DarkMantle

C of G on a Sig 270

27 posts in this topic

It is where the boat looks correct from any angle in fresh or salt water.  Or on a full plane. Is it sinking a little bit at 1 end ?  Pictures would help other owners make a decision.

Some pictures compared to that boat size in Boattest reports would help you.

My 186 SSIs with a 5.0L  always cause me to look at the transom. When going by in another boat. No water in the bilge.

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29 minutes ago, cyclops2 said:

It is where the boat looks correct from any angle in fresh or salt water.  Or on a full plane. Is it sinking a little bit at 1 end ?  Pictures would help other owners make a decision.

Some pictures compared to that boat size in Boattest reports would help you.

My 186 SSIs with a 5.0L  always cause me to look at the transom. When going by in another boat. No water in the bilge.

I have to move my trailer axles. Just want an basic starting point. 

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Somewhere fore of the base of an arch would be my starting point.

FWIW, here is my custom made trailer for 2007 Sig 270 with oddly spaced axles ...

page3-1009-full.jpg

page3-1007-full.jpg

 

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1 hour ago, Richard W said:

Somewhere fore of the base of an arch would be my starting point.

FWIW, here is my custom made trailer for 2007 Sig 270 with oddly spaced axles ...

page3-1009-full.jpg

page3-1007-full.jpg

Worth a lot. I pretty much ended up setting mine the same way

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9 hours ago, Richard W said:

Somewhere fore of the base of an arch would be my starting point.

FWIW, here is my custom made trailer for 2007 Sig 270 with oddly spaced axles ...

page3-1009-full.jpg

page3-1007-full.jpg

 

Was that intentional?  If so, why?

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16 minutes ago, TNBrett said:

Was that intentional?  If so, why?

I too am interested in the reasoning.  Looks like the front axle was added later and probably divorced from load equalization with the middle and rear axles.  

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This is a custom trailer made specifically for this MY boat. Judging by the labels the trailer was made either for Chap or Chap dealer, and came with the boat. The axles are indeed torsion axles and all are mounted into fixed brackets. All brackets look same, are welded into the frame and painted over at the same time with the rest of the trailer. No signs of after market mods. The spacing looks intentional, but the reason escapes me. Any guesses?

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You would think that the front set is lightly loaded when static allowing for adequate minimum tongue weight at speed, but keeps excess weight off the tow vehicle during braking. I've never seen this before. Be interesting to see how the tires wear as an indication of who's doing the work.  I'd like to shoot the tires with an infra-red thermometer after a long tow, and compare the values.  W

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Do a Google search for spread axles.  It's a popular option for enclosed race car haulers.  I've never seen them do a spread axle in that manner with triples, but it seems the forward axle on that boat axle is a spread axle.  Moving the axle forward like that helps reduce tongue weight.

 

I own a trailer dealership (not boat trailers).  I've ordered spread axles several times for customers hauling large enclosed trailers with half ton trucks.  Really helps prevent excessive squat on the truck.  Looks good too on a custom built tandem axle race trailer. 

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My guess is the axles were spaced based on the standard size fender. The middle axle center-line should be the CG.  You want the forward axle as far forward as possible to minimize tongue weight. So you locate the rear axle as close as possible to the middle axle, which locates the fender as far to the front of the trailer as possible. 

brick

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It looks to me like the center axle is actually moved rearward from what would be the normal spacing.  Perhaps there is a crossmember that was preventing the axles from being spaced equally.  The thing to keep in mind is that trailers aren't built on assembly lines at Ford or GM.  Most trailers, particularly custom ones, are essentially hand built.  It would be pretty easy for a welder to position a cross member on the wrong side of a mark when setting it up.  Another scenario would be that the crossmembers were laid out for spring suspension where the axle would be in line with the hub versus offset by the length of the torsion arm.  I just can't see this being a engineered design element.  I don't think its hurting anything either though.  It appears to have been serving you well for a decade now.  I will also add to this that from what I have looked at, no axle manufacturer recommends torsion axles in a triple axle configuration until you get up to 7k axles with dexter.  Even then it has to be a 7k spec'd for triples.  

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They also make triple spread axles.  Spread axles cost around 500 in tandem.  Could've just been cost related. I don't think any engineering genius was used.  I see a lot of head scratching stuff done on trailers to keep the cost down.

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The wheels fit the fender perfectly, so I don't think the spacing is a "goof".  I still think the spacing was set to minimize tongue weight, while keeping the middle axle at the CG.

brick

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40 minutes ago, TNBrett said:

It looks to me like the center axle is actually moved rearward from what would be the normal spacing.  Perhaps there is a crossmember that was preventing the axles from being spaced equally.  The thing to keep in mind is that trailers aren't built on assembly lines at Ford or GM.  Most trailers, particularly custom ones, are essentially hand built.  It would be pretty easy for a welder to position a cross member on the wrong side of a mark when setting it up.  Another scenario would be that the crossmembers were laid out for spring suspension where the axle would be in line with the hub versus offset by the length of the torsion arm.  I just can't see this being a engineered design element.  I don't think its hurting anything either though.  It appears to have been serving you well for a decade now.  I will also add to this that from what I have looked at, no axle manufacturer recommends torsion axles in a triple axle configuration until you get up to 7k axles with dexter.  Even then it has to be a 7k spec'd for triples.  

Just looked at some photos of tandem axles.  You're right, the rear axles are closer together than standard.  

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The only time i can recall seeing uneven spacing on a triple axle trailer is when one of the axles is a tag.

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11 hours ago, Richard W said:

This is a custom trailer made specifically for this MY boat. Judging by the labels the trailer was made either for Chap or Chap dealer, and came with the boat. The axles are indeed torsion axles and all are mounted into fixed brackets. All brackets look same, are welded into the frame and painted over at the same time with the rest of the trailer. No signs of after market mods. The spacing looks intentional, but the reason escapes me. Any guesses?

Who made the trailer? Call and ask them. 

Inquiring minds want to know...

My bet is still on moving the front axle as far forward as the fender allows to minimize tongue weight.

brick

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10 hours ago, brick said:

The wheels fit the fender perfectly, so I don't think the spacing is a "goof".  I still think the spacing was set to minimize tongue weight, while keeping the middle axle at the CG.

brick

If you have the boat Cg directly over the middle axle the tongue weight would be the same with or without the boat on the trailer.  Basically the tongue weight becomes a product of the Cg of the trailer itself.  All in a static scenario.

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I think I have the answer or probable cause of not evenly spaced axles on my trailer. Some ideas expressed above were close to what I found out ... but first a bit of background why I've got into finding out.

Last fall the marina that was lifting my boat from water, power washing the bottom, and setting it on a trailer dropped the boat, the bow, onto the trailer. Inept and lazy marina owner and operator decided to use double belt method instead of supporting the boat by block and jack from the bottom while removing the primary belt from under the boat  ... he said, too much jacking, jackass. The secondary belt positioned too closely to the bow curve slipped and the boat had fallen down 10 or 12 inches onto a trailer that was not properly supported at the tongue. Again, the trailer's jack stand was not used, the trailer's tongue was resting too low on the old yard truck's hitch. Bottom line, the left front wheel torsion assembly sheered inside the axle and subsequently, the wheel traveled up and rested against the fender that got slightly damaged as well.

I got home on five wheels somehow, braking was affected, and backing up and clearing a small hump at the head of our driveway was a real challenge as the broken wheel jammed against fender got stuck in crushed stone and I had to plow thru the hump. I did not have the time to repair the trailer then, the boat got winterized, wrapped and left on the property for winter. Only this summer I was able to get replacement axle, all three actually based on axle manufacturer (UFP/Dexter) advice, paint them, take trailer apart, replace axles, fix the fender, redo/replace brake lines, and ... oh that was fun ... bleed the brakes. All is well now, I finished all and tested the trailer today.

While taking the trailer apart I noticed the axle mounting brackets are asymmetrical. The middle axle was positioned differently, kind of front to back, than the other two. There was nothing, not a crossbeam nor other obstruction preventing to orient the middle axle the same way. The boat's CG falls somewhere in the middle between front and back axles so it does not seem to be a reason for uneven axle spacing. The only reason I could second guess was ... the brackets for trailer's steel brake line were welded on the wrong side of the axle which had to be turned around for the brake line to be on the correct side. Go figure!

Some pictures to illustrate the story ... coming soon ...

 

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State of the affairs last Fall, boat stuck on the broken trailer ...

large.image.jpeg.f1ee05547ce50cfde4e445f

Wheel and fender detail ...

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Finally got the boat off the trailer in September this year, just before another Fall ...

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About to replace the first axle, note the asymmetrical axle brackets, brake line and its brackets is visible, a blue tape marks the center ...

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All three axles replaced and oriented the same way, the middle axle aligns with the center now ...

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All done and finished ... the wheel spacing looks much better now ...

large.image.jpeg.11a71dc1b55b3fa4e71ebca

Some people and their actions the rest of us need to deal with!

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How much tongue weight reduction is safe? Don't you need tongue weight to keep the hitch on the ball in case of hitting an unexpected bump or coupler failure?

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