RV3 Tailwheel Size

[UAA105]

Hi All,

Doing a bit of pre Christmas shopping for myself and thinking about tailwheels for my RV-3B build. I'm aiming to build a light and fast RV3 and would like to move away from the standard tailwheel fork. With my current aircraft I mainly operated off tarmac but regularly visit grass strips and occasionally strips with loose stones so prop clearance is a player.

I've been looking at the Flyboys Screaming Eagle and Doug Bell forks with lightweight tailwheel (5.5" diameter) and the JDair tailwheel fork. All will reduce prop clearance but not significantly, my concern is if I also go for smaller lamb main wheels (to reduce drag from the spats) that'll bring the prop even closer to the ground. The 'fix' for this is to go with a 4" tailwheel but that introduces different issues that come with a small tailwheel... My Taylor Titch has a 4" tailwheel but that's a smaller aircraft and 270lb lighter than the RV will be!

Everything is a compromise but wondered if anyone has real world experience they could share? Here's a photo I found of the standard and Lamb (now Cheng) 11-400X5 spats

https://vansairforce.net/community/a...1&d=1638564307
_____________

Cameron
Scotland
RV6A - bought and sold
Taylor Titch - Flying
RV3B - Empenage almost finished

[David Paule]

I believe your photo is of Andy Hills RV-3B. Unfortunately I don't know which tailwheel he installed, but I think he operated off of a grass airstrip. He made many of his decisions, including the wheels and tires and wheelpants, based on weight. His RV-3B came in at 733 pounds.

I know a fellow who has the larger (and heavier) pneumatic tailwheel plus the larger (and heavier) 380x150x5 tires on the main gear. I am installing both on my RV-3B, because I expect to be operating some of the time from a grass or dirt strip. The bigger tires are to gain back some of the body angle lost to the larger tailwheel and associated fork. I am planning on a 70" prop. With stock tires all around and a 72" prop, there was a 5" ground clearance to the prop tip when level on another RV-3.

There are always trade-offs, aren't there?

Dave

[Ironflight]

We’ve been running the Bell fork and a DJM solid (small) tailwheel since day 1 on our -3B, and like the setup. We rarely operate off of anything but pavement or gravel, and if you hit an airport with those big expansion joints, it really feels like there is a Viking with a hammer behind you banging on the fuselage every time you hit a crack….but we get the same thing with a stock RV tailwheel on those airports, so unless you go “large” pneumatic, you’re not going to win.

In terms of prop clearance, we run a 68” diameter three-blade Whirlwind, and have honestly just never thought about clearance. You’d have to get scary nose-low to worry about hitting the prop on the ground, at least with stock mains.

About 750 hours with this setup.

Paul

[UAA105]

Thanks for the information Dave and Paul.

I think Andy's RV-3B has a Bell fork as well (at least it looks like that from pictures). I'm probably over thinking it when you consider RV7's and 8's that are much heavier will run with 5.00-5 mains and the 1-1/2" wide tailwheel without issue.

Luckily there aren't many places with those big expansion joints in my neck of the woods, so soft grass and stone chips on the prop are the only concern!

When I get the time I'll maybe work out the contact area and psi for each setup and compare that to the larger aircraft. If the results are presentable I'll post them on here

[YellerDaisy]

I've got hundreds of hours with this tailwheel on my RV-4 (https://www.flyboyaccessories.com/Li...ire-p/1002.htm) and am frequently operating from dirt/gravel strips. It did fine. Our tailwheels are so small that they frequently just plow a small trench when soft (not doing major damage to the airstrip or anything, just not 'floating' on the surface).

I recently changed to this tailwheel (https://www.flyboyaccessories.com/De...ire-p/1001.htm) and think it is slightly better (for my use in dirt). Very subjective but it doesn't seem to dig into soft dirt quite as much and is more compliant for the big cracks in pavement.

I used similar tailwheel tires on my RV-3B and had similar results. Unless moving up to the large 'condor' tire, I suspect they are all pretty similar. I thought about the condor but decided against it due to the chance of having it go flat.

[David Paule]

Originally Posted by UAA105

....When I get the time I'll maybe work out the contact area and psi for each setup and compare that to the larger aircraft. If the results are presentable I'll post them on here

A very long time ago I did that for my C180. I compared 600-6 tires on my C180 to 850-6 tires on a C185, and found that the contact pressure was similar, since the C185 is a heavier plane than mine. I installed the 600-6 tires and over the years found that it's not contact pressure that counts, it's the ability to ride over small obstacles like rocks, sticks or pavement discontinuities. There, the smaller tires are at a disadvantage. Which is why I'm going with the bigger tires for my RV-3B.

Granted, I might not need them.... Guess I'll find out.

Dave

[RWoodard]

I wouldn't bother with going to smaller main wheel tires. If you're using an O or IO-320, you'll probably be able to exceed Vne in level flight anyway. The difference between the little tires and regular 5" tires will be less than measurement error.

[Andy Hill]

Hi Cameron

David is correct when he says:

I believe your photo is of Andy Hills RV-3B.

I have attached a better sized version for the forum.

Here's a photo I found of the standard and lamb spats

I'm not sure what you mean by "lamb" spats? The smaller (black) spat is from a mould I took from a Vans nosewheel spat, but with the top slightly raised.

my concern is if I also go for smaller lamb main wheels

Again, unsure about "lamb"? They are Beringer wheels, with a tubeless Beringer type.

The spats are profiled so they are one piece, and with suitable jiggling, go over the wheel/tyre, without needing all the screws etc to join 2 spat halves together.

I'm aiming to build a light and fast RV3 and would like to move away from the standard tailwheel fork

Mine is a Doug Bell fork, which I think are no longer built... however, there are numerous similar ones about.

The motivations for the design:

• Weight! The Beringer wheels/brakes are (much) lighter than whatever Vans were supplying at the time (and also more expensive ). Beringer "allowed" me to use them on an RV-3, but were harder to convince than the LAA. The tyres are a bit lighter (and smaller), but being tubeless saves lots of weight
• Drag: The smaller spats must be less drag - how much??

I think in considering the tailwheel fitting v weight you are missing a trick You will not get an easier way to shift the CG than alter the tailwheel hardware. RVs move between "unpleasant" (heavy), "correct" (balanced), "frisky" (light) and "dodgy" (super light) as the CG moves aft, and unlikely you will know where the CG is until it is built.

I fitted the standard RV tailwheel, and the CG / handling for me was perfect. I had bought the lightweight Vans tailwheel as well (which I think had a reputation for failures? less rubber?) but never fitted it since I did not want to shift the CG forward.

I am an advocate of the 380x150x5 tyres on the RV-8 v UK strips. The Berniger tyres I've got seem an equivalent for the much RV-3 lighter weight. Look which is digging in more / leaving marks on soft ground - main or tail wheel(s) (as per JD above)?

If you are tinkering with the gear legs / wheels / spats, a major RV-3 issue is "gear leg shimmy" for some. Never had an issue with it, can only put down to pure luck with the changes moving the harmonics out of the operating envelope.

Hope that helps? Best wishes

[UAA105]

Hi Andy,

Many thanks for the detailed reply. I should have said spats to fit Lamb tyres - probably the wrong name for the tyres actually. When I spoke with Beringer they said they supply 11-400X5 tyres for the RV3, my Taylor Titch has the same size tyres manufactured by Cheng, which was formally Lamb. James Aircraft make spats specifically for that size of tyre so I assumed that's what you had, but quite impressed that you made them yourself.

I think the sensible thing, as you allude to, would be for me to go with the standard Vans wheel/fork and then refine from a W&B point of view. My problem is, I get an idea in my head and want to order the parts straight away.

[Andy Hill]

Hi Cameron

Beringer have told you what I did not have to hand - I think they are 5.00" wheels but take 4.00" (tubeless) tyres.

My problem is, I get an idea in my head and want to order the parts straight away.

We've all been there... in fact I did as above and ordered (and still sitting around) the Vans "lightweight tailwheel"