Ideal tongue weight?

[Drcoffee]

My trailer is a single axle trailmaster for a 21’ Rinker captiva 212. I just weighed the tongue and its 172#. Max for tow vehicle is 500#. Is there an ideal weight range for best performance?

 

[Lou C]

it should be a LOT more than that. My boat which is about the same size has 420 lbs of tongue weight. Trailer companies recommendations vary from 5-10% of total weight, mine's at about 8.8% or so, total weight is 5050 lbs, 4650 lbs on the axle.
To increase tongue weight the boat has to come forward, or you can move the axle backward, or a bit of both depending on how the trailer is designed.
If you can you should get it weighed, you have a 5 lug axle there, they only go up to 3500 lbs, for a 21' boat, you may be overloaded. Might need to upgrade to a 5200 or 6000 6 lug axle. That's what I did with mine. With a 3500 lb axle, if you can get 400 on the tongue, then the boat & trailer weight on the rear axle shouldn't exceed 3500 lbs, this would allow an total weight of 3900 lbs if you have 400 on the tongue. I'm kinda thinking it will exceed that though. Not too many boats that are 21' with a 5.7 I/O (heavy) are less than 3500 lbs then there's the weight of the trailer too (700-850 or so?)....your true weight may be closer to 4200-4400 or so.
Towing that much on a single axle is possible, but you really want a 5200 lb capacity axle & springs to match, 12" brakes, 15" rims and 225/75-15 load range D tires at a minimum, load range E would be best. That is how companies like Load Rite and Venture set up their HD single axle trailers.
As it is now I would not tow that at highway speeds, with only 172 lbs of tongue weight it is at risk of fish tailing which is very dangerous.

 

[airshot]

The 10-15% rule works most of the time, I always start at 10% for the initial starting point. Some trailers differ so some experimenting is needed. Never heard of a towing problem with to much tongue weight, so error on the heavy side. Another thing to look at is keeping your trailer fairly level, over my many years I have saw many trailers being towed at extreme angles from nose down to extreme nose up. This can cause serious handling issues when applying the brakes hard in emergencies!!!
Get your trailer close to level by adjusting the hitch ball height, get hitch weight in that 10-15% weight range, tires properly inflated and towing should be a breeze as long as your tow vehicle is rated to tow the weight of your rig....

 

[Drcoffee]

I do need to get the actual weight on my boat setup. That single axle looks to be working too hard. Im at 5% if I weigh 3500#. And close to 6% at 3100#. Should I move the vertical support forward a few inches? How many?
Ive been looking for a good used dual axle trailer to replace this one.

 

[briangcc]

I had to look it up....Rinker (per that wonderful magazine that touts vaporware) states the dry weight is 3050 for the boat.

As long as the trailer isn't swaying around, I'd leave it....why fix something that ain't broke?

 

[Lou C]

Well I can see not fixing what ain’t broke but if you have to tow that over 30 mph, get it weighed and fix it. There is no way that a tongue weight of 172 lbs is safe for a boat that size. 3100 lbs? Well FW said the dry weight of mine was about 2600 lbs! I thought it was more more like 3500 but it was way more than that in reality.

 

[Drcoffee]

Taking into consideration 40 gallons of fuel is 240# plus anchors, etc. Im guessing Im close to 3500 full trailer weight. I plan to get it weighed on Saturday at the local truck stop on the way to the lake. $13 is what they charge. “CAT scale”

For context, I have driven a trailer once which started to fishtail on the highway at 65 mph. One of the scariest days of my driving life. You dont want to be in that position with the family in your truck/car. Thats why I am asking the question. I can imagine that a tire blow-out at speed would be very bad with a imbalanced trailer.

 

[briangcc]

So it is broke - ie trailer is swaying.

Then in that regard looking at your trailer about your only recourse is to move the winch stand closer to the coupler. You may have to reposition your bunks in the process so the transom is properly supported.

You're not moving the axle unless you break out a grinder as those fenders are welded onto the trailer frame.

 

[Drcoffee]

So it is broke - ie trailer is swaying.

Then in that regard looking at your trailer about your only recourse is to move the winch stand closer to the coupler. You may have to reposition your bunks in the process so the transom is properly supported.

You're not moving the axle unless you break out a grinder as those fenders are welded onto the trailer frame.

No not my boat trailer. It was a dual axle uhaul that I was pulling on a house move. I havent really taken the boat on the highway yet, just local country roads.

 

[tpenfield]

The highway will be really exciting . . . best to get the tongue weight to about 10% of your total weight. Probably around 350-400 lbs.

 

[Drcoffee]

we got rained out this weekend and didnt get to the scales either. In the meantime Im playing with some numbers to see how far to move the boat forward to add 100# to the tongue. Assuming the boat and trailer are 3200#. The ball hitch is 17’ from the axle and the transom is 6’ to the axle. If I am already 175# heavy on the tongue the weight is roughly 1700/1500 front to rear. To add 100# on the tongue, I am taking the 1500/6’ = 250 Lbs/ft. To move 50# from the rear to front I come up with 20#/inch or moving the boat forward 2.5”. Does that sound about right. Of course , I need the actual weight first.

 

[tpenfield]

The dry weight of the Rinker 212 is listed as about 3200 lbs, which sounds about right. So you are probably 4,000 lbs with the trailer (assuming 800 lb trailer).

My calculations get you needing to move the total C.G. (center of gravity) forward about 5", which would mean you need to move the boat forward about 6", since the trailer C.G. will not be moving.

 

[Drcoffee]

Checking the math, please correct me. If the CG of the boat is 6’ from the rear, I would be shifting 333# forward of the axle (~2000/6’=333#)(2) and at the same time losing 333# from the rear, net 666# shift in weight forward. Assuming the boat is 4000#.
Does that translate to 272# 17’ forward of the axle at the coupler?
the ratio of leverage over the axle 17/6 or 3:1. It looks like I would be adding 200# at the coupler, not 100#. Net 372# at the coupler.
again, algebra was a requirement, and not my favorite class in high school. LOL

 

[Lou C]

I’d be surprised if the boat + trailer are only 4,000. Probably more like 4500. But won’t know till you get it weighed. Would be interesting to see…

 

[Drcoffee]

I’d be surprised if the boat + trailer are only 4,000. Probably more like 4500. But won’t know till you get it weighed. Would be interesting to see…

And that would mean that Rinker sold this boat on a trailer rated at 3500#. Isnt there some liability by doing that? I know they are defunct, but even back then it would have been an issue.

 

[tpenfield]

Checking the math, please correct me. If the CG of the boat is 6’ from the rear, I would be shifting 333# forward of the axle (~2000/6’=333#)(2) and at the same time losing 333# from the rear, net 666# shift in weight forward. Assuming the boat is 4000#.
Does that translate to 272# 17’ forward of the axle at the coupler?
the ratio of leverage over the axle 17/6 or 3:1. It looks like I would be adding 200# at the coupler, not 100#. Net 372# at the coupler.
again, algebra was a requirement, and not my favorite class in high school. LOL

We have been through this before in a thread from a few years ago. Just ask @harringtondav

The center of gravity is probably not 6' from the rear (axle location), else you would have zero tongue weight. Based on the figures you posted, the CG is 8.77" forward of the axle. In order to gain 100# of tongue weight the new CG has to be 13.87" forward of the axle (or about 5" forward of its current location).

It is not a matter of math so much as it is a matter of physics.

You may find that 272lbs is still not quite enough tongue weight and may have to re-configure further.

 

[Lou C]

Well Four Winns sold my style boat on a trailer with a 3700 lb carrying capacity. The boat was “supposed” to weigh about 2700. My own measurements found it to be far more and, when I replaced the deck 15 years ago the original flotation foam wasn’t water logged either.
On their current website FW lists a weight for the boat that is closest in size to mine (but about 7” shorter) at 3500 lbs. They will still sell it on a single axle trailer too but with a 5200 lb capacity axle & 6 lug hubs. Mine turned out to be even heavier than that. Total 5050 lbs and the trailer weighs 850 lbs. Really glad I upgraded from the 3500 lb axle last year to the 6,000 6 lug I have under it now. Despite it being overloaded for years never had a failure other than the 4 leaf springs getting flattened out too soon. That’s what got me thinking. So added that axle, 5 leaf springs 12” brakes & 15” rims with 225/75-15 load range D tires. Finally it’s not overloaded! 4650 on the axle.
I don’t know how hard that would be for you to do. Galvanized trailers are easy because it’s all modular everything is bolt on. You can slide the spring mounts back to increase tongue weight on these.

 

[harringtondav]

We have been through this before in a thread from a few years ago. Just ask @harringtondav

Yea, yea. ...rub it in.

 

[Drcoffee]

Update:
I was able to get her weighed tonight. The boat/trailer is 4,280# by itself and 4,060# attached to the truck. Tongue weight looks to be 220#. On the reweigh, I lifted the coupler off the ball. I will need to shift the bow stop forward to get closer to 400#. The axles cant be moved. The fenders are welded in place.
*the drive axle is the boat
*the steer axle is the truck

 

[tpenfield]

It looks like you have some room to move the bow stop/pillar forward to gain the tongue weight desired. You may not need to go all the way to 10% (420 ish lbs.)

Is there enough support at the stern/transom area (bunks. . . right?)