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Author Topic: shovelnose hull  (Read 9044 times)

sheerline

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shovelnose hull
« on: March 14, 2007, 12:20:06 AM »

My son just bought a 40 inch shovelnose hull and associated bits off e-bay, it is an unbuilt kit with no plans or instructions and it looks like its been around for some time. It's of lightweight glass construction and came with an ally prop stamped with the number '22 27'. It also has the skeg for the propshaft and a straight parallel sided rudder with water pickup, along with fuel tank and a tuned pipe. We would like to try to put this thing together for a bit of fun but can't find any information re maximum engine size, location within the hull or C of G. Basically we are in the dark with the general layout of this type of boat and wonder if anyone can help or knows of a website where all this kind of info can be found. We reckoned a 61 size engine would be about the maximum and would really get it moving but wer'e just guessing .
Never been stumped over a model before but this type is all new to me...............HELP!!
Regards.......... Chris
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glennb2006

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Re: shovelnose hull
« Reply #1 on: March 14, 2007, 01:19:33 AM »

Maybe some photo's so that the hull may be identifiable would help. There are sites you can try that are American where you may find what you are looking for. Try here:

http://www.rcuniverse.com/forum/forumid_229/tt.htm

Look foward to seeing some photo's.

Glenn
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sheerline

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Re: shovelnose hull
« Reply #2 on: March 14, 2007, 10:20:38 AM »

Thanks for that Glen, when it comes back inthe workshop I will attempt to post some pics. Having surfed the net, there is surprisingly scant information regarding this type of boat so it's become something of a challenge to get it together. There seems to more interest across the 'Pond' than here in the UK.  I will come back with some pics very soon.
Regards. Chris
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BobF

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Re: shovelnose hull
« Reply #3 on: March 14, 2007, 12:20:43 PM »

Hi sheerline,

This site may also be of some interest.

http://www.rcunlimiteds.org/
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OneBladeMissing

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Re: shovelnose hull
« Reply #4 on: March 14, 2007, 12:28:38 PM »

A 10cc "sport" engine should make it go ok. A similar 15cc engine would be ..... interesting!
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Re: shovelnose hull
« Reply #5 on: March 14, 2007, 03:29:25 PM »

Go to Roger Newtons web site http://www.newtonmarine.com/plans.htm for 1/8th scale hydroplane plans. His plans cover most of the boats since 1967. See http://www.newtonmarine.com/pop_ups/101a_pop.html as a typical boat.
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sheerline

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Re: shovelnose hull
« Reply #6 on: March 14, 2007, 05:33:46 PM »

Great, I knew I could rely on the chaps who breath nitro and methanol fumes to come up with something. We've ordered a 91 marine unit for it and have other bits to get like the drive shaft and possibly a couple of new 'waterproof' servos. I believe the rudder servo has to be a bit of a beast to take the pounding, probably needs loads of torque and metal gears.  I hope this all works out ok as I am really looking forward to giving this thing a damned good thrash. This is certainly a deviation from the subs but who knows, if we get it all wrong, we may yet end up with another sub!!
 I will get back with some pics soon.   
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sheerline

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Re: shovelnose hull
« Reply #7 on: March 14, 2007, 10:19:12 PM »

Hello all, finally got some pics of the hydro, its actually 48 inches long by 21 inches at its widest point. We found some pics of a boat on a site which showed the layout of the rudder and skeg at the aft end so we fixed them in place but once done, found another pic on another site which showed the rudder on the opposite side... I think it depends on which circuit you run eg clockwise or anti clock... not sure though. We even found a pic with the rudder right in the centre, mounted on the skeg assembly  but the skeg for that boat was specifically designed for that application.. unlike ours.
I would guess that one has to fit a piece of thin ply on the inside, along the  bottom of the hull so blocks can be bonded in place to accept fittings like the motor mounts etc.. The hull is wafer thin so it needs something in here. I believe these types of boat use something like expanding polyeurethane foam to fill the nose and sponson cavities for floatation and siffening of the cavernous glass areas which are rather delicate.
With aboat of this length and based on a little data from a smaller model, we calculated the c of g to be around two to two and a half inches behind the sponsons but not entirely sure yet.
Regards........ Chris
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martno1fan

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Re: shovelnose hull
« Reply #8 on: March 14, 2007, 10:21:15 PM »

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martno1fan

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Re: shovelnose hull
« Reply #9 on: March 14, 2007, 10:30:14 PM »

DONT use expanding foam or your boat will split apart!! the foam is strong ,easier to by pipe insulators from B&Q and stuff those in the hull where you can not just up front or if you flip your boat will float nose up !! if you have floatation the full length of the boat she will float level and some things might stay dry.also in the hull you may try to install engine rails inside, you epoxy them in and then use glass cloth strips either side and epoxy to fix them in.use slow setting epoxy usually 3 hr is the best.hers a pic of engine rails.notice the pipe insulators,these are cheap 42 p per mtre  and will not soak any water up and yup they float.
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sheerline

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Re: shovelnose hull
« Reply #10 on: March 14, 2007, 11:39:15 PM »

Thanks 'M', we will avoid the expanding foam and take your advice. Looking at your engine which appears to dwarf your boat made me think of an  American saying when referring to race cars... "There's no substitute for cubic inches' I bet that thing of yours is going to be a real flyer. We did think of buying a petrol motor for this hydro but figured it would be a bit too bulky and would'nt churn out the rpm for the kind of response we might need. I know there are a lot of tuned petrol engines out there which would probably do the job but they can be very costly for the kind of use my lad seeks from this model. If he gets hooked (or I do), we can always look at that as an option with some other kind of boat.
Thanks for your help and advice.
Chris
Ps my workshop does'nt normally look this grotty but the pics suggest I ought to paint that ruddy wall one day!!
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glennb2006

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Re: shovelnose hull
« Reply #11 on: March 15, 2007, 02:04:22 AM »

Looking at the photos I would say that yes, the wall needs painting.
Might I suggest the calming and non - offensive tones of Magnolia as an option?

To the boat: The pipe you have looks to be a water cooled Prestwich pipe, I may be mistaken but am fairly sure it is. If it the size I am estimating it would indicate it is for a 10cc motor. About.

The drive on these boats I am not sure of, the hardware you have looks kind of like what you would use on surface drive, but the strut you have looks like it is placing the prop too high on the transom on your boat to achieve surface drive.

Can you adjust it up?

Engine mounts: You have basically two choices:

1; fit "rails" - 1/4" ply running fore and aft at 5" centres which the engine mounts are bolted in between.
2; bond fixings into the hull that the rubber mounts fix to.

Choice is yours, both systems have advantages and disadvantages.

Looks like you need the following to complete:

radio box, engine and mounts, prop shaft tube, prop shaft flexi, prop drive dog, water pick up (unless the rudder has one built in), a fuel tank.

Just noticed that you are planning a .90 in it. Might be a bit too much engine, will be interested to hear other members input.

I have never seen one of these running in the flesh, will be interesting to see this one get up and going.
Good luck. Have fun.

Glenn
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glennb2006

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Re: shovelnose hull
« Reply #12 on: March 15, 2007, 04:13:39 AM »

Have a look at this lnk for finding the balance point on your hull, sound advice that will apply to your boat even though it is Methanol burning.

http://p086.ezboard.com/Finding-Your-CG-of-your-Hull-when-building/fjimsrcboatdockfrm7.showMessage?topicID=697.topic

By the way, have asked some Americans for advice on finding out what your hull is, this may lead us to be able to track down some fit out instructions for it.

Glenn
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martno1fan

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Re: shovelnose hull
« Reply #13 on: March 15, 2007, 09:46:08 AM »

hi CHRIS the engine is only a 28 cc strimmer engine air cooled hence the open hatch and the air scoop to aid cooling it wont be too fast ,35 mph roughly but thats fast enough for me.the boat is 4 ft long 15 wide and heres a pic to show the engines not oversize lol.i have a build thread on here if you care to check it out.id say a zen 260 pum might fit in your hull ,you can pick them up for 134 quid from the usa shipped all depends what you have to spend.
http://http://www.oneillbrothers.com/rcboat/index.htm
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BJ

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Re: shovelnose hull
« Reply #14 on: March 15, 2007, 10:52:05 AM »

Just refering back to floatation, did you see the comments in the link .... ?

http://www.modelboatmayhem.co.uk/forum/index.php?topic=2149.msg21362#msg21362
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martno1fan

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Re: shovelnose hull
« Reply #15 on: March 15, 2007, 11:32:05 AM »

thats why you need enough floatation so your boat wont sink even if its swamped!!
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sheerline

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Re: shovelnose hull
« Reply #16 on: March 15, 2007, 11:54:05 AM »

thanks for the advice and links Chaps, we are slowly building up a picture now of how this lot's going to go together. We have most of the running hardware including aluminimum engine mounts with rubber shock absorbers. Looks like the only real missing piece is the drive shaft and its tube but it looks as though Prestwich can supply this. The aft skeg is adjustable up and down and I reckon that will need some setting up in the initial stages but I notice it does not have the facility for angular fore and aft setting so the prop angle in the water is preset. I look forward to any 'Stateside' info that may turn up re the C of G because I beleive these boats were very popular there at one time. I might put some feelers out on some of the other forums.
By the way, my missus has told me that green is a naturally calming colour as it's abundant in nature... given the choice, the wall will stay grotty!
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martno1fan

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Re: shovelnose hull
« Reply #17 on: March 15, 2007, 01:34:34 PM »

hi mate is it a surface drive? if so keep it level with the hull also the balance point on most boats should be about 25% to 35% .that boat is made for a zen im sure if not then a .60 nitro would do the job.
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sheerline

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Re: shovelnose hull
« Reply #18 on: March 15, 2007, 03:37:20 PM »

Hi 'M', I guess by surface drive you mean a surface piercing prop and I believe thats what we have included with the bits that came with the boat. It's a rather beautifully sculpted ally prop with the numbers '22 27' stamped on the side.
We have ordered an SC 91 to put in this boat so as yet, don't know if that prop will be suitable for use with that size motor.
Going on the C of G, your figures of 30 - 35% are roughly where we marked the hull. When we finally get all the bits together, we will locate them in the boat and position the engine to gain the desired position. I suppose when the boat is finally tested it will become apparent if the C of G is out in much the same way as it is with our model aircraft experience but as I said before, this thing is quite new to me and I bow to your superior wisdom and experience.
I am impressed with the level of feedback and help we have been receiving from everyone and really look forward to getting this on the water and wringing its neck... if I can prise the TX out of my sons hands! Gotta a lot of work to do yet and still waiting for the motor so must be patient.
Best regards..... Chris
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martno1fan

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Re: shovelnose hull
« Reply #19 on: March 15, 2007, 04:57:05 PM »

i think the .90 will be a bit too much motor for it to be honest but i could be wrong seeign as its a sports engine you might get away with it.i had a sc .61 in a deep v 32" long its a modded plane engine with a flywheel fitted and cooling coil for the head works good but ive given up on nitro to build this petrol boat.
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OneBladeMissing

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Re: shovelnose hull
« Reply #20 on: March 15, 2007, 05:51:24 PM »

The 1/8th scale hydros they run in the States have 11cc engines in them (rcunlimiteds.com) of around 3bhp. Your SC.91 is around the same power so should be ok for a hull of 48". That pipe looks a bit small for a .91 though.
Great looking boat. We watch with interest.
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Re: shovelnose hull
« Reply #21 on: March 16, 2007, 02:35:30 PM »

The 1/8th scale hydros they run in the States have 11cc engines in them (rcunlimiteds.com) of around 3bhp. Your SC.91 is around the same power so should be ok for a hull of 48". That pipe looks a bit small for a .91 though.
Great looking boat. We watch with interest.

SC91's are not the easiest engine to start. On cold engines they usually require a big Sullivan 24volt starter and two 12v batteries plus decompression by loosening the plug. Not sure about your power figure - I thought it was well below your 3hp figure
Found this for SC91 AERO engines from Hobbins Models site.
480360 - SC91A AERO RC ABC ENGINE (MKII)
C.C. - 14.93
Bore - 27.30
Stroke - 25.50
Power (kW) - 2.0/15,000
R.P.M. - 2000-11500
Weight - 825g
Piston - ABC
 
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martno1fan

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Re: shovelnose hull
« Reply #22 on: March 16, 2007, 07:13:29 PM »

i agree with that i have the .61 sc engine and it just about turns over well enough on a 12 v starter using a motor bike battery for power,but only if i loosen the plug first  ;).still say stick a zen in it the americans say that boat was designed for one?.
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OneBladeMissing

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Re: shovelnose hull
« Reply #23 on: March 16, 2007, 11:54:02 PM »

I had a read of a SC.91 instruction/specs. booklet and I seem to recall that it gave a power figure of around 3bhp. Anyway, 2kw is around 2.72bhp. What about a CMB or OPS 11cc?
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sheerline

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Re: shovelnose hull
« Reply #24 on: March 17, 2007, 11:04:49 AM »

Hello all, the SC91 has arrived and having read the booklet, can confirm BJs figures on rpm but it does'nt give BHP delivery. It specifies a 25 50 prop (recommended). As we have a 22 27 we are going to try it with that first and I reckon it will probably work ok but we will, after initially having the pants scared off of us at the first attempts to run the boat, play around with prop sizes to gain optimum performace from this motor. I am not too worried if this prop is inclined to load the engine a bit too much as we will be running it rich for a while and if the prop keeps the rpm a little lower than normal, it should run the motor in quite nicely prior to blasting it to death. Just waiting for the drive shaft and coupling to arrive then we can get down to assembly.
I am in the process of knocking together an electric boat to act as a rescue craft. As a submarine builder, I am not used to having to rescue boats and have no intention of getting my feet wet.
I don't normally run or build boats but looking around the workshop, found an old racing hull which has been gathering dust here for years. I broke up an old electric drill which rendered up an FRS750 motor which originally ran with an 18volt pack. I found an old drive shaft and 40mm three bade brass prop and bunged it all in the hull and find I can barely keep hold of the thing in the test tank when run at 12 volts. I boosted it to 18 volts and the tractive effort of this combination is scary. The current at 12 volts was 12A (did'nt measure it at 18v) so given a power dissapation of 144W, am going to watercool the motor.
All this work is my lads fault for buying the shovelnose hull but I must admit, it's all a bit addictive and pretty interesting.
It will be good to get the smell of methanol and castor back up our noses again as we have'nt been flying for a few years.
Will keep you posted as things progress.
Regards... Chris   
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