1QwkSport2.5r

I think some who've had problems with spinner nuts haven't had the right approach to using them. I find them to be well balanced and easy to use. I use them exclusively on all of my engines. 2-strokes, even high compression ones, rarely kick the prop off. They have to backfire pretty hard to kick the prop. I use jam nuts behind the spinner nut on my 4-strokes and only use the electric starter on them. Most of my engines will backflip start easily, so I don't need the starter on the 2-strokes. On inverted engines, I highly suggest using a starter.

Whether you use the prop washer and a spinner nut or not doesn't matter; the washer isn't needed but can be used. Get the spinner nut really snug and wail away. Jett Engineering sells their engines with spinner nuts. Those engines are so tight, you almost have to use a starter on them when new. I am never concerned with losing a prop.

Just my my little rant about that. The build is looking pretty good so far, looking forward to seeing the boat hauling the mail!

arcdude

Thanks appreciate the input from anyone with experience. Although if I go ahead with the aluminum nut I'll be putting some loctite on the threads just as a precaution or double nutting, can't be too safe! Jeremy_H had some good tips on nose cones and all in the best interest of safety for sure. I witnessed a prop come off a guys plane once while I was on the field and I'm glad I wasn't in the path and I exercise extreme caution to stay out of the side path of a prop as much as possible. I start all engines even inverted with a chicken stick and if everything is in proper order an electric starter shouldn't be req'd IMO, even after 12 yrs of sitting the Super tigre started after 4-5 flips. Thanks for the compliment on the build, looking forward to getting it in the water, Cheers,

1QwkSport2.5r

It's been pointed out to me I don't know what I'm talking about, so I won't give any further advice. Sorry for stirring the pot.

arcdude

Well at long last the entire boat is in one piece and after a few more tanks of fuel ready for the water What I had to do until I can come up with an insert for the aluminum tube for the back of the sponson is make a couple of strut's, the short aluminum rods from the engine mount down to the sponson tube. The strut's take out approx 90% of the flex in the tube so they'll work great until it it resolved, at least enough to get it out on the water for some testing. I tapped a new pressure fitting in the muffler as well because with it on the bottom it was filling with oil and may have been impeding the air flow for the tank. As it sits the sponson's are adjusted out to 23.5" so that should be a good starting point.

Jeremy_H

Well it looks superb! Do make sure there's someone willing with you to video it

arcdude

The video duty will fall on my wife so don't be too critical Any thoughts on the width of the sponson's? I've never actually seen one in person so guess work I'll be running a few tanks through the engine tomorrow so this week some time I should have video posted.

Jeremy_H

Finding folk to hold a camera is not always easy, I ended up making a simple transmitter mount for my phone which helped get something of a record of events, so long as we get some idea of what's occurring that's all that matters.

The sponson spacing dictates the boats roll or 'heel' resistance. Assuming calm waters, in a straight line the only the prop torque is trying to roll the boat, so we need enough spacing for that. On my little red boat that spacing is not enough resulting in realy weird starts where one sponson easily lifts out of the water. Until it gets on to the plane, where it's on the five points and stabilises out. At full speed that red boat's stability is quite surprising, but that's fully realised when turning, and I suspect it's the turning of a rigger that is most influenced by sponson spacing because of the way the complex mix of hydrodynamics and the mass of the boat have to work together. The wider the sponson spacing is the more the lever principle applies, I.e. the outside sponson's force can impart itself on the boat easier the further out it is. But at some point it must influence turning through the effect of its drag, the further out it is the more it's able to yaw the boat against the direction of turn. So I figure that somewhere in between there's a compromise between roll resistance and turn resistance, though to be honest I think there's quite a lot of latitude there. In conclusion then there's only one way to find out if yours is ok of course, but I think it has a good chance of being fine as it is.

Jeremy_H

Here's my phone holder thingy. I need to make a new one for a better phone but this has served me well:

arcdude

The attachment comes up as an invalid link

Jeremy_H

Hmm, looks like a file name character problem. Try again...

arcdude

That's a slick idea, a bracket and some heavy duty stick on velcro

Jeremy_H

I just bought a cheap phone case from the bay and stuck it on to a piece of heat bent plastic sheet clamped to the transmitter handle. It's fixed quickly and is unfussy. The new phone, whilst still midrange, will be a lot better when the time comes, saves troubling other modelers too much ;-)

arcdude

Still haven't had time to run another tank of fuel and go for a test run, life keeps getting in the way of the fun stuff Hopefully this week I'll have time to get it in the water.

fuma

what happend ? let's see that baby run.

arcdude

Lol, that's kind of how I feel when I've followed a thread to find out there is no results. I do feel somewhat of an obligation to anyone that has followed along wanting to see the end result and will share as soon as I'm able. Been quite ill lately and getting the outside work done up and changing tires and so on.....winter, ho hum. Looking at the long range forecast it appears Wednesday looks like the best day this week and then dipping into the minus range, so I'll make an effort to get it in for a run, really don't want to stare at it all winter long wondering.
Cheers,
Al

arcdude

Finally got the shark in the water, looks good just sitting there. As you can see in the pic the sponson tips are about an inch above the water line as well as the sponson tubes, that is without the motor running. Once I started the motor to go for a run the outward/downward force of the prop caused the sponson tips to dive and there was no way it was going to come up onto plane. There was no spray whatsoever from water hitting the prop so plenty of height there and I didn't get much of a chance to rev the engine or anything when I noticed that in turning the boat it would turn right approx twice as much as it would left so I was a little nervous that it would pop up onto plane so I just idled around a bit to get the feel of it. The engine is still running a little rich so it ended up bogging down and died after about two minutes puddling around. So it looks like the downward force is a defining characteristic that needs some extra experimentation to find the right balance of floatation to enable it to plane out on it's own or resort to alternate methods of starting out. If someone can offer any insight into the turning issue it would be most appreciated. There is as much throw in both directions and everything checks out fine, one bit of a note is the rudder is a speedmaster 21 that is 6.25" top to bottom. Blade tappers from 1" at the top to 5/8" wide at the bottom. Could the rudder not be suited to outriggers? Thanks

arcdude

I'm certain if I pushed down the tail of the boat rev it up and give a forward nudge the boat will come up onto plane however, with the steering issue in appearing to turn to the right far more than left is of real concern and I'm very hesitant to try it again without some insight as to why it is doing this. Don't want to experience a nasty situation if it can be helped so if anyone has any thoughts on the issue it would be greatly appreciated, Thanks

1QwkSport2.5r

It looks to me as though your engine is too far forward. The prop centerline appears to be in front of the trailing edge of the sponsons. This may prove to be a problem as you've noted with it wanting to submarine when throttled. I believe it is said you want the prop at or behind the trailing edge of the sponsons. My rigger has the prop 1-2" behind the trailing edge. If you can move your engine back, I'd try that. Also, you may need a second set of hands to launch it. Run her at half to two-thirds throttle and give it a toss. It takes a LOT of thrust to get on plane, don't be surprised if the idea of pushing down on the transom and nudge forward will work. It might be better to build a launch ramp so you can really throttle it at first if you cannot get a helper to toss it out for ya.

As to the steering - my rigger doesn't steer for beans either with a good 40-45* of throw in either direction. It will steer better at speed. Mine steers decent if I'm going into a turn at WOT. It may need a wider blade, but don't change that until you get her up on plane.

arcdude

Thanks for the feedback 1qwksport2-5r, appreciate that. You may very well be right in the engine location being too far forward however, I went and looked at Hooty's rocket and it appears his thrust line is about 3" ahead of the trailing edge, no idea where his CB is at. I doubled checked mine and the thrust line is at 2" ahead of the trailing edge and the CB is approx 3.5" behind the trailing edge. I'll try to explain what happened in greater detail, I don't know if submarine is the apt description of what was taking place, as it moved forward it was like the water in front of the sponson's was being deflected forward and up over the tips of the sponson's which were visibly above the water line. Peculiarly the tub didn't seem to experience the same effect being at the same height, I can only attribute it to the deeper angles of the sponson bottoms. So with that behaviour I suspect the boat is on the cusp of taking off with little encouragement whether a nudge or chucking it in will suffice guess I'll find out, and I don't think with the 90 there will be a shortage of thrust.

Glad to hear that the steering issue may be related to the drag of the hull sitting so low in the water. Currently the control rod is on the middle hole on the rudder's control arm so I'm going to move it to the inner most hole and hopefully that will help. The strange thing is why it appeared to turn right with ease and seemed to have difficulty turning left, thought airboat's turned to the left easier than the right Honestly I was quite nervous not having a control in my hands for over 12 yrs so that may have played a role so I didn't bother attempting any other method of launching in fear of having limited control of the boat once it got going.

I'm reluctant to make any physical changes to the boat until it's running abilities are realized and in light of the similar attributes between Hooty's rigger and mine I suspect I'm not too far off the mark, at least from what I can gather. Because there is so few of us venturing down this path there is limited validation on methods used, experimentation is obviously the way to go.

1QwkSport2.5r

Keep in mind you didn't build Hooty's boat. His boat is balsa and really thin birch plywood and barely floats. The CG of his boat is not going to be the same as yours. Find a way to get it on plane and see how it runs. You likely won't be able to get it on plane without help. Just speaking from my own experience.

Jeremy_H

I agree with all of that entirely, adding that thrust line, CoB, lift and hull drag all have to be considered when a boat has to go through a transition from displacement to planing. The key thing to remember here is that your original design idea called for something that could go through this maneuver, so a lot of the made for speed riggers' setups may not fully apply here, not so much geared towards a wide usable speed range, or swell absorbing ability mentioned.
What would be good to know what the way throttle was applied, as marginal planers seem to very often benefit from punchy throttle ups looking at various vids around. My SI3 certainly needs this should I be starting out with anything other than a full tank to weight the rear down.
Methinks some leaps of faith into full throttle ups and some encouraged starts are indeed needed.

arcdude

Thanks Jerry, appreciate the input as always. This isn't entirely unexpected, as to my initial design which I've not given up on and thoughts are already geared to ways to add onto the front sponson's to give the extra bit of buoyancy req'd to take off on it's own. I do believe I'm not too far from lift off as it sits, as mentioned it seemed to be deflecting the water forward and up so the down force wasn't significant enough to push the sponson's down. As stated I only idled around in fear it would take off in light of the steering issue.

Leaps of faith and a full throttle are definitely in the cards at the moment, the nerve barrier is also a factor at the moment Unfortunately I've nothing on the tame side to ease back into getting my feet wet, talk about jumping into the frying pan. The weather is a factor now as well and I'll be watching next week for a suitable day and give her a good kick in the rear to she what she'll do. So that's one kick in the rear for the boat and one for myself Lol

arcdude

Agreed, other than the overall concept being a rigger style and approx thrust line location that is about where the comparison ends. The intended outcome is night and day, Hooty for all out speed, mine for a more user friendly design. As it sits it will need a little encouragement for sure. Cheers

arcdude

Sorry no video yet, I've been plagued with a few issues. The engine seems to flood at the drop of a hat so I modified the boat stand to start the engine with the boat upside down. Then I discovered an intermittent grounding issue causing the glow plug to light up but dimly. Even with the engine up side right it seems that with every flip of the prop and I have to remove the glow plug and dry things up definitely no fuel delivery problem here. Anyone else have an engine that seems to flood regularily? and what could be the issue? is there a way around this?

1QwkSport2.5r

Most often with inverted engines, the problem lies with fuel tank height or over-priming. The raw fuel pools at the glow plug. What I do with inverted engines is use an electric starter and let the engine draw fuel to the carb (provided the tank height is proper). Hand flipping an inverted engine is a royal pain. If you start the engine upright, always warm it up and throttle it up to clean the crankcase out while right side up. A couple WOT jabs usually does the trick.