- About the Boler Frame
- Problems with the Boler Frame
- Removing the Body from the Frame
- Building a New Frame – New Design
About the Boler Frame
Consider the stresses exerted on your Boler frame as you travel down highways, hit bumps, swerve around pot holes and experience wind forces equal to a hurricane. Like the foundation of your home the frame and axle keep every part of your Boler body straight, square and stable. Many problems seen throughout a Boler can be traced back to a bent, twisted or broken frame.
The frame can be considered a problem area or weak point with the Boler, but let’s start with the original concept and design. With the fiberglass body mounted securely to the frame the combined integral strength is considerably higher than each component (body & frame) separate. The frame was built with overall weight a prime consideration, the initial frames built in 1968 & ‘69 used 1.5”x3” 0.083”/0.109” or 12/14 gauge “C” channel. From 1970 and onward a rectangular box section frame was used made from 1.5”x3”, 0.0625” or 16 gauge rectangular tube, this entire frame with axle and wheels weighed 300 lbs.
Problems with the design of the Boler frame contributes to the structural issues commonly seen on the 13’ Boler. The right hand frame rail (curb side) is cut or notched to accommodate the lower kitchen floor and the doorway, a small angle iron or 2”x2” square tube is welded under the doorway to carry the load, but because of the reduced size and strength this area is prone to flexing this greatly compromises the strength and load capacity of that member.
Compounding the above is the design of the tongue. Boler used a narrow 30 degree tongue angle (50 degree tongue angle is now the industry standard), this made the tongue length longer and resulted in the angled tongue members joining to the frame under the body on the right hand side right where that rail in notched for the doorway.
Problems With the Boler Frame
Now is the time to take a closer look, the frame on a Boler is strong enough as designed, the main problem occurs when the bolts and screws holding the body to the frame get loose or break. When the body and frame are held securely together they function as one unit and support each other, when the bolts get loose the body and frame flex and twist separately and this is what causes the damage. It is important the the frame rails are straight, parallel and flat, any bend or twist will cause problems. There are 3 main area that often show damage, bends or cracks.
In the above diagram point “A” experiences very high stress loads due to the fact the frame is notched at this location to accommodate the doorway and the lowered kitchen floor. Crawl under the trailer and look closely for any reinforcements, patches, crack or broken welds.
Point “B” is the most common area for the frame to actually break, again check this area for reinforcements, patches, crack or broken welds. while under the trailer at this time try to look to see if the two frame rails (right & left) are level with each other. You are looking to see if the entire frame is twisted. A twisted frame is common when a frame is repaired and a patch is just welded on without making sure the frame is straight first.
This shows an excellent repair on the drivers side frame rail, but unfortunately the entire frame was twisted when this was welded, it caused major problems with the body.
The final area, point “C”, causes the most problems with the body. When the bolts that attach the frame to the body loosen or break the body will actually start to rock and move in relation to the frame, this rocking action puts very high loads on the back section of the drivers side frame rail, the result is this frame rail will actually start to bend down from the axle mount to the back bumper. When this rail bends it causes the body to twist which will cause the problems seen at the door opening and the dimple above the drivers side wheel arch. From the back of the trailer look down the frame rail and make sure it is not bent down
The above pictures show a frame rail that is bending, the earlier picture shows what will eventually happen to this frame also. It is critical to regularly check the frame to body bolt and keep them tight, this only happens when those bolts fail.
Removing Body from Frame
Removing & Reinstalling Body on Frame Removing the Boler body from the frame is actually quite easy, but throughout this process remember you are working with heavy items that react very quickly and unexpectedly to gravity. They will fall and can cause a lot of damage and injury so proceed with caution and always consider your personal safety.
The Boler body is usually connected to the frame with 16 bolts and/or wood screws into the frame rails and cross-members
Standard locations for the fasteners are:
3 fasteners are under each side under the rear dinette seats (6 total)
1 fastener under the sink – if you have a furnace it has to be removed to access it
1 fastener is under the fridge, the fridge has to be removed to access it
2 fasteners are in the closet
3 fasteners are under each side in the front storage compartments (6 total)
1 additional screw is sometimes located in the middle of the kitchen floor area
You may be thinking at this point there is not a lot holding the body to the frame and you would be correct, a common problem I have seen on Boler’s are the mounting bolts pulling loose which will allow the body to “rock” on the frame. This rocking will usually cause the left frame rail (drivers side) to bend downward from the axle location to the rear bumper. If you look down the left frame rail from the back and notice an arch or downward bend that is the cause.
NOTE: any time you are lifting or supporting the body on the fiberglass floor always use 2″x6″x12″ long pieces on wood between the jack and/or stands and the floor of the Boler to distribute the load over a larger area. NEVER support the body by the edge of the body.
- Automotive hydraulic jack
- 6 – jack stands
- 2 or 3 – 8′ long 2″x6″ cut into 12″ long pieces for blocking to support the body
- 2 – 9′ 4″x4″ (or larger) fence posts to support the body. (makes sure these timbers have straight grain with no large knots or cracks)
Tools to remove body bolts and screws
For this job it is best to use a high quality hydraulic automotive jack and jack stands. Start by lifting the trailer up at both ends and supporting the frame with jack stands; next remove all bolts and screws that are attaching the body to the frame. With all the bolts and screws removed you need to relocate the jack stands supporting the frame to the Boler body floor. Jack up one end of the frame slightly and position jack stands under the floor of the Boler, use 2″x6″x12″ long pieces on wood between the jack stand and the floor of the Boler to distribute the load over a larger area. With the stands in position slowly lower that end of the trailer, the frame should start to separate at that end, but only let the frame separate slightly at this point, continue to support the frame. Repeat this process at the other end of the trailer, lifting by the frame slightly, supporting the body under the floor using wood to distribute the load, and then lowering carefully. Now the moment of truth, the frame should separate from the body, it may take a little wiggling or gentle persuasion; if it does not separate easily make sure you didn’t miss a bolt or screws
With the frame now sitting on the ground and the body supported by jack stands the job is not finished, you will notice the locations of the jack stands prevent the frame from being removed from under the body. The next step is to slightly lift the body and support it on 4″x4″ timbers that are set on jack stands positioned outside the frame. To do this lift each end of the body slightly with the jack, leaving the first set of jack stands in place for safety, position the 4″x4″ timber across under the body. Use a stack of lumber between the top of the timber and the floor of the body. Make sure the edges of the body do not rest on the sides of the body that overhang the floor. Once the timber and blocking are in position and stable, the original jack stands can be removed and that end of the body can be slowly lowered onto the timber and blocking. Repeat this process for the other end, the frame can now be removed by sliding the frame out from the front.
Building a New Frame
After seeing all the problems with the original Boler frame I set out to build a better frame.
The design considerations included:
- Strength – The frame had to be strong, not bend or break
- Reduce the stress areas – eliminate the stress areas especially where the tongue connects to the notched frame by the entry door
- Light weight, trying to keep the new frame close to the weight of the original
The first consideration is the material used for the frame, although aluminum is lighter it requires much larger sectional dimensions to give the strength required, larger size material also increases the weight. The second concern with an aluminum frame is that it requires special skills and equipment to weld, the welding process can also weaken the material which can become susceptible to cracking and failure, The final concern with aluminum is the cost, although using aluminum would have resulted in a frame weighing about the same as the original the other concerns made it unacceptable for this project.
Steel being the best solution it was deciding on the best profiles to use. For the two main side rails I decided to use (2”x6”x0.125”) C channel, custom made from 1/8″ steel plate bent into a 2″x6″ profile by a fabrication shop. This profile is common in truck frames where strength, weight and ease of connecting components is critical. Although a 4” profile would have been ample I chose the 6” because the dropped floor in the kitchen area is a 6” drop and the design included installing a Flexi Ride axle in the recommended trailing arm configuration, this meant the axle tube needed to pass under the kitchen floor area. An additional advantage of using C channel is it allows the body to be securely bolted to the frame, no more long bolts that crush the tubing or metal screws that work loose over time, the body can be bolted through the top flange using 3/8”x 1 ½” bolts, large fender washers on the inside fiberglass of the body and lock washers with lock nuts under the frame.
Although the C channel is extremely strong it does require blocking or boxing at critical load bearing areas like where the axle bolts to the frame, the front tongue connection and at the cross members. For the boxing, the cross members and tongue I used (2”x3”x0.125”) rectangular tube, this same material, laid flat, is used under the door area when the passenger side frame rail is notched. Finally I used lighter (1”x1”x0.0625”) square tubing in the cut-out for the original porta-potty, if your Boler does not have the porta-potty storage you can just bridge this area with a straight cross-member
Finally the design, as mentioned earlier the original Boler frame used a very narrow 30 deg tongue coupler angle which places the tongue connection right at the frame notch at the doorway, by extending the frame rails forward and using a 50 degree coupler angle it allows for a greater bridging area to support the doorway notch and eliminates that stress area. The weight of the original frame including the axle and wheels (does not include brakes) is 300 lbs, The redesigned frame described here weighs 395 lbs including axle with brakes (weight of brakes is 22 lbs each) which means the new frame only weighs 50 lbs more than the original
I have many skills but making CAD drawings is not one of them, if you would like to build a similar frame I have included some simple drawings along with a pictures that should guide you in building a similar frame for your Boler.
- The 13′ Boler was made in a number of location and there could be minor variations. Please use this information as a guideline, double check the actual measurements on your frame.
- In the picture the diagonal cross brace is optional, I use it to mount a spare tire. Do not install this brace if you intend to install the fresh water tank under the rear or the trailer.
The following pictures document the build of the frame for my boler using the new design.