Virgin Atlantic Challenger II plans

[John W EParticipant @johnwe]

hi ya there

had time to have a bit think about the boat's performance in both models and I think part of the problem is the actual hull design. The original/lifesized vessel is an offshore power boat, specifically designed to go in straight lines in rough weather and therefore a very deep v in the hull. Therefore, it doesnt take a turn in tight circles easily – all deep v's tend to fall off the plane because of the increased wetted area on the side when turning.

I built a model of the Surfury with an IC engine and it suffered the same problems, brilliant in a straight line come to corner,….. and she would come off the plane.

Also, if you look at the Virgin Atlantic Challenger's propshaft design; how it stick out from the back of the boat; I dont think this would help either because of the tunnel that you had to create in the back of the hull to accommodate the propshaft.

The last, which we definitely think is the problem, is the U shaped rudder – its acting like a nozzle – but not a very efficient one. Replacing this with a single rudder may help the problem – and it would be interesting to see if you see any great improvement. But, I do have my doubts.

I have built several models – semi scale – one of Glyn Guests MTB – and the other one of Dave Milbourn's Fairy Swordsman and they have moderate V on the bottoms and they outperform the Atlantic Challenger any day in overall performance in turning and in a straight line. They have very similar motors and props on them.

Also they run on the same voltages.

food for thought….aye

john

 

Edited By bluebird on 11/10/2013 10:36:58

Edited By bluebird on 11/10/2013 10:37:23

Edited By bluebird on 11/10/2013 10:37:51

[Joseph BookerParticipant @josephbooker97221]

Thinking something like this

**LINK**

It should fit under the transom above the prop/shaft and should stick out enough (40mm) to clear the prop

[Joseph BookerParticipant @josephbooker97221]

Tried it with a different prop…Problem only got slightly better….But also noticed that the boat isnt ballanced and needs abit of weight towards the stern, so only weight I had on me was a spare battery,lol…So I put that in centrally with the other battery to just weight it down abit, and that made the problem even slightly better.

So next try will be afew fishing weights inside on the stern with one battery and see how it goes then….If it doesnt work then time for a new rudder,lol

[John W EParticipant @johnwe]

Hi Joseph have a look at this build

**LINK**

aye

john

[John W EParticipant @johnwe]

hi ya Joseph

is there any progress with getting the Virgin Atlantic to run correctly? Or, has it been put on hold for the time being?

aye

john

[Joseph BookerParticipant @josephbooker97221]

Its on hold due to waiting for a delivery from hobby king…Got various different rudders coming so just waiting for them to arrive and can get on with it.

Just getting on with the cabin and deck area, just going through the priming and sanding stages of it

[John W EParticipant @johnwe]

hi ya there Joseph,

Did you try the model with extra weight in it? If you did, did it make any improvement???

aye

john

[Joseph BookerParticipant @josephbooker97221]

Yeah put abit of extra weight in the stern….It helped slightly but only minimal.

At a notch off full speed it has a turning circle of about 20-25 metres, try to do it tighter and it starts cavitating

So just waiting for new rudders and hope that improves it more

[Joseph BookerParticipant @josephbooker97221]

Ok tried it with the conventional rudder…It helps in the turn, but when on full throttle in a straight line the bow bounces more and when the boat does little jumps and comes out of the water and comes back down again it starts cavitating

Barring in mind I dont have trip tabs on yet and dont know if that would help it with the bow bouncing around and keeping it in the water

[John W EParticipant @johnwe]

hi ya Joseph

Good to hear that the single rudder improves it slightly and yes if you fit the trim tabs it will improve performance a bit more by keeping the nose down. With the boat coming out of the water, its proven that you have sufficient power and that the hull is performing well. Now I think we need to look at the propeller – you are entering the field of surface piercing props and therefore need a coarser pitch on the prop. So, in theory you are actually trying to encourage cavitation to get the best performance.

Honestly I think we on the limits of the hull design now.

aye

john

Edited By bluebird on 05/11/2013 19:50:04

[Joseph BookerParticipant @josephbooker97221]

cant seem to find any M5 threaded Surface propellers between 35mm and 42mm

[Joseph BookerParticipant @josephbooker97221]

Still having issues…trim tabs have stabilized it and inproved performance in the turn…but its increased cavitation/ventilation in a straight line…will post pictures see what you suggest what to do because im thinking about dropping the prop shaft and also think the trim tabs maybe abit to big

[Tony HadleyParticipant @tonyhadley]

For the prop, try contacting Dave Marles at Prestwich Model Boats— **LINK**

[Joseph BookerParticipant @josephbooker97221]

What are your thoughts? trim tabs to big and overlapping the prop? does the prop shaft need dropping so the prop is more in the water?

[John W EParticipant @johnwe]

hi ya Joseph

 

After looking at the photographs that you have put on and comparing it with the plan and my model – I think the angle on your propshaft is a bit shallow – and also a bit close to the transom. This, I am afraid, will cause cavitation and/or bad performance. It is up to you now – as it is a major job removing a propshaft and increasing the angle slightly – but it can be done – however for the extra bit of performance you will gain from it – is it worth it? It is up to your goodself – and how much time you wish to spend on the model.

 

As I have said before, what we must realise is that this is semi scaled model and we arent going to get any spectacular performance out of it. The trim tabls look about the right size and altering them by decreasing the length wont really increase the performance.

 

I know when I built my model and sailed it, of the Virgin Atlantic, I too was unhappy with the performance but I have (as I have said) other model plans which are semi scale such as the MTB and the Fairy Swordsman that I have built; and they do outperforme this model. They are the same style of build nice n easy.

aye

john

Edited By bluebird on 17/11/2013 11:09:07

Edited By bluebird on 17/11/2013 11:10:55

[Joseph BookerParticipant @josephbooker97221]

Time to take all the electrics out and make room for removing the prop shaft then…Done it before when the old prop shaft was bent so I'm ok doing it again just to see if changing the angle helps…Just worried about heating up this prop shaft tubing because its expensive and dont want to warp it,lol

Wish me luck and thank you john <3

[Joseph BookerParticipant @josephbooker97221]

Think this looks more like it??? waiting for the epoxy to cure properly then can test it

[John W EParticipant @johnwe]

hi ya Joseph, that looks about right now. But, Ive just noticed where your water pickup is for your cooling – that might be causing you some trouble as well. Normally, water pickup scoop is placed behind the propeller – I know its a bit awkward on these boats where it would have to be mounted on the back shelf of the transom – lets knowhow you get on to see if it makes any great improvement.

aye

john

[Joseph BookerParticipant @josephbooker97221]

I had a feeling you might pick up on that because I didnt like putting it there either,lol

Only place I could put it to make sure there is always a constant water flow….Did have a metal hydro rudder on it with water pick up but the inles hole was to small, so I switched to this black plastic rudder that has a smaller trigger from the transom so I could fit a bigger prop…Thats why you also see the filler above the platform because thats where the water pipes were going through ^^

But yeah see how it goes

Transom is taking abit of a hammering with all these changes all the time,lol but is my first boat build so still learning <3

Edited By Joseph Booker on 18/11/2013 20:01:17

[Joseph BookerParticipant @josephbooker97221]

Fix one problem another one props up…Now close to full throttle it sometimes suddenly decides to slightly tilt left and turn right,lol

It happens mostly on a 40mm deep pitch prop

Videoed the worst of it for you ^^

[Joseph BookerParticipant @josephbooker97221]

Heres a video of it with a shallow pitch prop

[John W EParticipant @johnwe]

Hi there

well I think you have reached perfection now and I dont think you are going to get the boat to perform any better. To answer your question about why the boat all of a sudden veers off left to right is because you have reached the limits of the hull's performance and you are riding on your propeller. In other words the boat has come so far out of the water, in theory it is balancing on the propeller – that is the main reason and I am afraid there is very little you can do with that – just enjoy the performance. I certainly have enjoyed watching your videos. Obviously on the last video with the smaller prop you have lost a bit of performance but you will get a longer running time.

aye

john

[Keith BirchallParticipant @keithbirchall34951]

Hi I know this is a old thread now but was wondering if anyone managed to find a copy of the july 1995 magazine. If anyone does have a copy that they would be willing to sell could you get in touch please. Or if anyone has a copy and would be willing to photo copy the pages about the virgins atlantic challenger I would pay all costs. I built this model a long time ago. Whilst rooting around in my attic I found the plans but can not find the magazine and would like to build another model with my young son. Any help with this would be much appreciated. Thanks Keith

[harry smith 1Participant @harrysmith1]

Hi Joseph

The boat requires the weight moved forward to stop the bow bouncing up and down.

About 20-25mm to start with and go from that .

Canabus

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