the old way of build and test will have to do. On the prototype I think I like Jake's idea of making a trunk that will accept both type of boards. Then I can tell which is best.
I believe the Flyer boards are symmetrical. Sym. sections do generate lift as a function of their angle of attack...most aerobatic airplanes have a symmetrical wing section and they fly just fine. An asymmetrical foil doesn't generate lift as well when inverted (which is why most aerobatic planes have a fully symmetrical wing). You do depend on your daggerboards to provide lift on both sides depending upon which tack you are on. However, the marstrom curved daggerboards, which have also proven to be pretty quick, are asymmetrical and conceptually mostly rely on the leeward board to provide the lateral resistance for sailing upwind.
Posted By: dacarls Re: The Man Shed News - 03/04/10 10:55 PM
So far as I KNOW in A-class, only the commercial Marstrom boards are assymetric. All others appear to be symmetrical, but there is discussion/controversy whether they can/should be canted forward to provide a positive angle of attack. Also there are several opinions on location: fore, mid or aft between front and rear crossbars.
IMHO, None of this is clear to the builders/experimenters. But you are allowed to buy a new A-boat for $US 25,000 based on your best guess!
Posted By: TheManShed Re: The Man Shed News - 03/05/10 03:59 AM
Busy day I have the connecting beam plug fared and ready for epoxy & glass. Guess what starting to look like a hull need to match, fit, and build bulkheads.
Description: ready for epoxy and glass
Posted By: TheManShed Re: The Man Shed News - 03/05/10 04:01 AM
Posted By: Jake Re: The Man Shed News - 03/05/10 04:12 AM
lookin' great Mike!
I'm having trouble picturing the final shape of your beam you're molding...why does it appear to have such an irregular shape?
Posted By: TheManShed Re: The Man Shed News - 03/05/10 04:37 AM
The beam is going to be an elliptical shape. I had some engineering done on the shape it is stronger then a circle or teardrop mast section shape. The beam will be low profile and will fit in a sleeve by design it will take care of twist so no pin is needed. Plus it is different and blends with the boat nicely; the designed connecting beams were funky. That is one reason I had more freeboard designed in the ama's to meet the beams better. I may build a channel and cut a groove in it to slide a tramp boltrope inside like a mast.
Posted By: Jake Re: The Man Shed News - 03/05/10 01:12 PM
OK - I got it now. Thanks. It's also more aerodynamic too!
Posted By: TheManShed Re: The Man Shed News - 03/05/10 09:39 PM
I figured it would help reduce beam slap from the waves.
Posted By: TheManShed Re: The Man Shed News - 03/06/10 06:51 PM
Marking bulkheads.
I picked up this laser on a sidewalk sale at Harbor Freight last year it was good deal and figured I’d use it some time. I was going to use plum bobs to mark the hull then remembered the laser stuffed away in the cabinet.
Description: Still makes me made I was shorted on peel ply.
Description: Dueling tape measures may the best one win.
Description: All that for lines?