External Fuel Tanks on RAF? [Archive]

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Hoges

01-13-2008, 11:02 PM

Gyropilot007

01-14-2008, 04:20 AM

Scott:

I'm been thinking about this too, but for other reasons. It would be nice to lower the seat to get more head room.

RAF was working on an external tank arrangement before they closed. I don't know if the new RAF in South Africa will be continuing along those lines.

Bob

Harry_S.

01-14-2008, 05:29 AM

I imagine solving the problem of having a 4 hour fuel supply, external to the cabin, is a bit in the future. A few years back, RAF had a static display of their "spraying gyro" at BD. The conformal tanks were vertically situated behind the doors. Looked really good. I did see some photos of it flying, but not actual flying.

Other than my Bensen B7 with the boat tank, the Bensen styled machines I built after all had the Brock seat tank. Sorta got used to being in the hot seat since then and really think nothing of it.

I've had people turn down a ride in my machine when they found out where the fuel was. ;)

Cheers :)

reelmule

01-14-2008, 05:59 AM

Scott, There is a good bit of structural integrity built into the RAF fuel tanks. These are beefy tanks. When RAF came out with the new batch of tanks we were required to cut the old tank in half and send photos to RAF. It gave me some reassurance. In addition the tank is surrounded by a substantial fiberglass shell. I know its only antedotal but the Monard accident did not result in a post crash fire.

Hoges

01-15-2008, 12:16 PM

lanichol

01-15-2008, 05:17 PM

Gyropilot007

01-16-2008, 05:46 AM

Larry:

I ordered my RAF kit in May of 2003 and received it in June of 2003. The seat tank that was included with my kit was the fiberglass model. Once my gyro was completed and I was taking my flight training the fiberglass tank developed several leaks. When I notified the RAF factory about the leaks they sent me a replacement tank at no charge. The replacement tank was plastic instead of fiberglass. This occured in the fall of 2004. So you have the approximate timeframe as to when RAF made the change over.

Personally, I like the plastic tank much better. The seat back can attach to the plastic tank with no problems.

Bob

Harry_S.

01-16-2008, 12:36 PM

Yes Walt, I see what you mean. I'd also be saving myself a lot of work as well. Just an idea though. It would be good to see the photos of the external tanks, you don't have them around at all Harry?
Scott

Well, I don't have any photos per se, but if you can locate someone that has some of the old flyers that RAF distributed, there are a couple photos of it flying. It's a black and yellow machine with the spray bars out to either side, at about wheel height.

Sorry I can't help you out any more on that point. Maybe if you contacted the old RAF Marketing, you may get some help.

My new scanner is not compatible with my old 'puter so if I found an old picture, I couldn't scan it, to send.

Cheers :)

Gary_in_Orygun

01-17-2008, 08:47 AM

Does anyone remember the pictures Larry Martin posted on the old forum years ago of the external tanks he built for his RAF? They were located on the outside/rear of the fiberglass cabin.

Doug Riley

01-17-2008, 09:12 AM

The PRA mag featured a picture of a Canada-based RAF 2000 a few years ago. It had a GA aircraft engine (or GPU?) instead of a Soob and external tanks mounted high and outside, on either side of the cabin (like a Bell 47).

The one thing it needed and didn't have was a H-stab, but the direct-drive engine and high tanks probably lessened the thrustline-CG offset a bit.

LARRYEBOYER

01-18-2008, 08:00 AM

Larry M made some nifty external tanks. Don't know what ever happened to molds but his seat arrangement and external tanks were very appealing. The seats lookes like race car seats.

Gyropilot007

01-18-2008, 11:12 AM

I actually spoke with Larry many times. He did make some very nice extrernal tanks but had a lot of problems with them leaking.

Harry_S.

01-18-2008, 11:57 AM

Did you ever see any photos of his installations, Bob?

Cheers :)

Mayfield

01-18-2008, 12:01 PM

Here you go.

Jim

Harry_S.

01-18-2008, 12:34 PM

Yeah, there you go, I had seen that photo before. Thank you, Jim.

You know, IMO, we lost a good man when Larry M. was run off by some insinuations that he had infringed on someone else's design of a horizontal stab.

A terrible loss indeed.

Cheers :)

Gyropilot007

01-18-2008, 02:06 PM

Sorry Harry, but I just couldn't let this one go.

I used to think Larry was a OK guy too. I bought his Ultimate Stab and his overhead console for my RAF.

When I decided I needed to put a bigger engine in my gyro I started looking on the NET and lo and behold, Larry Martin had a 2.5 Subaru for sale.

I called Larry and he assured me that the engine was in excellent shape and that it would easily fit directly on my RAF as equipped, without ANY modifications.

To make a long story short, I bought the engine and it did not fit as configured. I had to replace the intake manifold among other things. But here is the real kicker. Once I had everything together and mounted on the gyro I could never get the engine to run smoothly.

I then decided to have a local mechanic look it over. As it turned out, the engine was full of silicone sealant. There were globs of the stuff inside. I ended up having to completely dismantle the engine and clean it completely.

When I tried to explain this to Martin, he called me a bunch of names and told me to NEVER call him again or contact him in e-mail. He went crazy and then he hung up on me!!

So...please don't tell me what a great guy Larry Martin is.....I don't buy it.

Oh, and one other thing, I don't believe that Larry was "run off" of here. Larry personally told me that he realized he didn't like flying in gyros. He was very uncomfortable in them. He changed over to fixed wing. That is why he's no longer a part of the gyro community.

Bob

Hoges

01-18-2008, 06:52 PM

Thanks guys for the info it has given me some ideas.
Scott
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Harry_S.

01-19-2008, 05:51 AM

That was bad news, Bob.

Didn't mean to ruffle your feathers. :tape:

I liked his designs. Wasn't he into showcasing cars, or somethin' like that?!

Cheers :)

Gyropilot007

01-19-2008, 08:24 AM

Harry:

No problem. You didn't "ruffle my feathers", just touched a sore point. I was very upfront and honest with Larry as to what I was looking for but he was not upfront as to what he was selling me.

However, after a lot of time and money I was able to get the engine into top flying condition and it served me well until the rollover two weeks ago. I'm sure after a complete inspection it will continue to serve me in the future.

I know Larry was somewhat into cars but I'm not sure exactly what he did. When I bought the engine from him he told me he was going to come up to Indiana to the Auburn Auto Auction. I met him there to pick up the engine.

Best regards,

Bob

Hoges

06-09-2008, 02:07 AM

Hi Jim,
Do you have contact details for the owner of the external fuel tanks in the photo?
They are really neat and I would like to build something very similar, seats as well.
Scott
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KenSandyEggo

06-09-2008, 02:08 PM

This is a photo of an aluminum tank that I was about to install on my RAF/Sparrowhawk on each side when I owned it. I had the logistics figured out. One tank would be slightly smaller than the other one because of the engine layout on each side and bumping into the cabin. They were to be mounted horizontally on the side of the engine, just about on the thrust line. I think I was going to use a 5 gallon and a 7.5 gallon, but I'm not sure.

If you look on the side of the Soob, there are numerous threaded holes to use. I can't remember if I was going to use band-type holders or make something out of aluminum. I recall that they would have been a very simple addition. They could be plumbed together underneath and gravity fed into the main tank with some hosing/tubing and a simple on/off valve, or a simple fuel pump with a switch on the panel. The filler caps can be gotten either on the end or on top.

The only other mod I recall that may have had to be done was a heat shield between the tanks and exhaust. A simple asbestos wrap would probably work fine. I doubt there would be a heat problem when in motion, but maybe when taxiing or waiting to take off. The tanks come from 3.5 to about 11 gallons in size and there are numerous sizes in between. They are sold mostly by off-road stores specializing in VW buggies. I've also seen them in plastic or Fiberglas at a lesser price.

Hoges

06-10-2008, 04:27 AM

Ken,
Thanks for that.
I was thinking of completely replacing the internal fuel tank with outside tank/s.
One possibility would be a tank over the cabin close to the mast. This would have an effect on the thrust line, positively I'd think but hey, would look pretty weird maybe?Also, 2 tanks similar to the ones you've shown but about 40 litres each and fitted like Air Command outrigger tanks at the centre of mass line so as not change the hang test too much.
Scott
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animal

06-10-2008, 12:46 PM

Hoges

08-14-2008, 06:16 PM

I am in the middle of making a foam mock up of an external fuel tank for my RAF to see how it will look and sit.
Because it will have a flat bottom fore and aft, I will need to angle the bottom so that the fuel will not run away from the outlet when climbing or descending.
To do this I need to work out the maximum nose down and nose up angles that could be encountered in flight.
I will be taking my own measurements but wondered if anyone has taken the time to do this already?
Scott
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birdy

08-14-2008, 07:15 PM

Just have an outlet at both ends.
That way you loose no capacity and will never suck air, till you run out.

scandtours

08-14-2008, 10:47 PM

I have also thought of tanks mounted above the engine and close to the mast on cross bars, kind of like a Bell 47 or one longer round tank mountd behind the mast like they are on the Scorpion helicopter.

I still don't like the idea of seat tanks,from pics of the fires i have seen.

seat tank would make a great oil tank for a smoke system... :)

Humla gyro has its alum fuel tank on the must as per attached old photos.
All Humlas have also home build rotorblades and cost few hundred dollars to build them.
It was designed by Helger Svesson, Stockolm Sweden.
I must say that it is a stable machine with relatively effective stab and its very CLT gyro
Giorgos.

Hoges

08-17-2008, 03:13 AM

As a matter of interest, I did some testing today to get an idea of keel angle when descending and got a bit of a surprise.
When cruising at just under 50 knots (IAS), straight and level (keel level) and then reducing power to idle, pushing stick forward to descend, my Indicated Air Speed increased to nearly 80 knots in less than 10 seconds with a 10 degree keel down angle.
The doors were fitted so it was as slippery as possible.
It would seem that a higher than 10 degree angle down could not be maintained for very long without exceeding the VNE of my aircraft.
I thought it might be a greater angle than this.
Has anyone ever measured their descent, and/or climb angles?
I'd appreciate any feedback.
Scott
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SARAF

08-17-2008, 08:06 AM

HI Hoges

Please send me an email to eben@rafsa.co.za we have some external tanks and bracket that I can provide.

Regards

Eben Jnr

C. Beaty

08-17-2008, 08:25 AM

You know, IMO, we lost a good man when Larry M. was run off by some insinuations that he had infringed on someone else's design of a horizontal stab.

A terrible loss indeed.

Cheers :)Larry Martin had never flown a gyro and never planned to do so after a straight and level introductory ride or two with Ron Menzie scared him out of his wits.

For Larry, his RAF was simply a non-functional art project like his show cars.

Doug Riley

08-18-2008, 04:46 AM

Scott:

The angle of your keel in any flight regime will depend on the combined effects of (1) your hang setup, (2) engine thrust, (3) rotor thrust, and (4) air striking the frame. There isn't the simple one-to-one relationship between frame angle and rotor angle that exists in an airplane.

Turn the engine off and you're left with the other three influences on your frame angle.

At high speeds or with wild body shapes (the machine's body, not yours), airframe aerodynamic effects can be predominate. With a more typical gyro, the hang setup will mostly determine your keel angle.

The rotor will fly at the angle of attack that creates one gyro's worth of lift. The frame will dangle under the rotor at roughly its static hang angle -- possibly increased a bit by frame drag. Again, this is true only with power off.

I understand that the stock RAF hang angle is around -7 degrees on the keel. Toss in a couple-three degrees for frame drag and the effects of any thrust from an idlung engine, and you have your -10 degrees.

Minus 7 is quite a nose-up (i.e., a rotorhead forward) hang spec, but it helps the craft fly more level in the presence of a strong nose-down moment created by the high thrustline. If you were to eliminate the HTL by moving the cabin up a la Sparrowhawk, or by using a large, downloaded H-stab, you'd need to increase the hang angle to the more typical -11 or so degrees

Hoges

08-19-2008, 04:15 AM

Doug,
Thanks for the response.
I think I will be dealing with the resultant keel angle from the inputs you have described in your post.
My intention was to get a maximum nose down/up keel angle from my simple test.
Gravity will dictate the rest for tank design purposes as I was trying to work out the minimum angle required on the bottom of any fuel tank design to make sure the fuel never drained away from the outlet when climbing or descending at maximum angles. Baffling will also slow any fuel movements.
I'm keen to get the 'gas' out of the cabin but it is not going to be simple.
Scott
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Doug Riley

08-19-2008, 05:16 AM

Scott:

There was a picture in the PRA magazine a few years ago of a RAF based in the Canadian north woods. It had two cylindrical fuel tanks outside, above the rear wall of the cabin. The setup was very much like a Bell 47 (and the tanks may in fact have been Baby Belle (now Safari) units, since that company is also based in Canada. Perhaps the system was dictated by the need for a gravity fuel system.

Petrol sitting above the hot engine is not the ideal solution from the fire-safety viewpoint, but perhaps it's a little better than seat tanks in an enclosed cabin...

lanichol

09-28-2008, 09:20 PM

Has anyone in RAFLAND had any experience with alternate fuel tank locations to replace the seat fuel tank on a RAF?
I'm thinking of a fuel tank under the engine, or beside the cabin (on both sides of course) or even overhead and rear of the cabin maybe.
I just don't want to be swimming in a pool of fuel if something unfortunate happens.
Any ideas or past experience appreciated.
Scott

I have been thinking about an "External Fuel Tanks on RAF" for several years now and suddenly I realized I had the solution already built into my gyro that Kenny J did originally. KenSandyEggo filled his gyro from his Volkswagon with an external pump mounted on the cabin. He also used this same pump when he flew to have the first RAF AAI modified at Buckeye. He sat a tank in the seat and then transfered the fuel after he had been in the air from the gas can to the seat tank.

We all think about placing the tank for the purpose of gravity feed.

Why?

Place the aux tank on the keel close to the mast and then transfered with the aux pump during flight to the seat tank. The aux tank could be any shape, added or removed quickly as it only needs a couple bolt and a fuel line to the aux pump. Thus it does not interfere with your original fuel system. After all they transfer fuel on FW all the time.

The problem I have with external tanks is the fire hazard. But why not dump Halon gas into the fuel tanks in the case of an emergency. If the seat tank or aux tank ruptures, then the Halon goes where every the tank is ruptured. Maybe use an airbag type trigger. Or maybe a explosive cap with a pointed bolt that ruptures the tank. The resulting explosion from the cap would be killed by the halon. Crazy, but there sould be a way to trigger the halon in case of dire situation.

Halon Fire Extinguisher (Small) (http://www.sportys.com/acb/showdetl.cfm?DID=19&Product_ID=6803)