YPC

Hi Fish

This is very much of a 'IF - BUT - & - MAYBE discussion - great never the less - always looking for a better solution.
Love Change !

The thing is - we ideally want a board that 'handles on the face of a hollow wave - & - we want a board that 'flies' flat out, like a racing boat - there has to be a compromise.
With Surfboards - a board with big rocker is great in a very hollow wave - turns well - But paddles like a dog. deep in the water.
A long board has little rocker - paddles well and can handle smaller waves. not good on fast hollow face. Pearls easy
So - even with full size surfboards - you have to chose your board ! there is no ideal hybrid solution

I lean more toward a board being able to handle 'hollow face' riding - not just straight down the line runs - I want to be able to carve up and down the face, big cut backs, bottom turns etc. The speed is important to make a section or to get some big air - but the experience should be kept in a true surfing perspective. Styling !

The concave tail angle ( JIMMI ROCKER), as you say, keeps the nose down - but perhaps 'also' when you want it up ! . It will also effect the turning at speed, pushing the inside side nose rail in.

My new board has some good rocker in it - from nose to tail. I want to get in the real hollow sections.
I have mounted the motor as far forward as possible to achieve the drive shafts thrust 'in front of the CG' and at a low degree (7.5 degrees) The allen key marks the anticipated CG

My thinking is that at speed - with the thrust aft of the CG

as the hull speeds up, the lift point from the water surface pressure moves backwards under the board toward the CG, and even beyond- if your thrust line protrudes behind the CG (AFT) the closer the lift point gets to the CG - the sooner the upward prop thrust will pivot around the CG and push the nose of the board down - like a see - saw effect - this cycle will continue to repeat itself - generating the bouncing/porpoising motion.

With the aft concave JIMMI rocker you have introduced - it simply does not allow the lift point to move back as the nose cant lift as much, so you dont have the eventual tripping effect - but as you say - the board rides deep and generates drag.

My first board was flat toward the tail with little rocker - has little bounce when Bro is more rigid - but - gets pitched on a hollow face. If you flat your board out you will have the same net effect of the JIMMI rocker, as the tail will be lifted in a hollow wave and the nose will be pitched down for a Pearl !
Draw as bigger circle as you can imagine a hollow 6 ft wave would have in the sand - imagine the size of your board on the radius - it does not look like much rocker but draw a straight line on the waves radius and see where the nose of your imaginary board goes - down. PEARL

With my new build. Thrust in front of the CG - big rocker.

My thrust line is 'in front of the CG - as the water lift point moves back, even beyond the CG - the thrust line' in front' of the CG( forward) should still hold the nose up at speed. The faster I go , the more the thrust is able to hold the nose up. Like some one actually holding the nose of the board up in front.
Using the see-saw example - if you are supporting the see-saw up on the one side ( thrust pushing up) and some one is pushing the see-saw up from the other side (lift point moving aft) - you have relative balance around the CG (pivot point) - effectively it should not bounce and ride very light in the waster 'at speed' hopefully balancing around the CG.
There are plenty of other factors that will effect the actual ride............................................en dless

Lets see how my board works when I get it wet - would it be all that hard to establish your motor more forward and fitting a new shaft stuffing tube ?

Regards
Dominic (YPC)

YPC

Hi Fish

Thought a few rough sketches would add some value to your thinking and my explaining.

The first picture shows the two thrust line scenarios - A = above/behind the CG ( pushes the bow down) b = in front/below CG (lift the bow up)

Looking at the second picture A - Behind CG
As the board speeds up and the water lift point moves aft, the thrust line rotates around the top of the CG (pivot point) pushing the bow down. (tripping over the lift point) When the bow is pushed down, it is pushed into the water. slows down, the lift point moves forward again, and the 'hopping' cycle happens all over again. (all this happens in a moment) Lift point moves back - bow lifts up up - thrust line rotates around the CG downward - bow pushed down - board pushed down into the water - and so on ..... and on....... and on

The reason the JIMMI rocker seems to resolve the bounce with the above scenario is because the wedge at the back does not allow the bow to lift and the lift point to move back so the board does not trip - BUT - it remains deeper in the water - driving with more drag, effecting the turns and acceleration nose lift.

Looking at the third picture B - Infront CG
As the board speeds up and the lift point moves aft, the thrust line rotates around the CG (pivot point) lifting the bow up. As the water lift point moves back, the board is lifted both forward and aft, balancing around the CG. running light on the water. An ideal running thrust line.

Scenario B will also lift the bow better on acceleration - helping keep the nose up on the wave and when jumping white water etc.

Regards
Dominic (YPC)

RC HAWAIIAN STYLE

kite

Tina looks unreal ,you have her body weight nice and low , she looks so real in the pics , i love the look of your new grilfriend , great work kitepro


maui john

itsfishi

Dom i think you have nailed it A is what is happening. i can run nice up to a certain speed then that effect comes into play and throws it. I hear what your saying about the rocker, at the moment my board is more of an S shape shape with the neg rocker.
yeah it would be a job to redo the motor placement shaft flex etc but i think it is gonna have to happen if i want to be happy with it and have it surf the way i want it too. Need the speed.
its raining here so will hold up on the speed test, im just itching to get figure for how fast these things actually are going. might just do it anyway.

later

itsfishi

Rain has held of for a bit so managed to get speed test done. 24.8mph or 40kmph was the max speed. so my original guess of 30-50kmph was pretty good, im sure it used to go quicker before i added the rocker. at full speed it was not really controllable. would like it to be stable at 40. got to say im a bit dissapointed, i had hoped it would hit 50. gonna go look at moving the motor etc to try to achieve better results. i do realise that speed is not everything but it will be necessary if im gonna put this thing on a big face.

itsfishi

board is completley dissassembled anyone know how to remove flex cable from stub shaft and fix back in again, gonna move motor forward so need to lengthen flex. hope this works, i wont be getting any waves for a few days(i hope it only takes a few days)

YPC

Hey Fish

Could you send me the details of your SPEED APP that you are using on your phone. Its sounds like a awesome devise. Very pleased to see that it works.

I have no doubt that 50km/h plus will be doable once you have sorted the ideal running set up of your board out - If you do the theoretical maths - you should be close to 65km/h.

Drag is a huge speed and run time debilitation - to go fast you want as little of the board touching the water. LIFT/BALANCE is the key words.

I would love it if you could do a drawing of where your 'anticipated CG is going to be and where the motor and shaft thrust line will be situated in relation- I would also like to see where it is 'currently' - remember you want to balance the board so try to establish your CG between 40-45% from the tail first - then - establish your thrust line infront/ below that CG point. Your CG is in reality on two axis lines - front to back - top to bottom - so if you are looking at your board from the side - it will be approximately 1/3 up from the hull bottom given the heavy keel set up.

For most rc surfers this would be 'OTT' - but if you nail it - you will have a awesome board that will deliver great performance all round.

Hats of to you for 'going for it'

Thanks for the prompt Shipping payment !

Regards
Dominic (YPC)

kitekook

I have been trying to get Video for a while now and the helmet cam has been a challenge to say the least. Filming and doing at the same time is difficult(ask Itsfishi)

Went out for a lunch session at WindanSea, just didn't have it in me to try again with the video today, we just wanted to surf.

After my first battery pack, PK, a professional surf videographer walks up all stoked up! You know what I mean, it happens all the time. People just can not believe what they are seeing.

PK filmed for the remaining three packs...told me he would make a video and well...here it is, enjoy.

[youtube]http://www.youtube.com/watch?v=lUKjl6W-9nI&feature=youtu.be[/youtube]

I am glad I finally have a video to share with you all.
I could never have made a video like this with my helmet cam. We all look forward to future projects with him, kid has skill with that camera.

itsfishi

Dom the speed app is called Max Speed its a free app in the itune app store there are a few different ones to choose from but this one is free and very basic but it does what it says, its only in mph but thats easy to convert. tested it in the car for a while before putting it in the board and seemed to be very accurate so i believe its a good tool. i have heard of boat guys using gps device to get speed for their boats and tried to fit our gps from the car into lisa but was too big so ithought maybe their is iphone app that does the same as iphone has gps. it only just fit, but how cool.

will get those drawings for you soon im still working on it and when i know you will too. cheers for all the info/help with this tech stuff would never have got here without it. Cant believe i just ripped my whole board apart but i just am not satisfied with it yet so it has to happen. hope this incarnation is the one. getting closer. the drag and it nosing in was getting to me although it did ride good for the most part, but i know it can be better.

later

YPC

Hey Kite Book

That was really wonderful - I really like the realism of Diva's hair moving around - its looks so cool.

Its also great to 'meet' you - it personalizes the relationship that much more.

I think it would be nice if each one of us published a photo of ourselves and our Boards - always great to associate a name with a face - nice workshop wall paper.

Thanks for tis contribution.

We all - the kids - really enjoyed the vid - Diva is now a Household name in South Africa.

Regards
Dominic (YPC)

itsfishi

here is diagram hope you can work it out. cg will stay at approx same spot for new motor position. does this look like what you had in mind

cheers

YPC

Thanks Fish

What is the distance from the hull to the centre of the propshaft - I want to calculate the Angle

Re
Dom

itsfishi

dom not exactly sure what measurement you mean but if it is right up at the prop end it is approx 20mm to centre of shaft from hull

itsfishi

nothing is set yet just ripped out so can do anything with it

YPC

Fish

You assumption for the measurement was correct.

Based on the info - you will be reducing your thrust line angle by 2.5 degrees & lowering your thrust line by as much as 10 mm in respect to the point of CG which will have a great effect on the moment around the CG.

I cant say whether it is above or below the CG - BUt - it will definitely reduce the nose downward rotation force.
I would need more accurate details to establish if it is above or below.

Try and fit the motor as far forward as possible

Regards
Dominic (YPC)

Cananzi

fish

the NQD board on my youtube channel has that same mod done. i did it also so i could fit the 5000mah 3s packs in nicely with out scrubbing the coupling.it was a noticable improvement with the way the board went. it seemed to carve alot better.


kite

nice footage!! board looks great. love the hair

itsfishi

ok thanks that what i thought but its a balancing act to get it more forward moves cg forward. thanks again for all the info this is great stuff.

do you know how to pull the flex cable out of a stub shaft. Need to do this to attach stub to longer flex

cheers

YPC

Kite

How long run time do you have per pack - what mAh/V pack are you using.

Re
Dom (YPC)

itsfishi

the motor will be as low as it can physically go in the hull.

YPC

Fish

Either run a bigger battery pack or add weight to keep the CG at 42%

Usually the flex is soldered into the stub - use a blue flame to melt it out.

Spent some time simulating my new board set up with all ordered running gear ( total weight of complete set up = 1500 grams) - self rights without any added weight.

Re
Dom(YPC)

itsfishi

thats a bonus doing this can fit larger packs.

bet you cant wait to try that new board out

itsfishi

gotta get this all done ready for bro

YPC

Fish
Show me a pic of the inside of the compartment and a pic of the bottom of the hull if you can
Do you have weight built into the keel ?
Re
Dom (YPC)

itsfishi

just doing a quick vid will upload in a minute

YPC

Please tell me in detail how to upload as you do with the YOU TUBE box.
Step by Step
I use a small hand held camera (not a phone)

Regards
Dom (YPC)