Outrigger design reward sponson to cg.

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Christian Lucas

Well-Known Member
Joined
Aug 23, 2012
Messages
339
Hi,

i start this tread as i want to show you my thought ,to set the sponson back to the cg.

I want this for SAW and for Oval racing as the rigger will less cickt by a wave at the bow .

Most waterairplane start with a design where the sponson are placed near the wing and the end of the sponson is often behind cg. As i want not to fly i will not use a wing or say a very small wing like a rotorblad from helicopter and very tini sponson .For start the rotorblad will be under water acting as a hydrofoil and there it will produce lot of lift .But when the boat is faster and going out of the water with the blade this lift will breack down doing hydrogliding and the rigger has to step up on the small sponson. To ad moore lift at the bow ,a smaller starting hydrofoil can be placed at the bow ( little withe blade) .

I have a lot of experience with the comon designs rc and tethered boats and know how to counter to much lift at the bow sponson but now i want it different like the wige boats/planes .

For a first test i use a 2S Rigger from Graupner the Silver Bullet .

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These resemble some of the tether boats ive seen. Really interesting build Christian. How do you get from your prop molds to the real thing?
 
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Hi Hugh,

you aske for the laserlito foam props ? You see the pic with the props ,some are withe and some are a bit dirty .The dirty are wax infiltrated ,suck full of wax. Now you can ad the fillingchannel and the airchannels if used. Now i put it in the casting mold ,fill it with potting compound ,let it harden and burn it in a furnace where the plastic and the wax combustible as they are combustible. For a berilliumcopper based propeller i use a high vacuum casting and for dentist steel a g-force centrifuge.for the laserlito i have a friend Pierre Mousel ,he makes the drawing and the data for it and a other friend who is working at EOS Laserlito Maschines is doing the preform.They can also laserprint the prop direct in steel but they are not so strong as the dentist steel propellers.My friend at EOS does also the preform for the JAGs Team record propeller ,but they limited the use of there prop only for them selfe. But it´s not a very intresting design i my eye with a pitch factor of 2,4 the motor rev for the record at 50000 rpm ,dia 42mm (1,65") .I want to go with a pitch factor of 1,4 and a dia of 40mm or with tethered line props pitch of pi 3,1415.. and a dia of 60mm .
 
See my reply in the props section. Below is a picture of an earlier version of Joerg's current RC record holder at 140 mph. There's a lot of careful aerodynamic design in this boat.

Lohring Miller
 
Chris Harris also has some unique wings on his record hydros as well. Really nice thread here guys.
 
Hi Christian, i have a question about the A2 tether boat you have pictured as it looks very familiar. Would that be Ivan Vankov from Bulgaria A2 boat. Thanks Martin.
 
Hi Martin,

yes it´s from Ivan Vankov so you know this is a fast boat . And you know they grind a flat on the sponson if the bow lift to much an ad lead on the strut to level the propriding deep. These are the normal way to trim a boat.

Lohring,

i am not with you ,that the record rigger is a good designe. I start some similar designs with not outrigged sponsons years ago in the 7 cell class and it took a lot of adjustment .Also the JAGs rigger need a lot of fine tune and adjustment and end in a blow over .Currently they have to set up the angle of attack for the sponson need zerro degree to hold the sponson down . The sponson are to far forward and the airpressure between water and the skidplate will force the bow to blow over .If the sponson are set at the center of gravity with there lifting point you can run them with an optimum low resistanc angle of attack of 4-6 degree belong how wide the sponson are. And if you design the boat only to get the lift of this sponson lift no other from the body ,you will not have any problems with blow over and wave kick ( at high speed waves are always dangerous ) .For me the long wingbody design is the problem as it´s a wing a wide wing and this has a big center of lift travel as you say if the high change. a small wing like a rotorblade has only a short center of lift travel and if the most lift is generated by the sponson to water pressure it has only a small influence . Have you seen my old 20 Wing Ding ,i run it with a straight propshaft.The Wing Ding was designed for parallel propshaft .My boat run at the first drive like a jumping somthing but when i installt the spoiler the boat runs very smooth and as the Wing Ding has also not very forward design sponson it has also less blow over tendency . I like this design .For higher speeds the centerbody is to wide ,for that i want the centerbody of my boat only 3cm wide with a sharp deep V to minimise the aerodynamic lift posibility. All openings on the side of the boat and a vacuumformed part at the motor section if the motor has moore dia as the 3cm of the centerbody wide.

By the way ,i start also a full scale electric speed boat with Torqueedo, http://www.torqeedo.com/ . I designed a front proprider ,that has a motor in each sponson with no skid plate ,only the propeller at the bow and a wingbody for the driver cockpit and the batteries.The sponson can change there angle of attack by servomotors so the motors can lift the bow out of the water from standing still .But currently to less time to do this do moore on this toy.see little handdrawing ,i have only this here at my home pc.

Watch the torqueedo outborder ,they use a variable ptich propeller designed by the German submarine propellerprofessor.

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Here is the bottom of the boat we have under design. the sponsons attach to the front with plates of carbon fiber to the sides.

The sponsons are forward of the fuselage.

The tub is a air foil design we have bin testing.

can't show much more or Dave might get mad.

Using a V drive for the over drive.

David
 
Christian I remember Vankov with this boat when we raced at the Naviga A/B European Championships in Rottadam in 1985, he allways built very nice boats. First saw him in 1975 at the European Championships in the UK, where Otto Strobel won the A3 (10cc ).
 
Hi Martin,

I was in Rotterdam 1985 and get the boat from him there.We start in F1 1kg Klass my friend Hans Lehner fight with the Chinese .I show in some Demonstration run a narrow Crapshooter rc-rigger how surfacepropeller work on this and wie start with Graupner the Hydrocup in 1985,that become the Hydro class 1,2 and 3 for Naviga.Maybe wie meet there.i meet also later some competition in Bulgaria ,Stara Zagora.Paul Otto Stroebel Is also a friend ,i have some propeller from him.
 
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Joerg's hydro did not blow off during its 140+ mph run. It hit something (turtle?) lost its transom, and sunk. There's a slow motion video that shows this. A long, narrow airfoil doesn't generate much lift. If you add air traps to it, it's a different story. The sponsons are the same story, but run a lot closer to the water so the effect is greater. Joerg's hydro has a horizontal tail running in ground effect that lifts the prop out and helps keep the center of lift back even when the bow lifts. The boat also has a lot of vertical tail area to hold the boat straight at speed. The water rudder mostly lifts out at speed reducing one of the main sources of drag. Slow motion video shows that the sponsons only touch occasionally during the run. The whole boat except for the prop runs in ground effect.

Stability is the big problem. I've seen dozens of SAW hydro crashes that started with sponson walking. Blow overs are also common. The general consensus is that lift is a bad thing. That's why riggers are the fastest model boats. Our experiments show that controlled lift is what you need. The boat must be stable and have really good height control. Our gas sport hydro made one way runs of over 100 mph in water that was too rough for any other boats to run despite the problem of a wing that was too far forward.

Lohring Miller
 
Hi Lohring,

you can set up every Rigger to fly in groundeffect .My old Wing Ding does it ,the Crapshooter does it and i bet the Eagle SGX does it .

It your skill to finetune it that the boat does it at that speed you want . The JAGs rigger was setup to 140mph on mirror like water .On little waves the rigger show some flips last year and at this year German SAW .This is not the egg laying pig .

If the lever arm distanc from sponson to c.g. is long ,every influence like lttle wind ,small wave ect. effect in a big result cicking the boot of.If the leverarm is neer the c.g. it will not effect in turning the boat over ,it will only cick it up .not moore ( ok belong to the high of the wave ,windspeed ect. ) . But it' less important. Have a look at seeplanes with skid ski and you will see that they have all placed the ski near c.g. Look at the Wing Ding pic and you will see not touch of the sponson on the water for a long distanc .

What are you thinking about the Eagle SGX . I my eye it's a wonderfull rigger as it runn at high speed for long distanc without trouble ,This show that the boat run stable . Also the tethered line boats run long distance for acclerating and for the messuring time .The JAGs rigger does only the very short dragstrip speed ,no moore . Wy ? They are anxious to blow over. They know that a rigger that comes out of a corner with say 60 mph acclerating down the lake will easy top the record . 2S batteries can deliver the energy .And you can go like the ic boats do it .

the Wing Ding 20 is electric ,going 75 mph with about 1000 watt and less powerinput .There are only 30 nicads with 700 mAh cells onbord.

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Christian

I'm confusing you with a combination of observations of Joerg's rigger and our experiments. Joerg doesn't use air traps anywhere, while we've done extensive work with air traps to enhance the ground effect. As a result, our gas riggers are very stable in rough water. We found that there needs to be quite a bit of weight on the prop as well as a fairly big footprint both from side to side as well as fore and aft. Too much lift on the center tub isn't usually needed, though Mike ran an aft wing on his 85 mph, 3.5 record holding outboard hydro. Initially the wing was too big, though. Think about air lubricated bearings for surfaces in very close ground effect. When the support surface is water, the pressure from the ground effect lift deforms the surface in an area ahead and behind the lifting surface. This effect surprised us but turned out to have benefits.

Lohring Miller
 
yes ,can be .somtimes i understand not everthing you wrote as i am not the language king in school ,was moore the lasy bone boy having other things in mind than school.But i understand now the air traps like you use it at your boats. This is ok and is also my position . i will do some simple drawing when i have time next days.
 
Don't apologize. Your English is lots better than my non existent German. Most of what I know about ground effects comes from a lot of testing on gas hydros. Gas engines are very consistent as are electric motors. This makes it a lot easier to try various ideas. Mike built several tubs, sponsons, and rudder blades. Spare plywood, sandpaper, and super glue are also essential tools. We just made lots of acceleration runs comparing peak rpm & speed. These days data loggers make testing even easier. We used an onboard tach and radar gun to get peak speed and rpm before our 2003 record runs.

Lohring Miller
 
Hi,

it´s like me ,lots of testing ,adding and removing part ,edges ,bend and grinding .But the last 5 years i was involved in some of the modelairplanes that took the speedrecord .My part was the motor but i have alway a look at the aerodynamics . Christian Rössler teh German electric pylon world champion works at the Munich university .He designe the Bartlet plane and they currently design a new record plane. He is doing his Dr. of aeronautic .They have a big windtunnel and if i have some luck i can do a windtunnelsecion this winter with my modelboat. Hope to see and learn some influence of aerodesign.

The airplane guys use the SM modelbau onbordsystem to record everything of intrest.Speed by gps and pitottube (airpressure) and revs,amps,volt and temperature of the motor and batteries. With the gps they do 3d prints of the flight showing all ups and downs . This give best result of realy working of propeller and the whole plane. Airplane propellers work here at about 15% slip of the 75%dia pitch.

i can show some of the print if you like.
 
I talk with the guys that designed the Profi engine pictured below. It's the only really modern model engine design I know of. I have lots of pictures and other data. Also below is a picture of Mike's outboard hydro. It's the most extreme wing design of any of his boats. We use the Eagle Tree data logger for our current testing, even on full size boats.

Lohring Miller
 
Hi,

that outborder is a nice wing riggerdesign. i have done some canards ,inspiration from Ed Fischer canard .i build one only 50cm (20 inches) long for the 1 kg class and converte it in a design from Craig Breedlove (landspeedrecordholder ) .

The most inovativ boat is in my eye the mono design from Camille (France) with, Hugh will love the boat, counterrotating propellers .We had a long discusion ,is it a mono ,as it has only one running surface ,or is it a hydro ,canarddesign without rear sponson. Intresting for that is that this twinprop can go with highpitch propeller no problem with propwalk.

. It's a monoboat with a trunk for batteries and some remote parts.
Have fun.

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Did i see right? That thing self righted???? :blink: Camille from offshore rc, yes I frequent that site. He has some sick designs. That counter rotating single motor setup is too cool. Never have sync issues with that. I love the out the box non tunnel vision thinking.

Lohring, I like that motor. I myself have been considering nelson long strokes 45's in a keps or sgx .21 for some saw runs. The idea of a wind tunnel is one Ive played with for some time for my scale boats. In doing things like active canards and such I think it would be a very usefull tool. Maybe one day someone will get slick and make the rear wings on and sgx autonomous or maybe put together a rigger with autonomous sponsons. Some of the old 1930 tether designs lend them self to this type of experimentation . Ive been thinking........

Speaking of offshore rc make me think of my friend PDA75 who passed untimely last year. His birthday just passed. I really miss that guy. So ingenious and adventurous. A big loss to the development and innovations of new things in rc boating.Never have I seen a motor mount like that guy put together on his rigger.

Hugh
 
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