Simon's home-brew hydro

[RandyatBBY]

Do not expect the changes in the shovel to work the same in a rigger they are different. That works for one may need to go a different direction on the other.

It is important to only make one change in the boat at a time, so you know the exact efect it has on the boat.

[Simon.O.]

Jay.
As always thanks alot for your input, the idea of ballasting (properly) first before attacking the hull with saws is a good idea. I will give it a go, hopefully tomorrow morning.
If adding weight works then to me that is the same as reducing lift.
I'll keep the knives and saws away from this hull until I have done a few honest laps to see if lead in the hull works.
Trust me, I would rather run with a little lead that have to do the cutting and rebuilding that I planned for.

For setups
I do use a nice flat build / set-up board for all of my adjustments and they are documented at the time and after the run in my setup folder ( paper)

Randy.
Thanks to you too. I always try to do one adjustment per pack run and then write my notes.
From here I can hopefully see what does what and make adjustments from there.

Let's see if I can get a few hulls on the water in the morning and get home in time for the local Santa Parade. If I miss that my ------ will be cut off !

[Simon.O.]

Well I am back from the lake with todays findings and some damage to some hulls.

I put approx 225g of lead in the hull just aft of the CoB, and as no surprise it ran a lot smoother. There was still a fearsome sponson tapdance at wot but not as severe as before.

I feel that I am going to have to rework the sponson lower surface as I currently have just over 5 deg AoA on there and with the strut I can only get it down to about 4 deg.
If I go for a shallower tunnel with less AoA on the sponsons then I can lose the ballast and use more of the power that I have in there.

[nauti-tucu]

Hi Simon:

As a follow on to my hybrid hydro I built this one.
The tub is a little wider, and the boat is a little longer to allow me to get 8 cells + in there.
So far it has run very well.
Given that it has a straight shaft I expected a little tail-hop at max speed and thatis fine for me. This thing flies !!

Basic setup is
Graupner 75A esc
Jamara 600 brushed can
8 x Camelion NiMh
All handmade hardware.
All balsa construction, varnished.
Nice!!
Estimated speed would be 40 kmh.

Now that I have figured out how to make wire drives I will develop the smaller hydro and design a small rigger to go in the fleet.

Nice job, really.
Any plans, perhaps?

[Simon.O.]

This as with all of my hulls was built from a set of sketches and my mind.
It has had a few alterations and is about to get more.
As I have suggested before in one of my other build threads, If you have the ability to build a boat from scratch then you have the ability to draw a set of plans.
There are a lot of freely available plans out there that can be scaled up or down to suit the size you are after.

[nauti-tucu]

Thank you.
I hope to build hulls as you in little time. Thank you to dedicate time to my questions.

When I finish my Canard (based on your plans), I´ll put pictures.-

[Simon.O.]

nauti-tucu. Thanks for the compliments. I am by no means an expert here, indeed the opposite. i come here to find the answers to questions I have about some of my unusual designs.

This hull is about to go for some surgury to remove lift.
Given that the rigger is a LOT happier now with narrowed sponsons I am inclined to do the same for this hydro.
Looking again at a lot of the photos I have of classic hydros i can see that the outer sides of my sponsons are too steep for a start. Narrowing the lower surface will increase the angle of this side.
Most if not all of the hydros that i have pictures of have a flat entrance to the tunnel and mine has a ramp. I did this to ensure enough air went in there when I ran the brushed cans.
Now with BL there is way too much lift as we know.
I will re-shape the sponson and see how things go from there.
I will not get a lot of water time over the next two weeks as it is gardening time here and I am of to Tauranga to see the GP hydros ( full size ) next weekend.

Have fun........I am

[Simon.O.]

After a nip and tuck on this one it went back on the water today.
With a narrowed sponson bottom and 4deg AoA it performed the same as before when I had about 250g or 8oz of lead in the centre section.
It is still a little flighty in the front but I have removed the tunnel dam for this experiment.

Next in went 200 g 7oz of ballast and it was a little smoother. The interesting thing now is that the CoB can be moved a lot more as a result of the power I have in there.

When it was first built I had to have the CoB at or just aft of the sponson or it would tail drag due to moderate brushed can, now with BL I can set the CoB a little further back and load up the rear again as this seems to settle it down a bit.
After watching full size hydros on Sunday I can see that a little bit of hop and skip is acceptable.

No more runs now for a week as I have a lot of other stuff to do.
I will refit a tunnel dam and see how it goes next week.

[Simon.O.]

I got a good run this morning as the pond was a lot cleaner.
With a 6mm 1/4"tunnel dam and 5 loose sub-C cells as ballast it was a lot better.
I ran it with 6 spare cells and it was very smooth but obviously a bit slow out of the turn.
There is a little bit of tail hop even with the strut at 0 deg.
CoB is about 1 1/2 "back from the sponson Te.
It has a bit of a tendancey to plough the sponsons in when the tail hops so I will move the ballast back a little to settle the tail and see what happens.

Off to work in the morning so no runs for a few days.

[Simon.O.]

After a week in the boat hospital this hull has been on the water again.
I added a second layer of balsa to the sponson bottom and then sanded back to produce a dihedral of 3-4 deg. This in addition to the tunnel dam has made this hull a lot smoother on the water.
It is still wild enough but the insane sponson tap dance has now gone and so has the wild tail-hop.
I will now reduce the ballast and see if this thing will really go nuts.

It is always fascinating to see how alterations in a hull form and setup will produce such different performance characteristics. This is how I learn, in addition to the fine knowledge that is shared here.

[Simon.O.]

It was time this hull was retired or rebuilt, it was not through damage but a lack of performance and handling that this cam about.
This hull was one of my first and has had many alterations and now is subjected to BL and Lipo, which was not in the original plans.

It is now being widened at the front to increase its stance and to ventilate more air from the frontal tunnel.
The setup now is a bit of a mix'nmatch of designs that I have and this will now be a fat rigger.

The sponsons are set a little further forward and out as can be seen in the pics.

I will refit a single motor to evaluate the hull changes and then if it is good I will run twins in this.
A pair or 450 size heli outrunners. 3500-4000kv on 3S to 430 counter-rotating props.

For the really observant you will see that reskining the front of the tub with the sponsons now fitted to thier frames is going to be a challenge.
That is what happens when you work without plans, and lack a bit of forethought.
I will get it done though.

Here we are today.

[nauti-tucu]

Hi Simon.O.:
I always read with a lot of interest this post... I learn a lot.
have you planned to make a flood channel in the hull, at some time?
... now you have a lot of space.

[Simon.O.]

Hi Simon.O.:
I always read with a lot of interest this post... I learn a lot.
have you planned to make a flood channel in the hull, at some time?
... now you have a lot of space.

Flood channel ?? I am not sure what you mean here, if you mean a flood chamber for self righting, then no way.
This has been widened to increase the stability, and a few other reasons.

[nauti-tucu]

Hi:

Flood channel ?? I am not sure what you mean here, if you mean a flood chamber for self righting, then no way.
This has been widened to increase the stability, and a few other reasons.

Sorry... I meant "flood chamber"
Thanks.-

[Simon.O.]

It is now ready to take to the water again.
I will try this setup and see how it goes. If it shows promise then I will consider a repower and do it with twins.

I believe there is a lot of room for development in this hull as the sponsons have a dihedral on the ride surface at the moment. That can be sanded out or I can fit narrower ride plates to flatten the sponson bottom.

Oh, so much potential and so much time to test, I love it.

Now it is a long hydro or a fat rigger, call it what you will !!
It is now a serious development hull.
Ignore the dodgy varnish finish, I will redo the top coat if it passes a few tests first.

Here it is for now.