Slo mo Shun

[Bob Abell 2Participant @bobabell2]

Thanks for the info, Phil

 

I`ll get on it right away……………..What would you say the 3 degree angle was relative to?

 

The waterline?………… or the base of the hull at the rear?

 

Do we know where the waterline is supposed to be?

 

Bob

 

PS….You sent me a picture of the proposed sponson mod, some time ago………Will you post it again, please

Edited By Bob Abell on 08/04/2010 09:17:12

[Phil Winks 1Participant @philwinks1]

I  understand it to be in relation to the base line of the aft plane, and no, there is no Design water line. Except perhaps that aftplane baseline, as that should be just about where the surface should be when doing what she’s supposed to

 

Regarding a mod for the sponson I don’t have it to hand so I’ll get one sorted soonest

 

 

Phil

[ashley needhamParticipant @ashleyneedham69188]

see Bob, its not your fault !!!    I can almost see the gap between water and hull…

 

Ashley

[Phil Winks 1Participant @philwinks1]

Ok Bob hope you can work it out from this drawing mate. Just remember to click on the pic and then wait for the little + in your mouse cursor and click  to view full size.

 

These lines are as mine has come out what your aiming for is the solid red line. if it turns out deep enough make it hollow! ie frame around the edge of the bottom of the sponson sect and skin it mine will prob end up as a light balsa sheet glued on and sanded to profile as it looks to be only a few mm as yours is twice the size a hollow pad may be possible.

 

Key to sketch

the dotted green lines are the frames

the solid blue line is what my frames have given me. -1 deg (another qualty issue lol)

the solid red line is the suggested optimun +3 deg

black lines are from the layout plan

 

 

 

Phil (whose had a hell of an evening because my drafting program updated (took an hour and a half) and I had to find my way round a whole new set of controls LOL)

Edited By Phil Winks 1 on 08/04/2010 21:54:30

[Phil Winks 1Participant @philwinks1]

Addendum to previous post

 

It would be ok if you felt you wanted to build up the sponsons from further forward than indicated above and make them a good bit deeper at the back as long as the finished item ends up with that sect between the last 2 frames in the sponsons at 3 deg to the datum.

 

obviously the deeper you go the more flotation you’ll get and the more you’ll raise the nose

 

however to far and it becomes I believe a counter productive exercise.

 

Assuming everything on yours is double the size of mine, I’d suggest no more than double the distance you currently have between the aft plane line and the bottom of the current sponsons. I’m looking at slightly less than a 50% increase in this dimension.

 

Phil

[Phil Winks 1Participant @philwinks1]

Me again Bob does your sponson line run anything like mine see pic

 

If so you’ll see that at 1st appearance the incidence angle issue is confined to the outboard edge. this after careful measuring isn’t the case its optical illusion time. however do make sure that as you mod it that the outer edge has the -ve 3deg angle and the inner can if necessary be a tad shallower but never +ve and the rake upwards from inner to outer edge remains +ve for lateral stability

 

Phil (Hoping not to confuse)

[Bob Abell 2Participant @bobabell2]

Hello Phil

 

Thanks for the info and the excellent drawing

 

I`ve added  a tangent to the hull curve…………..It is 20mm deep at the step, I`ve made it a straight line and it reaches forward for 200mm

 

Photo will be posted shortly

 

My hull shape was more of a gentle curve, compared to yours……..I used the natural curve of the ply.

 

Bob

[Bob Abell 2Participant @bobabell2]

Here it is………….Ply sides for strength, with a balsa block for the tricky stuff!

 

It`s actually 24mm high and 810 long

 

Any comments before the lid goes on?

 

Bob

[Bob Abell 2Participant @bobabell2]

 

Here we go, boyz……………Just waiting for the PVA to really harden, before painting

 

Will the mod have any effect?……..We`ll know on Sunday at Bury

[Phil Winks 1Participant @philwinks1]

Hi Bob sorry for being so notable by my absense my dear old doc got me on some new tablets and the side effects got me a little dizzy still looks like you got it sorted looks good to me  mate!!

 

 

Phil

[Bob Abell 2Participant @bobabell2]

Hello Phil

 

I`m to hear about your slight infirmity………Look after yourself my M8

 

Bob

[Bob Abell 2Participant @bobabell2]

Went to the Bury show today and spotted this giant Aqua-riva!

 

It ran on 6 flat Li-Po`s and two small brushless motors. The props were about 40 dia and had a built-in water pump

 

Unfortuneately, it ran amok at the onset and lost the rudder on a boundry marker, so I didn`t see it perform

 

Took my Slo Mo but didn`t sail…………….Too many spectators expecting a water speed record!……So I chickened out!

 

Mr Big was there and thought my boat was too heavy and grossly underpowered and if I had nearly 1HP….So what?……………….He had 7 HP in his and it was a third the weight of mine………………Hence, another reason for my no sailing demo

 

He liked my latest sponson mod, but would have made it twice as high!

 

Bought a little dash about………Since it was going cheap!

 

Excellent show…….Good turnout……..Scrumptious bacon butties……..Nice sunny weather!

 

Couldn`t ask for more!………..Bob

[Phil Winks 1Participant @philwinks1]

Hi Bob glad you enjoyed the show sorry about the prophets of doom but fear not your masterpiece will do your bidding soon enough.

 

as for the very pretty piece of eye-candy above have a look at this and it needs more spending on it to add motor rx esc bty’s servo etc!!!!!!! Not exactly a testament to the model builders skill is it? more a testament to the size of a mans wallet.

 

on top of which it prob ran amock due to bad electronics set up need I say more!!!

 

Disclaimer

If I’m wrong and it really is a product of the mans skill I apologise just don’t think it is.

 

 

Regards Phil (at the bath and west model engineering and model makers show Shepton Mallet next weekend)

[Bob Abell 2Participant @bobabell2]

Hello Phil

 

The model was definitely built by the chap concerned……………..He`d made a super job of it!

It was nicely finished off, using commercially available large Riva fittings

 

I didn`t actually see the first amok run, but assume, the chap didn`t see the floating barrier across the lake, which separates the speed merchants from the rest of the club….and can only assume, it ripped the rudder off!

 

Bob

[Bob Abell 2Participant @bobabell2]

This video shows Stavross`s MTB going through it`s paces at Llanberis using the same motor drive and gear that I`ve used in Slo Mo.

 

It has a single prop, whereas, I opted for twin drive of course

 

View here……     http://www.youtube.com/watch?v=fp3RNTVk1z4

 

Bob

[Phil Winks 1Participant @philwinks1]

Ok Bob ever willing to admit when I’m wrong hope you didn’t use all that ketchup mate.

 

That mtb is quite impressive I notice however it’s forever in for bty change, the price you pay for speed on bty powered vessels I suppose!

 

Which Lake in LLanberis is that? looks like one up in the pass as far as I can see. Llyn peris I think as oposed to Llyn padern!

 

Phil

[Bob Abell 2Participant @bobabell2]

It`s Llyn Padarn, mate

 

In the foothills of Snowdon…………….a lovely area!

 

Bob

[Phil Winks 1Participant @philwinks1]

Know it well Bob especiall the “flying buttress” about a mile or two up the pass on your left my 1st ever “V Diff” free climb a stunning route up as good a piece of rock as I’ve climbed  anywhere. Mind you thats a few years back now lol all a bit behind me now.

 

Must admit though my memory had Llyn Padern looking bigger but thinking on Llyn peris has a serious slate scree on the far bank does it not? and thats not evident in the vid.

 

Do you ever frequent the walker’s/climber’s cafe in the town? (Name escapes me) best bacon butties in Wales maybe even the UK (thats if its still there)

 

Phil (positively falling over his own feet on memory lane)

[Bob Abell 2Participant @bobabell2]

Hello Phil

 

I`ve never been in the town…………I`ve heard most of the shops have closed down!……Sad innit?

 

My next Slo Mo run, will be this Wednesday……..during the Club 500 event

 

Not hoping for much, just curious to see what effect the sponson mod has on performance

 

Bob

[Phil Winks 1Participant @philwinks1]

Thats very sad Bob, it was a lovely little town, mostly relied on tourism though, and we in the south west know only to well what that means in hard times!!

 

I truly believe the effect of those sponson mods will be positive. Do remember to check the balance before sailing though won’t you ? As I believe its a critical part of the setup! Be prepared to experiment with different settings either side of the point 10% of the aftplane rear of the sponson aft edge. Treat her like an aircraft. nose heavy will make her dive/dig her nose in, tail heavy and she’ll stall. Both will sap power !! 

 

Phil

[PierreParticipant @pierre]

Hello Bob

 

When I first took my Slo-Mo for trials I was also extremely disappointed – lots of wash and very little forward motion.  To my eye it seemed as if the prop was cavitating so I increased the size  from 30 to 40 mm (Graupner 2 blade plastic) . An improvement but still not very impressive.

I couldn’t increase prop size any  more due to the transom and  theorised that the water flow to the prop wasn’t sufficient (for whatever reason).  I increased the prop shaft length so the prop was approx 2 cm aft of the transom in what I theorised was “clear” water.  I could do this as I had the rudder offset as in the Billings model.  The improvement was dramatic – the boat got on the plane easily and skimmed across the pond. Even using half throttle it would remain on the plane.

Well it worked for me ………just a thought!

Regards – Pierre

[Bob Abell 2Participant @bobabell2]

Thank you, Pierre

 

I`ve suspected the prop for some time now

 

I`ve got the effect that you describe…….Lots wash and power…….But a brick wall upfront!

 

My prop is now at the max pitch……..but I could get a slightly larger prop on….with a bit of chopping!……………..But at £30 a pair……..I`m dragging my heels at the mo!

 

I`ll be getting more expert advice on Wednesday…..hopefully

 

Cheers M8…………..Bob

[Phil Winks 1Participant @philwinks1]

Extending the shafts is a bit out of the question for you is it not Bob are the rudders not in the way?

 

 also on bigger props watch the motor load mate.

 

 Why not try Ashley’s Idea of a finer pitch 3 blade prop it may be more efficient at the revs you have.

 

Good news on my motor selection for little slo mo  though is it not

 

 

Phil

[Phil Winks 1Participant @philwinks1]

It’s Tues evening Bob I do hope your absence is not due to any disaster ?? Hope some improvement  was seen today in the slo mo’s performance.

 

Phil

[Bob Abell 2Participant @bobabell2]

Hello Phil

 

Couldn`t sail today………Had visitors……………..( I did say Wednesday, anyway )

 

Tomorrow`s the day, after tea, when I meet our resident expert on club nite

 

I`ve been thinking……….Weight shouldn`t be a problem, getting on the plane……..as the boat is sliding along low friction water, effortlessly….sort of.

 

So If it is possible…….Why couldn`t it just be a matter of time to get on the plane, gradually…….instead of trying to take off…..ASAP?

 

It`s the brick wall effect that`s stopped me at the moment………so, with a bit of luck, the latest spon mod might cause the craft to rise up gradually and take off?……Hopefully!

 

Ever hopeful……..Bob

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