I need to add weight to my ucd 46 and I took some lead fishing sinker and pounded it to look good to add to my firewall . I mixed up some 5 min. epoxy and added fiberglass shavings for strenght to add strength and glued it to the firewall. Oh yes I did ruff up the both surfaces with sandpaper to hold better . Will this hold good or is there a better way? Thank you in advance . Ken

Did you glue the weight to the front of the firewall or behind it? I hope it's the latter because 5 min epoxy is not fuel proof.

Even if he did use slow cure epoxy, sticking the weight on the front of the firewall would expose the epoxy to engine heat, of which epoxy is none too fond.

Have you looked at the DuBro "Crankshaft" weights ? They come in 1 oz and 2 oz and go on the engine in place of the prop washer and fit under MOST spinners. By moving the weight further out you will also need less weight.

KJA:

A du-bro prop nut (chrome plated brass) can be used to balance out a slightly tailheavy plane.....I've used them before with great results. You can use an electric starter on them as well with the regular insert (standard size) with no problems.

[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXE191&P=7]Du-Bro 1/4 x 28 Prop Nut[/link] <--- that one is used on most 40-46 size motors but double check your thread size

I have been using the du-bro prop nuts for over a year and haven't had any problems. Actually makes a prop change very easy as you don't have to mess with the plastic spinners. If you like the look of the plastic spinner you could use the weighted prop nut under the plastic spinner (would have to use a fairly large spinner 2 1/2-3").

Madd_Maxx

My favorite way to add weight up front is to make a metal strap to fit the bottom of the front engine mount bolts & hang the weight on it with a bolt + loctite. -- U may have to form it into a u shape to clear the working parts. this wants to be hidden from view but is an inch or so forward which cuts down the wt required

Bolt or clamp the weight in place as well as epoxy. If the weight comes loose in flight then the centre of gravity will change, probably rearwards, and you will have difficulty regaining control. A crash is almost certain if the weight vibrates loose!
You can drill or pierce a hole in the lead weight or use a steel or brass weight.

What kind of epoxy are you using? I've used thinned 5 minute epoxy for fuelproofing before with no problems.

I like to use shoo goo to stick the weight on. You can stick it to the cowl and glue it on. Not 100% fuel proof but it works real good and give you the ability to remove the weight if you want to.

This is my question too....
I always thought that thinned epoxy was an acceptable fuel proofing method?

Please elaborate

5-minute epoxy is not fuel proof. 15-minute epoxy is 50% fuel proof. 30-minute epoxy is 100% fuel proof. There is no need to thin the epoxy if you use either 30-minute or 45-minute epoxy.

My thinned 5 minute (actually 6 minute) takes over an hour to cure, and about 24 hours to harden. Does this qualify as fuel proof? Is it all in the cure time? You've got me worried now.

Thinning 5-minute epoxy does not make it fuel proof. Adding more alcohol to epoxy does not make it fuel proof in any shape or form because alcohol is not fuel proof. It is not in the cure time. It is in the chemical composition of the epoxy.

Richard L.,

I am curious - what is the definition for 0%, 50% or 100% fuel proof?

Better let Frank T. know about that 5 minute epoxy not being fuel-proof thing . . . 'cuz he says it is : http://www.franktiano.com/epoxy.htm

Here is an interesting reading about thinned epoxy: [link=http://www.seqair.com/skunkworks/Glues/WestSystem/Thinning/Thinning.html]Thinning Epoxy[/link]

I've seen too many glued weights come off. I always add a screw for good measure

Hi!
Why add weight???? I always try to remove weight!
Why not change position of the servos, battery and radio gear?
5 minute epoxy not being fuelproof?? At least it is over here in Europe! But using CA glue is much better.
I would not recommend adding weight to an airplane....[&:]
Regards!
Jan K
Sweden

I have both 5-minute and 30-minute epoxy on my firewall, and the 5-minute version has turned yellow and cracked, with fuel underneath it (I use 20% nitro). Maybe the only fuel proof 5-minute epoxy is Z-Poxy. Here is another thread on this topic: [link]http://www.rcuniverse.com/forum/m_1516662/anchors_1520745/mpage_1/key_fuel%252Cproof/anchor/tm.htm[/link]