downunder wrote: ↑Thu May 31, 2018 7:22 am"* Rear wing on the top fuse. That means the bolts don't take all the load. "
- which load? The stab bolts are definitely not taking the longitudinal load but a side one.
* Ensure an easily adjustable rear wing aoa.
- umm why? Without knowing the front wing specs it can be even near 0 degrees...
* 8mm hardware is robust.
- 6mm is not near enough.
* Rear stable about 2/3 surface area as front wing.
- Umm, Levitaz is not 2/3, or any race by that matter.
* Fuse could be a bit long.
- that's why there might be more holes to move a wing...
C'mon Plummet, you riding a DIY board, I recon all knowledge you've got is from reading and not seeing it in person?
Anyways, not to bash you, just pointing to leave to more Authoritative guys on the topic to answer. Which I'm not. But nice try tho...
I think you do mean to bash me. You aim to discredit my input. My knowledge is based on my research and the fact that I have successfully designed and built, learned on and refined my own hydrofoil that works very well. I have been riding it for 18 months and have a number of lessons learned which I would like to share.
Here is the link to my build if you are interested.
viewtopic.php?f=199&t=2394150&p=1000544 ... d#p1000544
I know you have been working on a hydrofoil. Have you completed it yet? ridden it yet? post details on your progress. Are you up and riding yet?
PS my day job is mechanical engineering design, prototype and manufacture..... So I know a thing or 2 about prototyping,
None the less i'll answer your questions.
"* Rear wing on the top fuse. That means the bolts don't take all the load. "
- which load? The stab bolts are definitely not taking the longitudinal load but a side one.
As you know the rear stab wing profile is flipped compared to the front wing. It is designed for negative lift (correct term?). Stab on the top of the fuse means the stab is getting pushed into the fuse. The bolts need to locate the stab, But the most of the lifting force of the stabstab is taken by the fuse. Put the rear stab on the bottom of the fuse and the bolt need to take all the lifting force of the stab as the stab is trying to tear away from the fuse. If the bolts start to loosen the lifting force of the stab can potentially loosen the stab faster. I have seen a bottom mounted stab on a production foil with loose bolts. When you consider design you want to limit failure. This is one small way of doing that. Another advantage of the rear stab on the top is that it is less likely to be damaged with ground strikes.
PSS The opposite is true on the front wing of course. Front wing on the bottom is best.
* Ensure an easily adjustable rear wing aoa.
- umm why? Without knowing the front wing specs it can be even near 0 degrees...
When you first design a foil the optimal AOA of the stab is unknown. Sure you can go with industry accepted settings. However the tune the foil for optimal performance you want to be able to easily adjust the rear stab aoa. Also as your riding progresses you will find you may like a looser feel. The ability to adjust the stab gives you easy tuning as you progress. Lastly, for the prototype you most definately wany adjustability to get the ultimate tune. Once happy with that setting you may choose to lock that in for the production run. Personally I like the adjustability feature.
PSS typical AOA of rear stab sits between 1-3 Deg
George at Delta hydrofoil explains it better than.
https://www.youtube.com/watch?v=q1abYwkEscE
* 8mm hardware is robust.
- 6mm is not near enough.
I agree. Many production foils use 6mm and sometimes smaller!....
* Rear stable about 2/3 surface area as front wing.
- Umm, Levitaz is not 2/3, or any race by that matter.
Its a good rule of thumb. As you increase stab size you increase stability and drag. Less stab less stability, less drag.
The longer the fuse the smaller the stab can be in relation to the front wing. So when looking at stab size the fuse fuse length must be considered as does the intended purpose of the foil.
* Fuse could be a bit long.
- that's why there might be more holes to move a wing...
Fair enough. Additional holes will increase drag. I's suggest to test fuse length then lock it in for production.