WikiWirral its great, register, enjoy and welcome.
Forum Statistics
Posts1,030,302
Topics75,825
Members13,709
Forums65
Posts in last 24hrs6
Most Online14,906
Nov 23rd, 2019
Who's Online Now
39 registered members (Adamthomas89, 9 invisible), 1,189 guests, and325 spiders.
Key: Admin, Global Mod, Mod
Social Media : Follow Us


Popular Topics(Views 7days)
New General Forums
Very quiet Wikiwirral.
by Fidelio. 9th Feb 2021 12:00pm
Cruising with casper
by casper. 6th Feb 2021 2:13pm
Hobbies and Pastimes
by granny. 6th Feb 2021 10:28am
Hotel Isolation
by casper. 5th Feb 2021 6:57pm
New Wirral History
Guinea Gap
by mikeeb. 25th Feb 2021 12:22pm
79 Caledonia 42 Cathcart Street 237 Cleveland St
by mikeeb. 20th Feb 2021 11:10am
Birkenhead Carnival, 1902
by bert1. 12th Feb 2021 7:29am
Birkenhead aerial photo, 1945
by yoller. 9th Feb 2021 9:28pm
62 Sun Inn 203 Bridge Street 203/205
by . 10th Oct 2016 4:03pm
Forum Tips
Photo Gallery Forums
Boaty McBoatface takes shape
The gathering storm: Mersey waterfront today
Topic Replies
Wirral Council budget.
by Salmon. 1st Mar 2021 4:55pm
4 Bridges
by philmch. 1st Mar 2021 4:07pm
Birkenhead centre development
by mikeeb. 1st Mar 2021 2:20pm
Hobbies and Pastimes
by mikeeb. 28th Feb 2021 12:07pm
62 Sun Inn 203 Bridge Street 203/205
by bert1. 27th Feb 2021 6:03pm
79 Caledonia 42 Cathcart Street 237 Cleveland St
by mikehaynes. 27th Feb 2021 4:34pm
153 Royal Duke Hotel 1 Duke Street
by casper. 27th Feb 2021 2:58pm
Guinea Gap
by Greenwood. 27th Feb 2021 11:27am
21 Angel Inn 1 Beckwith Street 1 Camden Street
by mikeeb. 27th Feb 2021 9:43am
March
M T W T F S S
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31
Recent Posts : What's On ?
Previous Topic
Next Topic
Print Topic
Rate Topic
Help building a model hydroplane? #1067324
6th May 2019 7:03am
6th May 2019 7:03am
Joined: Aug 2015
Posts: 174
Bebington
G
gerrymoore Offline OP
Enthusiast
gerrymoore  Offline OP
Enthusiast
G
Joined: Aug 2015
Posts: 174
Bebington
I already have a radio control TX and RX and suddenly fancy building a very fast little boat. Saw a guy on Gautby road lake when I was a kid (what a memory I have!!) who had a hydroplane/airboat powered by a little glow plug engine and airscrew - wow that went FAST!!!

I want to use an electric motor with a an ESC and lipo battery but not sure what sort of power I need to go FAST!!! Also what size/type of prop.

Anyone here know anything about what I'm talking about and can offer any advice??? Thanks Gerry

Google Ads
Re: Help building a model hydroplane? [Re: gerrymoore] #1067329
6th May 2019 10:05am
6th May 2019 10:05am
Joined: Jul 2008
Posts: 13,912
Birkenhead
diggingdeeper Offline

Wiki Master
diggingdeeper  Offline

Wiki Master
Joined: Jul 2008
Posts: 13,912
Birkenhead
I’ve seen those sort of things and they are stupidly fast like you say. Trouble is that the smaller they are the stiller the water has to be and you might not get very many “sailing” days in.

The main one I saw was about 3ft across which would be a bit big for some boating lakes especially at those speeds.

You are probably much better off sticking to combustion engines, with racing model cars and aeroplanes the running time of electric is hugely less than fuel.

I’ll try and work out some power figures later if I can.


The further you are down the pay scale, the more 'essential' you are when the s--- hits the fan... Sue Farbysmith 2020

Insults are engendered from vulgar minds, like toadstools from a dunghill - Charles Caleb Colton

We don't do charity in Germany, We pay taxes. Charity is a failure of governments' responsibilities - Henning Wehn
Re: Help building a model hydroplane? [Re: gerrymoore] #1067330
6th May 2019 10:28am
6th May 2019 10:28am
Joined: Aug 2015
Posts: 174
Bebington
G
gerrymoore Offline OP
Enthusiast
gerrymoore  Offline OP
Enthusiast
G
Joined: Aug 2015
Posts: 174
Bebington
Wow DD you are the 'master' - thanks for replying so quickly!!

I'm thinking around 30" -36" size with a powerful brushless motor and 3S lipos's - should give around 10 - 15 minutes running but not sure what size prop and motor.....problem with glow engines is they are very noisy even with a 'silencer' fitted....also I have a few 3S lipos from my drone (which never gets used now).

Re: Help building a model hydroplane? [Re: gerrymoore] #1067413
7th May 2019 12:12pm
7th May 2019 12:12pm
Joined: Jul 2008
Posts: 13,912
Birkenhead
diggingdeeper Offline

Wiki Master
diggingdeeper  Offline

Wiki Master
Joined: Jul 2008
Posts: 13,912
Birkenhead
What sort of sped do you want to go to?

In my eyes, fast is probably 30mph, racing 60mph, straight-line stuff over 100mph (real speeds, not scaled).

I haven't gone to detail yet but very very rough work is showing that for 18" wide (36"length, they are normally a 2:1 ratio) to do over 60mph it the motor would probably probably have to be around 800w. I'd guess it is best to keep the airscrew speed down (water hitting a high speed blade is probably going to destroy it) so limiting to say 7000rpm is going to be something like a 6X5 blade.

The other extremely rough estimate was 36" wide (72" long) needing 1.2kW (around 1.5 horsepower) to get above 60mph and maybe a 10X5 blade.

You'll probably need two 3S's in series as you will need at least 20V to be efficient at those sort of powers and will need relatively low Kv motor ratings as you might not want high revs.

Part of the problem is the inefficiency caused by having to drive the front of hydroplane down into/onto the water to ensure it doesn't do a Donald Campbell. If it truly skims the water with very little pressure then the slightest ripple could kick it over at high speed, this will be worse when de-accelerating, the thrust being above the centre of gravity will help keep the nose down when accelerating or keeping speed constant.

Trying to design an aeroplane that will never take off is one heck of a challenge and not dissimilar to formula 1 other than you don't need the downforce on the rear for traction.

Designing these things to be stable in a straight line is very difficult, to make stable fast turns is an even bigger problem.


The further you are down the pay scale, the more 'essential' you are when the s--- hits the fan... Sue Farbysmith 2020

Insults are engendered from vulgar minds, like toadstools from a dunghill - Charles Caleb Colton

We don't do charity in Germany, We pay taxes. Charity is a failure of governments' responsibilities - Henning Wehn
Re: Help building a model hydroplane? [Re: gerrymoore] #1067455
8th May 2019 8:11am
8th May 2019 8:11am
Joined: Aug 2015
Posts: 174
Bebington
G
gerrymoore Offline OP
Enthusiast
gerrymoore  Offline OP
Enthusiast
G
Joined: Aug 2015
Posts: 174
Bebington
Hi DD ...my 'new' thinking is a normal speedboat V type hull with inboard motor and propeller and either single or twin rudders....so not really a hydroplane but more practical.

I've got my eye on a secondhand bare hull that's 70cm long and 24cm wide. Interesting about the Kv size of motor as I don't know much about the volts/rpm linking. If I was to use a normal 2 or 4 blade prop, what sort of rpm for the prop are we talking..I'm wondering whether I may need a reduction gearbox of some sort.

I would like to achieve 30mph if possible...any faster and it would frighten me .....and any poor kids near the pond!!!

Must add I am impressed with your knowledge:-)) Thank youGerry

Re: Help building a model hydroplane? [Re: gerrymoore] #1067462
8th May 2019 1:31pm
8th May 2019 1:31pm
Joined: Jan 2010
Posts: 1,764
wirral
E
Excoriator Online content
Forum Addict
Excoriator  Online Content
Forum Addict
E
Joined: Jan 2010
Posts: 1,764
wirral
If you want high speed you have to get the drag down, and the way to do that is to get the hull out of the water.

You can do that with active (controlled) hydrofoils on legs with only these and the propeller in the water.

You'd need a microprocessor (An Arduino might be up to the job) to control the hydrofoils of course, but as I think you are a drone enthusiast which must use very similar control algorithms and sensors, it shouldn't be a huge problem.

It will be a lot faster on the same power than trying to shove a hull through the water. Also, as it is out of the water it will tolerate much rougher conditions.

Re: Help building a model hydroplane? [Re: Excoriator] #1067475
8th May 2019 4:28pm
8th May 2019 4:28pm
Joined: Jul 2008
Posts: 13,912
Birkenhead
diggingdeeper Offline

Wiki Master
diggingdeeper  Offline

Wiki Master
Joined: Jul 2008
Posts: 13,912
Birkenhead
Originally Posted by Excoriator
If you want high speed you have to get the drag down, and the way to do that is to get the hull out of the water.

You can do that with active (controlled) hydrofoils on legs with only these and the propeller in the water.


I'm sure from your own argument you can see that its not active hydrofoils you need in order to minimise drag, it is active aerofoils.

Active hydrofoils on a model are almost impossible to control, it is extremely difficult to sense a reference position, 2mm height difference can be the difference between ploughing through water and being airborne.

Propeller in the water is also an increased drag as it has to be in a significant depth, at least the diameter of the propeller and more to reduce cavitation and centrifugal splatter. Worse still a propeller tries to lift the nose when you accelerate unless it is angled downward which is inefficient and lifts the rear end.

There must always be a downforce to prevent it being an aeroplane, you cannot hydroplane out the water, the faster you go the more downforce you need unless the water is absolutely ripple free.

Lots of studies have shown that legged hydrofoils/hydroplanes are not stable enough at really high speeds especially with turns, a design more like concord is often found to be best, the wide rear gives it stability without significant drag, the light nose just needs sufficient downforce to stop it lifting, the wide heavier rear will naturally skim the water and needs little control or downforce.


The further you are down the pay scale, the more 'essential' you are when the s--- hits the fan... Sue Farbysmith 2020

Insults are engendered from vulgar minds, like toadstools from a dunghill - Charles Caleb Colton

We don't do charity in Germany, We pay taxes. Charity is a failure of governments' responsibilities - Henning Wehn
Re: Help building a model hydroplane? [Re: gerrymoore] #1067601
9th May 2019 10:42pm
9th May 2019 10:42pm
Joined: Jan 2010
Posts: 1,764
wirral
E
Excoriator Online content
Forum Addict
Excoriator  Online Content
Forum Addict
E
Joined: Jan 2010
Posts: 1,764
wirral
Fast averaging will give you an adequate reference position.

I don't accept that its almost impossible to control hydrofoils. given that fast averaging system. It's a straightforward control problem which you can probably best solve by a relatively simple analogue circuit using op-amps. Although I guess a slower digital system would be preferred these days.

Re: Help building a model hydroplane? [Re: gerrymoore] #1067602
10th May 2019 12:43am
10th May 2019 12:43am
Joined: Jul 2008
Posts: 13,912
Birkenhead
diggingdeeper Offline

Wiki Master
diggingdeeper  Offline

Wiki Master
Joined: Jul 2008
Posts: 13,912
Birkenhead
Average what, from what sensor(s)? I don't know of a g-force sensor that doesn't drift and I struggle even more to think of a possible analogue sensor.

Ripples and waves are always complex, peaks can be tens of seconds apart or one-offs, there is no Bayesian solution.

Near instantaneous height correction would not work, you can't attempt to steer the contour of each ripple without knowing the future contour.

The attitude of the hydroplane isn't constant, you could attempt to force it to be constant but sooner or later you are going to plough into the water.

Much like a hovercraft, it is the physical design that what does most of the work not an electronic control system.


The further you are down the pay scale, the more 'essential' you are when the s--- hits the fan... Sue Farbysmith 2020

Insults are engendered from vulgar minds, like toadstools from a dunghill - Charles Caleb Colton

We don't do charity in Germany, We pay taxes. Charity is a failure of governments' responsibilities - Henning Wehn
Re: Help building a model hydroplane? [Re: gerrymoore] #1067604
10th May 2019 7:20am
10th May 2019 7:20am
Joined: Aug 2015
Posts: 174
Bebington
G
gerrymoore Offline OP
Enthusiast
gerrymoore  Offline OP
Enthusiast
G
Joined: Aug 2015
Posts: 174
Bebington
Wow guys ..... I only want a 'relatively simple little boat' not planning to cross the Atlantic !!! :-))


Moderated by  Mod 

Random Wirral Images

Click to View Topic.
Newest Topics
Wirral Council budget.
by mikeeb. 1st Mar 2021 3:38pm
4 Bridges
by mikeeb. 1st Mar 2021 2:28pm
Birkenhead centre development
by mikeeb. 28th Feb 2021 12:06pm
Guinea Gap
by mikeeb. 25th Feb 2021 12:22pm
Pier House New Brighton
by Moonstar. 21st Feb 2021 10:31am
For Sale & Free
CUPS & SAUCERS FREE
by gerry1. 20th Feb 2021 11:52am
Black and Purple Puma Suedes
by Julie64. 16th Feb 2021 1:55pm
Red leather Lacoste bag
by Peter0787. 14th Feb 2021 1:08pm
PLASMA TV/MONITOR £££ 4 U
by _Ste_. 13th Feb 2021 9:44pm
Vauxhall meriva 1.4 VXR rep
by paul110180. 1st Feb 2021 11:21am
Member Spotlight
Moonstar
Moonstar
Wirral
Posts: 1,390
Joined: July 2011
Show All Member Profiles 
Newest Members
Sustu, PJPlease, jamiel, Rebeccacurran, Bebington75
13709 Registered Users
Today's Birthdays
No Birthdays
New Wirral Info
Wirral Council budget.
by mikeeb. 1st Mar 2021 3:38pm
4 Bridges
by mikeeb. 1st Mar 2021 2:28pm
Birkenhead centre development
by mikeeb. 28th Feb 2021 12:06pm
Pier House New Brighton
by Moonstar. 21st Feb 2021 10:31am
Business now demolished Late 70s Higher Beb.
by philstreet. 20th Feb 2021 11:49pm
News : New Topics
Perseverance
by cools. 19th Feb 2021 10:22am
Lucky horse
by cools. 6th Feb 2021 9:12pm
Brackenwood
by cools. 30th Jan 2021 8:08pm
Fishing
by diggingdeeper. 29th Jan 2021 5:16pm
New Meseyrail trains
by Excoriator. 26th Jan 2021 3:16pm
New Enthusiast Forums
Pooch perfect
by cools. 20th Feb 2021 10:29am
SystemOfADown
by GaryFromWirral. 9th Feb 2021 3:59pm
Free Dog with your Pizza
by granny. 7th Feb 2021 10:15am
Wirral Covid
by diggingdeeper. 4th Jan 2021 2:59am
If You Want To Know More About Mental Health
by diggingdeeper. 1st Sep 2019 12:20am
Popular Topics(Views 24hrs)
Wirral Sunrise Sunset
Sunrise Mon 6:57am
Sunset Mon 5:50pm
Local Time Mon 11:41pm
Powered by UBB.threads™ PHP Forum Software 7.6.1.1