IVO Prop Clearance to Cowling

I am installing my Sam James "Rotary" Cowling with an IVO in-flight adjustable prop and was wondering how much clearance I will need between the widest section of the blade and my cowling. The instructions say the tips will move quite a bit and I have plenty of clearance there, but the "P-40" style intake on my cowling is currently about 3/4" from the blade so would like to determine if this is enough to allow for the bending / twisting inherent in the design of these blades. Translation...I really don't want to have to adjust the cowling again later if it can be avoided!

Thanks for any replies.

Doug Lomheim
RV-9A; 13B; IVO Magnumum, In-Flight Adjust.

I've watched mine cone on the ground and the tips do seem to move close to an inch at high power settings. They also feel like they move from air loads in flight and gusts on the ground when taxiing.

I'd guess that you would be completely safe with one inch of clearance at your cowl inlet. This would equate to maybe 2+ inches at the tip. I haven't seen anywhere near this much movement on the ground at least. In flight video and photos at cruise power shows maybe a 1/2 inch deflection at the tips. The worst case would be idle power with the nose pointed way down, flexing the blades towards your cowling inlet. Note that the inner foot of the blade does not flex much as the torsion rod is anchored about mid-span and the root area is quite stiff.

Be sure to check this clearance with the prop in full coarse pitch as this brings the trailing edge of the blades closer to the cowling. Also be aware that on A models using a 3 blade prop, you may have to lengthen the landing gear slot to be able to install/ remove the cowling and don't get the spinner backplate to cowling clearance too tight either as this can make the cowling nasty to install. Some of my cowling mods are detailed here: http://www.sdsefi.com/rv9.htm

More info here: http://www.sdsefi.com/rv13.htm and here: http://www.sdsefi.com/air18.html

Hopefully you got the high pitched (45-105 inch) version as the low pitched model in unsuitable for the higher speeds of an RV.

I'd install a simple prop ammeter to judge pitch angle. This works great and allows to to set consistent pitch angles for takeoff and landing.

I think you will love this thing. Awesome takeoff and climb. Cruise seems good too. Dirt simple and reliable. Follow IVOs prop torquing instructions to the letter. Brush wear is initially high and then tapers off as carbon is laid down on the slip rings. Have a spare set handy in the first 20 hours.

I'd be interested to see how your prop/ engine performs. This was the fun part: http://www.sdsefi.com/rv14.htm

Do you have the 2.17 gear ratio and a 3 blade? What diameter blades?

Doug,
Id love to hear any comments and experiences regarding your combo... Im planning a 3-blade IVO/4-port Renesis combo possibly next year on my 9A. Ill be using the 2.85 redrive and likely a 76" prop.

My guess, the normal operating envelope will be 1800-2100 rpm at the prop and 5200-6000 rpm at the engine (160 and 180 hp). The engine should be capable of a bit more if needed, perhaps to the hp peak (210 hp) at 7200 rpm/ 2600 prop. From what Ive gathered, the best engine speed target for the 13-B's is around 6000 rpm- least friction and best efficiency.

[/QUOTE]Do you have the 2.17 gear ratio and a 3 blade? What diameter blades?[/QUOTE]

Ross:

I have the 2.17 gear ratuin and a 67 inch IVO in-flight adjustable that flew for 60 hrs. on a Glastar in 2005. Can't wait to just get the engine started and will go from there...

Doug

I'd guess that the 67 inch 3 blade, 45-105 IVO will absorb up to about 225hp at 6000 engine rpm with your drive ratio so this should be ok. Make sure you have the high pitched version, the low pitched one will be useless at RV speeds IMO.

High Pitched IVO...

>Make sure you have the high pitched version, the low pitched one will be useless at RV speeds IMO

Ross:

Is there an easy way to tell if I have the "high pitched version" via part number on hubs, etc. or do I need to simply cycle it and attempt to measure the degree of twist imparted?

Thanks.

Doug

Have to check your invoice or phone IVO and I think they will have a record on what you have. Ask nice and they may exchange them for no charge if they have not been bolted up to the hub. They did this for me.

High Pitched Version?

I guess I will have to call them up and see if they can tell me what I have...this prop. came with my 13B as a part of a FWF purchase that had flown for about 60 hrs. on a Glastar. The owner the aircraft and the new owner didn't want the 13B so it was removed and offered for sale on our rotary list.

Doug Lomheim
9A, FWF installation
OK City, OK

dlomheim said:

I am installing my Sam James "Rotary" Cowling with an IVO in-flight adjustable prop and was wondering how much clearance I will need between the widest section of the blade and my cowling. The instructions say the tips will move quite a bit and I have plenty of clearance there, but the "P-40" style intake on my cowling is currently about 3/4" from the blade so would like to determine if this is enough to allow for the bending / twisting inherent in the design of these blades. Translation...I really don't want to have to adjust the cowling again later if it can be avoided!

Thanks for any replies.

Doug Lomheim
RV-9A; 13B; IVO Magnumum, In-Flight Adjust.

Click to expand...

Hi Doug,

As I recall, Ivo recommended 5" of clearance. It's best to call the manufacturer. I found Ivo tells it like it is.

Regards,
Jim Ayers