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Hydroplane weight?

Old 01-25-2009, 06:53 PM
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Ramon(tug)
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Default Hydroplane weight?

Hi Guys
I'm new to this forum and would appreciate a bit of advice.
I'm building my first hydro - Atlas Van Lines - from scratch from the Gary Finlay drawing downloadable from the Astec models site.
The drawings are proving to be very accurately drawn , all components fitting extremely well.

It's 1/8 scale 44inches long and will be powered by an older OPS60.
The framework is coming along nicely and currently weighs just over 2 1/2 pounds as pic but without engine

My question is what would be considered an optimum all up finished weight for a hydro of this size.

Any input would be most appreciated
Regards - Ramon
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Old 01-26-2009, 12:06 AM
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misshydro
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Default RE: Hydroplane weight?

The way I'd read&heard the total weight with everything in it,should weigh about 12 to maybe 13 pounds?
Old 01-26-2009, 01:07 AM
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Rocket-J
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Default RE: Hydroplane weight?

Many years ago, our .60 powered wooden 1/8 scale hydros would weigh 15 to 18 lbs. I had one with fuel and ballast at nearly 20lbs. It still ran fast, just doesn't accelerate as fast. Just keep it as light as possible in the beginning. Everything you do, even paint and sealer, will add weight. You also may have to add weight in specific areas to tune it's ride. And after it has run many times or seasons, it grows, no matter how well you seal it. Maybe I just spent too much time, up-side down in the water. :-) Good luck .
Old 01-26-2009, 01:45 AM
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Default RE: Hydroplane weight?

I've seen a scale boat that weighed in at a whole 8 pounds INCLUDING FUEL, but I've also seen hulls that weigh over 20. More so than weight, which needs to be minimal, balance is critical. If those two cans are going to be your fuel tanks, move them forward as far as you can so they don't affect the boats balance as they empty. Also, don't hard mount the engine until you have the boat finished except for the decks. At that point you need to have the rudder, skid fin and strut all mounted, as well as your vertical tail mounts. Lay the tails, wing, drive shaft and tuned pipe in their approximate locations and then experiment with engine and radio locations. You want the boat to balance in the 1-1.5" behind the sponson range so that balancing the boat will not take near as much work or weight later
Old 01-26-2009, 07:45 AM
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Ramon(tug)
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Default RE: Hydroplane weight?

Hi Guys
Thanks for your response which has proved enlightening – ahah no pun intended! and as a result have spent the morning weighing and balancing which has proved interesting indeed.

As said ‘hydros’ are a very new experience but I have spent many years building and flying control-line aerobatic models where the CG and weight are major factors to be considered at all times. With this in mind your advice is timely and understood.

Currently as it stands it weighs 6.7 pounds all up of which 3.7 is the engine, radio gear and hardware (strut, rudder, uncut shaft, coupling) I do not have a pipe for this engine at this time. If I aim for a max of 15 pounds and keep lightness in mind I would imagine the 8.3 left would be more than enough for the rest of the build and finishing.

The balance however is a bit more difficult.
HJ – I can move the fuel tanks about 2 inches forwards which will put them roughly evenly over the desired CG. The engine position though is more problematic. If I move this forward then the intended position for the radio gear is lost and it will have to go to the rear. Checking this out as it stands now there is minimal distance of balance point between either option. The mass of the engine is forward of the CG so I think this will have to remain. Laying out all the hardware gives me a very rough idea of the weights involved and I would (g)estimate that I will have to put about 6 ounces of ballast at the front. I think the best place for this will be under the front of the fixed part of the cowling but on top of the bridge piece between the sponsons. I would reinforce this area to take the stresses that this will undoubtedly create.

Thanks again guys, your input is much appreciated. This build is alongside but secondary to another project so it will be a while before I can take it further though I would hope to finish it by May or so.

Regards - Ramon
Old 01-26-2009, 12:13 PM
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Rocket-J
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Default RE: Hydroplane weight?

The most common place for the RC gear is in the rear. Put the fuel tank in front of the engine. Good luck and have fun.
Old 01-26-2009, 05:20 PM
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Default RE: Hydroplane weight?

Hey Ramon(tug) - This might interest you. I too built the 1/8 scale Atlas Van Lines. Although yours is a Newton, Mine is a Dumas Kit.
I lightened the build where I could, cause Dumas is notorious for Tank like structures and a little heavy.
I also am running the OPS .60 engine.
Dont blow that engine. Youll have a heck of a time getting parts for it. As I have Searched on this forum as well as others for them. Found a couple of chaps with parts, one was in Norway of all places. These people helped out a lot with my parts search.. I have exactly enough parts to rebuild it 2 times and then it is gone. So the engine is just waiting for a new .67 Mac or something to take it's place.

Boat came out too 10 1/4 lbs.

You have a lot of gluing to go and that epoxy adds more weight especially the step when you coat the inside of the boat and coat the bottom of the top deck before placement.


1/8 scale Hydro Hardware was one of my thread names.

Jeff

Edit: Forgot too mention, Make sure your using a Jig. The jig I built is very strong!! If you do not use a Jig, It will not be straight and cause you some problems later on.
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Old 01-26-2009, 06:08 PM
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Default RE: Hydroplane weight?

ANother pic with the OPS .60

ALso did this drawing of the Con rod for that engine way back cause I was going to see about having the local machine shop make me some rods.
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Old 01-26-2009, 08:50 PM
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Default RE: Hydroplane weight?

Hate to say it Rocket-J, but on a pickleforked scale size boat, VERY FEW have radio gear in the back. If you were talking round nosed boats or the Sport 20 and 40 clases, then I would have to agree with you. The radio gear is put in front to reduce the weight in the back, which needs to be as little as possible. Fuel tanks are normally put as close to the CG as possible to minimize CG movement as fuel burns off. Ballast is normally put all the way up in the sponsons so that less is needed to balance and trim a boat. Here are just two examples, both have the radio in front of the engine
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Old 01-26-2009, 10:01 PM
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Default RE: Hydroplane weight?

Noticed something else. Your OPS has the Air cooled Head on it. I am sure you know this but in case you don't. The OPS 60 INboard Marine engine came with 2 styles of Heads.
The Aircooled / Finned Red head as you have there and The water cooled head.
The Red head needs to have either "Kool Clamps" mounted or any rendition there of or change the Head out to the water cooled version. It gets Extremely Hot.
See images SO you know what I am referering too. It is A Great Engine. Just want to make sure you were aware of this.

1st image is of the Finned head, Second is of the Water cooled head on it and the Third is of a 25+ year old OS engine converted to A marine with Water "Kool clamps" on it.

OPS went with the Red Head Finned and Water cooled Combination with the .65 series

Jeff

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Old 01-27-2009, 02:06 AM
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Rocket-J
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Default RE: Hydroplane weight?

I guess that shows how long it has been since I built a Hydro. Mine was a shovel that is in the AVATAR. Thanks fo rthe update. Keep me honest.
Old 01-27-2009, 04:18 AM
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Ramon(tug)
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Default RE: Hydroplane weight?

Good morning everyone,
Though I didn't intend to cause 'disagreement within the ranks' it is good to see different opinions and to receive such good advice. Thank you all for your interest and input.

When I held the fuel tanks in the position advised by HJ it was immediately apparent that there would be little effect on the CG as the fuel reduced. I hate to use model aircraft as an analogy but this is just what happens to an aerobatic model, the model becoming more tail heavy through the flight. I don't know but would imagine that this situation would have a more influential effect on a Hydro given the same situation. The tanks are ex hair spray aerosols and are drawn ally. I shall make caps and bond them in place with JB Weld.
These 'containers' appear ideal for the task in hand, my only concern is that they will not stand up to the vibrations and may eventually split. It will be impossible to get them out without major surgery if they do!

Regarding the build Jeff I did make a jig and the hull fits to it firmly. I am used to using jigs (aircraft again) and am a firm believer in there use wherever possible. Apart from skinning the sponsons the underneath is finished and it sits true on a flat surface without rock.

Thank you also for your helpful advice and concern regarding the OPS. I first owned one of these in the early seventies when they first became available in the UK. As I recall this had a conventional water jacket and was plain alluminium all over. Unfortunately I lost the pipe overboard - inadequate brackets! and sold it shortly afterwards (BIG regrets now - hindsight is such crystal clear vision!!)

The type I have now recently came into my hands when a friend passed away and I was asked to dispose of his marine engines. As soon as I saw the OPS the old flames rekindled and here I am again making a boat after some thirty years or so. It does have a Kool Klamp. I took it off to strip and clean the engine which was well gummed and have not refitted it yet. I was surprised to find the conrod was very slightly bent when removed however there appears to be no evident wear and after straightening the engine turns very freely. Fortunately I am able to make a new one if the worst happen so the drawing is very useful. Thanks indeed. I notice your flywheel is brass. On mine it is steel and has a very uneven surface that gives the impression that it has been heat treated - that is hardened. I'm reluctant to try the normal 'file test' to see as I don't want to spoil the black finish.
Thanks once again I take note of all you have said
Regards - Ramon
Old 01-27-2009, 06:30 PM
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Default RE: Hydroplane weight?

Ramon(tug) - Glad to hear your familier with the jigging. Not as many peaople are as you may think so Just wanted to be clear. Glad Some of my info was useful for you.
The Brass Flywheel on mine was the original. I have an aftermarket Aluminum one on there now and it is 1/2 the weight.
Thats a cool idea on the Fuel Bottles. Post more pics of it if you can, I am intrigued to the idea and want to see more of it as I can use that on some of my designs.

If there is anyway to make the holes just a tad bigger and surround the interior in a foam edging or U shaped soft rubber for metal/ glass etc.
Could always go with Silicone caulking too as a 'gasket' let dry and trim it to fit. then glue the tanks in.
This will hinder some of the vibrations and actually make the boat "Rattle" less when running.

As I recall this had a conventional water jacket and was plain alluminium all over.
Yes that would be correct.
Wish they had the Built in Jacket on the .60 as they did the .65 and the now .67.
Those engiones are awesome. Youll get a lot of power out of it. If you are in the market for a new pipe as the gremlins seemed to have snatched yours.
Unfortunately I lost the pipe overboard - inadequate brackets!
(Never admit fault - - Geeez)
I went with the AB67 - Andy Brown Pipe found on CMDRacing.com. Not the Parabolic but the one under it. It is actually a new design this past year then the one I got but still the AB67 pipe.
Seemed to be the common consensus on the pipe to get.
Good Luck on your build and Have Fun. Post them pics!!!!!
Jeff
Old 01-28-2009, 05:09 PM
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Default RE: Hydroplane weight?

Ramon, the biggest reason for my fuel tank suggestion is that a tail heavy hydro will always be trying to blow over, just like the Pro Boat ones are prone to do. Another problem would be that the back is carried by the prop, so the more weight on the prop, the lower the top speed that can be attained. As for engine location, the radio can be put in front as it will ballance out the engine to a certain extent. This is why I said to "experiment" with the radio AND engine placements. Putting the radio in the back is not beneficial for a couple of reasons, more weight in the back and having to route the exhaust over or around the radio box. Electronics don't like heat, so if it can be avoided getting the exhaust too close............................................. ......
Old 01-29-2009, 04:37 AM
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Ramon(tug)
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Default RE: Hydroplane weight?

Good morning Jeff and HJ.
Thanks again for your continued interest and helpful input. I fully take on what you are saying about the fuel location HJ. I am able to move them forward about 2 inches which puts the centre very slightly forward of the optimum CG. I have taken another look at how to mount them and think I may have the answer. I have to open up the front former to allow them to go forward so will have to make a new 'false' former to support the front end. I shall make this one to fit the cap end tightly and make another for the bottom end. This bottom end former will have a facing of 1/4 balsa with a hole in it to locate the end of the container. This way the tanks should be supported at each end without any part between making contact with anything. It will be a day or two before I can get on to this stage but this will need doing before I can progress the top deck. Jeff, I will take pics of all the mods and make up of these tanks and post them on here.

Here are some pics which show my intended layout The radio and rudder servo will both be boxed in and watertight (well hopefully!) the steel plate is placed to show the area I shall put ballast in the form of sheet lead to trim the CG. Ideally this weight should go as you say as far forward in the sponsons to reduce the amount of ballast for a given effect. I have considered 'weight boxes' in the sponsons but think that this will lead to leakage problems - what do you do and use for trimming aids like this?

Jeff it was interesting to hear that you have an aluminum flywheel fitted. I had wondered about this as one of the engines I sold was a KB 40 with such a flywheel. I will make one up to replace the one fitted which I have to say and as you can see I'm less than happy with.
Thanks for the info on the pipe which I may look into - buuuutt - yesterday a friend who I have not seen for some time called and brought me a brand new 60 pipe which he thought 'I might find useful'. Before I knew him he apparently flew semi serious R/C aerobatics and had this spare! It has a long chamber so it may not be suitable, it's baffled -where the three marks are and fits the exhaust perfectly. Do you know anything about these pipes? I have owned many many engines over the years but only one with a pipe, that early OPS so am totally in the dark here.
I need to ask your advice on fuel 'feed' but will leave that to later.
Now!
This build is alongside but secondary to another project so it will be a while before I can take it further
Your interest has had an influential effect on this comment!! I can see this is not going to sit idle for very long - Thanks guys - Ramon
Old 01-29-2009, 04:53 AM
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Ramon(tug)
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Default RE: Hydroplane weight?

It appears something has gone awry in posting the pics
See if this works.
These three show the projected layout






This is the state of the flywheel


And these two the pipe details


Old 01-29-2009, 05:43 AM
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Hydro Junkie
 
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Default RE: Hydroplane weight?

I see one thing I would do before you start skinning the boat. Along both sides, where you have the two sides laminated together, drill some lightening holes through them to lighten them up. As it is now, they are considerably heavier than needed. Another reson is that it will let air circulate trough the boat so it won't rot from the inside due to trapped water. Trust me, water will get in. Just out of curiosity, is that 3mm ply in the framing? Let me help you out a little. Here are some pictures of boats i'm working on to show you what I'm talking about
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Old 02-11-2009, 03:14 AM
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Ramon(tug)
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Default RE: Hydroplane weight?

Sorry for the late reply HJ but I've been out of it for a few days. Thanks for the advice and your offer to help. I put the 'lightening' into practice yesterday. I have a few more questions and would value your thoughts but as this will be going off topic I shall start a new thread - 'First Hydro' later tonight.
Thanks again - Ramon

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