Globetrotter 25FB Twin External Measurements

[goldenchase]

Originally Posted by jeffmc306

No, unfortunately I don’t have a dry as delivered weight. That 1100 lbs was ready to camp. We also have dual A/C and factory solar.

What’s the GAWR rating on your F150? I’m wondering how the onboard batteries/generator might impact your total on the rear axle. Our 1500 had a 4100 lbs rating. We were 150 lbs over on the rear axle which prompted the upgrade to a 3/4 ton.

F150 PowerBoost front GAWR=3900, rear GAWR=4150, GVWR=7350 and payload=1317. Yes, the PowerBoost Hybrid battery and electric motor adds a lot of weight to the F150 but then I have a 7.2kw generator. This all makes the Airstream all electric concept work.

Everything I have simulated so far suggests an all electric conversion of the FB25 Twin gets all the weights into comfort range for the F-150 PowerBoost.

However, while the Globetrotter is now overdue for delivery, I still have not bought the trailer yet. I warned the salesman if it arrives far outside the brochure specification for weight and weight distribution, I will pass on delivery. That is why I am running all these numbers.

What I expect is an FB25 Twin with 2nd AC and solar to have an empty weight of 6,194 lbs, with 914 lbs on tongue. Those are the brochure numbers plus the options. Based on my simulations after the all electric conversion the empty weight will be 6116 lbs with 788 lbs on the tongue. With balanced payload loading of the trailer, those weights work for an F-150 PowerBoost with 2 people on board. But it is close.

[nryn]

I applaud this effort. You've done your due diligence and are working through things systematically.

I trust you're aware that the PowerBoost's engine will run to charge the batteries and when there is significant load. I know that a running truck is quieter than a typical generator, but it's not silent.

You mention that you are a veteran RVer but not a trailer person. I'm not sure where and when you plan to camp, but a lot of campgrounds have quiet hours and/or non-generator hours and I'm not sure where a truck-engine-powered generator falls into those categories. To be fair, I don't know how those policies work for motorhomes or large 5th wheelers with built-in generators.

Perhaps this is not a concern for you, just thought I'd bring this up as something to think about. Maybe with 400A of lithium it's a non-concern.

[goldenchase]

Originally Posted by nryn

Maybe with 400A of lithium it's a non-concern.

The weights I posted include 4 x 100ah Lithium batteries in the storage area at the foot of the driver side bed. 400ah of Lithium is like 700ah of AGM so without the F-150 running there is more than enough power for everything except air conditioning (actually with the Victron Multipass I could run the air conditioners for a few hours). Certainly in a far better energy position than propane+2 100ah AGM's. The exception being Winter camping (which I don't do).

To hedge my bets on heating, I am thinking about leaving the 25lb Dometic propane furnace in the tailer with associated plumbing. Could always hook up a portable propane bottle if needed. Also the furnace is mounted aft so the additional weight helps with tongue weight.

As to running the F-150 PowerBoost for trailer power, the engine cycles on and off. Unless you are drawing the full 7.2kw load, the engine is mostly off. When it is on you have two idle settings (regular and high). At regular idle setting the engine is much quieter than any generator with maybe the same noise level as a typical RV air conditioner. How this will ultimately all be handled with campground quiet hours remains to be seen.

When the engine is off depending on generator load and outside air temperature the truck electric air conditioning compressor runs more or less continuously keeping the hybrid battery cool. Compressor is less noisy than normal idling engine, but it can be heard around the truck.

[PatLee]

golden chase - if you're spending $100K for a trailer, your requirement that it meet the tongue weight on the spec sheet seems reasonable. I am intrigued you are going to hold your dealer's "feet to the fire" if the trailer is not at 914 pounds tongue weight because your trailer is almost identical to my International floor plan (sans one A/C). Please let us know if the dealer met your requirement and if not, then did you walk away from the sale? If your trailer comes in at 914 tongue weight, I will be left thinking there must be a significant weight difference between the queen bed and twin bed configurations. I've always thought there was a potential to make the front end even heavier with the queen config than with the twins because you can store a LOT of stuff under a queen bed. The twin beds, not so much.

[goldenchase]

Originally Posted by PatLee

gI am intrigued you are going to hold your dealer's "feet to the fire" if the trailer is not at 914 pounds tongue weight because your trailer is almost identical to my International floor plan (sans one A/C).

The dealer can do nothing about out of specification tongue weights. I am still looking for owner's reports of tongue weights, as delivered, before anything is added to the trailer including water and waste. Tanks can sometimes be hard to completely empty. But the biggest difference twin and queen versions is storage. The twin version has 3 external storage areas versus 1 in the queen and internal storage area in the twin seems to be more than the queen.

To be clear, 914 lbs in tongue weight empty is a computed number based on accounting for the 2nd AC and solar package to the basic specification weights. Production variations will happen. Those variations should primarily impact total weight and only 15% on the tongue. For instance, if the trailer is 100 lbs in total weight over specification only 15 pounds should go to the tongue unless some production change happens close to the tongue.

Propane and batteries on the tongue is the real problem in the short coupled FB25. I estimate those two items alone add nearly 190 lbs to the tongue weight. Add a 2nd AC unit and you have an empty FB25, as delivered, before payload, with 15% of the trailer weight on the tongue. That means the majority payload must go aft to keep tongue weights between 10 and 15 percent. All the storage space is useless with so much initial weight on the tongue.

[goldenchase]

Some subtle changes in specifications for the Globetrotter 25FB Twin 2021 to 2022 models. Unit Base Weight is now 6,100 lbs for 2022 up from 6,075 in 2021. Hitch weight is up 3 lbs in 2022 to 885. Hitch weight as a percent of base weight is essentially unchanged at 14.51% with the trailer empty.

Of interest, looking at the 25FB Twin models for the Flying Cloud, International and Globetrotter, they have hitch weight as percent of unit base rate of 14.9, 15.6 and 14.5 percent respectively. All pretty close with the International having the heavier hitch as a percent of empty weight.

This is in comparison to the 27FB Twin models with 13.0, 11.2 and 11.5 percent respectively hitch weight as a percent of unit base weight.

So, as noted repeatedly in these forums, all the 25FB's twin models start empty with hitch weights, as a percent of unit base weight, at the extreme of the ideal range of 10 to 15 percent. Running my weight and balance models against the Globetrotter 25FB twin, you would have to add around 200 lbs more payload aft (exact amount depends on position after of C/G) of the C/G to get the hitch weight back to a more ideal 12.5% of total weight in a full loaded trailer.

This is all very sensitive to the actual placement of heavy payload items fore and aft, but it is clear the 25FB twins have around a 200 lb problem forward of the C/G, unloaded. The problem is made worse because most of the storage (outside and under the beds) used for payload in the 25FB twins is nearer the hitch than it is to the C/G of the trailer.

[jriffel]

Why do you need a 7.2kw generator? That is a Mammoth of a generator. All these numbers you are crashing may work, however the first long downhill or uphill grade in hot weather will tell you the real world numbers. They probably spell 3/4 ton truck with good brakes.
I pulled my 25FB for two years with a 1/2 ton 2016 GMC crew cab, until I got pushed down a long 5000' grade in 95 degree weather. That changed my mind. I now pull the 25FB (3.5KW generator) with a 2020, 2500 crew cab Chevrolet Diesel. I don't need to worry about extra weight from fire wood or cargo in the trailer. Issue solved.

[PatLee]

Golden chase - how illuminating your posts are. Seriously. Your comment about the twin bed “200 pound problem” was sort of an epiphany for me. I always thought it was the FBT versus RBT that made the difference. Now I think it comes down to the additional weight of the TWIN BED option versus the queen bed option. It makes me think that if I had only gone with a queen, my tongue weight would be 200 pounds lighter. That’s considerable. Would I now go with a different option if I had it to do over again? Hmm. No. The twins make the this Trailer feel twice as long. Thanks so much for doing all the work and analysis. Very impressive.

[goldenchase]

Originally Posted by PatLee

Golden chase - how illuminating your posts are. Seriously. Your comment about the twin bed “200 pound problem” was sort of an epiphany for me. I always thought it was the FBT versus RBT that made the difference. Now I think it comes down to the additional weight of the TWIN BED option versus the queen bed option. It makes me think that if I had only gone with a queen, my tongue weight would be 200 pounds lighter. That’s considerable. Would I now go with a different option if I had it to do over again? Hmm. No. The twins make the this Trailer feel twice as long. Thanks so much for doing all the work and analysis. Very impressive.

Thanks. But the problem is not just the twin version. Based on the Airstream website both the Globetrotter twin and queen have the same unloaded hitch weight at 885 lbs in 2022. The difference for the twin is that there is more storage space for payload, thus an all ready heavy hitch empty gets heavier as payload is added to all that storage space in the twin. It appears the hitch weight problem involves all the FB25 models not just the Globetrotter.

Coincidentally the problem is solved by not having propane and batteries on the hitch. Thus the project I am investigating. The solution is not a bigger truck, it is a lighter trailer.

[PatLee]

So where would you relocate the propane tanks and batteries?

[goldenchase]

Originally Posted by PatLee

So where would you relocate the propane tanks and batteries?

That is exactly what I am working on. I need to get my overdue trailer to finish the analysis. The best solution is to eliminate the propane, converting the trailer to all electric and placing lithium batteries as close as possible to the center of gravity. Center of gravity is just a few inches ahead of the front axle, unloaded. That will cure the 200 lb hitch weight problem for the 25FB models, unloaded and loaded.

Of interest, there is one other solution that AS could do. By simply moving the 25FB model axle set about 3" forward of the present position totally solves the problem. Of course that is impossible as a retrofit because the wheel well position would be impossible to move. So the 200 lb problem is a design issue in the 25FB models. The axles are simply too far aft in this model.

Lithium batteries make the all electric conversion feasible. I estimate the cost of this conversion to be between $4,000 to $8,000, depending on how many lithium batteries are used and an option to increase the inverter capacity. The standard 1,000 watt inverter is insufficient for an all electric conversion.

So all of my work to date is to identify the problem with the 25FB models and figure out some solutions. Up to now it appears the hitch weight problem in the 25FB models is pushing people into bigger trucks and beefier weight distribution systems. Seems like a brute force solution when other options are available.

[WHUDS22]

Originally Posted by PatLee

I wish with all my heart that the tongue weight of my 2019 25' FBT Airstream weighed 882 pounds. I travel alone and light and tongue weight at last weigh-in was 1150 pounds. The brochure weight it a lie; I don't know why Airstream doesn't correct it.

they dont lie, 15% of 5503 (FC 25FB) is 825.45 lbs

Loaded for us the calc comes to 975 lbs tongue
TV tongue is 1100lbs :/

[Texarado]

Originally Posted by WHUDS22

they dont lie, 15% of 5503 (FC 25FB) is 825.45 lbs

Loaded for us the calc comes to 975 lbs tongue
TV tongue is 1100lbs :/

The concern being expressed is that the tongue is approaching (or exceeding) the “max” when it’s an empty trailer and it seems like a justified complaint. There are things I will be doing to lower the tongue weight and increase performance (e.g., swap in lithium batteries).

[goldenchase]

Originally Posted by WHUDS22

they dont lie, 15% of 5503 (FC 25FB) is 825.45 lbs

Loaded for us the calc comes to 975 lbs tongue
TV tongue is 1100lbs :/

Thanks for the report. Do you have the 2nd AC unit?

[WHUDS22]

Yes, add 100lbs so my tongue is closer to max :/
But we dont boon dock we try to keep it lower
Just us two

[goldenchase]

Originally Posted by WHUDS22

Yes, add 100lbs so my tongue is closer to max :/
But we dont boon dock we try to keep it lower
Just us two

My "guesstimate spreadsheet" assumes an 85lbs for the 2nd air conditioner. Given it's position on the roof it comes out to 46.4lbs on the two axles and 38.6lbs on the hitch.

[foobar]

Originally Posted by goldenchase

My "guesstimate spreadsheet" assumes an 85lbs for the 2nd air conditioner. Given it's position on the roof it comes out to 46.4lbs on the two axles and 38.6lbs on the hitch.

Hi goldenchase,

Hopefully you will see this post given it’s been a few months since this thread was active.

I’m expecting delivery of a 2022 Globetrotter 27FB Twin in the late June timeframe (in 2022, of course :-)).

Can I ask where you obtained the drawing of the airstream?

Also, also have tongue weight challenges as I intend to tow with a 2016 Cayenne S. To manage this, I am also developing a load analysis spreadsheet that calculates changes in axle loads, tongue weight as well as tracks compliance (or not) with respect to GVWR, GAWR, GCWR, etc for the travel trailer and tow vehicle.

I am also planning on removing the factory installed batteries and put a large 1200ah LiFePO4 battery bank to the rear of the axles along with an inverter, etc and I factor this into the spreadsheet as well.

How has your spreadsheet development progressed? Did you take possession of the trailer? How did your plans work out?

[foobar]

Originally Posted by foobar

Hi goldenchase,

Hopefully you will see this post given it’s been a few months since this thread was active.

I’m expecting delivery of a 2022 Globetrotter 27FB Twin in the late June timeframe (in 2022, of course :-)).

Can I ask where you obtained the drawing of the airstream?

Also, also have tongue weight challenges as I intend to tow with a 2016 Cayenne S. To manage this, I am also developing a load analysis spreadsheet that calculates changes in axle loads, tongue weight as well as tracks compliance (or not) with respect to GVWR, GAWR, GCWR, etc for the travel trailer and tow vehicle.

I am also planning on removing the factory installed batteries and put a large 1200ah LiFePO4 battery bank to the rear of the axles along with an inverter, etc and I factor this into the spreadsheet as well.

How has your spreadsheet development progressed? Did you take possession of the trailer? How did your plans work out?

Never mind. I found your other thread and caught up with the project. Well done by the way !!!

[Rickeyt]

I am reading thru this thread and seeing that none of the calculated tongue weights allow for the acutal hitch weight. My E-Z Hitch Stablizer weighs 102 lbs. That weight should also be considered in the calculation of trailer tongue weight.

[foobar]

Originally Posted by Rickeyt

I am reading thru this thread and seeing that none of the calculated tongue weights allow for the acutal hitch weight. My E-Z Hitch Stablizer weighs 102 lbs. That weight should also be considered in the calculation of trailer tongue weight.

Agree. I do include hitch weight in my tongue weight calculations.