I have inherited a BareCat, 1/2A stunt model with a AME .049 for power, and is designed around using a bladder for fuel pressure. I need to get it down and weigh it and measure it, I had thought of just installing a hard tank in it, but thought better of it when it comes to balance issues. It's got a LONG nose!! I think it was published in Flying Models magazine and is a Netzeband design. I'll find the article and read up on that also.

  I have a message into Melvin at MBS Model Supply on what I need to materials to make bladders and thought I would post the question here also and in the Combat section and ask those that have some experience with 1/2A engines like the AME and Norvel .049/.061 for any tips and hints. I have some ideas on how things work after helping others with some combat models, but this 1/2A size should have some differences I think.

  So, what do I need for a bladder tank to run the engine for about 5 to 6 minutes? It's a largish model and I think it will fly on close to 50 foot lines and keep lap times manageable for my aging brain!! Any suggestions on what fitting and such to buy will be appreciated!!
  Type at you later,
  Dan McEntee


  EDIT: The model is a BareCat designed by Bob Baron, with I'm sure a heavy Wild Bill influence!! It was published in Model Aviation in June of 1999

            I assume this is going to be used for stunt. The run of the AME might not lend itself to a stunt friendly run . Running bladder generally equates to running a smaller prop because a larger prop offers a significant load which makes needling the engine not so friendly. Higher nitro certainly helps and the AME does work in my opinion with higher nitro percentages. Now I have never done this but Ray Copeland has and I recall his mentioning of this some time back in regards of using mufflers for the AME and muffler pressure to a hard tank.

         The only fitting I use in terms of 1/2A bladders is end cap fittings and sometimes I even forego those. Melvin does carry the small end caps. The problem I've come across using end caps is that after a few uses, seepage occurs and the fitting wants to pop out. I use fine copper wire to tie my end caps and it still does it at times. Many times I use just a knot in the tubing itself. This works but it does stress the area around the knot which is going to be the first sign of rupture. As for the other end, I use a long op rivet with the center removed. I place the flanged portion of the rivet into the bladder and I use a piece of standard fuel tubing to secure around the neck of the rivet stem. This can be a real bitch to put on . Having rounded needle nose pliers works better because the round portion of the pliers are the same diameter. Standard needle nose jaws are tapered so when you slip the tubing onto the jaws and pull the handles apart to spread the tubing open, it immediately pops off of the pliers.

           Melvin has various or had various styles of tubing. One tubing he had which i used for a little while was pink.It blew up to the diameter of a hot dog no larger but it would lengthen quite a bit. I was getting more pressure in the early portion of the run which would drastically change my needle setting throughout the run. At about 2-2.5 minutes into the run, the engine was going too lean and surging because the pressure wasn't as great.

           This brings me to the next question as to what needle is in the AME engine? The stock AME needle isn't good and it will not offer a reliable setting. I have done many mods to enable a Norvel to accept a Cox 128 TPI needle valve assembly. It really essentially depends on what version Norvel you own. The older versions used the epoxied venturi assemblies while the newer offered the bolt in style. The older epoxy style venturi can be removed using heat. I don't even use a venturi, I place the spraybar right through the case and bush the Cox assembly using 5/32" tubing. I make the bushing by filing through the center which I align the spraybar hole up to and I solder this tubing to the spraybar. When I solder, I clean the outer portion of the spraybar and I don't clean any of the area around the hole because I don't want solder to wick into it.

        This setup has worked the best for me next to the unobtainable VA needles which were offered with the VA MK II for combat. You just have to insure that you certainly have the 128 if your using the Cox assembly because Cox made a similar looking needle which isn't the fine thread. I generally find these spraybar and needles in the postage stamp backplate not the horseshoe style product style. It may have been available in the horseshoe style but to insure I have the correct version, I keep a Kustom Kraftmanship spraybar which I screw the needle into just to check.

Dan we need pictures 😉

Quote from: Paul Taylor on June 24, 2026, 10:19:52 AMDan we need pictures 😉

  OK, ask and ye shall receive!! Finally remembered to get it down! I'm making a quick day trip up to Muncie and one of the things I want to do is see Melvin Schutte and get some bladder materials for it. Just moving a  little slow on this project but hope to try running it on pressure and fly it this summer yet. Pics are a little foggy. I think I lost the lens cover off the main lens on my phone. Gonna see if it can be replaced, otherwise I think it might be time for a new phone.

  Type at you later,
  Dan McEntee

The Barecat was published in the June 1999 Model Aviation by author Bob Baron. It is a Netzeband design from around 1980. The published plans show a Norvel .049/.061 engine. And Bob recommended a "Kustom Kraftsmanship needle-valve assembly to replace the sensitive stock unit." Running on a high-pressure bladder I can see the logic in that.For the .061 he sleeved the venturi to assist with fuel draw.

If you want to compare to something similar, go look at the Ridiculous by Rich Porter, as published in the July 1985 Model Aviation. Very similar design themes as it was inspired by Netzeband's ideas, just without Bill's signature "pointed-triangle vertical stabilizer." (Check out the Cat's Paw, too.) Porter used a tricked out Cox TeeDee on pressure as I recall.

Quote from: Dave Hull on July 08, 2026, 02:20:57 AMThe Barecat was published in the June 1999 Model Aviation by author Bob Baron. It is a Netzeband design from around 1980. The published plans show a Norvel .049/.061 engine. And Bob recommended a "Kustom Kraftsmanship needle-valve assembly to replace the sensitive stock unit." Running on a high-pressure bladder I can see the logic in that.For the .061 he sleeved the venturi to assist with fuel draw.

If you want to compare to something similar, go look at the Ridiculous by Rich Porter, as published in the July 1985 Model Aviation. Very similar design themes as it was inspired by Netzeband's ideas, just without Bill's signature "pointed-triangle vertical stabilizer." (Check out the Cat's Paw, too.) Porter used a tricked out Cox TeeDee on pressure as I recall.

  I think I haver a KK needle for a TD in my stuff but will have to look. The way the spray bars and venturis work on the Norvels, I'm not sure how easy that will be to adapt. I di have some of those Wasp .061s that I adapted too take a Cox TD venturi, so may switch over to that. been to busy with other life's little pleasures to get back to it. I made a quick one day trip to Muncie on Wednesday and one of the things on my agenda was to see Melvin at MBS Model Supply and pick up supplies for bladders, but he had already packed up, but I did get to talk with him, and that was one of the reasons for the trip also. I'll wait until he gets rested up  and get an order in to him next week. In the mean time I'll check out those other models and look into my parts box to see what I have.

  Type at you later,
  Dan McEntee

              Dan, I have done a few mods to adapt spraybars to Norvel's when using bladders. The problem with the Norvel and others such as Stels or Zeus AME engines is the oval opening in the case. The Stels came with inserts which were two colors grayish white and black. Almost 90% of the time, they're missing because it's a loose part and the owner isn't using it and now it's gone. Later Stels engines didn't supply these with the engines probably due to one more added cost. These engines utilized a fairly wide spraybar because the hole through the case was large and the spraybar was a continuous diameter. I have essentially used the Norvel on bladder without using a venturi at all. The case style differs through the years, the older case used the epoxied in venturi which had the venturi glued in but the spraybar passed through it essentially behind the opening similar to Super Tiger sprinkler. 5/32" tubing fits through this opening and a Cox 128 tpi spraybar can be soldered into the tubing and then glued in with JB weld. To get the fuel through the 5/32" tubing, align the bar into the tubing prior to soldering or gluing and mark the exit of the spraybar. File the tubing using the file on edge and break through it and insert the spraybar aligning it with the hole . Newer Norvel cases used a very small retaining bolt through the case, through the venturi with a lock washer and nut on the opposite side. For this style, I generally remove the assembly and drill the case itself to accept a Cox postage stamp spraybar. These can be pressed out of the backplate and inserted through the case of the Norvel. The downside to this is that the width isn't quite long enough but there's enough that protrudes to get the fuel line on. In the past, I've even wrapped a bit of copper wire around the fuel line connection side and soldered to form a barb. You could also use the solder style dubro fuel barbs on the Cox spraybar. This has to be perfectly clean and tinned first because once in the case, it's difficult to solder due to the convection of heat into the case.

            Another method I used which was a bit more difficult was to take a broken APC propeller hub which I had plenty of from 1/2A propellers. I used a razor saw and cut the blade off at the root and used the hub as a bushing filing it to fit into the bathtub opening of the case. I was using the prop screw hole as a way of keeping the piece centered within the opening of the case. I filed it on a slight bevel to fit snug into the case all the way around the part. On the bottom, I had to file a radius to clear the crank and a slight angle due on the bottom. I left a bit of material protruding above the top of the case and my reasoning for this was to offer me some leeway in regards to squaring the top later on with a file.  I then used JB weld to insert this bushing, it cleans up well with a Q-tip and rubbing alcohol. When drilling, I'm well aware that a drill bit will follow the existing hole in the hub but you want to insure your following the angle of the case and keeping the drill as perpendicular as possible. Use a tap drill for 1/4"-32 and tap it when complete. You can now screw in a Cox TD venturi assembly and you can use a true KK needle assembly if you have one.