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(Fwd) tandem axle trailer

I posted this under Betsy and Dave's previous message in 
the archives but thought it might be a good reminder to all 
you who are getting ready to trailer in the new season.

Thanks Dave and Betsy


------- Forwarded Message Follows -------
To:  ,
Date:          Mon, 13 Apr 1998 15:02:07 -0700
Subject:       tandem axle trailer

Randy & Diana

	2 years ago I converted our trailer to a tandem axle vs. the
single it originally was. I did this for several reasons, I've never felt
comfortable towing with just two tires under the boat, a high speed blow
out could easily result in very catastrophic accident. We noticed with
two tires they got rather warm even hot on long hauls! This was with
highest rated (hard to find & $$$$) tires. 7.00 - 15 LT  load range D
Cooper 6 ply tread, 4 ply sidewall Max load single 2040 lb. @ 60 psi. Our
San Juan 23, Low Overhead & single axle trailer weighed in at 4375 lb.
with very little gear in the boat. The tires where overloaded by 300 plus
pd. The trailer seemed to fish tail & just generally wandered a lot. The
tandem axle cured all these problems.

	Its unfortunate people build (professionally) trailers that are
under rated . I wont even go into some of the home made disasters I've
seen at boat launches . I've also picked up some very good ideas looking
at trailers & incorporated these into my own trailer . The finale straw
was a broken front spring hanger, found in my driveway late one night
after a 100 mile tow home after a week in the San Juan Islands. This was
a result of the previous owners (an engineer for Boeing) misinstallation
of a heavier axle, the spring assembly  was to long for the existing
frame attachment points, this stress eventually broke the weld at the
frame. I've been a professional heavy duty diesel mechanic for the last
20 or so years, most of those years as a an engine specialist. I wasn't
qualified to really tackle this modification. I'm very picky about the
quality of work, & am generally dissatisfied with 89% of what I see go on
in this world. Over all I don't honestly believe any one else would have
done as good a job as I did and was very pleased with the results, I am a
competent welder & had lot of advise & am very resoursfull , able to
differentiate between good & inaccurate advise. I mention all this and
caution against diving into projects that may be beyond your abilities be
very sure & comfortable with what you are doing or pay someone who is.
Certified mobile welders are abundant, and usually very good.. Mistakes
in design, or workmanship could easily result in an accident & loss of

	Is your current trailer worth upgrading is it structurally 
sound. Our trailer is galvanized & an open channel design.  My project
involved at least a 100 hours of my time, & $1000. Plus in material.
Another problem I discovered was rust build up on the inside of the axle
tube, which resulted from salt water trapped in the tube entering through
the poorly sealed brake wire holes. I replaced a 5200 pd. Axle with 2
3500 pd. Dexter axles w Marine drum brakes & 4 springs & mounting
hardware (4" spindle rise 84 1/2 " rim mounting surface to rms ) All
Dexter axles come with those pre drilled holes for the electric  brake
option. I tapped those holes & installed pipe plugs, after I got the
axles back from the galvanize.  I managed to do this work with the boat
still on the trailer. That coupled with the fact I wanted every thing
galvanized, lead me to weld the spring hangers to a long piece of flat
stock & U bolt this to the existing trailer, this is a common practice 
it enables you to move the axles to get your tongue weight right. Our bow
support is also U bolt attached so I have the option of moving the boat
forward on the trailer if need be.

	Axle location becomes a function of tongue weight  10% - 15% , my
center spring hanger is approximately 1/3 back on the window. The center
spring hanger is in the same location as the center of the old single
axle. San Juan's seem to be stern heavy, outboard, fuel, & water commonly
stored in the aft. Sailing & trailer performance can be improved by
moving weight forward,  moving our water tank forward is on my project

	Brakes are likely law on trailers in this weight class, I would
not even considering towing this kind of weight with out a functioning
brake system. I heard a good idea the other day Disc brakes they are more
open less likely to corrode , easier to clean, I would look into this
option. We use a Surge -o- matic  hitch activated master cylinder. This
should give you some ideas good luck       Dave.    

P S  Dave did not write the original letter in the archives but I don't
remember a mention to memos.  We don't have before photos and may get an
after some day.  Our trailer brand was Fleet Cap'n.  We looked at
Caulkins and other power boat trailers for ideas on attaching the
spring/axle assembly with the U-bolts.  We convinced the galvanizer to do
the interior of the axle but the responsibility of protecting the
spindles from the process without warping was all ours.  They were very
hesitant.  Dave wrapped them well and it was fine.

Betsy Schultz

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