# Longer rod.

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#### DynaSoar

##### Well-Known Member
I need a bit more rod on my Mantis than the rod that comes with it. Ideally I'd like an extension, with male and female ends, to go in between the two stock rod pieces it comes with.

Anyone know if such a thing exists, or at least of a source of a 1/4" rod made of two 4 foot sections?

#### rbeckey

##### Well-Known Member
Lotsa rod whip with a longer rod. I suppose making it sectional would stiffen it, but I have never seen one advertised. I decided to go with a rail for heavier midpower rockets. No rod whip.

#### bobkrech

##### Well-Known Member
Rod stiffness determines the amont of rod whip. For a metal, steel is already pretty stiff, and only titanium is stiffer.

The longest 1/4" rod you are likely to find is 6'.

You can get them from https://www.mcmaster.com

I would recommend 4140 chome-moly steel as it is far more reasonably priced than stainless and reasonably corrosion resistant and quite stiff. This material worked well for TARC egg lofter rockets in the 1.5 to 3 pound class.

8927K21 4140 Alloy Steel Rod 1/4" Diameter, 6' Length $3.74 Each The following is a drill rod stock which is probably a bit stiffer but less corossion resistant and far more expensive. Not worth it. 88565K52 (Same as 88565K3) Grade D-2 Steel Precision Ground Rod 1/4" Diameter, 6' Length$ 26.84 Each

The stiffest material for launch rods is titanium. It is twic as stiff as steel, but it is very expensive, and really not worth it for a launch rod.

89055K33 (Same as 89055K53) Titanium Grade 5 Rod 1/4" Diameter, 6' Length \$ 97.86 Each

Adding a joint will in all likely hood make a rod of the same length weaker.

You are much better off going to a larger diameter launch rod than by going to a more expensive material solution. While the relationships are dependent on a number of factors, a 3/8" rod (50% larger diameter increase) is usually more than a factor of 3 stiffer than a 1/4" rod. Obviously a rail is even stiffer.

Bob Krech

#### Stymye

##### Well-Known Member
according to stines handbook , some tests were done with a high speed camera and the finding was that an aluminun rod occilate less than a steel rod...
an aluminum rod will dampen out ,a stiff steel rod will occilate like a guitar string right at the tip where you don't want it too..
all of my rockets that have rod whipped so far were from steel rods.
one in particular, was a modified fatboy that I flew from my aluminum rod 3 times without problems,than the first time I flew it on a steel rod at a club launch, it whipped horizontal.
after a lot of head scratching...
I'm now convinced the difference was in the rod material

#### Bill

##### Well-Known Member
Originally posted by DynaSoar
I need a bit more rod on my Mantis than the rod that comes with it. Ideally I'd like an extension, with male and female ends, to go in between the two stock rod pieces it comes with.

Anyone know if such a thing exists, or at least of a source of a 1/4" rod made of two 4 foot sections?
The club has some threaded 1/4" rods (3 foot sections), but they were not off-the-shelf items. We had to start with steel rod stock and find a metal shop to machine the ends. The work needs to be fairly precise to avoid an uneven joint.

Bill

#### DynaSoar

##### Well-Known Member
Originally posted by Bill
The club has some threaded 1/4" rods (3 foot sections), but they were not off-the-shelf items. We had to start with steel rod stock and find a metal shop to machine the ends. The work needs to be fairly precise to avoid an uneven joint.

Bill
Problem solved for me and for anyone else that needs an extension for the Mantis rod. See "Vendors".

#### DynaSoar

##### Well-Known Member
Originally posted by Bill
The club has some threaded 1/4" rods (3 foot sections), but they were not off-the-shelf items. We had to start with steel rod stock and find a metal shop to machine the ends. The work needs to be fairly precise to avoid an uneven joint.

Bill
Zackly what I did, only in aluminum. And the pieces are 2.5'. Folds up real nice for traveling and fits in a 3' piece of PVC with caps. Holds the Mirage real nice. Doesn't wobble much at all. Besides, the amount of rod whip from a 7.5 foot rod is likely to be less than the amount of rocket whip it'd have coming off a 5 foot rod at less than stable speed. The top lug is already 40" north of the base of the retainer.

I only added the lugs recently because I haven't finished my tower. When I do, I won't have this problem again for quite some time. No more ugly lugs, buttons or anything else to break the lines and cause drag.