John Cobb’s Crusader

[ashley needhamParticipant @ashleyneedham69188]

Cheers DM. What a bit of paint will do!

Will it work?? Good question. My worry is that the lifting wedges front and rear (sponsons) may not be wide enough to support the craft as it sets off, making it too wet to separate and plane, but..

Ashley.

Worried of Molesey.

[Bob Abell 2Participant @bobabell2]

Looking really nice Ashley

How are the engine trials doing?

Bob

[Paul TParticipant @pault84577]

Talking of engines I saw this one and thought of Ashley.

A proper engine for his jet boats.

Paul

[Chris FellowsParticipant @chrisfellows72943]

Ashley – Looking really good. Just an observation, wouldn't the spray rails be better continuing to the nose and being higher? From the photo they don't look as though they will do what you want, stopping water getting into the intakes at lower speeds.

Chris

[Ray Wood 3Participant @raywood3]

Hi Ashley,

Have you done the indoor flotation test with the gear & battery aboard ?? I imagine lack of buoyancy at the bow will be an issue, and the fan thrust trying to bury the front end, I suppose time will tell, but she looks great, and good to see your stuff not being On the secret list 😃

Let's hope Boris let's us out to go boating soon 😎

Regards Ray

Edited By Ray Wood 2 on 10/05/2020 07:32:46

[ashley needhamParticipant @ashleyneedham69188]

Bob. Have not yet fired up the engine. When I do install it, I expect there to be loads of whoosh at the back, but this will not tell me if it’s adequate…

PT. yes. I wouldn’t mind betting that a modern bug brushless is more powerful??

Chris and Ray. I pondered this aspect for a good while, but continuing spray rails eithermore forward or higher would compromise the look a bit. The garden pond test shows that the nose sits high and the back down, so although the thrust line is slightly downwards and will tend to push the nose down I hope the wedge will lift before it starts to swamp.

The spray rails hopefully will only come into play when going fast, stopping water off the lower wedge portion climbing up. Will try and post a pond floatation snap so you can see. My Crusader front is that much wider than scale to try and get more lift. If I have problems the proposed fixes will be..another strip of say 5mm foam on top of the existing wedge or possibly widening the wedge at the rear a bit?

Ashley

[Ray Wood 3Participant @raywood3]

Hi Ashley,

The new brushless units are in a different league all together, my original Wetjet design with a hot race 480 & Womotec fan unit wouldn't pull the skin of a rice pudding !! On 9.6volts.

I know you have the brushed units but think you will be disappointed, and use 3 cell lipos 11.1 volts with you 50mm units for max thrust !!

Only my thoughts, time will tell 😃

Regards Ray

[ashley needhamParticipant @ashleyneedham69188]

Ray, the Cobb has a brushless 50mm on 3s ! Bluebird has a 64mm brushless.

I used a GWS 55 brushed to test out the Bluebird, and As expected it was slowish! It did make the right noise though and there was the jet wash pattern on the water.

Swordfish will use the GWS unit, on a 2s but this will be much much lighter than the other two.

Ashley

[Ray Wood 3Participant @raywood3]

Hi Ashley,

Just me with the wrong end of the stick !!!! I knew you had mentioned brushed motors in the past 😃

Just finish my Jet Provost with the 50mm the fan .. In case we are let out .

Regards Ray

[ashley needhamParticipant @ashleyneedham69188]

A bit of red paint. Not quite finished but I am not doing more red. There is no margin for error as the silver has been varnished and the humbrol red stains this instantly so there is no wiping away errors. Bit of retouching to do yet of course.

All the curved bits have been hand done and I don’t trust myself to do the much larger red swoop at the nose as accurately as I would like.possibly I might mask off and do a straight red line along the bottom.

Swordfish shown alongside!

Ashley

 

Edited By ashley needham on 10/05/2020 14:15:58

Edited By ashley needham on 10/05/2020 14:16:26

[ashley needhamParticipant @ashleyneedham69188]

Rereading the thread from the start, it was 9/2012 I said “looks like an interesting project” and here we are 8-ish years later building same!

Have just been reading up on John Cobb and he was a local man! Born in Esher, just 4 miles away from me.

Also buried in I think Christ church in Esher, which I have been in once, and there is a site called “find my grave” which has a picture of his resting site.

Unfortunately we have my wife’s brother Stewart’s funeral this afternoon, but I will make a point of cycling to Esher in the next few days to visit the grave.

BTW…how do you mask curves? I have only tried once or twice with esc’s than great results. Presumably you can get bendy masking tape or is a matter of. Cutting a curve on your masking tape and doing it that way?

As I said, there are no second chances on my red paint wok, but I can see that if I put red along the bottom it will have to meet the red at the nose..?

Ashley

[Bob Abell 2Participant @bobabell2]

Very attractive model, Ashley

Hope it performs as good as it looks

Bob

[Ray Wood 3Participant @raywood3]

Hi Ashley,

Tamiya do reels of mini masking tape 1/16", 1/8",1/4" it's great and goes round corners easily,

regards Ray

[John W EParticipant @johnwe]

hi Ashley

I have tried Ray's suggesting using Tamiya tape to mask circles and radius' off – and – it is okay if you have a radius to follow but its difficult to freehand a radius (for me anyway ) so what I did on my last model was, I purchased 2 inch wide – cheap masking tape from the 'cheap shop' – and masked the whole area off to be done and as you have already thought of, draw round with a pencil using a template and then with a scalpel following where you have marked and remove the unwanted area – you can then paint to your heart's content. I will be honest with you though there was a bit of 'bleed' through on the tape when I did this. I would try the cheap masking tape on an unseen area where you have painted (underneath the hull maybe) just to check it doesn't pull the paint off. I do have that medal as well.

Really, I am saying very little and I am watching your build, with these air duct fans you are going to use. A while ago, I happened to purchase from a guy who was emigrating to Canada, all of his aircraft stuff. Amongst it was a ducted fan, it has a brushless motor attached and speed controller. I do still fancy building a Bluebird from balsa wood and fitting the ducted fan as you have done – but – I am unsure about the power of this ducted fan as I have heard that they may not actually produce much thrust for a model boat (too much water drag on the hull) so, what I was going to do – until you came along with your build – was build a Catamaran hull from balsa and stick the fan on the top – just to see how it would perform or, build a Go-cart from Meccano for land based trials but this will be on hold until I see your models perform.

so here's hoping – HAPPY MODELLING

John

[Chris FellowsParticipant @chrisfellows72943]

The kids at Bushey Park are going to love that. Looks the biz now with the red paint.

Chris

[ashley needhamParticipant @ashleyneedham69188]

Thanks chaps. A brushless edf should produce a fair amount of breeze. When I tested the bluebird with a brushed fan it was pants, very slow.

Actually, it went almost better than I thought, but it was slow.

Other chaps brushless edf boats go quite well, fast even, so I am hoping both the Bluebird and Cobb will be ok, as the hulls are very light!

Only reservation I have is the slow and medium speed behaviour of the Cobb. The only one I have seen on the pond ( a surface piercing prop powered craft) was VERY wet until going fast.??

My gut feeling as a builder of odd things is that we will be ok….

Ashley will put a pic of bluebird tested with brushed edf on my todays boating thread.

[Dave MilbournParticipant @davemilbourn48782]

I've always used this stuff, even back when it was called Frisk Film and wasn't a Jeff Bozo price! Frisket Film

Dave M

[ashley needhamParticipant @ashleyneedham69188]

Cheers DM, something to make a note of.

however… a steady hand, a soft brush well loaded with paint…

[Bob Abell 2Participant @bobabell2]

You`ve made a really nice of job of it

Can`t see John though?

Bob

[Dave MilbournParticipant @davemilbourn48782]

Ashley
I have neither a steady hand nor a soft brush, but I'm something of an expert at being well-loaded…..

DM

[CookieParticipant @cookie15923]

LOL

[ashley needhamParticipant @ashleyneedham69188]

Cookie….exactly !

JD makes a steady hand difficult……

Ashley DM.luv you really

[Colin BishopModerator @colinbishop34627]

You are wrong! JD helps you develop a REALLY steady hand – otherwise you might spill some…

Colin

[Dave MilbournParticipant @davemilbourn48782]

DM. luv you really

[ashley needhamParticipant @ashleyneedham69188]

yes. a moment of weakness. (Or did I have one too many)

Ashley been imbibing too much lately, but what the heck…..

[Author]

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