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Author Topic: Malcs Hms Fearless build  (Read 14668 times)

derekwarner

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Re: Malcs Hms Fearless build
« Reply #25 on: November 24, 2016, 07:36:40 AM »

Malc....a long & brilliant post & a lot or reading O0...........find the section of internal hull flooding & the resolution fix..... :-)) Derek


http://www.modelboatmayhem.co.uk/forum/index.php/topic,36872.msg519344.html#msg519344
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Derek Warner

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malcf

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Re: Malcs Hms Fearless build
« Reply #26 on: November 24, 2016, 12:58:25 PM »

Have just read part of the build blog, as the vessel is submersible I would imagine that there is some pressure on the system, on the fearless the two tanks are vented to the atmosphere  and as such the only pressure will be from the pump that is in operation  either filling or emptying, the tanks are made of fibreglass about 2mm thick  glassed to the inner hull as are the tubes albeit they are not barbed, the weak link in the system is the flimsy neck on the pumps but if they work in a pond they should be fine.
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Bob K

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Re: Malcs Hms Fearless build
« Reply #27 on: November 24, 2016, 04:14:37 PM »

Hi Derek not heard of bob k any chance you can send me a link or more info on his problem?.
BTW I am planning to secure the pipes with cable ties at a later date do you think that will solve the problem?.

http://www.modelboatmayhem.co.uk/forum/index.php/topic,36872.0.html

Building semi submersibles can be harder that it may appear
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Dave Cook

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Re: Malcs Hms Fearless build
« Reply #28 on: November 24, 2016, 07:03:19 PM »

Hi Malc , Bloody hell mate you are getting on with things , You must tell me when you are going down to the club for first sea trials.
Best Regards Dave  :-)) :-)) :-)) :-)) :-))
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derekwarner

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Re: Malcs Hms Fearless build
« Reply #29 on: November 24, 2016, 08:33:14 PM »

Malc.....life ain't that simple......lets go back to high school physics  %).......

Unfortunately the batteries are still flat in my solar powered abacus..... and I do have trouble  >>:-( with the decimal point.......so lets consider the following examples with hypothetical submersion or head measurements  .....

Bob K's semi submersible vessel submerges 100 mm below his vessels water suction port
Atmospheric pressure is 1 Atmosphere, ~~1 Bar or 14.7 PSI at the waterline
For every 10.06m of depth of water, we experience an increase in pressure of 1 Bar or 14.7 PSI
So the only pressure his tank silicone tube & push on fittings are subjected to is 0.00147 PSI over atmosphere @ +100 mm suction depth 

Your HMS Fearless ballast tanks tops are 100 mm above the water suction ports, pressed up fully then open to an atmospheric port

.......so without repeating the computations above....

Your silicone tube & push on fittings are subjected to the same 0.00147 PSI over atmosphere @ +100 mm tank head above the water suction ports

I mentioned in another thread this week....'it is easier to detect and eliminate fluid leakage at 250 Bar than to cure fluid decay from 1 Bar"

Derek



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Derek Warner

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ballastanksian

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Re: Malcs Hms Fearless build
« Reply #30 on: November 24, 2016, 09:11:21 PM »

It was heart breaking to see the footage of Bob's Poly tale a dive so can only reccomend that you do secure the ends of your pipes. Your Fearless is lovely and no one wants to have to read your efforts on drying and repairing all your hard work  :o

By the way, I like your printed switch unit. That is a product that would sell I reckon.
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Bob K

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Re: Malcs Hms Fearless build
« Reply #31 on: November 24, 2016, 09:19:08 PM »

In my case, I had the ballast tanks free vented at the bottom, a simple air release valve system at the top, and a 32 psi air pump to blow the tanks. 

The air pressure was enough to 'blow' the silicone tubes off the unbarbed spitots which resulted in water venting into the hull.  Using wire-secured barbed spigots solved the problem.  ie:  It was not the static water pressure at 100mm depth, but the air pump pressure required to vent the tanks at 2 litre per minute.

I would definitely recommend using wire secured barbed connections.
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malcf

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Re: Malcs Hms Fearless build
« Reply #32 on: November 24, 2016, 10:59:33 PM »

Thanks ballastanksian for your appreciation of the switch unit, I may well make a few units to trade or swap but the big downside is the printing time as it is about one hour and a quarter at 100% fill to print one, and thank you to bob k and derek for the guidance regarding the tubing, I have read a portion of bobs build (in due course I will read all of it) bob uses compressed air to blow the tanks and I can fully understand the problem of the seals leaking and also the need for the hoses being secure preferably with barbed hose tails, I have already tested the system in my test tank using the bare hull with one forward  bulkhead bonded in with silicone sealant and the fibreglass well deck sealed in transferring around 2 1/2 litres of water between the  open topped forward bulkhead to the tubes bonded into the well deck using two pond pumps and also ballasting the central motor battery area with 4 12 volt sla batteries as ballast and then later with 5 sla batteries using less water as ballast, by moving the water to the stern I could lower the stern to the flooded deck level albeit without the well deck area flooding as at that time the transom was still uncut but I did add extra water to simulate the well deck being flooded, level trim was achieved by distributing the water between the two tanks, when the rear tank was emptied the hull stern could be raised by about 2-3 inches out of the water so a little bit of fine tuning will be needed as to how much water will be needed when the model is finished, I will make sure the hose connections are secure and if need be I will use the crimp clips as used on compressed air lines, and I am planning to fit the speed controllers above the water line  along with the receiver allas the motors cannot be lifted and so in the event of a flooding may get damaged but the batteries would survive.
I will most likely block off the end of the forward ramp with a vertical bulkhead to around deck level as an extra bit of protection.
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malcf

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Re: Malcs Hms Fearless build
« Reply #33 on: November 28, 2016, 05:50:47 PM »

A few more pics here, I have been filling the outside of the hull around the A and P frames and the prop tubes plenty of sanding dust later and the hull is taking shape :embarrassed:, on the plan there is a faired in area around the prop tubes rather than using just filler I printed a tapering tube for these and sanded them to shape and bonded them in place and applied a fillet of p38 filler and blended it in, I have also added the two supports for the stern door these have been reinforced with 3mm stainless steel pins drilled and bonded to the hull.
Also there are a couple of pics of my first attempt at printing the funnel stacks, the cross piece has been added to give it strength, it was only after I had printed them that I noticed they are supposed to be different lengths >>:-( the tops of the funnels will be drawn up later, I also have to apply a fillet of either epoxy or filler to fair the bilge keels in, I reckon I will go for epoxy as filler can be a bit brittle.

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malcf

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Re: Malcs Hms Fearless build
« Reply #34 on: November 28, 2016, 06:37:01 PM »

A few more pics  :-))

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ballastanksian

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Re: Malcs Hms Fearless build
« Reply #35 on: November 28, 2016, 09:12:44 PM »

Good progress Malcolm. Can you cut one of the funnels down, or is the long one even longer than you have currently printed? I am sandng bits of a hull at present and need to get the vacuum out.
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malcf

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Re: Malcs Hms Fearless build
« Reply #36 on: November 28, 2016, 09:32:08 PM »

Alas they are both the shorter ones but they are only prototypes I will be modding the program so that the top of the funnel fits on and probably provide a connection at the base for a smoke machine to fit on. :-)) I am printing a funnel top at the moment and hoping it comes out ok.
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ballastanksian

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Re: Malcs Hms Fearless build
« Reply #37 on: November 28, 2016, 09:40:34 PM »

I cross my cringers for you malcolm.
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malcf

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Re: Malcs Hms Fearless build
« Reply #38 on: November 28, 2016, 10:03:52 PM »

It didn't come out as expected a couple of defects, slight drawing error ie tiny reversed faces on the drawing that I missed so mk2 on the way. {:-{
You can see the drawing below it is made up of flat faced triangles to make up the shape, also the curves are made up of straight lines, the more segments the more triangles. %%
The first photo of the part shows the error running diagonally across the inside, this is because the software cannot tell the difference between an inside face and an outside face, the second photo shows a hole on the outside of the funnel top this is also an inside face hence the build up on the inside of the item linking across to another face that is wrong.
Tiss a bit heavy going at times trying to spot the problems <*<
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ballastanksian

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Re: Malcs Hms Fearless build
« Reply #39 on: November 28, 2016, 10:21:19 PM »

Yes despite all the developments in the printing technology, it is still the Mk1 eyeball that needs to check the drawing! is this the case across the board, or are the cutting edge programs able to help spot flaws?

Very interesting stuff.
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malcf

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Re: Malcs Hms Fearless build
« Reply #40 on: November 28, 2016, 10:27:28 PM »

I cannot vouch for other software but I would imagine that if it is drawn wrong it will come out wrong , my software has a rudimentary error checking program built in but sometimes it can make it even worse still. <:(
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ballastanksian

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Re: Malcs Hms Fearless build
« Reply #41 on: November 28, 2016, 10:30:14 PM »

Sounds like spell check!
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Dave Cook

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Re: Malcs Hms Fearless build
« Reply #42 on: November 28, 2016, 10:34:26 PM »

Malc , You are doing a great job

best regards Dave  :-)) :-)) :-)) :-)) :-))
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malcf

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Re: Malcs Hms Fearless build
« Reply #43 on: November 28, 2016, 10:42:21 PM »

Thanks dave  :-))as you will have noticed I am hoping to use the 3d printer a lot in this build one reason is to further my drawing and programing experience and another is to save having to buy so many resin cast parts, and the other reason is after paying out considerable for the machine I had better make use of it  to keep her indoors happy after all she bought it for me. <*<
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malcf

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Re: Malcs Hms Fearless build
« Reply #44 on: November 28, 2016, 10:51:10 PM »

Second attempt much better, this one is still attached to its build raft and still has its temporary supports on the outer perimeter which will form a recess for the funnel body to fit on.
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Capt Podge

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Re: Malcs Hms Fearless build
« Reply #45 on: December 05, 2016, 05:23:49 PM »

Just found this one of Fearless - possibly another reference photo for you ?

www.flickr.com/photos/scottishmaritimemuseum/27488211956/in/photostream/

Regards,

Ray.
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malcf

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Re: Malcs Hms Fearless build
« Reply #46 on: December 05, 2016, 06:30:50 PM »

Thanks Ray  :-)) keep the links coming some nice pics on that site.
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malcf

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Re: Malcs Hms Fearless build
« Reply #47 on: December 05, 2016, 06:40:57 PM »

Thoughts please {:-{ should I fix the helli deck down or have it removable, I do need to access an area directly behind the superstructure for about 3 inches and nearly the full width of the deck where the servo's are situated, motors and batteries etc can be accessed by removing the superstructure so no problem there.
Forgot to say I am intending to make the deck out of 2mm or 3mm max styrene with I section cross beams to simulate the original.
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ballastanksian

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Re: Malcs Hms Fearless build
« Reply #48 on: December 05, 2016, 10:20:03 PM »

Hatches in flat surfaces seem to show up so maybe having the deck removable. Leaving the margin in place with nets or railings to help mask the gap could be fragile but less conspicuous. It is a shame there wasn't a lift  to double as a hatch.
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malcf

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Re: Malcs Hms Fearless build
« Reply #49 on: December 06, 2016, 12:54:42 PM »

A removable deck has some merits  as the majority of the area is above the well deck so if any water got in, it would be ok and drain away under sailing mode, the only area needing to be relatively watertight is above the servo's and fitting up to the superstructure locating raised section/ lip, so it may be screwed down in this area onto a gasket and magnets elsewhere.
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