Gallery, Projects and General > The Design Shop
designing a space-frame structure - which comes first - frame or body
RipSlider:
Thanks for the replies chaps.
I'll answer in backwards order to the questions:
Eric:
Carbon was my first choice for this - I'm pretty happy working in Carbon fibre, but I was put off for a few reasons. The first is that this boat will be designed to go as fast as I can possibly make it - 120mph+ is the end target, but will be based partly on a wave-piercing design ( with an Axe-bow and a 3 point hydroplane all thrown into the mix ). Because I'll be racing this at sea - it's almost impossible to use I.C or jet power on inland waters in the UK for boats - it could be hitting some fairly sizable waves at very high speed. I CAN just keep upping the carbon thickness, but I reckon I will end up with 1/2"+ thick of carbon all around the hull, and sadly Mrs Steve knows full well how much carbon is at the moment as she saw my last bill!
Also the boat will be between 5.5 foot and 6 foot long, and I have no access to an auto-clave that big without spending thousands to hire one ( and lets say 2x de-bulks and 1x bake x 3layers is at least 4 days that I would be hiring the clave out for. I reckon it would end up being £2,000 for the carbon, resins, waxs etc, and another £3,000 for the autoclave. - about $8,000 for a toy boat.)
My thinking is that a space frame will be good practise for working with metal, and will allow for a stressed Ali skin to go over the top of it. This should keep stregth up at a much lower cost. Weight I am less concerned about as it the boat is too light it will need a load of ballast in the nose anyway for the design to work.
Lastly, this may end up being a flash steam driven boat ( flash steam model boats were doing 150mph+ in the 1950's ) and I'm a bit wary about using carbon around lots of open flames from a flash steam plant.
Scott and Eric
I think the question I'm struggling with most is how I deal with the detailed design. It would be fairly simple to build an empty hull, and then fit a space frame into it - no real planning needed, just juggle the metal in based on a back of a fag packet sketch. That makes the design easy, but the build itself I would expect to be fairly tricky - how do you weld the frame inside the hull for example?
Designing the frame first, and then working a hull around it would seem to take a LOT more effort at the design stage, but I suspect it would make for a much easier build.
So I think that's my basic question - Do I go with "difficult design, simple build" or "simple design, complex build"?
Many thanks for all the responses so far.
Steve
Brass_Machine:
--- Quote from: RipSlider on June 23, 2009, 02:59:15 PM ---...
Designing the frame first, and then working a hull around it would seem to take a LOT more effort at the design stage, but I suspect it would make for a much easier build.
...
--- End quote ---
I like that option. The design process would be more difficult... but not certainly impossible. If you know the basic shape of the hull, then I imagine it wouldn't be that difficult.
I would like to see how this works out. Please, do a build (and/or design) thread when it comes time.
Eric
Brass_Machine:
--- Quote from: RipSlider on June 23, 2009, 02:59:15 PM ---...
Also the boat will be between 5.5 foot and 6 foot long, and I have no access to an auto-clave that big without spending thousands to hire one ( and lets say 2x de-bulks and 1x bake x 3layers is at least 4 days that I would be hiring the clave out for. I reckon it would end up being £2,000 for the carbon, resins, waxs etc, and another £3,000 for the autoclave. - about $8,000 for a toy boat.)
...
--- End quote ---
Steve,
That is much larger than anything I thought of building! That would be awesome to see running!
Eric
SPiN Racing:
I will dig through my archives of pictures.. and see what I have to compile a sidewinder post. I will also drag my tush down to the shop and snap some pics if the car is out of the trailer. :thumbup:
I think an option you might want to think of.. going down the road John mentioned with the CF strips internally used for the hull design... is building the external hull from CF or fiberglass, vacum bag it. Peel ply.. the works. We make the CF panels at the shop like that. Once you make the external hull, make yourself some layers out of say.... Balsa wood, that match the internal contours of the hull. That way uoi make say.. 20 layers of balsawood with a 1/4 inch gap between them. Then you will have a internal dimension of the hull.
From there.. you can make your frame to match the contours of the sides of the balsa layers.. and if you make sure they are able to be seperated.. you can lay them out one at a time to make each box shape, and make sure the metal matches the lines of the exterior.
Once the cage is made, you should be able to simply set it into the hull, and glass/CF it into it.
OR.. if you go with thin aluminum for the hull, and need to weld/tig it in.. you would have minimal gaps for the length of the frame.
RipSlider:
I'm not sure I will be able to vac bag - there are some very acute internal angles in the design, and those are an absolutely swine to Vac-bag.
from the point of view of "learning new skills" a stressed Ali skin would be good - and also light on the wallet ( cos I know a chap who can do wonders with a TIG welder ) but carbon is still feeling like the easy route forwards, although Mrs Steve will go absolutely metal if I buy in a couple of hundred feet of high-M tow.
Have had another crack at drawing out what I want tonight, but no luck. I think it might be easier to set to with a large lump of blue foam and make the hull as a prototype. From their it's a pretty simple jump to actually building the hull. And that sort of makes my decision for me - build the hull and somehow bodge in a space frame afterwards.
Steve
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version