COG on Zipp Missile

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J

Jeffrey Hammond

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Joined
Apr 8, 2024
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182
I am getting toward the end of my Zipp Kits Missile gas hydro build, and I decided to check the Center of Gravity before I put the deck and radio in. After placing all the parts, I found out that my boat was very A$$ heavy. It took almost 1.5 lbs of weight in the nose to get it to balance on frame #3. Has anyone else have this issue? The instructions say to put as much weight as you need to get it to balance at frame 3, but this seems like a lot.
 
Jeffrey Hammond said:
I am getting toward the end of my Zipp Kits Missile gas hydro build, and I decided to check the Center of Gravity before I put the deck and radio in. After placing all the parts, I found out that my boat was very A$$ heavy. It took almost 1.5 lbs of weight in the nose to get it to balance on frame #3. Has anyone else have this issue? The instructions say to put as much weight as you need to get it to balance at frame 3, but this seems like a lot.
Click to expand...
Don’t put a pound and a half in your boat. Put the decks on, you have more wood ahead of the cg instead of behind. Then check the cg about an inch behind the former and see where you are.
 
Hey Bill
I have placed all of the decks on in their approximate locations, as well as the turn fin, the radio, and the cowling. Now I may balance an inch behind the former…….I’ll go check.
 
Bill
I just taped all of the decks in place and put everything in the boat in the approximate locations. I set a balancing rod 1 inch behind the back edge of former 3. I needed 8 ounces of weight to get the hull to balance. Whadda ya think? Also, I have not cut the tops of formers 4 and 5 off. I kinda liked the anti-twist aspect of the tops of those two formers.
 
Jeffrey Hammond said:
Bill
I just taped all of the decks in place and put everything in the boat in the approximate locations. I set a balancing rod 1 inch behind the back edge of former 3. I needed 8 ounces of weight to get the hull to balance. Whadda ya think? Also, I have not cut the tops of formers 4 and 5 off. I kinda liked the anti-twist aspect of the tops of those two formers.
Click to expand...
You can get ride of 4 and 5. Once you get the decks on it will lock everything in place. It will not twist. I would put in the 8oz now and run it. You can always add more if needed. You would put stick on weight on the nose till you got the results you were looking for. Then mix epoxy and small sinkers that weigh the same. Set your boat on it’s nose and pour it in.
Jeffrey Hammond said:
Bill
I just taped all of the decks in place and put everything in the boat in the approximate locations. I set a balancing rod 1 inch behind the back edge of former 3. I needed 8 ounces of weight to get the hull to balance. Whadda ya think? Also, I have not cut the tops of formers 4 and 5 off. I kinda liked the anti-twist aspect of the tops of those two formers.
Click to expand...
Cut them off, not needed, decks lock everything in place. Put in the 8oz and run it. If after getting the set up it is still a little flighty you can alway add a little more.
 
Try the stick on weights first like OSRACER suggested. You can get them in various versions. You don’t necessarily need the repackaged ones RC companies sell. You can just get stick on wheel weights ( automotive tire balancing). Handle it however you want just a suggestion. Once you get it running like you want, then do the permanent fix.
 
Not really familiar with the build of that boat but a thought came to mind... Instead of gluing the decks directly to former 4 and 5, would placing additional plywood spanning the same distance of each be a better choice? ONE you won't have to glue the deck to the top of the formers. And still have the strength. Two you won't have the dip in the surface of the deck at each former. Three you would be adding constructive weight that's actually doing something besides going along for the ride.
Just a thought... Sorry if this has no relevance...

Ken
 
Ken
I don’t think their are any bad ideas, so I need to think about yours…….first off, I hope that my sanding job on the formers has been good enough so that there is no deck sag once I glue the decks on. Secondly, the center cowling takes up about 5 inches of the space in-between these two deck pieces, almost the entire length of the boat, and it has the motor cover and driver cockpit molded into it, so I can’t get rid of the cowling very easily. Plus, this is supposed to at least “ look” like a 50s-60s round nose hydro, and finally, the deck may appear that it is along for the ride, but other builders tell me that the deck pieces keep the hull from twisting, so you better have it right when those pieces get glued on.
Still, I like out of the box thinking, and some excellent advances are made that way. So all ideas should be carefully considered.
 
Jeffrey Hammond said:
Hey Rich, does this 2s 1800 last one full day of running, like 5 heats of racing?
Click to expand...
Yes. No problem. I’ve actually gone running two weekends in a row without balance charging in between, although I would recommend balance charging before each day of running. The LIFE batteries aren’t volatile like LIPO batteries and don’t form a memory like the old school batteries do. So you don’t need to worry about discharging to a certain level unless you are storing for a long period of time. I would recommend getting a good smart charger if you don’t have one. I use a Hitec charger with 2 channels so I charge my receiver and transmitter batteries at the same time.
 
Ok, here are some pics of my radio box in progress. I haven’t glued any servos in, and the box has not been epoxied yet. I still have to put the rubber boots on the control arms, so this is truly in progress.
Note that I am going to try the direct connect throttle arrangement…..I just thought it sounded like a way better idea than the other systems I’ve seen. Btw, the battery is a wooden mock-up, but i Did power it up today with a regular battery to check throws, etc. seemed to work fine. Small steps….
 

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That’s a tight fit inside radiobox I’m not a fan of the flex throttle dealing with those small set screws isn’t for me.I like the standard rod setup but that’s me with quick release ball link.No tools needed to pull throttle apart when pulling engine.Looks like a nice build.
 
Hey guys
I played with the radio box some more today and I found out that I had put the metal output guides in backwards! The nice looking side goes on the inside of the box, and the side with threads goes on the outside of the box! By turning them around, I’d did two things, 1) I gained a little room inside the box, and 2) it allowed me to figure out how to put the rubber bellows on the guide and the control rod. I glued the riser strips on the bottom of the box, and the lid guide on the top. Tomorrow, I’ll epoxy the box and get it ready to permanently install.
 

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