Jeremy_H

Looking good. How's the weight coming along? I like to put everything on board at this stage and see what's there in weight, for me it can help to tailor what's to come.

arcdude

Okay felt like I was weighing in a champion fighter ready for the fight of his life and holding my breath. Anyway piled everything rather precariously onto the scale and the total at this time is 4 lbs 15 oz, so about 1/2 lb heavier than planned due to the motor mount. I guess in the end the mount is of huge importance in that is has to be robust enough to withstand the rigors of the engine and all that weight flopping around in the wind. I have a few idea's on rebuilding the mount out of aluminum at a later time to lighten the load a little but rather eager to get finished to see what this puppy is capable of. From what I understand other boats of this design have been coming in around 6.5 lbs and heavier with smaller engine's so all in all not too bad I guess.

arcdude

Got creative and designed the the rear sponson. The hull is now extended 6.5" totalling 48" overall with the rear sponson out beyond the rudder which is housed under a hood so to speak that will be spring loaded in the event of a rudder strike it will lift the hood up at the same time. The aluminum angle provides attachment points for the rear sponson and will provide a bracket so the airfoil can be attached and the hood simply fits in between them and will be angled to match the rear sponson so there will be a nice angle up the rear. The rear sponson was constructed on 1/8" aircraft ply that will be trimmed on the sides to match the outside of the aluminum when attached and it will have a nice clean look on the side profile, right now it is oversize until everything is lined up.

Jeremy_H

Whoosh!, that a pretty aggressive degree of lift you have there. Can we see it with the sponsons in place? I'd like to see how that levels out.

I'll say it again, that's a big boat!

arcdude

It's not that aggressive, ya think? It sure is big and only weigh's in at a whopping 5 lbs 2.5 oz's with everything piled on so once the fiber glass is done and paint likely 6 lbs minus fuel. Ask and ye shall receive my friend, here ya go, took about every angle. What do ya think?

Jeremy_H

Yeah that helps a lot, it look less lifty now. I still think it's steep but what do I know :/

arcdude

That's it, that's all What do you think of the overall design? Think it'll float? You likely know more about the angles that should work on these things than I do, this is all guess work for me. The front sponson's are at about 5 - 6 degree's and the rear is slightly higher due to the fact it's so short being 6" long and 1 1/2" high.

Jeremy_H

Well really, I've no experience with riggers and my thoughts are based on trying to visualise the operation of it. I remain concerned about the engine position, and what I've seen of the little humpy bits on the tub rear the rigger boys use on their water prop jobbies at the club they are nothing more than thin wedges of no more than half tub width. As it's a bolt-on on yours I'd be inclined to make one of the same length but maybe half the height, so that the the angle drops. As we have a concern about nosing over right now a large lift angle and depth on that section is not going to help the problem if it turns out to be an issue. I'm also struggling with the effect on steering, again the sheer sides do have me thinking a turn fin of some size will be a must.

Overall design? Well it looks superb as I've mentioned, but whether it'll float well is academic, it only needs to float if it stops in the water, it's a rigger, so static buoyancy is immaterial, you just need enough so it does not sink to be able to rescue it if it goes dead in the water, and maybe some to allow lower speeds for launches. As it's a foam core I'd say that flotation is not an issue here. And, weight is also not what it might seem as it does not matter how heavy it is if there is enough thrust to offset dead weight with lift. That's what I mean about my SI3, it appears to handle exactly the same as any other standard SI3 even though it's two pounds over weight, so long as it's fast enough it's fine. It's more important to control where the weight is than how much of it there is to a degree.

Too early to worry about, but how are you going to paint finish it? Any graphics or are you going to be hitting the safe ground of lacquered ply?

Anyway I'm just jealous cuz I'm working on other people's models right now to earn some hobby tokens rather than my own I desperately want to get to

Jeremy_H

Oh by the way, I reckon adding a bit to the sponson spacing, just a feeling.

arcdude

Ha Ha, looked all over the boat and can't find any humpy bits, what's a humpy bit? I'm guessing were talking about the rear sponson, I've similar concerns and the two main issues to me are the forward angle may end up acting like an airfoil forcing the rear up and nosing over or as you state just the mere size of it could impact water turbulence with the same nose over effect. The issue is that the tub sits 1 1/2" off the water so in order to run horizontal the depth had to be matched in the rear sponson. In viewing all the riggers I've seen online to me most are designed for racing circuits and set up to do just that, my focus is on creating a rigger that is deeper wider and able to run at low or high speeds, launch on it's own and run on mild river conditions so I won't be restricted to waiting for ideal water conditions so in all a more user friendly boat, hopefully. Uncharted territory my friend! Another point I'd like to share is in the overall design I have in the back of my mind that if I wanted to downsize it is a simple matter of building a smaller motor mount and changing the rear sponson's to the side to shorten the boat and plunk a 46 engine or similar so that is in part why I've been what may seem preoccupied with the overall weight.

In another thread I considered using an aluminum foil rather than a sponson but haven't been able to come up with a viable design so it evolved into the rear sponson you see. The only other option I can conceive is to make two sponson's and lengthen them from the rear bolt on the tub to about the length it is now and each of those would be about 1" - 1 1/2" wide and about 9" in length. You mention the sharp cut of the sponson requiring a possible bigger rudder to compensate, that is why I earlier mentioned angling the trailing edge sides of the sponson to about 30 degrees or so in order to obtain a little give in the turning, I still will likely do that regardless of what route I go in the final design. The sponson spacing will likely be about 24" when done, I only set it up quickly on the table for the pic.

For finishing, well paint seems to be what I'll be doing with some hand painted design here and there. I have given this some thought so here goes, the name of the boat will be Slew Shark and the meaning of that is "turn or slide violently or uncontrollably in a particular direction" according to the dictionary anyway, I hope it's the violent slide rather than the uncontrollable part. The paint scheme will be sharks teeth around the front of the tub and the eyes will be on the outer side of the front sponson's. When I make the rear airfoil the uprights will look like the rear fin of a shark. I just hope the light grey paint isn't going to be too hard to see Could be fun

Hurry up and earn the needed token's to move ahead with your own creations, it's awful lonely on here all by myself!

arcdude

Set everything up with the motor on to give a better visual as to how things sit and placed a stick across the sponson's in line with the trailing edge to show where the engine lines up. The sponson's are set at 24" outside measurement in the pic to show the stance.

arcdude

Looking at these pic's, that back end has to go!!! For the most part it looks pretty good until your eyes meet the back end and it's WHAT hmmm. Open to suggestions, anyone?

Jeremy_H

Yeah I'm feeling much better about it now, don't really know why. It feels like the balance point is aft of the engine more so it's looking pretty sound now.

I like your paint idea, painted riggers are less common due to weight needs I'm guessing, but the shark Idea is cool, it'll be a sort of Hammerhead look with those eyes out on those sponsons .

FYI here's the boat I'm working on for someone else, an electric Daz Elson X-Cat.
There's a couple of days of signwriting to go on next:


After that is this one, for the local model shop owner. I've been left to design what I'd like with the theme of the boat's design name, Panther, and the colour pink, but I can't use Pink Panther as a theme . CMB 15 power


Next is one of these. It's coming from the owner of the Union Flag Cat above. Total open licence on this one, an overweight looking thing, I'm thinking of fitting an aero engine :



Finally two of these, rare Carbon/Kevlar PiP Bitberger's. This one's mine, two handed .40's in that one:



I have ages to get these last four boats done, so once the X-Cat is out of the way this weekend I'll be on to the Twins project again

arcdude

You certainly have your hands full, I especially like the PiP Bitberger's, has a bit of a futuristic look to it. Can you explain lacquered ply, what process is that and what do the guy's at your club do to finish their riggers?

1QwkSport2.5r

Here are I'm thoughts. Looks great! However I'd make these changes if it were me. I'd angle the front of the sponsons higher. Because of the downward curve on top of the sponsons, you may find it will want to submarine if it's too bow heavy. In my experience with mine, not even a launch ramp could counteract the water coming over the too of the sponsons. Next; I think the prop/thrust line should be at or aft of the sponsons' ride pad/step. I haven't tested this yet myself but seems to be common among other outrigger airboats I've seen. Experimenting with engine location will help determine this. Lastly, I'd pitch the rear sponson. I don't think its necessary. I do think you may need some sort of wing or airfoil to keep the aft section of the tub planted. It looks naked without some sort of stabilizing wing or spoiler.

Just my thoughts. In Jeremy's words, "but what do I know?"

arcdude

Good to see your still kickin! Thanks for the suggestions, appreciate the input. I've noticed what other riggers are trying to achieve in their design primarily working with a balance point just aft the front sponson ride plane, however, that is what I'm trying to avoid and am going by the balance characteristics of an rc airplane where the thrust line is well ahead of the balance point and the thrust line is pulling the weight, best I can describe it. So what I've done is place the balance point of the engine just aft the ride plane and the prop is just ahead of the trailing edge and in the end I hope my balance is well aft the engine. In my understanding the prop provides propulsion and the control surfaces control direction so to me the weight should be aft of the pulling point rather than at the balance point, I could be way off the mark on this. There really isn't much in the way of proven methodology so this is all one wonderful experiment that is why all major components are bolt on to discover what will work and what won't.

The concept I'm after is a play boat and not an all out screamer so the rear sponson will keep things balanced at lower speeds and keep the boat set at about 1/4" lower than horizontal and the airfoil will come into play at higher speeds lifting the rear sponson, at least that's the plan. I really don't think I'll have any flotation issues with the front sponson, I've taken a pic with a horizontal line showing the depth of them and the angle on the bottom is considerably steeper than the top. And to sound like a broken record "but what do I know?"

1QwkSport2.5r

Boats and planes are two different animals. The engine will be pulling/thrusting forward and if the majority of the weight is in the front half it is going to want to dig in. That I do know in my first runs of my rigger. Floating idle it was level, as soon as I throttled up the nose sank. It needs to be balanced such that when you throttle up you get lift instead of forward/downward motion. My rigger when held by the prop was heavy well aft of the engine.

Your mention of a play boat and not an all out screamer.... Outriggers are straight line racing type boats. My thoughts on a "play boat" is a flat bottom boat which is not near as finicky to set up as a 'rigger is. I'm not nitpicking, just being realistic and as factual as I can.

arcdude

Thanks for your advice, I will keep your suggestions in mind. As you say riggers can be finicky to set up and that is generally due to the fact they are designed that way with barely enough material to hold itself together, if side by side comparisons were made with an average rigger including your own mine is considerably different. As far as fun goes I guess we all have our own definition of what fun is I guess. I'll be doing a water test before long so I'll see just how it'll sit in the water when done. How this all turns out is anybodies guess.

Jeremy_H

Every rigger at the club that's ply is lacquered, or varnished, only GRP ones are coloured. I'm not sure what's behind this, I like wood a lot, but thinking about it there's no weight reason for clear finishing I can think of, but then again I've never done a weight comparison, maybe the pigment solids in colour coats add weight? I should find out.

This is a typical rigger from my club:



It's Hydro Night tomorrow evening (no big gassers or electrics allowed to keep the waters calm) so if one of those guys are there I'll ask what process they use.

This vid we've touched on before shows an airscrew rigger which seems pretty easy to get going, considering it's a little .28 it picks up well from idle, it looks to be about 28" using the 9" prop as a guide:

https://www.youtube.com/watch?v=QS2SQeb8Dfw&index=66&list=LLw8b4mq7g44FwvGq97q6aKw

arcdude

Thanks there Jeremy. I can't see that there would be any appreciable weight difference, maybe to the racers an ounce or two is a big deal. They do have nice looking boats though and I noticed there is quite an arc to the top of the sponson. The airboat in the vid is quite stubby length wise and get a load of the angle of attack on those sponson's, no wonder it pops right up on take off, but that would also be a huge negative in the speed limit I would imagine. There is also a small sponson on the rear as well it is just visible at 3:54. I'm starting to think you may be right in that an increase in rudder may be necessary.

Jeremy_H

Found another rigger pic, on this one one you can make out the kind of wedge under the stern I was referring to

1QwkSport2.5r

The wet-propped riggers use a stern mounted sponson or wedge. Probably due to the weight being spread further aft. I've not seen an air driven rigger using one or needing one. Comparing wet propped boats to air propped boats is an apples to oranges comparison. I'm just not sure why it's being added to this hull or why it would be necessary?

1QwkSport2.5r

The wet-propped riggers use a stern mounted sponson or wedge. Probably due to the weight being spread further aft. I've not seen an air driven rigger using one or needing one. Comparing wet propped boats to air propped boats is an apples to oranges comparison too, IMO.

I'm just not sure why it's being added to this hull or why it would be necessary?

arcdude

The rear sponson if that is the correct term appears to be set to run the boat at a horizontal plane, I could be mistaken. With my boat it's 1 1/2" above the water line so the challenge is to come up with something that will work without being too big. I'm bashing together a new back end and will post a pic later. Thanks!

arcdude

The reason being is the tub sits 1 1/2" above the water line and rather than have a balancing act with the trailing edge of the front sponson's I'd rather have something physical for the rear to ride on. I'm currently building more of a wedge type sponson and will post a pic later. To further explain the riggers utilize the tub as part of their flotation dynamics, I'm not in this design and rather edging closer to a running attitude similar to an SI3, hope that helps.