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Discussion Starter · #1 ·
I'm planning on making my trailer have a removable tongue.  My current set up is an all aluminum trailer with a 3" x 3" (1/4" thick) aluminum tongue.  I've purchased a 2.5" x 2.5" (1/4" thick) square aluminum tubing for the part that slides into the existing 3" x 3" trailer tongue (that will be shortened).  Can I use the 2.5" x 2.5" aluminum square tubing alone as the new trailer tongue or do I need to purchase a 3" x 3" tubing to weld to the new smaller tubing to mount the coupler?  Any thoughts appreciated.
 

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What size boat/weight and length of trailer? What grade aluminum is the 2.5" square tubing?

just fyi im a stuctural/mechanical engineer if you can answer these few questions i can tell ya if its gonna work or not. also im assuming your gonn pin the two sections together? how much material will be inserted inside the 3" tubing?
 

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Discussion Starter · #3 ·
17' skiff, weight including trailer I'd have guess less than 2,000 lbs. The new piece is 6061-T6, length of trailer is close to 20'
 

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I would think that it would have to be of the appropriate strength to either way as it will have the same amount of weight and force on it used either way. My trailer is aluminum and has a swing tongue which is made of galvanized steel. I would probably just cut my existing tongue and use one of these:

http://www.etrailer.com/Trailer-Coupler/Fulton/FHDPB330301.html

there is a lot more to the strength of a piece of tubing than it's dimensions and the metal on your trailer is the appropriate rated material. You could always call the manufacturer and ask them what kind of aluminum they used and spec out a piece of stronger tubing but to go smaller for your inner sleeve either way you want the joint to be stronger than the existing tubing otherwise it will be the weak link and you don't have safety chains at that spot. just my thoughts on it.
 

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Discussion Starter · #5 ·
Here's a pic

Swing tongue won't work in my situation.  The (2) SS bolts thru the I-Beam will be replaced with d handle hitch pins.  The existing tongue will be cut flush where the I-Beam ends, I'll add another piece of aluminum flat bar to the top of the I-Beam (just like on the bottom) to help keep the two I-Beam pieces together. The jack will be remounted on the side of the I-Beam, just past the winch
 

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ok i see what you're saying yeah that would probably work.  my only concern would be he holes in the aluminum rounding out over time and also that center piece of the triangle takes all the pull.   think I would do it like this:


the yellow is a  steel plate stainless or galvanized top and bottom with the trailer sandwiched between.  the black is new bolts to hold the a frame together.  i would remove the original 2 bolts and not replace them.  The red is where i would use the pins.  i would then use steel tubing to replace the tongue and sleeve it at least 6".  I've always been accused of doing thinks way overkill but I feel if you are going to do it, do it right or not at all.  I would never forgive myself if my homemade trailer modification broke on the highway and my out of control trailer killed someone.

hope this helps you brainstorm. Oh and let reel-dictated chime back in to as he is definitely more versed in the mathmetics of what you need
 

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Stripper in my own Mind!
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I spoke with Ramlin about this a few weeks ago. Their best advice on how they will do it is to cut tongue behind jack stand, insert smaller diameter tube and weld as a sleeve. Jack stand side remains welded and trailer side becomes receiver using pins to hold. If the trailer is 3"x3" then it should remain that way with proper sleeving to give support.
 

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ok i have run some numbers on some general assumptions such as tounge weight/balance/ and such... and if you want the engineering calcs behind it and explanation i can give it to you just pm me (ill save the masses from the boredom lol).. but no you may not just simply slide the 2.5"x2.5" tubing into the 3" and attach your coupling from there. your required section modulus for the weight & length of your trailer you need 1.64 (this is with a 30% safety margin). where your 2.5"x2.5"x1/4" has a section modulus of 1.35 and 3" square tubing has 2.10... like others said this stuff is designed to the min. allowance they can get away with (saves them cost of materials). but from engineering stand point don't do it, the numbers don't work.. could you proly get away with it with out any safety factor, yes... but i have spoke my $.02
 

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Discussion Starter · #9 ·
ok i have run some numbers on some general assumptions such as tounge weight/balance/ and such... and if you want the engineering calcs behind it and explanation i can give it to you just pm me (ill save the masses from the boredom lol).. but no you may not just simply slide the 2.5"x2.5" tubing into the 3" and attach your coupling from there. your required section modulus for the weight & length of your trailer you need 1.64 (this is with a 30% safety margin). where your 2.5"x2.5"x1/4" has a section modulus of 1.35 and 3" square tubing has 2.10... like others said this stuff is designed to the min. allowance they can get away with (saves them cost of materials). but from engineering stand point don't do it, the numbers don't work.. could you proly get away with it with out any safety factor, yes... but i have spoke my $.02
that makes sense, what if the 2.5" x 2.5" is solid? Would that make a difference?
 

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YES it would make a ton of difference.. and you would need a fork lift to pick it up ;D solid would work for sure but thats a little extreme..
 

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Discussion Starter · #11 ·
I like the feedback, these pictures are from a Beavertail trailer (removable tongue was from the factory)





the part that slides into the tongue is solid aluminum and is not welded. Can I copy this design, except with a solid square piece?
 

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Discussion Starter · #12 ·
YES it would make a ton of difference.. and you would need a fork lift to pick it up  ;D solid would work for sure but thats a little extreme..
so a 2' long solid aluminum piece would work or should it be longer?
 

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notice how they have rectangle tubing which is a lot stronger than square tubing (on the strong axis anyway). if i were to do what your planning i would use solid aluminum inserted into your existing 3" tounge and weld or bolt that where i have at least 12" inside. then slide the other end into (have at least 12" inserted also, totaling min of 2' solid square tubing) and have my removable pins. that way everything you have (connection wise) is equal or stronger than original
 

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Reel-
Can you do the same calculations for 3/8" aluminum and 1/4" and 3/8" galvanized for him...got to be a tube that will work other than a solid.
 

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Discussion Starter · #16 ·
thanks guys for the input
 

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Discussion Starter · #18 ·
update on the project, finally got the parts, the jack moved and the time to finish the removable tongue.  I started with this


next step was to grind the corners off the solid 2.5" x 2.5" bar


once I could slid the new solid bar into the existing tongue, I then used flat bar to join the top i beam (just as the existing piece on the bottom).  Next weekend, I'll replace the top flat bar with larger 1/4" plate.  I then cut the existing tongue at the i beam


next step was drilling the holes to attach the solid tubing to the existing tongue and coupler, along with drilling the holes for the 2 new 5/8" hitch pins


finished project, minus the larger plate for the top of the i beam



 
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