Trim Tab Installation on c.1985 OUTRAGE

[mwk4619]

Q1: (without cutting a hole in the hull bottom and shoving [some material identified by an unknown acronym as “MGPW”] into a hollowed out section of foam, followed by replacement of the foam, and followed by repair of the hull laminate) how can trim tabs be installed on a c.1985 OUTRAGE [of unspecified model length—always mention the full model name with length]?

[jimh]

For advice on trim tab installation read my article in the REFERENCE SECTION at

Trim Tab Installation
https://continuouswave.com/whaler/reference/trimTabs.html

The method you suggest is unknown to me.

The material you described as “MGPW” is unknown to me.

[mwk4619]

[Revived thread after a being dormant for almost three years]

On an 1985 OUTRAGE 25 the [reinforcement] wood does not extend past the [engine] splash well.

Q2: how are [trim tab] actuators [fastened to the hull] in the sections to the [port] and [starboard] of the engine wood reinforced section?

Q3: [is it necessary] to glass-in wood behind the transom to mount [trim tab actuators]?

This area appears [to be constructed with] unreinforced fiberglass.

[jimh]

Thanks for reviving the thread to identify that the boat under discussion is an OUTRAGE 25. Identifying the particular model of the OUTRAGE is important, as it identifies the actual model that is under discussion.

The transom of an OUTRAGE 25 is shown in an illustration at

https://continuouswave.com/whaler/refer ... tions.html

For details, see the illustration Figure 4 in the REFERENCE section article on the OUTRAGE 24/25 hull at

https://continuouswave.com/whaler/reference/25Outrage/

The notched transom of an OUTRAGE 25 appears to be similar to the notched transom of other OUTRAGE boats of that era in that the notched transom is not a flat surface, but has a thicker section in the area of the notch where the engine or engines will be mounted. The thicker area of the transom contains embedded wood to add strength that portion.

On an 1985 OUTRAGE 25 the [reinforcement] wood does not extend past the [engine] splash well.

The engine splash well is actually a full-width splash well that runs from one side of the hull to the other, so using the engine splash well as a location to describe where the embedded wood is located is not an accurate description. The small aft quarter decks actually have a recess cut into them to permit the full-width splash well to pass through the bulwarks of the quarter decks.

For details, see the illustration Figure 4 in the REFERENCE section article on the OUTRAGE 24/25 hull at

https://continuouswave.com/whaler/reference/25Outrage/

Q2: how are [trim tab] actuators [fastened to the hull] in the sections to the [port] and [starboard] of the engine wood reinforced section?

Regarding methods of fastening trim tabs and the actuators to the transom of an OUTRAGE 25, please read the article in the REFERENCE section that I mentioned and gave a link to in my initial response to you questions.

In the linked article that I mentioned in the original reply from three years ago, read the section under the heading

FARTHER MOUNTING FROM CENTERLINE

In that section read the material under the headings

HINGE MOUNTING

and

ACTUATOR MOUNTING

Those sections give answers to your question regarding how to fasten trim tabs and their actuators on OUTRAGE hulls when mounting trim tabs and actuators that are going to be farther outboard of the center reinforced section of the transom.

Also, now that you have revived the thread, I have to ask:

Q4: what is the material that you refer to with the letters MGPW?

[jimh]

Q3: [is it necessary] to glass-in wood behind the transom to mount [trim tab actuators]?

I can't answer with certainty that it will always be necessary to embed wood reinforcement in the area of the transom where the trim tab actuator upper mount will be attached. My sense of the strength of the unreinforced transom is that is will be sufficiently strong to stand up to the compression forces exerted on it.

Typically the upper mount of a trim tab actuator is provided with a mounting pad that has significant surface area. The larger surface area of the mounting pad will spread the loading of the forces attempting to compress hull laminate over a large surface, which should probably then have sufficient strength to resist those compression forces and avoid any compression of the hull laminate.

If you perform some calculations and determine that the surface area of the mounting pad of the upper mount of trim tab actuator is not sufficiently large to spread the loading of its forces acting to compress the laminate of the transom to avoid resulting in compression of the hull laminate, then you could employ some method to increase the area of the mounting pad, such as using wood to spread the load.

Because the concern about the forces is alway for their compression of the laminated, and there will seldom be any significant forces of tension on the mounting pad, you could locate the wood that spreads the load on the outside of the hull.

An example of using wood to spread the load of the mounting pad of the upper end of the trim tab actuator is illustrated in the article that I suggested you read in my initial reply three years ago. If you study the illustration under the heading "Alternative Mounting, Distant from Centerline" you will see an example of how an external wood piece was used to spread the load of the mounting pad at the top of a trim tab actuator onto a larger area of the transom where there was not embedded wood reinforcement.

The upper mounting pad of the trim tab actuator will exert significant shear force onto the transom. For that reason, the area of the transom may need to be reinforced where the screw fasteners that hold the mounting pad to the hull will be located. Rather that cut a window into the transom and remove the laminate, create a pocket in the foam, install new wood reinforcement inside the transom, then re-laminate the cut out hull portion back into the transom, I suggest a much simpler method to provide more strength to the screw fasteners and improve their purchase into the hull laminate to resist shear forces.

After locating the position of the screw fasteners that will hold the mounting pad of the trim tab actuator upper end to the hull, and after using some external wood to spread the loading on the hull over a larger area than just the mounting pad area, if you are still concerned that the screw fasteners--all of them, that is, including the new screw fasteners that hold the new wood that spreads the load over a larger area--you could use two alternative methods to your proposal to cut into the transom laminate to add embedded wood.

The first option (to avoid your proposal to cut out a section of the transom and install embedded) is to use a well-know method of creating an annulus or donut-shape or ring UNDER the original hull laminate which only removes the cured foam interior of the hull, then inject a mixture of epoxy resin and high density filler into this new space created under the hull laminate. Once the epoxy resin mixture has fully cured, you can then drill a pilot hole, and install a screw fastener into the hull, with the screw fastener now obtaining much more purchase to the cured annulus of epoxy that is below the gelcoat layer. To see how to create such a reinforcement, see this article that illustrates the technique:

Repair of Loose Screw Fasteners
https://continuouswave.com/forum/viewtopic.php?t=3224

The second option (which again is mentioned in the Reference Article I referred you to in my initial reply) is to use through-bolting to retain the mounting pad of the upper end of the trim tab actuator to the hull.

A very strong adhesive should be used to attach the external wood reinforcement to the hull laminate, giving the large contact area between the wood and the hull the ability to resist substantial shear forces, and also giving the screw fasters that will attach the mounting pads of the trim tab actuator upper arm to that external wood a very strong purchase into the wood and hull laminate.

[mwk4619]

[In the planned project yet to be undertaken to add trim tabs to an c.1985 OUTRAGE 25 transom] the actuators will mount [outboard] of the thicker reinforced [notched] section of the transom, where--in my understanding--there is no embedded wood reinforcement. This [material there consists of only] laminate and foam.

Q5: it the statement true that [because the hull outboard of the notched transom area consists of only laminate and foam] this location is not sufficient to [attach] the actuators UNLESS wood [is embedded] behind the inside wall of the transom in the curved sections inside each [aft quarterdeck] hatch?

Q6: is the above assumption is wrong, [that is, the area is suitable to attach trim tab actuators] what fasteners are best in this un reinforced area?

Q7: will the fasteners [mounting the trim tab actuators] be simply screwed into the hull laminate?

Q8: will the fasteners [mounting the trim tab actuators] be though=bolted?

Note: the SONAR transducer is simply fastened to the hull laminator in an areas without embedded wood, and I am not happy about that arrangement.

ASIDE: the c.1985 OUTRAGE 25 Notched Transom boat has twin engines, and I have used the engines as trim tabs. I have always wanted had actual trim tabs and be able to stop using the engines as trim tabs.

[jimh]

[In the planned project yet to be undertaken to add trim tabs to an c.1985 OUTRAGE 25 transom] the actuators will mount [outboard] of the thicker reinforced [notched] section of the transom, where--in my understanding--there is no embedded wood reinforcement. This [material there consists of only] laminate and foam.

You and I have the same understanding.

Q5: it the statement true that [because the hull outboard of the notched transom area consists of only laminate and foam] this location is not sufficient to [attach] the actuators UNLESS wood [is embedded] behind the inside wall of the transom in the curved sections inside each [aft quarterdeck] hatch?

No.

Q6: is the above assumption is wrong, [that is, the area is suitable to attach trim tab actuators] what fasteners are best in this un reinforced area?

See my suggestions in my reply above.

ASIDE: did you read my long reply?

Q7: will the fasteners [mounting the trim tab actuators] be simply screwed into the hull laminate?

See my suggestions in my reply above.

Q8: will the fasteners [mounting the trim tab actuators] be though-bolted?

That is an option, but I do not think it is necessary because the upper mounting base of the trim actuator will never really be in tension. For the attachment of the trim tab hinge there is no way to through-bolt them.

I see from the three-years separating your initial inquiry about installing trim tabs and this latest inquiry that you have been thinking about this for a long time. When you actually complete the process, you can follow-up with more details about how you decided to install the trim tabs and the actuators.