2026 Forest River Sierra3800RK

The Sierra 3800RK has 2,651 lbs of cargo capacity between 12,849 lbs dry and its 15,500 lbs GVWR, 17% of that rating; filling its 50-gallon fresh tank at 8.3 lb a gallon uses 415 lbs of it (how to read trailer weights).

Pin weight is 2,405 lbs, 19% of the dry weight as published; it rises as the trailer is loaded and comes off the truck’s payload, not its towing rating, so check it against the payload on your own door sticker (pin weight and payload).

Off hookups: 150 gallons of grey and black capacity against 50 gallons of fresh water, so fresh water runs out first (tank sizes by length).

Against the rest of the Sierra roster this is the 6th of 9 floorplans by dry weight, in a line that runs from 10,869 lbs to 13,864 lbs. It sits in the heavier third of the line.

Plan the tow on loaded weight, not the 12,849 lbs dry figure: half the published cargo capacity brings this plan to about 14,175 lbs, and the published GVWR of 15,500 lbs is the limit (how to read trailer weights).

Forest River’s line listing and this floorplan’s own factory page agree on all 4 shared figures. Dry weight plus cargo capacity equals the published GVWR exactly. A missing row means Forest River does not publish that figure (how figures are verified).

Forest River publishes no floorplan description for this plan in the channel this page is built from - only the numeric specification block. Rather than describe a layout from the floorplan code, which would be a guess dressed as a fact, this page carries what the factory publishes and says where it stops. 3800RK is a Sierra designation and this site does not decode it into a layout claim.

How the 3800RK differs from the other eight Sierra floorplans. Most distinctive first. Sibling pages may cover other model years than this one (2026). How these ranks are worked out.

• Length, 44 ft 1 in: longest of nine; next is the 3990FL (43 ft 6 in).
• Cargo capacity, 2,651 lb: third-smallest of nine, between the 4002FB (2,611 lb) and the 3900HBLR (2,801 lb).
• Cargo capacity as a share of GVWR, 17.1%: third-smallest of nine, between the 4002FB (16.8%) and the 3900HBLR (17.4%).
• Dry weight, 12,849 lb: fourth-heaviest of nine, between the 3710HBFB (12,649 lb) and the 4002FB (12,889 lb).
• Pin weight as a share of dry weight, 18.7%: fourth-largest of nine, between the 4002FB (18.2%) and the 3100RD (18.8%).
• Pin weight, 2,405 lb: shared with the 3710HBFB; of nine, six lighter and one heavier, nearest the 4002FB (2,340 lb) and the 3990FL (2,825 lb).
• Black tank, 50 gal: smallest of nine, level with the 3990FL and 4003MB; next are the 3100RD and 3480RL (52 gal).
• Grey tank, 100 gal: shared with the 4002FB and 4003MB; of nine, one smaller and five larger, nearest the 3990FL (80 gal) and the 3100RD, 3480RL and two others (104 gal).
• GVWR, 15,500 lb: shared with the 3710HBFB, 4002FB and 4003MB; of nine, three lower and two higher, nearest the 3990FL (15,375 lb) and the 3900HBLR (16,085 lb).

Next to the 3710HBFB, the nearest lighter floorplan by dry weight, the 3800RK is 200 lb heavier by dry weight, has 200 lb less cargo capacity, is 1 ft 4 in longer, stands 1 in lower, has a grey tank 4 gal smaller and has a black tank 54 gal smaller; the two publish the same GVWR, pin weight and fresh tank.

Next to the 4002FB, the nearest heavier floorplan by dry weight, the 3800RK is 40 lb lighter by dry weight, has 40 lb more cargo capacity, has a pin weight 65 lb heavier, is 8 in longer and has a black tank 50 gal smaller; the two publish the same GVWR, exterior height, fresh tank and grey tank.

Sierra's published pin weights spread further than its dry weights do, and that is the fact worth carrying into a dealership: nine floorplans run 10,319 to 13,864 lb dry - a 3,500 lb band - while pin weight runs 1,560 to 2,825 lb, nearly doubling. Two Sierras a thousand pounds apart on the scale can be far apart at the pin too. Every plan on the roster ties out exactly against its published GVWR.

A full 50-gallon fresh tank is about 415 lb of water (water counts as cargo: 49 CFR 571.120 S10.4.2), 16% of the 3800RK’s 2,651 lb cargo capacity, leaving 2,236 lb. Across 9 Sierra floorplans the water share runs 14% to 19%, and 4 give up more than this one. Nearest on that share: Sierra 3900HBLR at 15% and Sierra 4002FB at 16%. Your own unit’s figure is on the label inside its entry door (49 CFR 571.120 S10.4.3).