TCHedOff

I had the pleasure to get to listen to Rod Geraghty talk on the phone for over an hr yesterday on boat design. Rod said he likes/wants to help boaters but HATES typing, so I got his persmission to share some of what he said with you for him.... because my mind was BLOWN!

In a nutshell: ANY curved surface that contacts water will create drag (less speed and often undesirable handling). FLAT/STRAIGHT surfaces w/sharp edges are better.

Rod took me to a few websites to illustrate what he was talking about. Go to www.jmpba.com (click cancel on downloading the Japanese text). The column on the left is a series of links. Click on the first one (or any of them). The next page that comes up will have little PT boats - these are links to pics. Click on one. Look closely at pics of riggers on land. Look at the front sponson shape & surfaces - no curves! Now look for rear sponsons - arent any! Now look at pics of riggers on water - notice how the water surface is hardly rippled by the boat - just prop spray. In a number of them you'll see them running on prop & turnfin only and there is a reason for this - you'll have to hunt to find pics of the back end to see the bottom - you'll find even the stuffing tube is enclosed in an angled "box" - no curved surfaces in contact w/water anywhere.... and that box enclosing the stuffing tube becomes a "ski" the tub rides on!!

Using straight, flat surfaces w/sharp edges applies in to all boats.... riggers, tunnels, hydros, mono's.

Rod said he has seen these .21 Japanese boats run on open ocean [X(] (rough water, NO problem) followed by a chase boat with the driver in it. He also said they can just drop their boat in the water and GO (super launchability) - no need to toss [X(]. AND because they are launchable, they can get a way with larger & higher pitched props.

Hopefully a number of you will find this as interesting as I did.

todd

Dan S

Knowing Rod he talked about the Bernoulli effect and ........

did he talk to you about the spoon trick.

Dan

TCHedOff

No 'cause I had already read all that (and OF COURSE HAD TO TRY IT MYSELF - even funnier - AFTER I tried it, the very next post in the thread was something like. "Rod, do you know how many people are standing at their sink with a spoon in their hands" - I laughed til I cried over that!

He also had ALOT to say on engines - the guy has SO much knowledge!!!! I sent my Novarossi to him, and told him my riggers RTR weight (4lbs 5oz - kind of heavy) and that I wanted to heat race - He said, "I'm going to change your needle valve then". I asked how he was going to do this... he explained a needle works because of low pressure. as air moves past the hole, the low pressure pulls out the fuel. By anology, he explained if you take a beaker of fluid, put a hose in it vertically, and blow air real fast over the hose's hole in the top, it'll draw fluid up the hose. Needles work the same way... and he was going to mod the whole in the needle to draw more, so it'd run richer and launch/accelerate better.

TCHedOff

Somone was polite enough to PM and correct me (thanks)!

Rod actually was talking about "spraybar" design not needle valve design. "A needle valve regulates the amount of fuel being delivered to the motor. The spraybar design determines how the fuel is dispersed and the strength of the fuel signal coming from the "running" motor."

There is enough mis-information in the world!

Ron Olson

My Feedback: (1)

Rod's cool. He called me one night out of the blue and I just about had kittens when I saw his name on my Caller ID!
The Japanese run in water that we'd normally park ours in but they really don't have any calm conditions. I've watched the videos on the JMPBA site and their boats are unique. One outrigger that I worked on for development here in the US was originally designed to run there. The sponsons were wider as they handle the chop much better with less side-to-side rocking.
If you want to see one really different, look up the "Rocky Left Hook" outrigger. I use the Alta Vista Babelfish translator when I go in there. Some of the translations to English end up in being humorous. Rudder is Ladder and their names turn out funny.

d-lo

great information todd, thank you.

oh, i am a newb i guess, i don't know the 'spoon' experiment.........................


davey

Ron Olson

My Feedback: (1)

It's also known as the Bernouli (sp.?) effect. Put a spoon under running water like a typical faucet and see what the water does when you put it in different positions.
Don't do it in front of the mother, wife or girlfriend as you might end up by doing the test on the plates and cookware!

werdonmorris

My Feedback: (7)

how many boaters has really had the front of there boats, keep the front end down in the water, not many!

Ron, remember the old hydro-planes, the faster they went, the higher the boat would rise out of the water, with decreased water friction-more speed!

butch, howdy

Ron Olson

My Feedback: (1)

It still happens. A guy that I used to work with wondered why his bass boat would go faster into the wind than with it. Simple, the wind was helping to lift the hull out of the water.
It's true with R/C boats also. A lot of the Pro Boat owners are seeing that as once the boats get up to speed, handling goes away because the trim tabs are out of the water and not aiding in keeping the hull from chine-walking.

TCHedOff

Here is another website that shows Jpanese boats including the unique riggers and has video too:
http://www.hi-ho.ne.jp/snoopy/S_Boat_Team.htm.

If you click on the top left link (July 2006) and scroll all the way to the bottom of the page, on the left you find links P1050204 and P1050208. Check out those videos if you want to see some hi-performance action.... those boats arent losing ANY speed/RPMS in those sharpazz turns! [:-] I WANT one of those!!

I also got to speak more w/Rod on these rigger set ups. He said they dont have to fiddle w/sponson angle of attacks [X(] (they are fixed at 4* AOA) nor do they need to mess with strut angles/adjustments [X(] - they also are fixed in position.

This makes these riggers MUCH easier to a newbie to build & run - Ron, even you said "Riggers are GREAT when they get set up right - but they can be a PAIN to get set up properly". These designs solve many of the frustrations that people experience with riggers.

d-lo

that link doesn't work for me, but i am really interested in doing a rigger, but i am new to that style of boating. any information on 'the easiest in' to that style of boatin' would be great! thanks for the info,

davey

TCHedOff

Hmmm... Ok D-LO try this link: http://www.hi-ho.ne.jp/snoopy/Snoopy_Boat_Team.htm

Let me know if it works... if so you can get to where I was trying to take people.

d-lo

works! off to explore, thanks again......

davey

werdonmorris

My Feedback: (7)

RON OLSON, JETPACK, & MEMBERS:

I WENT TO THE WEB SITE IN JAPAN, AND GRABBED SOME OF THE PICTURES. IT SHOWS SOME VERY INTERESTING DETAIL OF SPECIAL COOLING LINES, GAS LINES, AND OTHER HARDWARE.

BELOW IS THE PICTURES AND HOPE THIS HELPS OPEN UP A FEW BRAIN STORMS, FOR I GOT A FEW FROM IT.

IT EVEN SHOWS SOME CUSTOM MADE EXHAUST.

BY THE WAY RON & JETPACK, WENT TO THE VA TODAY.-THE DOCTOR SHOCKED ME WHEN HE TOLD ME THE ANGIOPLASTY MAY HAVE BEEN HIS FAULT, AND REPLACED IT.

GOT TO SEAT BACK NOW, AND BE REAL CAREFULL.-GIVES ME TIME TO WORK ON A CARD BOARD V-8 ENGINE FOR MY SON. MADE OUT OF FILE HOLDERS, AND BOXES.

I MAKE THEM LOOK LIKE THEY COULD START UP, AND RUN. BUT THIS IS THE WAY I AM WITH DETAILING.

YOUR FRIEND-BUTCH

ATTENTION, I TRIED TO SEND PICTURE FILE, BUT TO LARGE FOR ULOAD, EITHER SEND ME YOUR EMAIL, AND WILL SEND. OR GO THE JAPAN SITE, AND GO TO THE OLDER DATES ON THE LEFT AND SCROLL.
YOU WILL FIND SOME EXCELLENT HARDWARE!!
[email protected]

TCHedOff

I just got back from meeting Rod in person and spending 4hrs talking RC boating and riggers in particular. [8D] It was a real honor and I learned a ton. It has become VERY clear to me that riggers DONT have to be a pain to build or run or require alot of fine tuning to run well - if you follow some basic "rules". In fact they should be one of the easiest to build and run.

I brought him about 12 pages of sketches and diagrams of every aspect of a rigger I could think of and discussed them all. I'll clean up all the doodling Rod did explaining to me and share what he taught me, scan them and post 'em here. Interested?

Ron Olson

My Feedback: (1)

Sure, let's see the scribblin'! [sm=teeth_smile.gif]

TCHedOff

Hey Ron - Glad you're up! You came up in my talks w/Rod; He thinks very well of you!!!

Anyhow I got to ask him about sponson boom tube lengths. Rod said "I spent days testing various widths and found there really isnt a d..mn difference in terms of speed (and you'll get some flack from some who know "better" but g$dd&mn it they havent spent 3-4 days just testing this - sound like Rod to you???)- just that wider is more stable. And more stable is better, so go wide and give it a big footprint.... you have to first finish a race to win."

TCHedOff

Hey Rod I SEEE YOU looking in!!!! Got home safe & sound - chime in in you would so everyone KNOWS I aint BSing here!!!! Cmon Please!!!!

Ron Olson

My Feedback: (1)

Yeah, I see him peeking in here too!
The Japanese must have been watching those Pontiac "Wider is better" commercials. We got used to using the 2 to 1 measurements, twice as long as wide but when running in rough water the wider ones will have more stability. Maybe what we Americans look at is flex in the booms and aerodynamic drag as a couple of reasons to go narrower.
I've got a local boater who somehow got into the Universities computer and did some aerodynamic testing on various outrigger hull designs and built one for kicks. The tub looked more like a submarine than the usual rectangular box with a pointy front end. If you think about it, not only does that design work for subs but aircraft as well. The roundedness (if there is such a word) makes the hull less darty and aids in keeping it from blowing off the water.
What the local guy ended up with was a 'rigger that was very fast, even with an old K&B .21 in it. It's too bad that it got badly rear-ended at a race when he backed off the throttle and lost the flex cable.

TCHedOff

The "scribblin" has begun! - I decided NOT to just present Rod's conclusions but all the we covered to GET to Rod's conclusions that he has learned from his MANY yrs of experience. UNDERSTAND: I brought to Rod a bunch of sketches I drew up to ask his opinion - and Rod just told me what would and wouldnt work and "penned over" my sketches to illustrate what was best.

Here is the 1st subject I asked him to cover - tub designs on riggers:

TCHedOff

Page 1 first focuses on 3 possible rigger tub bottom surfaces. The first (shown as 2 sketches) is meant to be a perfectly FLAT bottom surface. The other 2 bottom designs involve curves. As Rod has told me "x" times, curves create drag and other nondesirables - design 1 is the way to go.... AND he IMPROVED this design by making the front (bottom) of the tub as a 2nd angled flat surface... eliminating the need for a curve to make the point of the front of a tub. Think of the straight lines of a stealth B-2 bomber and you get the idea.

And for those reading: The relationship of the tub to the surface of the water in sketch 1 is WRONG (cause I drew it before I had talked w/Rod). The CORRECT way the tub should be compared to the water surface is PARALLEL to the water - riding on that back "ski" you on those Japanese designed riggers - more on that later).

The bottom row on page 1 is my question to Rod about whether a tub "nose" (front) should be neutral, pointing down or pointing up. Answer, neutral (sketch A), in general, because a tub can be a "control surface" - Rod's words (airplane guys use this term to describe ailerons I believe - they are "control surfaces" and affect whether a plane goes up or down). In the same way a tub, to some degree is a wing with air flowing by - to have a predictable, well performing rigger you dont want to induce a tendency to want to fly up OFF the water or drive down INTO the water.

Page 2 is my next set of questions I asked Rod.... still on tub design. I proposed 3 versions of a "US" style tub bottom lengthwise.... in the top center sketch, and top left sketch I was hoping getting air under the tub would be good. Rod's answer was again that the sketch to the top left was BEST - AND he IMPROVED this design by sketching over my drawing how to extend the bottom surface past the sides of the tub. IF you have a tub that is already put together, you could add strips of wood to get the same effect. The reason the extended edges IMPROVES the tub is because water will want to suck up the sides of the tub to some extent EVEN if the edges of the bottom of the tub to the sides is razor sharp, which creates drag. There's a technical word and explanation for why water wants to do this, but that isnt needed here - just the conclusion Rod has learned.

The next row shows 3 variations I brought up on the "ski" these Japanese riggers use. Rod's reply there is NO DIFFERENCE between the 3 variants - all would work because if properly built the sides of "ski" will be out of the water at speed. And Rod AGAIN improved things by extending the bottom surface out past the sides, just as he did with the tub as you see in the left and middle sketches and on Rod's scribbled example BELOW the one I drew on the left. This is to again to prevent water pulling up the sides of the "ski" and creating drag just as we see in the tub bottoms.

In the middle of the page where the "ski" is 2 dotted boxes, I was asking Rod how wide/deep (in relationship to the tub) should this "ski" be. His answer was that he was working with @33%. It also sounded like MORE testing could be done on this to find an optimum ratio.

In the next row, are 3 variations on where a flexshaft could be placed... normally they are in the middle - could it be on the left side of the tub, or even the right side - does it make any difference? Rod's answer was all 3 would work fine as long as they are perfectly straight - so they drive the rigger in a straight line forward.

One of the reasons I asked Rod about flexshaft placement was because I wanted to ask him about engine position within a tub - does it have to be vertical? Hence the bottom row.... Could I angle the engine on its right or left side (to lower the center of gravity and move it further to the right or left side of the tub to get balance), and then run the flexshaft straight back on the left or righ side? Rod said I could do this, but ultimately it is BEST to run the engine vertically and keep it as low in the tub as possible (for several reasons).

I'll conclude this for tonight by adding Ron's own sketches as he was explaining things to me and summarizing. The words ".12" and underlined "RPM" was Rod explaining to me that in a .12 rigger (what I'm going to build first) you are dealing with a TINY (power-wise) engine and the ONLY way to make that engine/boat fast is to get RPM's out of it AND (in terms of boat design) the way to get RPM's is to get as much of the boat out of the water as possible and eliminate all the drag you can - hence the extended bottom surfaces (past the sides and back) of the ski and tub, and to always remember to use FLAT not curved surfaces.

TCHedOff

Here is the next topic Rod Geraghty and I covered - Cowl Design. I wanted to know about possible shapes for the front surface. Basically he said all 3 would work fine (cocave/convex or straight line). Then I asked him if a full length cowl was better than a partial - he didnt say - he just said that a partial is more practical in that allows you access to the engine and other components. In the last row, I asked about the trailing surface for a partial cowl - he said id didnt make much difference as all 3 designs I sketched have turbulence flowing off them (represented by the circles Rod scribbled in). Best just to "Keep It Simple Stupid!".

TCHedOff

Now for some INTERESTING INFO for those who have read this far! I covered sponson shapes in detail with Rod as you see in the row at the top of the page. His reply was that sponson was that sponsons on a rigger DO NOT require any chine (angled surfaces on the outside) and that they are actually detrimental! [X(]

The BEST design are are the 2 on the far right... and of these, the one farthest right, with the strip of wood to prevent water sucking up the side of the sponson, is the best. He said you CAN use strips on both the inside and outside sides of the sponsons but it is PARTICULARLY important to do this on the outside side of the sponson.

In the next row I asked about how high or low the front edge (TIP) of the sponson should be and about using a stepped sponson. 1) He recommended a step design. As for how high the front edge should be, he said he is still testing and cant give a flat answer. But to understand things better, he explained that to a degree, the top and bottom are a control surface like having your hand in the wind out the windows of a moving car. If your hand is pointed up, the air pushes your hand up, and if angle it down your hand is pushed down - the effect one would want to achieve with the tip is to be neutral. Rod also pointed out that a narrower sponson acts less like a control surface than a wide sponson. So I asked what an optimum width for a .12 rigger would be. He said, "If you'd of asked me that years ago I'd of had an opinion. But now after seeing these Japanese boat that weigh almost nothing, with their wide (far from the tub) apart sponson using narrow sponsons (less than our typical US ones) running across the ocean, I just dont know".

The last row wa what I had hoped was a unique boat set up using alittle of both US and Japanese thinking - to wich Rod replied, Just stick with what I showed you (top row, far right) sketch.

TCHedOff

Here are pics that Rod gave me of some boats being built as we speak using the principles described in this thread.

Pic 1 This is an Eagle tub with these sponson mods and it has the entended edges on the bottom surfaces - but that doesnt show up well unless you got eagle eyes! You can see how wide the sponsons are from the tub (I'm guessing they could be as much as 12 inches [X(]) and the shapes used.

Pic 2 You can see the bottom of another rigger. If you look closely you can see these extended riding surfaces. On this one, if you look closely, you'll see that the bottom is a series of 3 flat surfaces - each with an extension on the rear edge.

Pic 3 This is Rod-scribbled sketch of how the rear edges are extended and how to achieve a curve (if you want to simulate one).

Pic 4 Here you can see a really good shot of that Japanese style bottom ski. You can also see a steplike flat surface on the front bottom of the tub that replaces a US style curved bottom on the front of a tub. And you can see an interesting take on a sponson here with cut outs to remove weight. I even got to SEE/HOLD a SAW rigger using these style sponson in person (it is owned by Glenn Quarles but was at Rod's house - I wont tell you the boat weight - you wouldnt believe me and Rod said that it was TOO lite!!).

Pic 5 Another rigger using these ideas. You can clearly see in this one what is meant by extending the edges of the sponson bottom - the sides and the rear edge. OOPs got that one upside down! .

I'll upload more tommorrow (I TOLD you we talked for 4hrs! )

TCHedOff

Ron - Are you finding this interesting??? See anything new to you? Its taken up a number of hrs to get this far and while I'm SURE many of us "newbies" will find this stuff surprising, I'm wondering about people like yourself?