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Open Fuse

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fluidity
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Re: Open Fuse

Postby fluidity » Fri Sep 18, 2020 9:12 am

Here's my latest:
https://pinshape.com/items/102151-3d-pr ... elage-body
Free to download the STLs for anyone who wants to have a go.

1. Glider open mould: The mould can be printed if your printer is big enough, I plan to CNC it, paint it with gel coat to seal it and cnc it again. It's a semi-open mould, the intention is to insert and align the mast after protecting it with packing tape to allow later extraction. As there are different mast types, holes vary. so to mark out cut the head off a bolt and grind the end of the bolt to a point. Insert it into the mast, press the mast inside and drill where the point of the bolt made an indentation. Repeat for all mast holes.
2. GliderBodyInt.stl is the insert that the composites need to be wound around. It includes voids for 12mm fibreglass rod to the stabiliser and for the mast.
3. GliderBodyExt.stl is a plug of the fuselage body shape without any of the voids.
4. GliderBodyCollar is a 3D printable part to smooth the transition from the stub end of the rear of the front wing's mast socket.

The idea is to wind all your composites around and through the mast hole of the internal part. Then push a 12mm fibreglass rod into the back end of it and close the mould around the composites and fibreglass rod after first polishing and applying release agent.

The internal part needs to be printed at high infill %, I recommend around 60% and cubic infil, max layer height of 0.175mm to ensure good overlap of the cubic infil.
Attachments
parts view Extended version.PNG
120mm extended version for Gong
parts view.PNG
60mm wing engagement

PrfctChaos
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Re: Open Fuse

Postby PrfctChaos » Sat Sep 19, 2020 1:27 am

12mm fibreflass rod... Thats gonna be a pretty wobbly ride I think. And the glass rod is usually pultruded, so only unidirectional fibres, very very flexible tortionally. That stab is gonna be wobling around a lot.

Might be a good idea if make a low effort prototype first, like chop a aluminium fuse and drill a hole to glue you fibreglass rod and stab onto and take it for a few riides. To see if you like the way it feels.

FYI, i made a wood core fuse once, wrapped in carbon fibre, but realised later my fibre orientations made it way too flexy tortionally. I did not like the ride.

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fluidity
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Re: Open Fuse

Postby fluidity » Sat Sep 19, 2020 3:08 am

PrfctChaos wrote:
Sat Sep 19, 2020 1:27 am
12mm fibreflass rod... Thats gonna be a pretty wobbly ride I think. And the glass rod is usually pultruded, so only unidirectional fibres, very very flexible tortionally. That stab is gonna be wobling around a lot.

Might be a good idea if make a low effort prototype first, like chop a aluminium fuse and drill a hole to glue you fibreglass rod and stab onto and take it for a few riides. To see if you like the way it feels.

FYI, i made a wood core fuse once, wrapped in carbon fibre, but realised later my fibre orientations made it way too flexy tortionally. I did not like the ride.
I've seen aluminium fuselages with a rear end thinner than the 12mm glass fibre rod I'm proposing but the aim for the stabiliser is not so much to make a rock solid ride, but to ballance the high up forward force against the low drag of the front wing. My theory is that a small amount of springiness will work with pumping to reduce the required energy to change attack angle of the front wing. Remember this is only a very short length of 12mm rod, likely between 400 to 600mm. It won't bend much. I was considering smaller diameters as well over that distance as 12mm may not have enough flex to test me theory. It's all rather academic for me though, as I'm not yet successfully foiling in control :lol:

Regarding your carbon fibre wrapped wood core that flexed, Diameter and fibre orientation are super important. if you used braid with no unidirectional then there will be capacity for flex related to the amount the braid is stretched axially vs radially as the more the fibres coil rather than run straight, the more it changes to be like a spring coil. Braid wrapped pultruded glass fibre would be more splinter resistant though which is certainly a consideration.

dirk8037
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Re: Open Fuse

Postby dirk8037 » Sat Sep 19, 2020 8:43 pm

Hi,
Does the printed core will have in your calculation take any statical load?
I wonder what you want to use for the print, since all the for mortal accessable filaments seems to me too week.
Also the bond between composite and print is a thing that, from what I know, none of them do realy do that.
Maybe not immeadiately but over time it might be a factor.

Could it be a solution only to print the Infille without toplayer and fill the spaces in between with a mis of cottenflakes, glassbubbles and epoxy.
Relativly easy to sand, good bond and most likely much more solid. (quite some work though)

For big wings and rider wight I would also opt more for 3mm through out the fuse and solid around the cup.
I have been trying arround with carbon tubes for that that had 2mm wall thinckness. The might seem stiff enough but seem still very fragile. If you have unwanted ground contact tha cause a small fracture the whole thing might fail suddently. Wich is maybe quite essential - to have a lot of impact resitance.

At this area you have, at least a I envision it, the highest stress.
Torque from the board and rider through the mast by stearing on the yaw axis and due to the inertia of the wing on the role axis.
In addition to that you have the upward force of the wind focusing there, too.
Since due to the cup the structure is not "solid" anymore, but having a whole, the forces will spread arround and the walls outward.
If the cross-section is round there will have on the top corner hardly any material to cope with that.
In one of the upper posts someone was talking about failurs of fuses in forced, loaded turns. I guess that could be one reason.
You have the spreading force from one direction in combination with torque on the yaw with lots of momentum behind it.
Having it square on the top side you have more material to take those forces.
I thought of making that part out of G10 plates on bottom and both sides that are rejuvenated on bothe ends and surrounded by the laminate. (because I have small plate rotting in the celler.
Or since you are anyway into making moulds, something to pour in a mix of epoxy and glass cuttings.

Dirk

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fluidity
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Re: Open Fuse

Postby fluidity » Sun Sep 20, 2020 12:44 am

dirk8037 wrote:
Sat Sep 19, 2020 8:43 pm
Hi,
Does the printed core will have in your calculation take any statical load?
I wonder what you want to use for the print, since all the for mortal accessable filaments seems to me too week.
Also the bond between composite and print is a thing that, from what I know, none of them do realy do that.
Maybe not immeadiately but over time it might be a factor.
Just PLA+
It's easy to sand and almost as hard as regular PLA with a small amount of flex. At 60% fill I would say it has more density than pine.
It's mostly intended as a former with the strength being in the composite fabrics wound around it. I'm now thinking that some short prickles on the surface would facilitate winding with carbon tow which is much more reasonably priced than in woven form.
Could it be a solution only to print the Infille without toplayer and fill the spaces in between with a mis of cottenflakes, glassbubbles and epoxy.
Relativly easy to sand, good bond and most likely much more solid. (quite some work though)
Or substitue PLA+ for PLA and print at 100% fill.
For big wings and rider wight I would also opt more for 3mm through out the fuse and solid around the cup.
I have been trying arround with carbon tubes for that that had 2mm wall thinckness. The might seem stiff enough but seem still very fragile. If you have unwanted ground contact tha cause a small fracture the whole thing might fail suddently. Wich is maybe quite essential - to have a lot of impact resitance.
Basalt is rated at 2/3 the strength of carbon but much more impact resistance
At this area you have, at least a I envision it, the highest stress.
Torque from the board and rider through the mast by stearing on the yaw axis and due to the inertia of the wing on the role axis.
In addition to that you have the upward force of the wind focusing there, too.
If you look at the Gong wings with big chord then you'll notice the fuselage is actually not attached right at the back, it starts a few cm in. It's leaverage we need to be most mindful of as a stress. Particularly during a wingtip breach during a turn. These stresses are at an angle to both mast and wing and best handled by braid weave or double bias cloth. Or hand wound tow.

Since due to the cup the structure is not "solid" anymore, but having a whole, the forces will spread arround and the walls outward.
If the cross-section is round there will have on the top corner hardly any material to cope with that.
In one of the upper posts someone was talking about failurs of fuses in forced, loaded turns. I guess that could be one reason.
You have the spreading force from one direction in combination with torque on the yaw with lots of momentum behind it.
Having it square on the top side you have more material to take those forces.
I thought of making that part out of G10 plates on bottom and both sides that are rejuvenated on bothe ends and surrounded by the laminate. (because I have small plate rotting in the celler.
Or since you are anyway into making moulds, something to pour in a mix of epoxy and glass cuttings.

Dirk
Maximum compression and tensile forces are carried near/at the surface of objects. That's why 3D printing is still successful with low infill ratios. The 3D printable insert doesn't carry those forces because it's designed to be completely wrapped with composites excluding the 12mm tail rod hole. Ideally with braid that can be pressed down through the fuse hole in the insert to bond with the braid underneath. In this way a double tube is formed surrounding the inserted mast for continuous fibre paths. Before assembly, the pressed down braid can be stitched with kevlar or polyester thread to itself where it lies under the insert. For stiffness of the wing tips from yawing during impact and from winglift at the front, it needs unidirectional along the same axis as the fuselage. I see this as best achieved with an inner layer of braid, a next layer of thick unidirectional and 3 or more outer layers of braid.
If hand wrapped with tow, this forms the primary controlled path for tension and compression forces but to prevent tow splitting apart from each other (weakest direction) it still needs an inner braid layer which can be kevlar. It's exactly the same for the outer layers except that these are also impact prone, I'd use basalt braid for the outer most layer.

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fluidity
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Re: Open Fuse

Postby fluidity » Sun Sep 20, 2020 8:27 am

Update: added the first free design CNC wing with cutout for Gong or open fuse. Needs the fuse to be wrapped with packing tape, several layers of braid fitted around and then inserted into the cutout and aligned while composites are fitted, infused and cured.
This is a massive learner and/or low wind wing with approx 2650 cm² lifting area!
I had a look on the Gong website to see where their screw hole/s are and it's terrible!
So close to the shaft entry that it places a disrupted section of fibres in a very high stress area. I've moved the hole much further forward in my demo wing. I also adjusted the shaft entry inside the wing at an angle to pitch the front of the wing up 3degrees. This should allow for a fairly level stabiliser fixing angle.
Update for wing with 3D file is on one of my pinshape design pages:
https://pinshape.com/items/93677-3d-pri ... -hydrofoil

To see what the current open fuse outside looks like I've printed a collar, external part shape and an internal part shape.
My printer is not quite long enough to print the full fuse body mould horizontally but I can print to 350mm vertically.
I believe Dirk is right that there needs to be more thickness to the composites covering the part of the core that inserts into the wing.
In my photo the adaptor collar is fitted, this is the piece that blends the wing tube thickness back into the fuselage body.
Attachments
20200920_191831.jpg
XXL wing with socket.PNG

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fluidity
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Re: Open Fuse

Postby fluidity » Wed Sep 23, 2020 7:41 am

dirk8037 wrote:
Sat Sep 19, 2020 8:43 pm
<cut>
For big wings and rider wight I would also opt more for 3mm through out the fuse and solid around the cup.
I have been trying arround with carbon tubes for that that had 2mm wall thinckness. The might seem stiff enough but seem still very fragile. If you have unwanted ground contact tha cause a small fracture the whole thing might fail suddently. Wich is maybe quite essential - to have a lot of impact resitance.
<cut>Dirk
Hi Dirk,
I took an additional 2mm radius off the core, now a total of 4mm between mould and core to pack fibres in.
Files updated here:
https://pinshape.com/items/102151-3d-pr ... elage-body
My soller composites thick glass sleeve arrived today. It folds into the mast cavity beautifully, I'll print up the modified part and post a picture showing the layup later. Because it's a high GSM weave only issue is the fibres easily split out of their woven bunches at the ends. Update: too tall for upright printing. Restarted with supports set diagonal position in heated bed at an angle for minimal supports requirement.
And updated again at the same location with a better block CNC cutout model of my wing that has a thin layer all around the edge of the wing to the outside of the block to assist in removal later.
This allows cutting with a short CNC router bit as the block is 6 sheets of 12.5mm making a total of 75mm (laminated and cured under vacuum).

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fluidity
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Front wing offset angle?

Postby fluidity » Fri Oct 02, 2020 10:08 am

For my first wings/fuselage combo I set the front wing flat.
I ended up using a -3 degree angle on the rear wing to provide very mild pitching up of the bow of the board.
So then I designed my second wing with a built in 3 degree angle of attack to put it in the right starting region and also to nestle the fuselage insert into the wing socket at a flat angle relative to the bottom of the wing.
However, I'm not certain this will work well because the mast is vertical in my board so I now have a 3 degree difference between my wing and the bottom of the board. Has anyone done this?
Did it make it hard to get started with extra drag?

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fluidity
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Re: Open Fuse

Postby fluidity » Sun Oct 11, 2020 5:45 pm

So I finished cutting out the new XXL sized plywood wing a couple of weeks ago. Took 6 evenings on my CNC with 13mm roughing stage and 4mm ball mill finishing stage. And then lots of sanding. That's got me busy on the fuselage again after I skinned the underside because I need to manufacture the fuselage insert. I ordered the 12mm x 2 meter pultruded rod and started a mould for the fuselage exterior but I've also done a fix for the wrong mast direction and made the mould deeper as well as smoothing the fuselage from 60 sides to 360. The CNC is fast enough on default settings to cut out a working stool with 5 legs and an interlocking lower peice in less than an hour but I've discovered that it really needs self clearing bits for reliability, regular router bits heat and blunt too fast. Meanwhile my 4mm taper ball mill has cut about 300 meters and still going strong. I'm finding CNC cuts take a lot more preplanning than I'd assumed previously. My CNC cutting bed is out of level from my budget garage build and sag of 18mm plywood over the smaller table I sat it on, fix will be making some wood islands and routing them level. Everything needs to be cut oversized to allow for holding and retaining tabs. And a lot of what I want to cut out involves first laminating something thicker. It's also more needy than my 3D printer. I'm scared to leave it unattended for too long on roughing cuts because of the volume of sawdust it produces and the potential for chaos if it gets stuck and starts a fire with friction and heat on the wood. Still, enjoying the new capabilities. In between times I cut 3 different Z gantry plates in the search for a rock solid Z axix. 4mm Aluminium wasn't strong enough. Finally I cut a 4mm ply one and laminated each side with: twill glass fibre, Unidirectional carbon fibre, glass surface tissue, carbon uni and Glass twill. After vacuuming over night and post curing on my printer with the heated bed at 100 celcius for an hour, drilling (itchy hands from the drilling dust) it's now a rock solid Z axis.
Updates to the mould, insert and fuselage outer profile on pinshape again.https://pinshape.com/items/102151-3d-pr ... elage-body
Attachments
20201003_151458.jpg
Cut and sanded, under finished wing.
20201001_221331.jpg
20200928_220226.jpg
open fuse mould 1.PNG
Mast direction fixed, smoothed, deepened.
open fuse mould 1.PNG (53.9 KiB) Viewed 2863 times

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fluidity
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Favorite Beaches: Plimmerton
Style: Wave, jump
Gear: Transitioned from Kiting to Wingsurfing late 2019. Building my own foils from my CAD designs and 3D prints, CNC machine.
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Re: Open Fuse

Postby fluidity » Tue Oct 20, 2020 10:40 am

Some more progress... moulds(still working on finish) and wing(thanks to prfctchaos for tip on bunnings jumbo vacuum bags, they save a lot of sealant!)
I have vacuum film which is more flexible but bought some different sized clothing vacuum bags from Bunnings today and can't recommend them highly enough! Be sure to gather extra plastic for areas that will suck inwards, but they have a long zip-lock side and seal very easily. I didn't plan completely, the vaccume connection is sitting right on the wing but it's not the only area that will need fairing, I have a lot of reinforcements centred around the mast socket that will need feathering out. 2 braid tubes arount the mast socket, followed by 3 biaxial under the socket, 2 over, carbon 100mm uni full length and double 300gsm twill glass over the top. I'll let it cure and then stand on the middle and listen for cracking noises.. check the spring back, may need an extra tension layer on the underside but I'm very confident about the top.
I think I'm going to have to switch to a hard 2-pot silicon mould but really keen to get a first fuselage done so I can test it's strength on my huge 1200mm wide wing.
I stuck a 3D printed test fuselage in the socket area after fibe-taping along the length of the insert, I may well have to destroy the fuselage insert to remove it but will try... the fibre tape will help.
Attachments
20201020_213814.jpg
20201019_185609.jpg


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