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Size of latex tubing for pressure bladder

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Size of latex tubing for pressure bladder Empty Size of latex tubing for pressure bladder

Post  layback209 on Wed Sep 02, 2020 6:42 pm

hey everyone.  I had my first successful pressure flight and I like it!  Do to my ignorance and availability in Canada the bladder I was using was really meant for a much larger combat plane i think (its at least 1/4" i.d.), but i really liked that it was ready to go http://aerohobby.ca/store/index.php?main_page=product_info&cPath=11&products_id=27.  I think the extra pressure was not helpful with tuning. It was not bad though could still fly and get it pretty close.

I'm wondering if this stuff would be better? i was watching one of Rusty's youtube videos on it and these looks much closer?  

https://www.amazon.ca/dp/B071YVYXS6/ref=cm_sw_r_cp_apa_i_OZcuFbZ31PYQH

Or
https://www.amazon.ca/dp/B071YWG8V1/ref=cm_sw_r_cp_apa_i_G0cuFbB1DT02P

Or

https://www.amazon.ca/dp/B089SVGLVC/ref=cm_sw_r_cp_apa_i_k1cuFbFSZ4B1N

I just can't seem to find the 1/8" I.d.? 1/32 wall anywhere in Canada.  International shipping ain't too appealing as its an order of magnitude more than the cost of it.

Appreciate your feedback.

Size of latex tubing for pressure bladder 20200810


Last edited by layback209 on Thu Sep 03, 2020 1:08 am; edited 2 times in total
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Post  Cribbs74 on Wed Sep 02, 2020 7:15 pm

Nice model!

If Rusty would pop on here he could tell you. The stuff I have used is pretty thin stuff, but it was given to me so I have no idea what the size is.  If you like that needle valve I would cut it down and put a 90 degree bend in it before it gets sheared off and takes the venturi with it.

Is that a fine thread NV? Could explain the tough needling you were having.

Anyway, others here use bladders so hopefully they pop on and help. Congrats on your successful flight.
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Post  aspeed on Wed Sep 02, 2020 10:48 pm

You may want to try a well stocked drug store. I found some 1/16" ID, and 1/8" ID that had too thick of a wall, and some 1/4" that worked OK on .15 size engines. There is also the Little Red Cap from Lee Valley Tools. It is a kitten size condom that is used to cover a caulking gun tip between uses. It gives a lower pressure so the needle is easier to adjust. We used the 1/16" stuff for 1/2A Proto back in the day. It would fit in the fuselage/pan and was about the size of a thumb. I think 15 cc was what we used. IIRC but I don't always recall things correctly.
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Post  fredvon4 on Thu Sep 03, 2020 9:52 am

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Post  Ken Cook on Thu Sep 03, 2020 2:46 pm

That tubing your using should work. As mentioned, your using the stock needle which is problematic on pressure. I will also add that it appears that your using a 6" prop. If so, not a good idea. It makes the plane difficult to turn not too mention that when running bladder it doesn't like a load on it. A Norvel in general doesn't like a load and a 6" pitch is too large for it on suction. For example, a Cox rubber ducky 5x3 would be cut down to 4 1/4" for that plane. This makes the engine unload and it offers better needling. Seeing that your bladder isn't housed within a compartment, the pressure shouldn't be all that high. Latex tubing offers slightly lower pressure but it also fails much quicker. The latex develops a embolism and the pressure becomes sacrificed.

Yaro at Aerohobby makes his own needle assemblies. These will fit the Norvel, they just require a little JB weld to hold the assembly in place. Seeing that your wire is hanging out of the needle, use caution there. In a inverted pass and you catch the ground, the wire will break the venturi out of the case which breaks the crankcase as well. Just a word of caution as I have about 6 cases for the non believers.
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Post  layback209 on Thu Sep 03, 2020 4:21 pm

Ken Cook wrote:         That tubing your using should work. As mentioned, your using the stock needle which is problematic on pressure. I will also add that it appears that your using a 6" prop. If so, not a good idea. It makes the plane difficult to turn not too mention that when running bladder it doesn't like a load on it. A Norvel in general doesn't like a load and a 6" pitch is too large for it on suction. For example, a Cox rubber ducky 5x3 would be cut down to 4 1/4" for that plane. This makes the engine unload and it offers better needling. Seeing that your bladder isn't housed within a compartment, the pressure shouldn't be all that high. Latex tubing offers slightly lower pressure but it also fails much quicker. The latex develops a embolism and the pressure becomes sacrificed.

        Yaro at Aerohobby makes his own needle assemblies. These will fit the Norvel, they just require a little JB weld to hold the assembly in place. Seeing that your wire is hanging out of the needle, use caution there. In a inverted pass and you catch the ground, the wire will break the venturi out of the case which breaks the crankcase as well. Just a word of caution as I have about 6 cases  for the non believers.

Thank Ken, im probably over thinking this.  But don't have a reference point.  Glad to hear your thoughts on Yaro's bladder.     Interesting I am running a 5x3 and it seems to wind up really good, but have not experimented beyond that.  I did order a 114mm combat prop from Yaro as well which is about 4.5" have to try to see im very curious.  Yaro did mention his Fora carb assembly but he didn't know if it would fit a Norvel. I assumed it wouldn't fit as this engine venturi is oval shaped / bathtub like. But I have no idea. I couldn't find it on his website though. I'll ask if he has a 1/2a needle assembly like you mentioned, i like the sound of it.

Good point on the carb needle I did not cut this one down yet.  

Sounds like I can run what I have successfully which is great news.  Im glad my tin tank rusted out to force me into trying this, as I was a bit intimidated by it.  I actually like the extra starting challenge now and it was not that bad at all to get it going.

A gent that was interested in seeing me fly stopped by as he had some CL roots.  He brought out all kinds of camera gear, when he gets his video together ill share it so you can have a peak. It rips good.  Im estimating its doing around 100 to 120km/hr or 60 to 75mph based on lap times. Using 15%nitro
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Post  Ken Cook on Thu Sep 03, 2020 5:19 pm

It's good that you have a 5" but it can also be modified slightly as I mentioned by clipping it down. The composite props that Yaro sells are really for higher performance engines but only experimentation will tell. These are generally dictated by color as far as diameter and pitch and most use the green colored version. While the size and pitch are somewhat spot on, the blade area is extremely narrow. These are really designed for rpm's of 34k and more whereas a healthy Norvel just gets into the 30k area.

I was making reference to the needle spraybar assembly that Yaro sells. He doesn't offer a complete venturi assembly. You can achieve more performance by removing your venturi. have just the spraybar going through the case with the jet hole pointing down the throat of the case. Some Norvels had a large hole in the case with their venturi glued in. Removing the venturi on these allows Yaro's spraybar to fit right into that hole. Newer version Norvel's used a screw and nut to retain the venturi assembly, this style would require the case to be drilled for Yaro's assembly. I have used a Cox spraybar 128 tpi for these style case by pressing the spraybar into the case in lieu of the screw and nut. I mic the spraybar and leave .002" and drill the case for a press fit. They can also be glued into the case.
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