zope_pope

I think this is a really cool thread. KEEP it here. and if it moves, let me know where, making stuff go fast is cool no matter if its on the ground, in the sky, or in the water.

proptop

My Feedback: (8)

From the times I've visited the boat forums, there doesn't seem to be anywhere as much activity?
And like hooty said, it is dealing with speed and air propellers, airplane engines, etc. (give 'em a break Razor [8D])

Hey..ya ever think about putting floats on your Patriot?

speedster 1919

My Feedback: (3)

First the MAS 11x7.5 is a proven speed prop for a 61. Would a hoover boat pass the rules. If they are ,you are talking zero friction from the water and probably more stable and less complicated that a hydrofoil. Look at the rooster tail on the hydrofoils at speed. That is friction. Rudder could be airboat type or in the water rudder to be in contact with water at all times. I'm a fisherman and if you take modern bass boats with large motor , when on plane they only ride on an 18" patch on back of boat with jack plate. Just my .02

I-Love-Jets

Hooty,

here we can see a trim tab device at the rear of a Deep V. However this one is not R/C functional.

I-Love-Jets

One of the most sophisticated pure straight line speed purpose built outriggers available is the Andy Brown Eagle SGX 80. That multiple record holder (currently about 120 mph) for nitro speed boats has refined his constructions to perfection.

www.cmdracing.com/updated/eagle.htm

For that it could be well spent money to buy one of his Eagle SGX 80 kits and to modify it adequately to finally establish an "all-time" airboat record. Similar to extreme speed purpose built planes an “elongated“ airboat hull should reduce pitch motions effectively…

Razor-RCU

My Feedback: (50)

Geesh... sorry I am just jealous that I never get this kind of interest in my topics [X(]

Sorry guys...I must have been in a "mood" when I posted that- Onward and upward to record-setting stuff!!!

have a great day!

zope_pope

Does that girl come with the boat?

hooty301

I was wondering if anybody might have a extreme RPM turning engine that they would be willing to sell for this project. Something from a .40 up to a .90. Im thinking now that the smaller .40's something like the JETT's that turn 25000rpms would probably be the fastest and best for my application but am not sure. I know that bigger is sometimes better, with the smaller I could definatly get the center of gravity lower.

Rudeboy

Hooty,
Try some smaller diameter props first... something like an 11x5 or 6! If that works at all, you can start experimenting with even smaller or higher pitched props. If going to less diameter hurts your performance, then don't bother going to high rpm engines. It will bring you nothing but heartache...

HighPlains

My Feedback: (1)

There was a boat?

Rudeboy

I like the 21-sized one... are those silicone pontons, or regular ones...?

EDIT... typo... I was blinded...

hooty301

What would give more power to a engine like my 61, a nonmuffled tuned pipe like the one made by Macs or a Performance Speicalty Ultra Thrust muffler?

Mike Connor

My Feedback: (5)

The nonmuffled tuned pipe may give you a little more power by letting you tune your engine to a particular prop but the UT and Jett tuned mufflers work well. Where would you mount a long tuned pipe on a boat with the engine in the rear?

High rpm racing engines turn small diameter props and work well on very clean air frames. They do not work well on not clean airframes because of drag. Boats have a lot of drag and that is why they are so much slower the aircraft. Therefore I suspect a high rpm racing engine will not work as well as a high torque engine. Until you reach the theoretical speed of the prop you should go for more thrust (large diameter props). A 12" prop at 12,000 rpm has more thrust then an 8.8 prop at 22,000 rpm. One of your post testing different props indicates more thrust may be needed for more speed. Just my thoughts and they could be wrong.

proptop

My Feedback: (8)

They're probably pretty close in performance boost?
The U-T is 1 piece and much easier to install...just bolt it to the engine and go...no tuning required...and cheaper over-all.

hooty301

Yes, this is exactly the type of boat I had in mind. A .91fx mounted just behind the front sponsons, pitched upwards a couple of degrees to pull the boat off the water should get me right where I want to be....fast! What do you think?

I went to the hobby shop today and bought a tach and a couple of smaller dia. props(11/6and11/5) to try. Going tomorrow to test.

hooty301

.....You guys have got lots of ideas going through my head now. I really like the Idea of using a Gyro to control wings. Im thinking a hydroplane similar to Miss Budwiesser or the fomula boat above with the engine mounted above the canapy, the bottom inch or so of the prop between the sponsons blowing air under the boat providing lift and making a coushion of air for the boat to ride on.The trick now would be keepin the boat from flipping and thats where the Gyro controlled wings come in to play. One on the front between the sponsons,in front of the prop and another on the back like the one on Miiss Bud. pitched accordingly to keep the boat level. I would like to know a little more aboat Gyros can they be mixed in to a control function on the radio. A pitch dial on a heli radio would be perfect to get the boat leveled just right and the gyro to hold it there. Not sure what I want to build first the outrigger like I had in mind to start with or a design like this with the gyro.

zope_pope

The dial on a heli radio just controls the gain of the gyro. The heading hold gyro mounted sideways is a good idea. I am brand new to heli's so I am not completely sure about all the mixing functions, but with all the advanced computer radios, I am sure something could be figured out. The trick would be to get the gyro to hold the right pitch.

Flyboy Dave

My Feedback: (21)

...this thread can stay right here as far as I'm concerned.

I might think about a Jett 90 Special, with the Jett ultra-thrust type muffler.

They make brutal power.

What I mean by Special is....tell Dub what you want the engine to do, and he will make it so.

FBD.

freakingfast

My Feedback: (3)

This could be close to what your looking for, loose the tether and add directional control...vela! A 150mph canard style hydro!
http://www.onthewire.co.uk/classes.htm

Tethered Hydroplane Classes and British Records.

NAVIGA International Classes. Current Records.

A1 up to 3.5cc Martin Hamilton 20/08/95 120.52 mph

A2 up to 6.5cc Roger James 3/08/03 129.30 mph

A3 up to 10cc Norman Lara 14/07/98 135.57 mph

B1 2.5cc airscrew Jim Free 10/04/00 154.91 mph Yahooooo!

Craig-RCU

The fastest boats are the b1 class. They also look to be as aerodymamicly stable as an arrow because they have that big wing in the rear. They wouldn't need a gyro to keep them stable any more than an arrow does. These B1 class boats are tethered and get their yaw stability from being tethered. If you were to make one untethered you might have to ad a vertical fin in back to make sure it wouldn't vear left and right. Here is a link to a proposed record breaking boat. It also has the wing and outriggers in the back and should be as stable. http://www.americanchallengewsr.com/craft.htm

proptop

My Feedback: (8)

The one on the right looks like it's ducted fan or turbine powered...[8D]
(or would be rather...)

I was talking to an old friend last night about boats...
He's 78 now, and has designed and built several 1:1 boats over the years...

The tether boats in the pics above have the center of flotation or bouyancy rather aft...that would lessen the tendency to squat under acceleration...and lessen the tendency to "blow over"...that was one of the things my friend talked about. (sponsons in the rear )

He raced small O.B. powered boats when he was (much ) younger...he said his were always at least a little bit faster than the traditional designs because he designed his with his model airplane experiences in mind
(He had one with the top "deck" made of a stringer and fabric covered construction, similar to a stick and tissue model airplane )

hooty301

Ohh... that is awsom! I would really like to know more about these canyard hydros, they look extremly fast. Just add a water rudder, flip the engine over to the other side to counter the torque and WOW!!

I-Love-Jets

Hooty,

if you don't like the idea of a ducted fan driven airboat I would like to recommend the following power unit:

OS .91 VR-DF (but this time with the large rectangular head for better cooling, see pics)

plus

JMP 2 tuned pipe

plus

a wide bladed propeller made of carbon fibre or of wood sized 10x6 to 10x8

I-Love-Jets

Let me explain:

A)

You definately need an engine that can turn the above mentioned 10x6 to 10x8 props at 21000 rpm minimum statically. Compared to other 15 cc ducted fan engines the OS is quite a “torquer” being beneficial for strong static thrust. Because of the aerodynamically advantageous RIRE design of a ducted fan engine, you could build a fully enclosed engine/pipe-unit similar to the purpose built R/C speed planes (see red plane below). This unit is to be mounted on an again aerodynamically optimised pylon like the tether Class B1 air speed boats.

I-Love-Jets

B)

A diameter exceeding 10” will give trouble with tip speeds approaching supersonic at 21000.
However, in your case a smaller diameter prop than 10” will most propbaly lead to a lack of thrust (the tethered speed boats don’t have that problem because they do have an “infinite” acceleration distance).

A wide blade propeller design will support static thrust, especially at pitches of 7 to 8 inches for an airboat.

Suitable props that can structurally withstand the power of a 90 sized ducted fan engine are hard to find. Wood and carbon fiber represent prop materials you want to look for to ensure safety (tensile and torsional prop strength). For a speed plane application a 10x6 to 10x8 prop would be too small for a 15 cc ducted fan engine, but in your case fortunately the engine cannot dynamically unload.

http://www.zingerpropeller.com/Tractor.htm
Besides a wide bladed 10-8W (#407) Zinger offers an extrawide 10x6 (#405 10-6XW) which could be worth a test too (about 12.5 lb of static thrust at 21000 rpm). These props are all wooden.

http://www.bollyprops.com/carbonprops.html offers carbon fibre props. In your case the 10.5 x 6.5 or the 10.5 x 8 would be a good choice for the OS .91 VR-DF in an airboat. If too high prop tip speeds do limit the engine rpm, you can shorten the Bolly prop diameter to 10.0” (rebalance the prop carefully).

APC props, independent of their attribute ”sport” or “D1 competition”, are too weak to cope with the power of such an engine. So these are not suited.